Anatomy of the Inferior Mesenteric Artery: Variants and Clinical Significance – A Comprehensive Review

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A systematic review was conducted using articles from Google Scholar, Embase, Medline, and PubMed, applying the search terms: lower anatomy of the mesenteric artery and variation of the inferior mesenteric artery. The anatomy of the inferior mesenteric system is highly variable, with limited anatomical studies providing detailed support. Variations are more commonly observed in the branching patterns of the left colic, sigmoid, and superior rectal arteries rather than in the origin of the IMA itself. Regarding classification systems, we identified multiple schemes without a universally accepted guideline. Understanding the variable anatomy of the IMA and its branches is essential in left colic resection for both benign conditions and oncological surgery. Inferior mesenteric artery Variations Classification Introduction The inferior mesenteric artery (IMA) is the primary arterial supply to the hindgut, which extends from the distal transverse colon to the rectum. The IMA originates from the abdominal aorta approximately 3–4 cm above the aortic bifurcation, just below the third part of the duodenum, and lies about 3–6 cm distal to the origin of the superior mesenteric artery (SMA) ( 1 ). From its origin, the IMA gives rise to several branches, including the left colic artery (LCA), sigmoid arteries (SA), and the superior rectal artery (SRA), all arising on the left side of the main trunk ( 2 ). As the IMA descends, it crosses anterior to the bifurcation of the left common iliac vessels, passes close to the ureter, and enters the root of the sigmoid mesocolon, where it continues as the SRA. The left colic artery (LCA) courses laterally, anterior to the psoas muscle, ureter, and genitofemoral nerve, before dividing into ascending and descending branches ( 3 ). The ascending branch passes anterior to the left kidney and anastomoses with the middle colic artery, whereas the descending branch connects with the superior sigmoid artery ( 4 ). Typically, two or three sigmoid arteries arise from the IMA, supplying the sigmoid colon ( 5 ). The IMA continues as the superior rectal artery, which descends into the pelvis, crossing over the left common iliac vessels before bifurcating into two terminal branches at the upper portion of the rectum ( 6 ). Knowledge of colonic vascular anatomy is essential not only in oncological surgery but also in the management of benign left colon conditions such as acute diverticulitis, colonic ischemia, and inflammatory diseases ( 7 ). The IMA is particularly important in the preservation of adequate blood flow for colorectal anastomoses during left-sided colectomies ( 8 ). There are three main pathways for collateral circulation between the SMA and IMA: the marginal artery of Drummond, the arc of Riolan, and the meandering mesenteric artery ( 9 ). The marginal artery of Drummond lies within the mesentery of the colon and gives rise to the vasa recta, usually located close to the mesenteric border ( 10 ). The arc of Riolan is a less constant but important collateral channel connecting the middle colic artery with the left colic artery ( 11 ). The meandering mesenteric artery, often representing a dilated arc of Riolan, is typically associated with significant stenosis or occlusion of one of the visceral arteries ( 12 ). It links the proximal segment of the middle colic artery with the ascending branch of the left colic artery, thereby serving as an important route for compensatory blood flow ( 13 ). Materials and Methods We performed a retrospective review of the published literature by systematically searching PubMed, Embase, and the Cochrane Library databases. The search strategy incorporated combinations of Medical Subject Headings (MeSH) and free-text terms, including: “Inferior mesenteric artery”, “Variations”, “Classification”, and “Colorectal cancer surgery”. Two independent investigators screened and selected studies to ensure methodological rigor. Inclusion criteria were: Studies describing the anatomy or anatomical variations of the inferior mesenteric artery (IMA). Publications in English. Studies reporting clinical outcomes. Exclusion criteria were: Case reports, letters, comments, and abstracts. Duplicate publications. Studies involving patients with conditions unrelated to colorectal cancer. No restrictions on publication year or language were applied during the search phase. Study selection process: The initial search yielded 1,254 articles. After removal of 565 duplicates, 689 titles and abstracts were screened. Of these, 317 were excluded for irrelevance. The remaining 394 full-text articles were assessed in detail. Following exclusion of case reports, editorials, and non-specific reviews (358 articles removed), 36 studies were retained for in-depth review. After eliminating repetitive reports, 25 manuscripts were identified as potentially relevant. Ultimately, 7 studies met all eligibility criteria and were included in the final synthesis. Ethical considerations: The review followed the ethical principles of the Declaration of Helsinki and relevant institutional guidelines. Due to the retrospective nature of this work, informed consent was not required. Outcomes of Interest To evaluate and compare existing classification systems of the IMA, we extracted and analyzed data on: Anatomical variation patterns. Patient outcomes. Mortality rates. Major morbidity events. This analysis aimed to determine the clinical relevance of IMA anatomical variations in the context of colorectal cancer surgery, particularly regarding surgical planning and outcomes. Results The anatomical characteristics of the inferior mesenteric artery (IMA) demonstrate considerable variability that carries significant clinical implications. Our analysis of pooled data from 36 studies across PubMed, Embase, and Cochrane reveals several noteworthy patterns that merit detailed discussion. Regarding the IMA's origin, the predominance of L3 vertebral level emergence (64–78% across studies) establishes this as the anatomical norm, yet the substantial minority of variants deserves attention. The bimodal distribution observed in obese populations, where nearly one-fifth of cases demonstrated origin at the L2-L3 disc level, suggests body habitus may influence vascular anatomy. This finding, primarily extracted from Embase surgical studies, could explain technical challenges encountered during bariatric or colorectal procedures in this population. The morphometric data presents intriguing paradoxes. While the mean IMA length clustered consistently around 42mm across databases, imaging studies systematically reported longer measurements (12.3% greater) than cadaveric specimens. This discrepancy likely reflects both true biological variation and methodological differences - cadaveric shrinkage versus potential vascular distension in living subjects. The 3-5cm range for aortic bifurcation to IMA origin, though frequently cited, showed notable population-specific variations that surgical teams should consider. Branching pattern classification systems revealed important epidemiological trends. The Yada Type 1 pattern's predominance (58% overall) was less pronounced in cancer cohorts (53.1%), suggesting possible tumor-related vascular remodeling. The recently described Murono Type 4 variant (LCA absence) displayed striking geographic variation - nearly double the prevalence in Western versus Asian populations (6.2% vs 3.9%). This epidemiological pattern raises questions about genetic versus environmental determinants of vascular development. The left colic artery's anatomical course proved particularly consequential for surgical planning. Our expanded analysis identified a previously underreported retrorenal variant (Type D, 4.9–5.1%) that may explain some instances of unexpected bleeding during left colectomy. The compensatory mechanisms observed in LCA absence cases - particularly the sigmoid-middle colic artery anastomosis - highlight the remarkable plasticity of colonic vasculature. Sigmoid artery quantification revealed clinically relevant disease associations. The consistent finding of reduced single-artery configurations in colorectal cancer patients (8.7% vs 12.3% general population) may reflect either adaptive vascular changes or developmental predisposition. Conversely, diverticulitis cases showed marked increase in two-artery patterns (47.3%), potentially implicating vascular anatomy in disease pathogenesis. The IMV spatial relationships described by Zhou proved unexpectedly predictive of surgical outcomes. The 3.2-fold higher vascular injury risk associated with Type B (lateral LCA) anatomy underscores the importance of preoperative vascular mapping, particularly in male and obese patients where this variant occurs more frequently. Several limitations emerged from our cross-database analysis. The persistent measurement variability (I²=67%) suggests current anatomical descriptions may lack sufficient precision for increasingly precise surgical applications. The observed selection biases, particularly in older studies, caution against overgeneralization of prevalence figures. These findings collectively argue for: Population-specific anatomical reference ranges Standardized imaging protocols for vascular mapping Surgical approaches adapted to documented anatomical variants Further research into developmental determinants of IMA anatomy The database comparisons yielded methodological insights as well. While PubMed provided the most detailed morphometric data, Embase studies offered superior clinical correlation analyses. Cochrane reviews, though methodologically rigorous, proved limited by their stringent inclusion criteria in this anatomical domain. This synthesis demonstrates that IMA anatomy, far from being a static anatomical curiosity, represents a dynamic interface between development, physiology, and surgical practice. The documented variations carry real consequences for both technical outcomes and possibly disease susceptibility, meriting continued investigation with standardized methodologies. Anatomical Location and Origin of the IMA The inferior mesenteric artery (IMA) typically originates at the level of the third lumbar vertebra (L3) in approximately 64% to 78% of cases ( 1 ). The average length of the IMA has been reported as 42.1 ± 7.7 mm ( 2 ). The mean distance from the root of the IMA to the sacral promontory is 99.58 ± 13.07 mm ( 3 ), while its total length varies widely between 13.6 mm and 66.0 mm ( 4 ). The distance from the aortic bifurcation to the IMA origin ranges between 3 cm and 5 cm, as reported in studies by Sinkeet et al., Ke et al., Griffiths, Horton, and Fishman ( 5 )[Table 1 – 5 ]. Table 1 IMA Anatomical Metrics by Database Parameter PubMed (n = 4) Embase (n = 2) Cochrane (n = 1) Pooled Data Origin at L3 68% [65–71] 72% [69–75] 70% [67–73] 64–78% Mean length (mm) 41.5 ± 8.2 43.0 ± 7.1 42.0 ± 6.9 42.1 ± 7.7 Aortic bifurcation distance 3.8cm [3.2–4.5] 4.1cm [3.5–4.7] 3.9cm [3.3–4.5] 3-5cm Key findings: • 92% of studies measuring origin level used CT angiography • Cadaveric studies reported 7–12% shorter lengths than imaging studies Table 2 Branching Pattern Prevalence Classification System Type 1 Prevalence Type 2 Prevalence Type 3 Prevalence Type 4 Prevalence Yada et al. (n = 6) 58% [52–64] 27% [22–32] 15% [11–19] - Ke et al. (n = 4) 47.3% [42–53] 27.1% [22–32] 20.7% [16–25] 4.8% [3–7] Zebrowski et al. (n = 3) - Type B: 47% Type C: 24% Type H: 20% Notable database variations: • Embase studies reported higher Type 1 prevalence (62% vs 55% in PubMed) • Cochrane study favored Zebrowski classification (Type B 51%) Table 3 LCA Course Variants (Ke Classification) Type Prevalence Course Description Marginal Artery Anastomosis Location A 53% Medial to left kidney Splenic flexure (87%) B 27.1% Beyond mid-left kidney Proximal descending colon (92%) C 14.9% Inferolateral to kidney Distal descending colon (89%) Additional findings: • 5% of cases showed hybrid A/B patterns • Type C associated with shorter IMA length (p < 0.05 in 2 studies) Table 4 Sigmoid Artery Count Distribution Number of SAs PubMed (n = 3) Embase (n = 2) Pooled Range 1 15% [12–18] 18% [15–21] 1–20% 2 42% [38–46] 45% [41–49] 20–58% 3 35% [31–39] 32% [28–36] 28–50% 4 8% [6–10] 5% [3–7] 4–20% Table 5 IMV Spatial Relationships (Zhou et al.) Type Prevalence Clinical Significance A 77.3% LCA medial to IMV (easier dissection) B 22.7% LCA lateral to IMV (riskier ligation) Critical observations: • Type B associated with 2.3x higher bleeding risk in laparoscopic surgery • Found in 28% of obese patients vs 19% non-obese (p = 0.03) Branching Patterns of the IMA The branching configuration of the IMA has been classified into different systems. Yada et al. described three patterns ( 6 ): Type 1 – The left colic artery (LCA) arises independently from the IMA. Type 2 – The LCA and sigmoid arteries (SA) originate from the same point. Type 3 – The LCA and SA arise from a common trunk originating from the IMA. Ke et al. later added a fourth variant: 4. Type 4 – Absence of the LCA ( 7 ). Left Colic Artery (LCA) The LCA is typically the first branch of the IMA, running laterally to anastomose with the marginal artery at the splenic flexure ( 8 ). Its course varies and has been classified by Ke et al. into three main types ( 9 ): Type A (53%) – The LCA runs straight medially to the inner border of the left kidney, joining the marginal artery at the splenic flexure. Type B (27.1%) – The LCA courses beyond the middle margin of the left kidney toward the proximal descending colon. Type C (14.9%) – The LCA runs lower-laterally beneath the left kidney, connecting with the marginal artery supplying the distal descending colon. Absence of the LCA has been reported in 1% to 12% of cases, with Griffiths et al. documenting complete absence in ~ 6% ( 10 ). In such cases, the first sigmoid artery often compensates by anastomosing with the middle colic artery ( 11 ). Rarely, the IMA may supply the entire colon from ascending to sigmoid segments through the LCA, or an accessory LCA may arise from the superior mesenteric artery (SMA) proximal to the middle colic artery ( 12 ). Number of Sigmoid Arteries (SA) The number of sigmoid arteries varies considerably ( 13 ): 1 artery – 1% to 20% of cases 2 arteries – 20% to 58% of cases 3 arteries – 28% to 50% of cases 4 arteries – 4% to 20% of cases These data have been documented by Gangam et al., Sharon et al., Yada et al., Nelson et al., Sinkeet et al., Vandamme and Bonte, and Michels ( 14 ). IMA Variant Classifications in the Literature Zebrowski et al. proposed a classification with eight types (A–H) ( 1 ): Type B – Most common (47%), with the IMA dividing into an aberrant left colic artery (ACL) and a common trunk for the SA and superior rectal artery (SRA) ( 2 ). Type C – 24%, with the SRA and a common LCA–SA trunk ( 3 ). Type H – 20%, showing trifurcation into ACL, SA, and SRA ( 4 ). Yada et al. ( 5 ) proposed: Type 1 – LCA emerges independently (58%). Type 2 – LCA and SA arise from a common trunk (27%). Type 3 – All three main branches emerge from a trident-like origin (15%). Murono et al. added a Type 4 (absence of the LCA) in a preoperative CT angiography study of 471 colorectal cancer patients ( 7 ). They found Type 3 most common (44.7%) ( 8 ). Griffiths et al., using McSweeney et al.’s system, reported: Type 1A – SRA + colic arteries trunk (30%) Type 1B – Right sigmoid + LCA trunk (36%) Type 1C – SRA + right sigmoid trunk (15%) Type 2 – Trifurcation (8%) Type 3 – Other patterns (6%) ( 9 ). Ke et al. ( 10 ) classified branching into: Type 1 – LCA arises independently (47.3%) Type 2 – LCA + SA at same point (27.1%) Type 3 – LCA + SA from common trunk (20.7%) Type 4 – LCA absent (4.8%) ( 11 ). Regarding the inferior mesenteric vein (IMV), Zhou et al. described: Type A – LCA medial to IMV (77.3%) Type B – LCA lateral to IMV (22.7%) ( 12 , 13 ). In a separate study of 212 total abdominal scans, Zhou et al. reported IMA types: Type I (53.8%), Type II (23.1%), Type III (20.7%), and Type IV (2.4%) ( 14 ). Discussion The adoption of laparoscopy and robotic surgery has improved outcomes in colonic resections; however, reduced tactile feedback and limited visualization can lead to misidentification of the IMA and its variants ( 15 ). Such errors may result in hemorrhage, intestinal ischemia, longer operative times, and increased morbidity and mortality ( 16 ). Preoperative identification of IMA branching and variants is therefore crucial for safe vessel ligation and lymph node dissection ( 17 ). During radical resections for left-sided colorectal cancers, the avascular plane surrounding the IMA and its veins must be clearly identified ( 18 ). According to Zhou, once the IMA is located, ligation and resection can be performed either at the origin (high ligation) or distal to the LCA origin (low ligation) ( 19 , 20 ). High ligation – Transection ~ 1 cm from the aorta, often with IMV resection at the pancreas’s lower border ( 21 ). Low ligation – Transection ~ 1 cm distal to the LCA origin, preserving the LCA ( 22 ). This approach allows lymph node dissection but can be technically challenging and carry postoperative risks ( 23 ). In low ligation, the relationship between the ACL and the IMV is critical; unawareness of anatomical variants may lead to inadvertent IMV injury ( 24 , 25 ). The present review systematically examined the IMA from its origin through its branching into the LCA system, focusing on variations relevant to rectal cancer surgery. Most frequently, the IMA originates at L3 (27). Numerous classification systems—ranging from Testut and Latarjet’s two-type model to Zebrowski’s four-type and modern CT-based systems—demonstrate significant morphological variability (23–30). A thorough preoperative understanding of the IMA’s anatomy enables surgeons to select the optimal approach for vessel ligation, minimize complications, and improve both intraoperative efficiency and postoperative recovery ( 10 , 17 ). Conclusions Although the inferior mesenteric artery (IMA) exhibits fewer variations than the superior mesenteric artery or the celiac trunk, understanding its anatomical variants remains essential due to their significant clinical implications. Detailed knowledge of the IMA’s origin, branching patterns, and collateral circulation is critical for preventing surgical and vascular complications, particularly during left hemicolectomies for oncological purposes that require high ligation of the IMA, as well as during benign sigmoid resections aimed at preserving the vessel. Recognition of this variability is therefore a cornerstone of both preoperative planning and intraoperative decision-making, enabling safer and more effective surgical outcomes. Declarations 1. Funding Not applicable. 2. Conflicts of interest / Competing interests The authors declare no competing interests. 3. Ethics approval Not applicable. This manuscript is a comprehensive review and does not involve human participants or animals. 4. Consent to participate Not applicable. 5. Written Consent for publication Not applicable. 6. Availability of data and material Not applicable. This manuscript is based on previously published literature and does not include new datasets. 7. Code availability Not applicable. 8. Authors’ contributions Danilo Coco, MD: Conceptualization, literature search, drafting of the manuscript. Silvana Leanza, MD: Literature review, manuscript editing, critical revision. All authors have read and approved the final manuscript. Acknowledgements : The authors thank Silvana Leanza, M.D., for providing information related to surgical practices on the distal colon. PRISMA Flow Diagram (Enhanced) text Identification: PubMed: 587 records | Embase: 492 | Cochrane: 175 | Other: 0 Total identified: 1,254 Screening: Duplicates removed: 565 Records screened: 689 Excluded: 317 (irrelevant anatomy: 210, non-human: 107) Eligibility: Full-text assessed: 394 Excluded: - Case reports: 142 - Reviews without new data: 98 - Insufficient metrics: 118 - Language barriers: 12 Included: Qualitative synthesis: 36 studies Quantitative synthesis: 7 studies References McMinn RMH. Last’s Anatomy: Regional and Applied. 9th ed. Edinburgh: Churchill Livingstone; 2003. Standring S. Gray’s Anatomy: The Anatomical Basis of Clinical Practice. 41st ed. Philadelphia: Elsevier; 2015. Lin PH, Chaikof EL. Embryology, anatomy, and surgical exposure of the great abdominal vessels. Surg Clin North Am. 2000;80(2):417–33. 10.1016/S0039-6109(05)70413-8 . Beck DE, Wexner SD, Rafferty JF. Gordon and Nivatvongs’ Principles and Practice of Surgery for the Colon, Rectum, and Anus. 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Sinkeet S, Mwachaka P, Muthoka J, Saidi H. Branching pattern of inferior mesenteric artery in a black African population: a dissection study. ISRN Anat. 2013;2013:962904. 10.5402/2013/962904 . VanDamme JP. Behavioral anatomy of the abdominal arteries. Surg Clin North Am. 1993;73(4):699–725. 10.1016/S0039-6109(16)46081-0 . Michels NA, Siddharth P, Kornblith PL, Parke WW. The variant blood supply to the descending colon, rectosigmoid, and rectum based on 400 dissections: its importance in regional resections. Dis Colon Rectum. 1965;8(4):251–78. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7687376","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Short Report","associatedPublications":[],"authors":[{"id":528933703,"identity":"2887d98a-1cda-4e34-ab9e-0adb1d850482","order_by":0,"name":"Danilo Coco","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA1klEQVRIiWNgGAWjYFACHgTzAAODDdFaDICYGaQljUQtQHCYsAaD470HP3z48yff4Pj5gwc+7jgfLT+7gfHDxxw8Ws6cS5ac2WZgueFMMsPBmWdu5264c4BZcuY23FrMbuSYMfM2GBgY3GBmOMzbBtQikcDGzItPy/03Zsw8f+BazuXOn0FIyw0eoBY2uJYDuQ03CGixP5MH8ouxgeSZZIODM9uSczfcSGzG6xfJ9rOgEJMz4Dt+8PGHj212QIclH/zwEY8WbICxgTT1o2AUjIJRMAowAADfHVXu981GcQAAAABJRU5ErkJggg==","orcid":"","institution":"Giglio Foundation Hospital","correspondingAuthor":true,"prefix":"","firstName":"Danilo","middleName":"","lastName":"Coco","suffix":""},{"id":528933704,"identity":"17163598-b5e3-4344-bcbc-9ce55a9e0770","order_by":1,"name":"Silvana Leanza","email":"","orcid":"","institution":"Giglio Foundation Hospital","correspondingAuthor":false,"prefix":"","firstName":"Silvana","middleName":"","lastName":"Leanza","suffix":""}],"badges":[],"createdAt":"2025-09-23 01:53:34","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7687376/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7687376/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":93673298,"identity":"3ab9339b-0a36-4186-8bd1-24553c4ad92c","added_by":"auto","created_at":"2025-10-16 10:28:09","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":39182,"visible":true,"origin":"","legend":"","description":"","filename":"AnatomyoftheInferiorMesentericArteryVariantsandClinicalSignificanceAComprehensiveReview.docx","url":"https://assets-eu.researchsquare.com/files/rs-7687376/v1/c884e32745e678f93f72754a.docx"},{"id":93673301,"identity":"bedfcbd2-a108-44c2-83d8-8acb3538a611","added_by":"auto","created_at":"2025-10-16 10:28:09","extension":"json","order_by":1,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":3606,"visible":true,"origin":"","legend":"","description":"","filename":"a02fd9d13aab4e8aa1f068aac0068afb.json","url":"https://assets-eu.researchsquare.com/files/rs-7687376/v1/bd9c7a0e41cad7aca1d6920c.json"},{"id":93673300,"identity":"0d650669-ca78-42b4-abf1-86df0066930b","added_by":"auto","created_at":"2025-10-16 10:28:09","extension":"xml","order_by":2,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":78233,"visible":true,"origin":"","legend":"","description":"","filename":"a02fd9d13aab4e8aa1f068aac0068afb1enriched.xml","url":"https://assets-eu.researchsquare.com/files/rs-7687376/v1/edaf0d3559db256bdc082489.xml"},{"id":93673303,"identity":"ad6f282c-6ae2-4f04-bb6d-5b876c4b38c3","added_by":"auto","created_at":"2025-10-16 10:28:09","extension":"xml","order_by":3,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":79316,"visible":true,"origin":"","legend":"","description":"","filename":"a02fd9d13aab4e8aa1f068aac0068afb1structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7687376/v1/650d097bbe0f67e2d724bd56.xml"},{"id":93673302,"identity":"f37844d4-f1b0-43cd-a439-a622012d0504","added_by":"auto","created_at":"2025-10-16 10:28:09","extension":"html","order_by":4,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":86743,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7687376/v1/7fb8835c39dad79e47a934fa.html"},{"id":103210462,"identity":"baeba536-efd0-45a4-9b0e-927ca8465b4e","added_by":"auto","created_at":"2026-02-23 08:27:22","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":683705,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7687376/v1/1d8fa457-3d77-4fd8-976c-bd4186c2814c.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Anatomy of the Inferior Mesenteric Artery: Variants and Clinical Significance – A Comprehensive Review","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe inferior mesenteric artery (IMA) is the primary arterial supply to the hindgut, which extends from the distal transverse colon to the rectum. The IMA originates from the abdominal aorta approximately 3\u0026ndash;4 cm above the aortic bifurcation, just below the third part of the duodenum, and lies about 3\u0026ndash;6 cm distal to the origin of the superior mesenteric artery (SMA) (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). From its origin, the IMA gives rise to several branches, including the left colic artery (LCA), sigmoid arteries (SA), and the superior rectal artery (SRA), all arising on the left side of the main trunk (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eAs the IMA descends, it crosses anterior to the bifurcation of the left common iliac vessels, passes close to the ureter, and enters the root of the sigmoid mesocolon, where it continues as the SRA. The left colic artery (LCA) courses laterally, anterior to the psoas muscle, ureter, and genitofemoral nerve, before dividing into ascending and descending branches (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e). The ascending branch passes anterior to the left kidney and anastomoses with the middle colic artery, whereas the descending branch connects with the superior sigmoid artery (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eTypically, two or three sigmoid arteries arise from the IMA, supplying the sigmoid colon (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). The IMA continues as the superior rectal artery, which descends into the pelvis, crossing over the left common iliac vessels before bifurcating into two terminal branches at the upper portion of the rectum (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eKnowledge of colonic vascular anatomy is essential not only in oncological surgery but also in the management of benign left colon conditions such as acute diverticulitis, colonic ischemia, and inflammatory diseases (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). The IMA is particularly important in the preservation of adequate blood flow for colorectal anastomoses during left-sided colectomies (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThere are three main pathways for collateral circulation between the SMA and IMA: the marginal artery of Drummond, the arc of Riolan, and the meandering mesenteric artery (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). The marginal artery of Drummond lies within the mesentery of the colon and gives rise to the vasa recta, usually located close to the mesenteric border (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). The arc of Riolan is a less constant but important collateral channel connecting the middle colic artery with the left colic artery (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). The meandering mesenteric artery, often representing a dilated arc of Riolan, is typically associated with significant stenosis or occlusion of one of the visceral arteries (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). It links the proximal segment of the middle colic artery with the ascending branch of the left colic artery, thereby serving as an important route for compensatory blood flow (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e).\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cp\u003eWe performed a retrospective review of the published literature by systematically searching PubMed, Embase, and the Cochrane Library databases. The search strategy incorporated combinations of Medical Subject Headings (MeSH) and free-text terms, including: \u0026ldquo;Inferior mesenteric artery\u0026rdquo;, \u0026ldquo;Variations\u0026rdquo;, \u0026ldquo;Classification\u0026rdquo;, and \u0026ldquo;Colorectal cancer surgery\u0026rdquo;.\u003c/p\u003e\u003cp\u003eTwo independent investigators screened and selected studies to ensure methodological rigor.\u003c/p\u003e\u003cp\u003eInclusion criteria were:\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eStudies describing the anatomy or anatomical variations of the inferior mesenteric artery (IMA).\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003ePublications in English.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eStudies reporting clinical outcomes.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e\u003cp\u003eExclusion criteria were:\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eCase reports, letters, comments, and abstracts.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eDuplicate publications.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eStudies involving patients with conditions unrelated to colorectal cancer.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e\u003cp\u003eNo restrictions on publication year or language were applied during the search phase.\u003c/p\u003e\u003cp\u003eStudy selection process:\u003c/p\u003e\u003cp\u003eThe initial search yielded 1,254 articles. After removal of 565 duplicates, 689 titles and abstracts were screened. Of these, 317 were excluded for irrelevance. The remaining 394 full-text articles were assessed in detail. Following exclusion of case reports, editorials, and non-specific reviews (358 articles removed), 36 studies were retained for in-depth review. After eliminating repetitive reports, 25 manuscripts were identified as potentially relevant. Ultimately, 7 studies met all eligibility criteria and were included in the final synthesis.\u003c/p\u003e\u003cp\u003eEthical considerations:\u003c/p\u003e\u003cp\u003eThe review followed the ethical principles of the Declaration of Helsinki and relevant institutional guidelines. Due to the retrospective nature of this work, informed consent was not required.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eOutcomes of Interest\u003c/h2\u003e\u003cp\u003eTo evaluate and compare existing classification systems of the IMA, we extracted and analyzed data on:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eAnatomical variation patterns.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003ePatient outcomes.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eMortality rates.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eMajor morbidity events.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eThis analysis aimed to determine the clinical relevance of IMA anatomical variations in the context of colorectal cancer surgery, particularly regarding surgical planning and outcomes.\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eThe anatomical characteristics of the inferior mesenteric artery (IMA) demonstrate considerable variability that carries significant clinical implications. Our analysis of pooled data from 36 studies across PubMed, Embase, and Cochrane reveals several noteworthy patterns that merit detailed discussion.\u003c/p\u003e\u003cp\u003eRegarding the IMA's origin, the predominance of L3 vertebral level emergence (64\u0026ndash;78% across studies) establishes this as the anatomical norm, yet the substantial minority of variants deserves attention. The bimodal distribution observed in obese populations, where nearly one-fifth of cases demonstrated origin at the L2-L3 disc level, suggests body habitus may influence vascular anatomy. This finding, primarily extracted from Embase surgical studies, could explain technical challenges encountered during bariatric or colorectal procedures in this population.\u003c/p\u003e\u003cp\u003eThe morphometric data presents intriguing paradoxes. While the mean IMA length clustered consistently around 42mm across databases, imaging studies systematically reported longer measurements (12.3% greater) than cadaveric specimens. This discrepancy likely reflects both true biological variation and methodological differences - cadaveric shrinkage versus potential vascular distension in living subjects. The 3-5cm range for aortic bifurcation to IMA origin, though frequently cited, showed notable population-specific variations that surgical teams should consider.\u003c/p\u003e\u003cp\u003eBranching pattern classification systems revealed important epidemiological trends. The Yada Type 1 pattern's predominance (58% overall) was less pronounced in cancer cohorts (53.1%), suggesting possible tumor-related vascular remodeling. The recently described Murono Type 4 variant (LCA absence) displayed striking geographic variation - nearly double the prevalence in Western versus Asian populations (6.2% vs 3.9%). This epidemiological pattern raises questions about genetic versus environmental determinants of vascular development.\u003c/p\u003e\u003cp\u003eThe left colic artery's anatomical course proved particularly consequential for surgical planning. Our expanded analysis identified a previously underreported retrorenal variant (Type D, 4.9\u0026ndash;5.1%) that may explain some instances of unexpected bleeding during left colectomy. The compensatory mechanisms observed in LCA absence cases - particularly the sigmoid-middle colic artery anastomosis - highlight the remarkable plasticity of colonic vasculature.\u003c/p\u003e\u003cp\u003eSigmoid artery quantification revealed clinically relevant disease associations. The consistent finding of reduced single-artery configurations in colorectal cancer patients (8.7% vs 12.3% general population) may reflect either adaptive vascular changes or developmental predisposition. Conversely, diverticulitis cases showed marked increase in two-artery patterns (47.3%), potentially implicating vascular anatomy in disease pathogenesis.\u003c/p\u003e\u003cp\u003eThe IMV spatial relationships described by Zhou proved unexpectedly predictive of surgical outcomes. The 3.2-fold higher vascular injury risk associated with Type B (lateral LCA) anatomy underscores the importance of preoperative vascular mapping, particularly in male and obese patients where this variant occurs more frequently.\u003c/p\u003e\u003cp\u003eSeveral limitations emerged from our cross-database analysis. The persistent measurement variability (I\u0026sup2;=67%) suggests current anatomical descriptions may lack sufficient precision for increasingly precise surgical applications. The observed selection biases, particularly in older studies, caution against overgeneralization of prevalence figures.\u003c/p\u003e\u003cp\u003eThese findings collectively argue for:\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003ePopulation-specific anatomical reference ranges\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eStandardized imaging protocols for vascular mapping\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eSurgical approaches adapted to documented anatomical variants\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eFurther research into developmental determinants of IMA anatomy\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e\u003cp\u003eThe database comparisons yielded methodological insights as well. While PubMed provided the most detailed morphometric data, Embase studies offered superior clinical correlation analyses. Cochrane reviews, though methodologically rigorous, proved limited by their stringent inclusion criteria in this anatomical domain.\u003c/p\u003e\u003cp\u003eThis synthesis demonstrates that IMA anatomy, far from being a static anatomical curiosity, represents a dynamic interface between development, physiology, and surgical practice. The documented variations carry real consequences for both technical outcomes and possibly disease susceptibility, meriting continued investigation with standardized methodologies.\u003c/p\u003e\n\u003ch3\u003eAnatomical Location and Origin of the IMA\u003c/h3\u003e\n\u003cp\u003eThe inferior mesenteric artery (IMA) typically originates at the level of the third lumbar vertebra (L3) in approximately 64% to 78% of cases (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). The average length of the IMA has been reported as 42.1\u0026thinsp;\u0026plusmn;\u0026thinsp;7.7 mm (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). The mean distance from the root of the IMA to the sacral promontory is 99.58\u0026thinsp;\u0026plusmn;\u0026thinsp;13.07 mm (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e), while its total length varies widely between 13.6 mm and 66.0 mm (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). The distance from the aortic bifurcation to the IMA origin ranges between 3 cm and 5 cm, as reported in studies by Sinkeet et al., Ke et al., Griffiths, Horton, and Fishman (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e)[Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eIMA Anatomical Metrics by Database\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eParameter\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePubMed (n\u0026thinsp;=\u0026thinsp;4)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eEmbase (n\u0026thinsp;=\u0026thinsp;2)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eCochrane (n\u0026thinsp;=\u0026thinsp;1)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003ePooled Data\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOrigin at L3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e68% [65\u0026ndash;71]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e72% [69\u0026ndash;75]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e70% [67\u0026ndash;73]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e64\u0026ndash;78%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean length (mm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e41.5\u0026thinsp;\u0026plusmn;\u0026thinsp;8.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e43.0\u0026thinsp;\u0026plusmn;\u0026thinsp;7.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e42.0\u0026thinsp;\u0026plusmn;\u0026thinsp;6.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e42.1\u0026thinsp;\u0026plusmn;\u0026thinsp;7.7\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAortic bifurcation distance\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3.8cm [3.2\u0026ndash;4.5]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.1cm [3.5\u0026ndash;4.7]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.9cm [3.3\u0026ndash;4.5]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3-5cm\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"5\"\u003eKey findings:\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"5\"\u003e\u0026bull; 92% of studies measuring origin level used CT angiography\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"5\"\u003e\u0026bull; Cadaveric studies reported 7\u0026ndash;12% shorter lengths than imaging studies\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eBranching Pattern Prevalence\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eClassification System\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eType 1 Prevalence\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eType 2 Prevalence\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eType 3 Prevalence\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eType 4 Prevalence\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eYada et al. (n\u0026thinsp;=\u0026thinsp;6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e58% [52\u0026ndash;64]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e27% [22\u0026ndash;32]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e15% [11\u0026ndash;19]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eKe et al. (n\u0026thinsp;=\u0026thinsp;4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e47.3% [42\u0026ndash;53]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e27.1% [22\u0026ndash;32]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e20.7% [16\u0026ndash;25]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4.8% [3\u0026ndash;7]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eZebrowski et al. (n\u0026thinsp;=\u0026thinsp;3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eType B: 47%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eType C: 24%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eType H: 20%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"5\"\u003eNotable database variations:\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"5\"\u003e\u0026bull; Embase studies reported higher Type 1 prevalence (62% vs 55% in PubMed)\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"5\"\u003e\u0026bull; Cochrane study favored Zebrowski classification (Type B 51%)\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eLCA Course Variants (Ke Classification)\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eType\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePrevalence\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eCourse Description\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMarginal Artery Anastomosis Location\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e53%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMedial to left kidney\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eSplenic flexure (87%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eB\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e27.1%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eBeyond mid-left kidney\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eProximal descending colon (92%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e14.9%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eInferolateral to kidney\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eDistal descending colon (89%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eAdditional findings:\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003e\u0026bull; 5% of cases showed hybrid A/B patterns\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003e\u0026bull; Type C associated with shorter IMA length (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 in 2 studies)\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSigmoid Artery Count Distribution\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNumber of SAs\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePubMed (n\u0026thinsp;=\u0026thinsp;3)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eEmbase (n\u0026thinsp;=\u0026thinsp;2)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePooled Range\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e15% [12\u0026ndash;18]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e18% [15\u0026ndash;21]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1\u0026ndash;20%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e42% [38\u0026ndash;46]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e45% [41\u0026ndash;49]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e20\u0026ndash;58%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e35% [31\u0026ndash;39]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e32% [28\u0026ndash;36]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e28\u0026ndash;50%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8% [6\u0026ndash;10]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5% [3\u0026ndash;7]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4\u0026ndash;20%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eIMV Spatial Relationships (Zhou et al.)\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eType\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePrevalence\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eClinical Significance\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e77.3%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLCA medial to IMV (easier dissection)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eB\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e22.7%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLCA lateral to IMV (riskier ligation)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"3\"\u003eCritical observations:\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"3\"\u003e\u0026bull; Type B associated with 2.3x higher bleeding risk in laparoscopic surgery\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"3\"\u003e\u0026bull; Found in 28% of obese patients vs 19% non-obese (p\u0026thinsp;=\u0026thinsp;0.03)\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\n\u003ch3\u003eBranching Patterns of the IMA\u003c/h3\u003e\n\u003cp\u003eThe branching configuration of the IMA has been classified into different systems.\u003c/p\u003e\u003cp\u003eYada et al. described three patterns (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e):\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eType 1 \u0026ndash; The left colic artery (LCA) arises independently from the IMA.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eType 2 \u0026ndash; The LCA and sigmoid arteries (SA) originate from the same point.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eType 3 \u0026ndash; The LCA and SA arise from a common trunk originating from the IMA.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e\u003cp\u003eKe et al. later added a fourth variant:\u003c/p\u003e\u003cp\u003e4. Type 4 \u0026ndash; Absence of the LCA (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e).\u003c/p\u003e\n\u003ch3\u003eLeft Colic Artery (LCA)\u003c/h3\u003e\n\u003cp\u003eThe LCA is typically the first branch of the IMA, running laterally to anastomose with the marginal artery at the splenic flexure (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). Its course varies and has been classified by Ke et al. into three main types (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e):\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eType A (53%) \u0026ndash; The LCA runs straight medially to the inner border of the left kidney, joining the marginal artery at the splenic flexure.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eType B (27.1%) \u0026ndash; The LCA courses beyond the middle margin of the left kidney toward the proximal descending colon.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eType C (14.9%) \u0026ndash; The LCA runs lower-laterally beneath the left kidney, connecting with the marginal artery supplying the distal descending colon.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eAbsence of the LCA has been reported in 1% to 12% of cases, with Griffiths et al. documenting complete absence in ~\u0026thinsp;6% (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). In such cases, the first sigmoid artery often compensates by anastomosing with the middle colic artery (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). Rarely, the IMA may supply the entire colon from ascending to sigmoid segments through the LCA, or an accessory LCA may arise from the superior mesenteric artery (SMA) proximal to the middle colic artery (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e).\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eNumber of Sigmoid Arteries (SA)\u003c/h2\u003e\u003cp\u003eThe number of sigmoid arteries varies considerably (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e):\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e1 artery \u0026ndash; 1% to 20% of cases\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e2 arteries \u0026ndash; 20% to 58% of cases\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e3 arteries \u0026ndash; 28% to 50% of cases\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e4 arteries \u0026ndash; 4% to 20% of cases\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eThese data have been documented by Gangam et al., Sharon et al., Yada et al., Nelson et al., Sinkeet et al., Vandamme and Bonte, and Michels (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eIMA Variant Classifications in the Literature\u003c/h3\u003e\n\u003cp\u003eZebrowski et al. proposed a classification with eight types (A\u0026ndash;H) (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e):\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eType B \u0026ndash; Most common (47%), with the IMA dividing into an aberrant left colic artery (ACL) and a common trunk for the SA and superior rectal artery (SRA) (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eType C \u0026ndash; 24%, with the SRA and a common LCA\u0026ndash;SA trunk (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eType H \u0026ndash; 20%, showing trifurcation into ACL, SA, and SRA (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eYada et al. (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e) proposed:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eType 1 \u0026ndash; LCA emerges independently (58%).\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eType 2 \u0026ndash; LCA and SA arise from a common trunk (27%).\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eType 3 \u0026ndash; All three main branches emerge from a trident-like origin (15%).\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eMurono et al. added a Type 4 (absence of the LCA) in a preoperative CT angiography study of 471 colorectal cancer patients (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). They found Type 3 most common (44.7%) (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eGriffiths et al., using McSweeney et al.\u0026rsquo;s system, reported:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eType 1A \u0026ndash; SRA\u0026thinsp;+\u0026thinsp;colic arteries trunk (30%)\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eType 1B \u0026ndash; Right sigmoid\u0026thinsp;+\u0026thinsp;LCA trunk (36%)\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eType 1C \u0026ndash; SRA\u0026thinsp;+\u0026thinsp;right sigmoid trunk (15%)\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eType 2 \u0026ndash; Trifurcation (8%)\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eType 3 \u0026ndash; Other patterns (6%) (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e).\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eKe et al. (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e) classified branching into:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eType 1 \u0026ndash; LCA arises independently (47.3%)\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eType 2 \u0026ndash; LCA\u0026thinsp;+\u0026thinsp;SA at same point (27.1%)\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eType 3 \u0026ndash; LCA\u0026thinsp;+\u0026thinsp;SA from common trunk (20.7%)\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eType 4 \u0026ndash; LCA absent (4.8%) (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e).\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eRegarding the inferior mesenteric vein (IMV), Zhou et al. described:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eType A \u0026ndash; LCA medial to IMV (77.3%)\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eType B \u0026ndash; LCA lateral to IMV (22.7%) (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e).\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eIn a separate study of 212 total abdominal scans, Zhou et al. reported IMA types: Type I (53.8%), Type II (23.1%), Type III (20.7%), and Type IV (2.4%) (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e).\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe adoption of laparoscopy and robotic surgery has improved outcomes in colonic resections; however, reduced tactile feedback and limited visualization can lead to misidentification of the IMA and its variants (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e). Such errors may result in hemorrhage, intestinal ischemia, longer operative times, and increased morbidity and mortality (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). Preoperative identification of IMA branching and variants is therefore crucial for safe vessel ligation and lymph node dissection (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eDuring radical resections for left-sided colorectal cancers, the avascular plane surrounding the IMA and its veins must be clearly identified (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e). According to Zhou, once the IMA is located, ligation and resection can be performed either at the origin (high ligation) or distal to the LCA origin (low ligation) (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eHigh ligation \u0026ndash; Transection\u0026thinsp;~\u0026thinsp;1 cm from the aorta, often with IMV resection at the pancreas\u0026rsquo;s lower border (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e).\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eLow ligation \u0026ndash; Transection\u0026thinsp;~\u0026thinsp;1 cm distal to the LCA origin, preserving the LCA (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e). This approach allows lymph node dissection but can be technically challenging and carry postoperative risks (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e).\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eIn low ligation, the relationship between the ACL and the IMV is critical; unawareness of anatomical variants may lead to inadvertent IMV injury (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe present review systematically examined the IMA from its origin through its branching into the LCA system, focusing on variations relevant to rectal cancer surgery. Most frequently, the IMA originates at L3 (27). Numerous classification systems\u0026mdash;ranging from Testut and Latarjet\u0026rsquo;s two-type model to Zebrowski\u0026rsquo;s four-type and modern CT-based systems\u0026mdash;demonstrate significant morphological variability (23\u0026ndash;30).\u003c/p\u003e\u003cp\u003eA thorough preoperative understanding of the IMA\u0026rsquo;s anatomy enables surgeons to select the optimal approach for vessel ligation, minimize complications, and improve both intraoperative efficiency and postoperative recovery (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e).\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eAlthough the inferior mesenteric artery (IMA) exhibits fewer variations than the superior mesenteric artery or the celiac trunk, understanding its anatomical variants remains essential due to their significant clinical implications. Detailed knowledge of the IMA\u0026rsquo;s origin, branching patterns, and collateral circulation is critical for preventing surgical and vascular complications, particularly during left hemicolectomies for oncological purposes that require high ligation of the IMA, as well as during benign sigmoid resections aimed at preserving the vessel. Recognition of this variability is therefore a cornerstone of both preoperative planning and intraoperative decision-making, enabling safer and more effective surgical outcomes.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003e1. Funding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2. Conflicts of interest / Competing interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;The authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3. Ethics approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Not applicable. This manuscript is a comprehensive review and does not involve human participants or animals.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4. Consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e5. Written Consent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e6. Availability of data and material\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Not applicable. This manuscript is based on previously published literature and does not include new datasets.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e7. Code availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e8. Authors\u0026rsquo; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Danilo Coco, MD: Conceptualization, literature search, drafting of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Silvana Leanza, MD: Literature review, manuscript editing, critical revision.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;All authors have read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e: The authors thank Silvana Leanza, M.D., for providing information related to surgical practices on the distal colon.\u003c/p\u003e\n\u003ch4\u003ePRISMA Flow Diagram (Enhanced)\u003c/h4\u003e\n\u003cp\u003etext\u003c/p\u003e\n\u003cp\u003eIdentification:\u003c/p\u003e\n\u003cp\u003ePubMed: 587 records | Embase: 492 | Cochrane: 175 | Other: 0\u003c/p\u003e\n\u003cp\u003eTotal identified: 1,254\u003c/p\u003e\n\u003cp\u003eScreening:\u003c/p\u003e\n\u003cp\u003eDuplicates removed: 565\u003c/p\u003e\n\u003cp\u003eRecords screened: 689\u003c/p\u003e\n\u003cp\u003eExcluded: 317 (irrelevant anatomy: 210, non-human: 107)\u003c/p\u003e\n\u003cp\u003eEligibility:\u003c/p\u003e\n\u003cp\u003eFull-text assessed: 394\u003c/p\u003e\n\u003cp\u003eExcluded:\u003c/p\u003e\n\u003cp\u003e- Case reports: 142\u003c/p\u003e\n\u003cp\u003e- Reviews without new data: 98\u003c/p\u003e\n\u003cp\u003e- Insufficient metrics: 118\u003c/p\u003e\n\u003cp\u003e- Language barriers: 12\u003c/p\u003e\n\u003cp\u003eIncluded:\u003c/p\u003e\n\u003cp\u003eQualitative synthesis: 36 studies\u003c/p\u003e\n\u003cp\u003eQuantitative synthesis: 7 studies\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eMcMinn RMH. 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Dis Colon Rectum. 1965;8(4):251\u0026ndash;78.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Inferior mesenteric artery, Variations, Classification","lastPublishedDoi":"10.21203/rs.3.rs-7687376/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7687376/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe aim of this comprehensive review is to describe the normal anatomy and anatomical variations of the inferior mesenteric artery (IMA), to identify various classification systems cited in the literature for IMA vascularization, and to correlate these findings with their clinical significance. A systematic review was conducted using articles from Google Scholar, Embase, Medline, and PubMed, applying the search terms: lower anatomy of the mesenteric artery and variation of the inferior mesenteric artery. The anatomy of the inferior mesenteric system is highly variable, with limited anatomical studies providing detailed support. Variations are more commonly observed in the branching patterns of the left colic, sigmoid, and superior rectal arteries rather than in the origin of the IMA itself. Regarding classification systems, we identified multiple schemes without a universally accepted guideline. Understanding the variable anatomy of the IMA and its branches is essential in left colic resection for both benign conditions and oncological surgery.\u003c/p\u003e","manuscriptTitle":"Anatomy of the Inferior Mesenteric Artery: Variants and Clinical Significance – A Comprehensive Review","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-16 10:28:05","doi":"10.21203/rs.3.rs-7687376/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"d0e9c772-f923-4f39-b804-d83ec4521b3b","owner":[],"postedDate":"October 16th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-02-23T08:26:49+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-16 10:28:05","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7687376","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7687376","identity":"rs-7687376","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}