Estimation of Blood Component Sequestration during Resection of Strangulated Small Intestine in Horses and a Derived Classification Proposal for Small Intestinal Lesions

Estimation of Blood Component Sequestration during Resection of Strangulated Small Intestine in Horses and a Derived Classification Proposal for Small Intestinal Lesions | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 12 November 2025 V1 Latest version Share on Estimation of Blood Component Sequestration during Resection of Strangulated Small Intestine in Horses and a Derived Classification Proposal for Small Intestinal Lesions Authors : Marco Gandini 0000-0002-1402-8261 [email protected] and Gessica Giusto 0000-0002-0714-6382 Authors Info & Affiliations https://doi.org/10.22541/au.176296166.68175179/v1 194 views 98 downloads Contents Abstract Supplementary Material Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Background: The mechanisms of ischemia and reperfusion in intestinal strangulation have been extensively studied in horses; however, most intestinal strangulation cases in horses are characterized by venous strangulating obstruction. As demonstrated in other species,blood sequestration results from venous strangulation, and results in blood loss when the intestine is resected, with potential consequences for the metabolic and physiological state of the animal. Objectives: Aim of this study is to evaluate the extent of blood sequestration in horses with clinical strangulated small intestinal obstruction and propose a new classification for small intestinal pathologies. Study Design: case-control study Methods: The study included horses submitted to euthanasia and with strangulating small intestinal obstruction diagnosed at necropsy. Blood sequestration was measured by evaluating the weight of affected bowel segments and calculating the volume of blood sequestrated per meter of strangulated intestine. Difference in weight between strangulated and normal segments was compared. Results: The weight of the strangulated small intestine was significantly different from the weight of normal intestine. (p<0.0001) On average, approximately one liter of blood was sequestered per meter of strangulated intestine. Main Limitations: The study did not account for all compartments where blood sequestration occurs, including the intraluminal and intraperitoneal spaces, thus the blood loss may be underestimated. The study was limited to grade 3-4 lesions. Conclusions: The findings confirm that significant blood sequestration occurs in strangulated intestinal segments, which can lead to substantial blood loss when resection is performed. These findings emphasize the need for careful assessment of intestinal viability during surgery to prevent unnecessary resection and improve prognosis classification in light of these results is provided. Clinical relevance: significant blood sequestration occurs in strangulated intestinal segments, which can lead to substantial blood loss when resection is performed. careful assessment of intestinal viability during surgery to prevent unnecessary resection and improve prognosis is paramount. Introduction Small intestinal strangulating lesions are a leading cause of colic in horses and one of the most critical emergencies in equine veterinary medicine. These conditions—including volvulus, strangulating lipomas, and both internal and external hernias result in mechanical obstruction of the intestinal lumen and vascular perfusion impairment.(Aird,1936; Aird, 1937; Aird, 1941, Cook et al, 2019) Most strangulating lesions involve the entrapment of a bowel segment, creating two points of constriction. This results in the formation of distinct pre-stenotic, stenotic, and post-stenotic regions. A defining pathophysiological feature of strangulation is that, within the stenotic segment, arterial flow persists for some time while venous drainage is either severely restricted or completely obstructed. This imbalance allows continuous arterial inflow but prevents venous return, leading to progressive blood accumulation within the affected tissue. (Cook et al, 2019) Consequently, submucosal edema develops, causing the mucosal layer to protrude from the underlying structures. Within hours, venous stasis and edema result in local hypoxia or anoxia in the bowel wall. This process is further exacerbated by the leakage of a transudate rich in proteins and electrolytes into both the intestinal lumen and the abdominal cavity. (Aird, 1941;Vallicelli eta la, 2011) 5 Initially, the vascular walls permit only the passage of fluid components from the bloodstream, but over time, they become increasingly permeable to cellular elements as well (Aird,1936; Aird, 1937) As the condition progresses, the affected bowel segment undergoes hemorrhagic infarction, characterized by diapedetic hemorrhage. At this stage, the bowel loop appears bluish-red externally, with pronounced edema and dilated blood vessels, while the mucosal layer takes on a medium to dark red hue. Despite these changes, arterial pulsation remains detectable. Over time, the infarction worsens, and increasing fluid sequestration within the bowel lumen and abdominal cavity exacerbates tissue swelling. This progressive distension further compromises arterial blood flow, accelerating ischemia and advancing intestinal necrosis. As structural integrity deteriorates, the bowel wall becomes increasingly permeable to toxins and bacteria, allowing their translocation into the peritoneal cavity. Bacterial activity within the stenotic segment leads to gas and toxin production, further aggravating the condition. The mucosal surface darkens to a reddish-black colour before developing a friable, grey layer due to villous denudation. Meanwhile, fibrinous exudates form on the serosal surface, and haemorrhagic gangrene sets in as bacteria invade deeper into the intestinal wall (aird, 1936, Aird, 1937, Aird, 1941; Sullins et al, 1985) Previous experimental work in other species, such as cats and dogs, has demonstrated that venous blood sequestration can account for up to 50% of the total circulating blood volume, contributing to significant hypovolemia (Aird, 1936; Aird, 1937; Hausler and Foster, 1924) However, the quantification of blood sequestration in horses despite their high susceptibility to strangulating intestinal lesions—has not been previously explored, except in the study by Ruggles et al (1993) which was conducted in an experimental isolated loop setting. The hypothesis is that blood sequestration in the bowel wall during clinically occurring strangulating obstructions of the jejunum in horses accounts for a significant percentage of total blood volume. First aim of this study is to quantify blood loss due to venous strangulating obstruction in the small intestine of horses. Second aim is to propose a classification for selected gastrointestinal diseases in horses, potentially leading to more accurate therapeutic approaches. MATERIALS AND METHODS This study included horses admitted for colic at XXX, which did not undergo surgery solely due to financial constraints. Upon admission, horses were evaluated clinically, and surgical intervention was proposed to the owner based on clinical findings. If permission for surgical treatment was denied, consent for euthanasia, necropsy, and tissue collection was obtained from the owner. Following sedation with detomidine (0.02 mg/kg IV), anesthesia was induced using ketamine (2.2 mg/kg IV) and diazepam (0.2 mg/kg IV). Once the horses reached lateral recumbency, euthanasia was achieved by administering pancuronium bromide intravenously. Death was confirmed by the absence of heartbeat on auscultation, absence of respiration, and lack of corneal reflex. After death, the horses were placed in dorsal recumbency, and a ventral midline laparotomy was performed. The abdomen was explored, and diseases were identified and resolved. The following parameters were recorded: • Disease causing strangulation of the small intestine • Location of the bowel obstruction, defined as oral, mid-, aboral jejunum, or jejuno-ileal, ileal • Viability index of the strangulated intestine, according to Freeman (2014) • Measured length (m) of the stenotic segment of the intestine. This was obtained after resolving the entrapment, measured from the antimesenteric side between the two points of narrowing using a measuring tape. • Effective length (m) of the stenotic segment, obtained by reducing the measured length by 20% 9 • Total weight (kg) of the stenotic segment, determined by weighing the segment after gentle milking of its contents • Relative weight of the strangulated intestine, calculated by dividing the total weight by the effective length of the segment • Length of healthy intestine, measured from the antimesenteric side of the remaining healthy bowel (both oral and aboral to the strangulation) • Total weight (kg) of the remaining healthy bowel, measured after gentle milking of its contents • Relative weight of healthy intestine, calculated by dividing the total weight by the total length of healthy intestine For this study, it was assumed that 1 liter of equine blood weighs approximately 1 kilogram. Total blood loss was quantified by measuring the difference in relative weight between the strangulated and healthy bowel segments for each horse, multiplied by the effective length of the strangulated intestine, and expressed in liters of blood. Relative blood loss was quantified by measuring the difference in relative weight between the strangulated and healthy bowel segments, expressed in liters of blood per meter of strangulated intestine. The presumed circulating blood volume was calculated as 8% of total body weight. Total hemorrhage was defined as the total amount of blood sequestered in the stenotic segment, expressed as a percentage of presumed circulating blood volume and in milliliters per kilogram of body weight. Relative hemorrhage was defined as the amount of blood sequestered per meter of stenotic segment, expressed as a percentage of presumed circulating blood volume per meter of intestine, and in milliliters per kilogram of body weight per meter of intestine. Median values and 95% confidence intervals (CIs) were obtained for each parameter. Data normality was assessed using the Shapiro-Wilk test. Statistical analysis was performed using a paired t-test to compare the weights of the normal and infarcted (strangulated) intestine, with a significance level set at p < 0.05. RESULTS Seven horses met the inclusion criteria: one male, two females, and four geldings, aged 6–23 years, with a median weight of 495 kg (range 426–530). Of these, three were Selle Français, two were Standardbreds, and two were Italian saddle horses. A description of the disease and results of measurements for each horse are grouped in Table 1. The median (95% CI) relative weight of the strangulated intestine (0.98 [0.83–1.3]) and the median relative weight of the healthy intestine (0.24 [0.19–0.29]) were significantly different (p < 0.0001). DISCUSSION While the mechanisms of intestinal ischemia and reperfusion have been extensively studied in horses, this is the first study to specifically focus on blood sequestration within the strangulated intestinal segment in clinical cases. As previously described, blood sequestration in venous strangulating obstruction of the small intestine (VSO) leads to an increase in the weight of the affected bowel, up to one liter per meter of intestine. (Fig.1) This finding aligns with Ruggles et al (1993) who observed an increase of approximately 1 kg per meter of intestine subjected to VSO in an experimental setting. This occurs due to the obstruction of venous drainage, with continued arterial perfusion. The volume of blood sequestration may vary, and this observation is consistent with findings from previous studies in small animals. (Aird, 1941; Gendel and Fine, 1939) The amount of blood sequestrated in the strangulated bowel is substantial, with approximately one liter of blood per meter of strangulated intestine on average and may help explain some of the metabolic changes encountered during small intestinal obstruction in horses. In some cases, this can result in blood loss equal to or even greater than that encountered in acute hemorrhage. In cases of resection involving 7 meters of intestine (which may correspond to approximately 50% of the small intestine length in a 500 kg horse), this represents a blood loss of about 16% (assuming circulating blood accounts for 8% of total body weight). If we assume that a similar blood sequestrum occurs in large colon volvulus in horses, we can likely estimate that the blood loss in these cases is even more extensive. Blood sequestration is not uniform in the strangulated obstructions included in our study, varying from less than half a liter to several liters. This variability may be due to different factors such as partial occlusion of vessels, the length of the entrapped intestine, and the duration of entrapment. For instance, if the intestine is entrapped but not yet strangulated, its arteries continue to inject blood intramurally and intraluminally, leading to an ongoing increase in the amount of fluid trapped.(Cook et al, 2019) On the other hand, if a loop of intestine is caught and strangulated at both its oral and aboral portions simultaneously, such as in the case of a short loop trapped by a lipoma, the duration of the process is shorter (withers and Mair, 2010) As a result, less blood is trapped within the strangulated segment, even if the same length of intestine is affected. The length of the affected intestinal segment also plays a role in the amount of blood it can accommodate before blood flow stops, as the intestine can increase both in thickness and length during distension (Freeman and Kilgallon, 2001). If the affected segment is long, it has a greater capacity to accommodate blood before flow is completely blocked. Conversely, if the affected segment is short, this elongation mechanism occurs to a lesser degree, resulting in a smaller quantity of blood. In this situation, the affected segment immediately thickens, and the arteries supplying it close off. Early closure of the arteries limits the accumulation of blood in the strangulated area. The duration of entrapment, combined with the specific vascular dynamics involved, determines the severity of tissue damage and the likelihood of successful recovery. Longer periods of strangulation result in more significant vascular damage, greater blood sequestration, and a higher risk of irreversible ischemia and necrosis. (Aird, 1936; Aird, 1937) Prompt diagnosis and intervention are key to limiting the duration of strangulation and preventing long-term damage to the bowel. In the rare case where strangulation or thrombosis blocks the arterial supply immediately and completely, ischemic necrosis develops rapidly. Grossly, the intestinal wall appears somewhat thinner than normal, with a parchment-like surface and pale grey color, later becoming green (dry gangrene). A zone of haemorrhagic infarction typically occurs at the junction between healthy and diseased tissue. (Aird,1936, Aird 1937) Clinical Considerations Vallicelli et al (2011), Cook et al (2019), Mair and Edwards (2003) report that segments of bowel that appear necrotic may, in fact, only be blood-infused, with hypoxia being reversible under the right conditions. Once the strangulation is corrected, these segments often return to normal function, dispelling the notion that they are necessarily necrotic. This has important implications for surgical decision-making, as it suggests that bowel resection may not always be necessary if the tissue can recover. Intestinal segments with a viability grade up to the 4th may not experience ischemia, meaning there is adequate blood supply and no irreversible damage to the tissue. These segments may not require resection and can often recover fully once the strangulation is relieved.(Cook et al, 2019; Freeman et al 2014) This emphasizes the importance of careful evaluation of bowel viability during surgery to avoid unnecessary resection and preserve bowel function. Understanding the differential effects on these portions of the intestine is crucial for surgical planning and determining which parts of the intestine can be saved. In cases where resection is not required, the blood loss during the entire procedure is reduced, as the blood contained in the intestinal wall and engorged mesenteric vessels is likely to be retrieved and made available to the body. This may allow for a more rapid return to normal physiological function, reducing the risk of complications and shortening recovery times. In horses with colic, particularly in cases of strangulating obstruction, significant hemodynamic changes and alterations in coagulation status occur. (Monreal and Cesarini, 2009) These changes are similar to those occurring in acute trauma coagulopathy observed in humans and small animals (Savioli et al, 2021) Acute trauma coagulopathy is characterized by a systemic inflammatory response, activation of the coagulation cascade, and microvascular dysfunction, all of which can lead to widespread clotting and haemorrhage. The body’s response to this stress activates the clotting system, often resulting in disseminated intravascular coagulation (DIC). This condition increases the risk of further bleeding and clot formation, complicating clinical management. This cascade of events contributes to ongoing hemodynamic instability and can worsen the animal’s condition if not managed appropriately. The similarity in hemodynamic and coagulopathy responses between horses with colic and humans or small animals with acute trauma haemorrhage suggests that horses could require treatments similar to those used in these cases. These include early recognition and intervention to stabilize the patient, managing the underlying cause, providing supportive care, and offering carefully managed, goal-directed fluids or blood component therapy. In cases of haemorrhage, excessive fluid administration can increase blood pressure and exacerbate metabolic and intestinal compromise. Arterial pressure plays a significant role in blood sequestration during strangulation. High arterial pressure can exacerbate the accumulation of blood in the bowel, while low arterial pressure may reduce sequestration but increase the risk of ischemia. Monitoring and managing arterial pressure during strangulating obstructions is essential for preventing complications and ensuring adequate perfusion of the bowel. However, excessive increases in arterial pressure with concurrent VSO may worsen intestinal edema and infarction. This, however, does not occur in ischemia when both veins and arteries are strangulated. An increase in arterial blood flow will not worsen the situation. In equine literature, the term “strangulating disease” is often used to classify a series of pathologies that may or may not cause VSO. These pathologies include internal and external hernias, volvulus, and intussusceptions. In all these conditions, there is potential for strangulation of vessels, which may occur completely, partially, or not at all. The term ”non-strangulating obstruction” is often used to describe what is better referred to as a ”simple obstruction”, 16 but this category may also include pathologies characterized by vessel occlusion, such as arterial thromboembolism. The term “strangulating” can therefore be misleading, as in cases where no VSO occurs. Defining whether a condition is strangulating or non-strangulating does not depend on the pathology itself but rather on the degree of vascular compromise. For example, all adhesions/fibrous bands cannot be classified into the same category because some cause strangulation with varying degrees of vessel occlusion, while others merely impair the flow of ingesta by causing kinking of intestinal segments. Further, while the classification for intestinal viability proposed by Freeman et al (2014) correctly identifies different degrees of intestinal infarction, it does not account for damage caused by ischemia without VSO, as seen in cases like arterial thromboembolism. For these reasons, we propose a classification of equine intestinal diseases that better describes the pathophysiology encountered by the surgeon in each case. According to this classification, further dividing strangulating and non-strangulating in occlusive/nonocclusive may help surgeons to better identify the characteristics of the steno-stenotic segment of intestine involved. Based on the findings of this study and the literature, future studies on treatments (either pharmacological or surgical) for small intestinal pathologies in horses should consider the degree and characteristics of vessel occlusion, as these have the greatest impact on the outcome. This is demonstrated by the difference in outcomes when small intestinal anastomosis techniques are applied to healthy horses (approx. 95% short-term survival rate) versus clinical cases (49-91% short-term survival rate) (GANDINI; UNPUBLISHED DATA), or by the differences in outcomes between different types of anastomosis (JJ vs JCE) (ggiusto et al, 2024) These differences in outcomes can only be explained by the disruptions caused to the intestine or the entire body by the underlying pathology. In this context, the new classification proposed here (Table 2) may serve as a guide for researchers to compare accepted or novel treatments, relating them to the pathology, the involved intestinal tract, and its viability, as suggested by Giusto et al. (2024) Limitations One limitation of the current study in assessing blood sequestration is the failure to account for all compartments where blood can accumulate. Blood sequestration occurs not only in the intravascular space but also within the intestinal lumen (intraluminal blood) (Hamilton and Hardenbrook, 1975) in the strangulated vessels (intravascular blood), and in the peritoneal cavity (intraperitoneal blood). These compartments can contribute significantly to the overall blood loss and should be considered when estimating the total volume of sequestrated blood. The contents of the stenotic intestine could not always be confined to the diseased segment and were not measured as a result, as well as fluid content of the abdominal cavity at necropsy. Another limitation is the absence of grade 1-2 lesions, which prevented us from quantifying intramural edema that is certainly present in many cases. Edema alone (i.e., without erythrocyte extravasation) is likely to be present in cases where resection is not appropriate and may have less impact on the metabolic state of the horse. A certain amount of edema is also present in advanced cases as part of the same problem, i.e., extravasation of fluid from vessels due to a pressure difference between arteries and veins. The absence of grade 5 lesions may also be considered a limitation of the study, although in these cases, we can assume that blood loss still occurs. The surgeon will find a thinner intestine compared to grade 2-4 lesions, likely because the intestinal wall layers are in such a deteriorated state that they leak all the blood they were filled with, both intraluminally and intraperitoneally. Conclusions and Future Research The results of this study demonstrate that blood is removed from the body when resection of infarcted intestine is performed. Moreover, demonstrate that the experimental setting described by Ruggles et al. (1993) closely mimics the clinical characteristics of VSO in horses as found also in other studies( Freeman et al, 2001; Freeman et al, 1988) For these reasons, the methodology described by Ruggles et al (1993), Freeman nd Kilgallon(2001, Freeman et al (2001) nd Freeman et al (1988) et al. 15,21-22 may offer a more realistic model than ischemia/trauma models for studying adhesions in horses (due to the presence of fibrin on the serosa and intraperitoneal blood) than other models and could provide a more accurate experimental setting for studying anastomotic techniques or treatments for small intestinal obstruction. This study also provides valuable, evidence-based information that can aid surgical decision-making and prognostication in horses with small intestinal disease. Strangulation does not equate to a lack of blood supply (ischemia). Infarcted intestines may still have the potential for recovery if blood sequestration is resolved. Infarction may be reversed, but ischemia cannot, and infarction can be worsened by certain therapies, while ischemia cannot. Early intervention, careful assessment of intestinal viability, and individualized treatment protocols can significantly improve outcomes in horses with small intestinal obstructions. Notes M. Gandini, G. Giusto: Survival and complications of small intestinal resection and anastomosis in experimental studies on healthy horses; unpublished data References Aird I. (1937). Experiments in Intestinal Obstruction: The Rôle Played by the Diminution of the Effective Circulating Blood Volume in Acute Intestinal Obstruction. Edinburgh medical journal , 44 (1), 28–32.Aird I. (1936). Intestinal Obstruction : The Results of Recent Experiment Applied to Clinical Practice. Edinburgh medical journal , 43 (6), 375–394.Aird I. (1941). Morbid influences in intestinal obstruction and strangulation. Annals of surgery , 114 (3), 385–414.Cook VL, Blikslager AT, Marshall JF. (2019) Principles of intestinal injury and determination of intestinal viability,in Auer J (Ed) Equine Surgery,5th ed; Chapter 34:529-536Divers TJ, Radcliffe RM, Cook VL, Bookbinder LC, Hurcombe SDA.(2022) Calculating and selecting fluid therapy and blood product replacements for horses with acute hemorrhage. J Vet Emerg Crit Care (San Antonio).32(S1):97-107Freeman DE, Schaeffer DJ, Cleary OB. (2014) Long-term survival in horses with strangulating obstruction of the small intestine managed without resection. Equine Vet J. 46(6):711-717.Freeman DE, Kilgallon EG. (2001)Effect of venous strangulation obstruction on length of equine jejunum and relevance to small-intestinal resection. Vet Surg. 30(3):218-222Freeman DE, Gentile DG, Richardson DW, Fetrow JP, Tulleners EP, Orsini JA, Cimprich RE. (1988) Comparison of clinical judgment, Doppler ultrasound, and fluorescein fluorescence as methods for predicting intestinal viability in the pony. Am J Vet Res. 49(6):895-900.Freeman DE, Cimprich RE, Richardson DW, Gentile DG, Orsini JA, Tulleners EP, Fetrow JP. (1988) Early mucosal healing and chronic changes in pony jejunum after various types of strangulation obstruction. Am J Vet Res. 49(6):810-818.Gendel S, Fine J. (1939) The effect of acute intestinal obstruction on the blood and plasma volumes. Ann Surg. 110(1):25-36Giusto G, Cerullo A, Gandini M. (2024) Anastomotic techniques for small intestinal obstruction in horses. A scoping review. Equine Vet J. 56(6):1103-1114Hamiliton DP, Hardenbrook HJ. (1975) Biochemistry, cytology, and microbiology of equine peritoneal fluid after experimental strangulation obstruction of the distal ileum. Am J Dig Dis. 20(6):595Hausler RW, Foster WC. (1924)Studies of acute intestinal obstruction. Different types of obstruction produced under local anesthesia. Reprinted from the Archives of Internal Medicine 34: 97-107Hurcombe SDA, Radcliffe RM, Cook VL, Divers TJ. (2022) The pathophysiology of uncontrolled hemorrhage in horses. J Vet Emerg Crit Care (San Antonio). 32(S1):63-71Mair TS, Edwards GB. (2003)Strangulating obstructions of the small intestine. Eq Vet Educ. 15(4):192-199Monreal L, Cesarini C. (2009) Coagulopathies in Horses with Colic Monreal. Vet Clin Equine Prac, 25(2): 247 – 258Ruggles A, Freeman DE, Acland HM, FitzSimmons M. (1993) Changes in fluid composition on the serosal surface of jejunum and small colon subjected to venous strangulation obstruction in ponies. Am J Vet Res. 54(2): 333-340Savioli G, Ceresa IF, Caneva L, Gerosa S, Ricevuti G. (2021) Trauma-Induced Coagulopathy: Overview of an Emerging Medical Problem from Pathophysiology to Outcomes. Medicines (Basel). 8(4):16Sullins KE, Stashak TS, Mero KN. (1985) Pathologic changes associated with induced small intestinal strangulation obstruction and nonstrangulating infarction in horses. Am J Vet Res. 46(4):913-916.Vallicelli, C., Coccolini, F., Catena, F. et al. (2011)Small bowel emergency surgery: literature’s review. World J Emerg Surg. 6:1-8Withers JM, Mair TS (2010) Internal (intra-abdominal) herniation in the horse. Eq Vet Educ. 20(12):639-646 Median (95%CI) 1 2 3 4 5 6 7 Disease EFE lipoma 2 loops lipoma EFE lipoma lipoma 2 loops GSE Intestinal tract Jejuno-ileum Jejuno-ileum jejuno-ileum Aboral Jejunum Mid-jejunum Mid-jejunum Mid- Jejunum Viability index 3-4 4 4 3-4 4 4 3-4 Measured length of strang.int. (mt) 3 (0.4-5.3) 5,3 4,8 1,25 1,9 0,4 3 3,3 Effective length of strang.int. -20% elongation 2.4 (0.3-4.2) 4,2 3,8 1,0 1,5 0,3 2,4 2,6 Tot. weight of strang. int. (Kg) 2 (0.28-4.3) 4 4,3 1,2 1,9 0,28 2 2,6 Rel. weight strang.int. (Kg/mt) 0.98 (0.83-1.3) a 0,94 1,12 1,2 1,25 0,86 0,83 0,98 Tot. length of healthy intestine (mt) 12 (11-14) 12,0 11,5 13 14 13 11 12 Tot. weight of healthy intestine (kg) 2.8 (2.4-4.1) 3,2 2,8 2,5 4,1 3,5 2,5 2,4 Rel. weight of healthy intestine (kg/mt) 0.24 (0.19-0.29) a 0,27 0,24 0,19 0,29 0,27 0,23 0,20 Total blood loss (liters) 1.5(0.19-3.4) 2,87 3,37 1,01 1,45 0,19 1,45 2,07 Relative blood loss (liters/mt of strang.int) 0.78 (0.59-1) 0,68 0,88 1,01 0,96 0,59 0,61 0,78 Presumed total blood volume (lt) 40(34-42) 42,4 39,1 40,1 40,9 38,5 34,0 39,6 Total blood loss (%) 4.3 (0.5-8.6) 6,8 8,6 2,5 3,6 0,5 4,3 5,2 Total blood loss (ml/kg) 3.4 (0.4-6.9) 5,4 6,9 2,0 2,8 0,4 3,4 4,2 Relative blood loss (%/ mt strang. int.) 2 (1.5-2.5) 1,60 2,24 2,51 2,34 1,53 1,78 1,98 Relative blood loss (ml/kg/mt strang.int.) 1.6(1.2-2) 1,28 1,79 2,01 1,87 1,22 1,42 1,59 Table 1: Case signalement and necropsy findings M: male, F: female, G: gelding; EFE; epiploic foramen entrapment, GSE: gastrosplenic ligament entrapment; strang.int.; strangulated intestine a: Mann-Whitney test, p<0.0001 Definition Intestinal wall status Vesssels status Intestinal viability Examples Non strangulating Non occlusive arteries and veins are pervious Ileal impaction, ascarid impaction, ileal hyperplasia, adhesions Occlusive Ischemic arteries are occluded, veins are not Intestine is usually non viable (grade 6) a arterial thrombosys Strangulating Non occlusive arteries are pervious and veins are not or only partially occluded Intestine is usually viable, no need for resection (grade 1-2) Pedunculated lipoma, intussusception, inguinal herniation, EFE, Volvulus, mesodiverticular bands, diaphragmatic hernia, GLE, omental/mesenteric defects, adhesion/fibrous bands Occlusive Infarcted arteries are pervious at least at the beginning of the diseases but veins are occluded-VSO Viable (grade 2-3, in some cases up to 4 th grade) Nonviable (grade 4-5) Ischemic arteries are occluded simultaneously with veins Intestine is usually non viable (grade 6) a Table 2 : Proposed classifications of small intestinal obstructions according to their pathophysiology. a: grade 6 is proposed to be introduced in the classification by Freeman 2014, to identify intestine that underwent arterial occlusion and ischemia without VSO. Supplementary Material File (table 1.docx) Download 18.97 KB File (table 2.docx) Download 15.36 KB Information & Authors Information Version history V1 Version 1 12 November 2025 Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords anastomosis colic haemorrhage pathophysiology small intestinal obstruction Authors Affiliations Marco Gandini 0000-0002-1402-8261 [email protected] Oregon Driver and Motor Vehicle Services Division View all articles by this author Gessica Giusto 0000-0002-0714-6382 Oregon Driver and Motor Vehicle Services Division View all articles by this author Metrics & Citations Metrics Article Usage 194 views 98 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Marco Gandini, Gessica Giusto. Estimation of Blood Component Sequestration during Resection of Strangulated Small Intestine in Horses and a Derived Classification Proposal for Small Intestinal Lesions. Authorea . 12 November 2025. 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