Ureter-related internal hernia causing intestinal obstruction after ureteral reimplantation: A case report and literature review.

A 64-year-old female presented to the emergency department with lower abdominal pain for 15 hours, cessation of flatus and defecation for 4 hours. She underwent ovarian cyst surgery followed by ureteral injury repair in 2015. Eight months ago, she underwent ERCP and laparoscopic cholecystectomy for choledocholithiasis and cholecystolithiasis. Physical examination on admission: Temperature 36.5°C, Heart Rate 99 bpm, Respiratory Rate 20 breaths/min, Blood Pressure 156/109 mmHg. Abdominal examination revealed a midline lower abdominal surgical scar, soft abdomen with lower abdominal tenderness and rebound tenderness, negative shifting dullness, and active bowel sounds. Non-contrast and contrast-enhanced CT of the abdomen and pelvis ( Fig. 1 : A-C) revealed: Disorganized and twisted mesentery in the left lower quadrant exhibiting a "whirl sign," localized small bowel dilatation with air-fluid levels suggestive of a closed-loop obstruction, bowel wall edema with reduced enhancement, compression and traction of the urinary bladder, involvement of the distal left ureter with proximal obstructive hydroureteronephrosis, and scattered intraperitoneal fluid. The findings were consistent with intestinal obstruction, possible volvulus, and suspected localized bowel ischemia. Fig. 1 Preoperative abdominal CT findings of internal hernia after ureteral reimplantation. A Left ureteral dilatation and hydronephrosis; B Hernia orifice of the internal hernia; C Obstructed and dilated bowel loops. Preoperative abdominal CT findings of internal hernia after ureteral reimplantation. A Left ureteral dilatation and hydronephrosis; B Hernia orifice of the internal hernia; C Obstructed and dilated bowel loops. Following preoperative preparation, the patient was scheduled for emergent exploratory laparotomy and intraoperative cystoscopy. Intraoperative findings ( Fig. 2 : A) included adhesions of the small bowel to the anterior abdominal wall and inter-loop adhesions. Approximately 200 mL of serosanguineous ascites was present. A segment of small bowel approximately 20 cm in length, located about 130 cm proximal to the ileocecal valve, was found to have herniated posterior to the previously reimplanted left ureter, resulting in torsion, incarceration, and necrosis. The proximal bowel was edematous and dilated, while the distal bowel was collapsed, containing bloody intraluminal fluid. Intraoperative cystoscopy demonstrated a normal right ureteral orifice; the left native ureteral orifice (blind ending) was visualized, but the reimplanted left ureteral orifice could not be identified. Surgical procedures performed included reduction and repair of the internal hernia, resection of the necrotic small bowel with enteroenterostomy, enterolysis, and diagnostic cystoscopy ( Fig. 2 : B-D). Postoperatively, the patient was managed with bowel rest, antibiotics, and nutritional support. Flatus and bowel movements resumed on postoperative day 3, allowing transition to a liquid diet. A follow-up abdominal CT performed one week postoperatively ( Fig. 3 : A-C) showed resolution of bowel obstruction and ascites. The drain was removed, and the patient was discharged without any perioperative complications. Fig. 2 Intraoperative findings and specimen of internal hernia after ureteral reimplantation. A Small intestine herniating through the peritoneal defect formed by the ureter, bladder, and lateral pelvic wall, resulting in an internal hernia with ischemic changes due to bowel compression. B After reduction of the incarcerated internal hernia, the ureter-bladder-lateral pelvic wall peritoneal defect is closed with absorbable sutures. C Ischemic and necrotic changes of the incarcerated small bowel after hernia reduction. D The resected specimen of the ischemic and necrotic small bowel segment. Fig. 3 Postoperative abdominal CT findings of internal hernia after ureteral reimplantation before discharge. A Resolution of left ureteral dilatation and hydronephrosis; B Relief of the internal hernia orifice; C Resolution of bowel obstruction caused by the internal hernia, no significant intra-abdominal fluid, and the pelvic drainage tube is in place. Intraoperative findings and specimen of internal hernia after ureteral reimplantation. A Small intestine herniating through the peritoneal defect formed by the ureter, bladder, and lateral pelvic wall, resulting in an internal hernia with ischemic changes due to bowel compression. B After reduction of the incarcerated internal hernia, the ureter-bladder-lateral pelvic wall peritoneal defect is closed with absorbable sutures. C Ischemic and necrotic changes of the incarcerated small bowel after hernia reduction. D The resected specimen of the ischemic and necrotic small bowel segment. Postoperative abdominal CT findings of internal hernia after ureteral reimplantation before discharge. A Resolution of left ureteral dilatation and hydronephrosis; B Relief of the internal hernia orifice; C Resolution of bowel obstruction caused by the internal hernia, no significant intra-abdominal fluid, and the pelvic drainage tube is in place.

Zilin Liu: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Resources, Software, Visualization, Writing – original draft, Writing – review & editing. Qin Zou: Conceptualization, Data curation, Formal analysis, Supervision, Validation, Visualization. Yuexin Zhang: Data curation, Validation, Visualization. Yue Kang: Funding acquisition, Supervision, Validation.

This study is funded by the Key Research and Development Program of Science & Technology department of Sichuan Province (Grant No. 2023YFS0169 ).

This case report was conducted in accordance with institutional ethical standards and the principles of the Declaration of Helsinki. The report was prepared in accordance with the CARE guideline and checklist (Supplementary File CARE checklist). Written informed consent was obtained from the patient for publication of this case report (Supplementary File Data and Sample Collection Consent).

Internal hernia following ureteral reimplantation is an insidious, preventable, high-risk surgical complication resulting from inadequate intraoperative restoration of peritoneal and mesenteric anatomy rather than uncontrollable factors. CT imaging currently enables precise preoperative diagnosis and is recommended as the primary diagnostic modality for evaluating the etiology of bowel obstruction in these patients. During ureteral reimplantation, routine closure of peritoneal defects, peritonealization of the ureteral pathway, and meticulous repair of potential hernia orifices, combined with early postoperative vigilance and multidisciplinary collaboration, can significantly reduce the incidence and prevent intestinal necrosis and mortality. Further large-scale or prospective high-quality trials are needed to confirm the clinical effectiveness of these measures and accumulate robust evidence-based support. Urologists and general surgeons should come to an agreement, accurately identify the cause of obstruction preoperatively or intraoperatively, and integrate internal hernia prevention into the routine surgical workflow, thereby effectively controlling this "eminently preventable" complication.

Internal hernia involves visceral protrusion through congenital or acquired defects, causing obstruction and ischemia; it constitutes an uncommon but high-risk etiology of acute small bowel obstruction. The overall population incidence is reported at approximately 0.2%–0.5%, accounting for 1%–3% of mechanical bowel obstruction etiologies. 6 The proportion of postoperative acquired internal hernias has been increasing annually, now representing over 50% of internal hernia cases, predominantly following pelvic and retroperitoneal surgeries. Due to atypical clinical presentations and diagnostic imaging challenges, the strangulation rate ranges from 30% to 50%, with delayed management escalating mortality beyond 20%, underscoring its importance in surgical quality control. 1 , 2 , 7 Internal hernia following ureteral reimplantation is an exceptionally rare complication, primarily documented through case reports with a paucity of large-scale data. Nonetheless, the severity of its clinical consequences necessitates heightened vigilance among urologists and general surgeons. Our team has summarized all reported cases of intestinal obstruction due to internal hernia following ureteral reimplantation since 1981 in Table 1 . Since 1981, 15 cases of intestinal obstruction caused by internal hernia after ureteral reimplantation have been reported. Among these, there were 4 male and 11 female patients. Ureteral reimplantation was performed during primary gynecologic/adnexal surgery in 10 patients, renal transplantation in 3 patients, and surgery for intrinsic ureteral/bladder pathology in 2 patients. Excluding 3 early reports, the remaining 12 patients underwent prompt CT evaluation upon presentation with internal hernia/obstruction, which identified adhesive bands as the cause of obstruction. Notably, CT explicitly demonstrated pelvicalyceal or ureteral dilatation/obstruction in 8 cases. All included literature adopted open exploratory laparotomy, with the exception of Cho's report, which utilized a laparoscopic surgical approach. Surgical management involved ureteral transection with primary reanastomosis or repeat ureteroneocystostomy in 9 patients, while simple reduction of the ureter was performed in 6 patients. Repair of the paraureteral defect was reported in only 3 cases: our team and the team of Flores et al. addressed the defect by retroperitonealizing/fixating the ureter to the pelvic sidewall after relieving the obstruction, whereas Spazzapan et al. 8 interposed an omental flap over the defect to prevent recurrence. In patients with a prior abdominal surgical history presenting with abdominal pain, distension, or altered bowel habits, adhesive disease or internal hernia should be primary considerations. Diagnostic approaches have evolved from clinical suspicion to precise radiological localization. Multidetector CT is the preferred initial imaging modality, with characteristic findings including clustered bowel loops, the "whirl sign," mesenteric vessel engorgement/traction, hernia ring boundaries, and diminished or absent bowel wall enhancement, enabling determination of hernia type, site of incarceration, and bowel viability. Recent advancements, such as AI-assisted CT interpretation, dynamic contrast-enhanced scanning, and 3D reconstruction, have further improved early detection rates, increasing preoperative diagnostic accuracy from under 50% to over 85%, providing robust evidence for early diagnosis. 6 As shown in Table 1 , 12 patients underwent preoperative CT, which confirmed obstruction due to adhesive bands, with 8 cases additionally demonstrating hydronephrosis/hydroureter, implicating a paraureteral defect as the etiology. Table 1 Summary of case reports on intestinal obstruction caused by internal hernia after ureteral reimplantation. Table 1 Author Year of publication Age (years) Gender Primary disease Previous surgical procedure Ureteral reimplantation side Time interval from initial surgery Preoperative CT findings Surgical strategy Measure to prevent relapse Hay DJ 9 1981 69 Female Uterine fibroids Hysterectomy; Ureteral reimplantation Right 20 years Not mentioned Small bowel reduction; Ureteral reimplantation Not mentioned Hocken et al. 9 1988 44 Female Cervical cancer Radical hysterectomy; Ureteral reimplantation Right 4 years Not mentioned Partial small bowel resection and anastomosis; ureteral repair combined with stent placement ended in failure and salvage cutaneous ureterostomy Not applicable Hussain et al. 10 1997 23 Male Vesicoureteral reflux Ureteral reimplantation Left 17 years Not mentioned Partial small bowel resection and anastomosis; Ureteral reanastomosis; Stent placement Not mentioned Takagi et al. 11 2002 46 Female Cervical cancer Radical hysterectomy; Ureteral reimplantation Left 2 years Left ureteral dilatation, bilateral hydronephrosis; Small bowel dilatation with fluid accumulation Partial small bowel resection and anastomosis; Ureteral reanastomosis Not mentioned Bircan et al. 12 2014 45 Female Cervical cancer Radical hysterectomy; Ureteral reimplantation Right 3 years Bowel dilatation, suspected jejunal perforation; Large amount of free intra-abdominal fluid Partial small bowel resection and anastomosis; Ureteral reduction Not mentioned Flores et al. 5 2015 34 Female Endometriosis Hysterectomy; Ureteral reimplantation Right 2 years Incarcerated small bowel loop; Right ureter extending from the right kidney to the iliac/lumbar bladder, bridged over the mesentery of the involved small bowel Partial small bowel resection; Ureteral reduction Parietalisation of the ureter to the pelvic wall Cole-Clark et al. 4 2017 79 Male Uterine transitional cell carcinoma Radical hysterectomy; Ileal conduit urinary diversion Left 12 days Dilated small bowel loops with two points of bowel incarceration, consistent with closed-loop small bowel obstruction Small bowel reduction; Ureteral reduction Imbricated omentum over the ureter to prevent further herniation Cho et al. 3 2019 53 Female Cervical cancer Radical hysterectomy; Ureteral reimplantation Left 6 years Closed-loop obstruction of an ileal loop in the pelvis with strangulation due to adhesive band; Hydronephrosis Small bowel reduction; Ureteral reduction Not repair retro-ureteral space due to the ureteral function and/or stricture concerns Anderson et al. 13 2019 34 Male End-stage renal disease Kidney transplantation; Ureter implantation Right 3 years Right-sided transplanted kidney with pelvic dilatation, mild perinephric inflammatory changes; Fluid accumulation in the abdomen and pelvis with diffuse mesenteric edema Partial small bowel resection and anastomosis; Ureteral reanastomosis, stent placement and nephrostomy Not mentioned Tovmassian et al. 14 2020 57 Female Pancreatic and renal disease Simultaneous pancreas–kidney transplantation; Ureter implantation Right 7 years Persistent dilatation of the renal collecting system; Large amount of free intra-abdominal fluid Partial small bowel resection and anastomosis; Boari flap and ureteral reimplantation; Stent placement Not mentioned Gupta et al. 15 2022 52 Male End-stage renal disease Simultaneous pancreas–kidney transplantation; Ureter implantation Left 5 years Closed-loop small bowel obstruction in the pelvis with a common turning point Partial small bowel and ureteral resection; Ureteral reanastomosis Not mentioned Spazzapan et al. 8 2022 80 Female Transitional cell carcinoma of the bladder and distal ureter Left distal ureterectomy; Left ureteral reimplantation Left 2 years Dilated and obstructed bowel loops in the lower abdomen, with the transition zone located at the left pelvic wall at the ureter; Left ureteral dilatation with fluid accumulation Small bowel reduction; Ureteral reduction; Omentoplasty and vascularised pedicle to ‘plug’ the paraureteric space Howk et al. 16 2024 46 Female Uterine disease Laparoscopic hysterectomy; Right ureteral reimplantation Right 8 years Partial colonic dilatation and obstruction Right hemicolectomy with anastomosis; Distal ureterectomy; Partial cystectomy; Ureteral reimplantation Not mentioned Permekerlis et al. 17 2024 58 Female Uterine disease Hysterectomy; Ureteral reimplantation Right 10 years Right hydronephrosis, no excretion from the right urinary tract, dilated small bowel loops Partial small bowel resection and anastomosis; Right ureteral reimplantation Not mentioned Our team 2025 62 Female Ovarian cyst Ovarian cystectomy; Ureteral reimplantation Left 8 years Small bowel dilatation with fluid accumulation, mesenteric torsion showing a "whirl sign", bowel wall thickening with reduced enhancement; Involvement of the distal left ureter with proximal obstructive hydronephrosis; Intra-abdominal fluid Partial small bowel resection and anastomosis; Ureteral reduction Parietal fixation to the lateral pelvic wall Summary of case reports on intestinal obstruction caused by internal hernia after ureteral reimplantation. Once diagnosed, internal hernia mandates prompt surgical intervention to relieve incarceration, close the defect, and preserve bowel and organ function. Timely surgical exploration mitigates the risk of bowel necrosis and septic shock. Prompt reduction, meticulous viability assessment, and decisive resection/anastomosis of necrotic bowel constitute the mainstay of management. Closure of the hernia orifice, peritoneal defect, or mesenteric rent is essential to prevent recurrence. Ureteral injuries commonly occur during gynecologic, colorectal, and retroperitoneal procedures, with iatrogenic injuries accounting for over 75% of cases. 18 , 19 Ureteral reimplantation (including ureteroneocystostomy, psoas hitch, Boari flap, and transureteroureterostomy) is the preferred technique for repairing distal ureteral defects and restoring urinary tract continuity, boasting success rates of 85%–95%. 18 , 19 In any procedure potentially involving the ureter or its adjacent anatomy, our team routinely places indwelling ureteral stents (rigid) on the affected or bilateral sides preoperatively to facilitate intraoperative identification of the ureter, effectively preventing inadvertent ureteral injury or transection unrelated to the target pathology. While the transperitoneal approach for ureteral reimplantation significantly enhances exposure and facilitates precise anastomosis, it simultaneously alters the anatomical planes of the pelvic peritoneum and lateral abdominal wall. Failure to meticulously reconstruct peritoneal and mesenteric structures may create potential hernia rings and pathological channels. Retro-ureteral hernia is the prototypical internal hernia following ureteral reimplantation, wherein small bowel loops become incarcerated in the anomalous space between the ureter and the bladder, lateral peritoneum, or psoas muscle, resulting in closed-loop obstruction. 4 , 5 The literature consists primarily of case reports and small series; the overall incidence is low, yet the consequences are grave. Presentation can occur weeks to years postoperatively with acute abdominal pain, vomiting, and obstipation, frequently misdiagnosed as adhesive small bowel obstruction. Current management predominantly involves emergent surgical reduction, hernia defect repair, and necrotic bowel resection, alongside preservation of the ureteral anastomosis and renal function. However, due to insufficient awareness and lack of early warning systems, management remains largely reactive, with a notable absence of standardized preventive protocols. The literature summarized in Table 1 reveals that despite preoperative CT evidence of ureteral obstruction, ureteral transection still occurred in several cases, necessitating concurrent ureteral repair or reimplantation. This underscores the critical importance of accurate intraoperative identification of the obstructive etiology. In the case reported by our team, correct identification of the ureter prevented iatrogenic injury that would have required ureteral reimplantation or even complex reconstruction using a bladder flap. Repair of a ureteral injury sustained after previous reimplantation presents numerous unpredictable factors. If the injury is close to the bladder and sufficient length permits, repeat ureteroneocystostomy may be feasible. If the injury is more proximal or the distal stump is ischemic/necrotic, rendering repeat reimplantation impossible due to inadequate length, options include transureteroureterostomy (anastomosis to the contralateral healthy ureter) or bladder flap reconstruction. The literature also contains reports of successful primary repair with stenting following transection, provided meticulous intraoperative assessment confirms adequate vascularity of the distal ureteral segment. Prevention is paramount in reducing this complication, and systematic, anatomically precise reconstruction can eliminate the risk at its source. Based on literature review and our institutional experience, we summarize preventive measures for internal hernia following ureteral reimplantation as follows: 1) Meticulous Closure of Peritoneal Defects: Following transperitoneal reimplantation, the lateral and pelvic peritoneum should be closed meticulously using continuous or interrupted sutures to obliterate any potential space between the ureter and the pelvic sidewall. 2) Peritonealization of the Ureteral Pathway: Position the anastomosed ureter in an extraperitoneal location or cover it completely with peritoneum to avoid creating a "suspended channel." 3) Repair of Mesenteric and Fascial Defects: Ensure watertight closure of any defects in the psoas fascia or paravesical mesentery, leaving no gaps. 4) Avoidance of Excessive Mobilization: In cases of distal or intramural ureteral pathology requiring reimplantation, limit ureteral and retroperitoneal dissection to the minimum necessary for a tension-free anastomosis, thereby reducing anatomical disruption and risk. Therefore, during ureteral reimplantation reconstruction, achieving both urinary tract reconstruction and restoration of abdominal anatomical integrity—with peritoneal closure, defect repair, and ureteral peritonealization considered critical steps—enables standardized prevention of this avoidable complication. For patients with a history of ureteral reimplantation presenting with unexplained acute abdominal pain and obstructive symptoms, prompt abdominal CT evaluation for internal hernia is recommended, rather than attributing symptoms solely to adhesive obstruction. Early surgical intervention minimizes renal and ureteral functional impairment and averts obligatory bowel resection necessitated by incarceration and necrosis. During surgical exploration in such cases, the initial step should involve inspection for paraureteral defects adjacent to the reimplanted ureter. Meticulous intraoperative differentiation between adhesive bands and vital structures such as the ureter is imperative; blind transection of any "adhesive band" must be strictly avoided to prevent iatrogenic injury.

Zilin Liu and Qin Zou collected the data, prepared the literature, wrote the manuscript text, and made the equal contributions to this article. Yuexin Zhang assisted with analyzing the data. Yue Kang supervised the research. All authors read and approved the final manuscript.

Internal hernia is defined as the protrusion of intra-abdominal viscera through a congenital or acquired orifice, defect, or mesenteric rent into an anomalous anatomical compartment, leading to obstruction and ischemia of the involved organs, thereby compromising organ function and survival. 1 It represents an uncommon but high-risk etiology of acute small bowel obstruction. The incidence of intestinal strangulation in such cases can reach 30%–50%, and delayed intervention can elevate the mortality rate to over 20%, establishing it as a critical quality control checkpoint in post-abdominal surgical care. 2 Internal hernia following ureteral reimplantation is a rare subtype of surgically acquired internal hernia, primarily documented in case reports in the literature. 3 , 4 , 5 Although the overall incidence is low, the consequences are extremely severe. Due to insufficient awareness and lack of early warning mechanisms regarding internal hernia after ureteral reimplantation, management remains predominantly reactive rather than proactive, lacking standardized preventive protocols. Furthermore, multiple reports in the literature describe instances where the mobilized ureter was misidentified as an adhesive band causing bowel obstruction and subsequently transected, resulting in iatrogenic urological injury and severe adverse surgical outcomes. Drawing from a typical clinical case managed by our team and our accumulated experience in ureteral reimplantation and the treatment of post-reimplantation internal hernia, combined with a comprehensive review of the literature on clinical characteristics, therapeutic strategies, and complication prevention, we present a detailed report and analysis regarding primary surgical prevention, early clinical recognition, and intraoperative management strategies for internal hernia after ureteral reimplantation.