Colovesical and Other Enterovesical Fistulas

Etiology

Colovesical and other enterovesical fistulas typically arise from bowel pathology that breaches the intestinal wall and invades the bladder. The underlying etiology and the specific bowel segment involved determine the severity, duration, and associated complications.

Diverticular Disease

Diverticular disease is the leading cause of colovesical fistula, responsible for approximately 87.9% of cases.[1] The sigmoid colon is most frequently affected, primarily due to its association with diverticular disease and anatomical proximity to the bladder. Among patients with diverticulitis, about 2% experience complications, eg, paracolic or pelvic abscesses, perforation, and fistula formation. The anatomical proximity of the sigmoid colon to the bladder facilitates the development of inflammatory adhesions following diverticular perforations, which may subsequently progress to fistula formation.[2]

Malignancy

Malignancy, including colorectal and small bowel cancers, represents the second most common cause of colovesical and enterovesical fistulas, accounting for approximately 10% to 20% of cases. Advanced tumors (T3 and T4) that penetrate the intestinal wall may invade adjacent structures, eg, the urinary bladder, resulting in fistula formation.[3] In rare instances, primary bladder cancers may extend beyond the bladder wall and infiltrate the colon or small intestine, leading to fistulous communication.[4]

Inflammatory Bowel Diseases

Inflammatory bowel diseases, particularly Crohn's disease, frequently involve the ileum, and the fistulizing subtype can result in inflammatory communication with the bladder, leading to an enterovesical fistula. Crohn's colitis may also cause colovesical fistulas. The incidence of enterovesical fistula among patients with Crohn's disease ranges from 2% to 5%.[5] Although uncommon, ulcerative colitis can result in colovesical and ureteric fistulas, particularly in cases with severe inflammation or complications, eg, perforation, fulminant colitis, and obstruction.[6]

Iatrogenic Etiologies

Iatrogenic causes are rare but may result from intraoperative injury to the bladder during bowel resection. These include inadvertent incorporation of the bladder wall into the staple line of an intestinal anastomosis, unintentional inclusion of the intestinal wall during bladder repairs, and retained surgical materials, eg, gossypiboma.[7] Specific procedures, including restorative proctocolectomy and ileal pouch-anal anastomosis, are associated with an increased risk of pouch-vesical fistulas.[8] Additionally, traumatic catheterization and long-term indwelling urinary catheters with complications have been reported to result in enterovesical fistula formation.[9]

Radiation Enteritis

Radiation enteritis may result in the formation of enterovesical or colovesical fistulas. The interval between radiation therapy and fistula development typically ranges from 20 months to several years, most commonly following treatment for gynecological or urological malignancies.[10] Patients frequently present with multiple fistulous tracts, which are often not amenable to surgical repair. Advances in radiation therapy modalities and techniques, eg, the use of intensity modulated radiation therapy (IMRT) and patient positioning to minimize small bowel exposure, have significantly reduced the incidence of radiation enteritis-related complications.[11]

Infectious Etiologies

Infectious etiologies, eg, ileocecal tuberculosis, perforated appendicitis, Meckel's diverticulitis, genitourinary coccidioidomycosis, and pelvic actinomycosis, have been implicated in the development of enterovesical fistulas.[12][13][14][15][16] Tuberculosis involving the bladder may also result in enterovesical and vesicocolic fistulas.[17]

Additional Etiologies

The other rare causes of colovesical and enterovesical fistulas include pelvic inflammatory disease, endometriosis, foreign bodies in the gastrointestinal tract, ischemic enteritis, and chemotherapy-induced regressive inflammatory responses of tumors (eg, lymphomas).[18][19][20][21]

Epidemiology

Colovesical and other enterovesical fistulas account for approximately 1 in every 3000 hospital admissions.[22] A marked male predominance exists due to the close anatomic relationship between the bladder and the sigmoid colon and rectum.[23][24] In women, the uterus and broad ligaments provide a relative barrier against colovesical and rectovesical fistula formation, though these same etiologies may instead produce rectovaginal or rectouterine fistulas.[25] 

The incidence of diverticular disease is increasing in the United States, with diverticulitis occurring at an annual rate of approximately 180 per 100,000 people and resulting in approximately 200,000 hospital admissions annually.[26] Colovesical fistulas develop in 1% to 4% of patients with diverticular disease.[27] Given this etiology, the age at presentation typically ranges from 55 to 75 years.[28] 

Enterovesical fistulas associated with Crohn's disease are more common in younger patients, reflecting the demographics of the underlying condition. The mean duration of Crohn's disease before fistula development is 10 years, with an average patient age of 30 years.[29] Locally advanced colorectal cancers and, rarely, small bowel adenocarcinomas or neuroendocrine tumors account for approximately one-fifth of cases.[30][31] Primary urothelial carcinoma may rarely infiltrate adjacent bowel segments, producing a fistula.[32]

Pathophysiology

Colovesical and enterovesical fistulas occur from a localized pathologic process that results in perforation or erosion of both the intestinal wall and the adjacent bladder. The underlying mechanism varies by etiology, but all pathways ultimately involve tissue destruction, inflammation, and adherence of diseased bowel to the bladder dome, followed by erosion through both structures to create an abnormal epithelialized tract.

Diverticular Disease

In diverticular disease, the most common etiology, fistulas develop when colonic diverticula become inflamed. These diverticula represent protrusions of mucosa and submucosa through the muscularis propria at points of vasa recta entry. Increased intraluminal pressure, combined with abnormal peristalsis, directs radial force into the diverticula, causing microperforation or macroperforation. The resulting peridiverticular phlegmon or abscess adheres to the bladder dome and subsequently erodes through both walls, causing the fistulous communication. The sigmoid colon is the most commonly involved structure due to its proximity to the bladder and high prevalence of diverticulosis.[2] 

Inflammatory Bowel Diseases

Crohn's disease causes enterovesical fistulas through sustained transmural inflammation that progresses to fistulization. Once these tracts penetrate the serosa, they extend to adjacent organs. Chronic inflammation triggers epithelial-to-mesenchymal transition, upregulation of matrix metalloproteinases, and impaired wound healing, all of which promote ongoing tissue destruction and persistence of the fistula. The ileum is most commonly involved, consistent with its predilection for Crohn's disease.[33]

Malignancy

Malignancy-related fistulas occur through direct tumor invasion into the bladder wall, with locally advanced colorectal adenocarcinoma representing the most common neoplastic cause.[30] These fistulas typically indicate advanced disease with T4 staging. Radiation-induced fistulas develop through a distinct mechanism. External-beam radiation induces endarteritis obliterans in small submucosal vessels, leading to progressive chronic ischemia, mucosal necrosis, submucosal fibrosis, and ultimately fistula formation. This process may manifest months to decades after radiation exposure.[34] 

Iatrogenic Fistulas

Iatrogenic fistulas result from direct surgical injury during colorectal, urologic, or gynecologic procedures, with subsequent inflammation and incomplete healing leading to the abnormal connection. Trauma-associated fistulas follow penetrating or blunt abdominal or pelvic injury with concurrent bowel and bladder damage.

Histopathology

Histopathological evaluation plays a vital role in determining the etiology of colovesical and other enterovesical fistulas. Treatment strategies are guided by histopathological confirmation of the diagnosis.

• Diverticular disease may resemble inflammatory bowel disease. Histopathological features include lymphoid aggregates, cryptitis, crypt abscesses, peridiverticular abscesses, and fistulas that may track longitudinally or circumferentially.[35]
• Transmural inflammation, lymphoid aggregates, sinus tracts, and fistula formation characterize Crohn’s disease. Biopsies are insufficient for assessing the depth of inflammation; therefore, radiological evaluation is essential.[36]
• Malignant lesions usually demonstrate well- or moderately-differentiated glandular tissue with a cribriform pattern, necrosis, and infiltration by inflammatory cells.[37]
• Radiation-induced changes include Paneth cell metaplasia, ulceration, and epithelial atypia, along with alterations in crypt architecture, atrophy, and fibrosis of the lamina propria. The submucosa demonstrates hyalinization and fibrosis of vessel walls, intimal thickening, vascular ectasia, thrombosis, and endothelial cell atypia.[38]
• Granulomas with caseating necrosis, conglomerate epithelioid histiocytes, lymphocytes, Langhans giant cells, and distortion of the colonic mucosa characterize tuberculosis. Acid-fast bacilli are often detected in necrotic areas and histiocytes.[39]

History and Physical

Clinical History

Patients with colovesical and other enterovesical fistulas present with a spectrum of symptoms determined by fistula type, severity, and underlying etiology. Urinary symptoms predominate and include pneumaturia, fecaluria, passage of foul-smelling urine, and dysuria.[3][40] These may be accompanied by fever, lower abdominal pain, nausea, and vomiting. Severe presentations include urosepsis and septic shock. Gouverneur syndrome, characterized by suprapubic pain, urinary frequency, dysuria, and tenesmus, is considered pathognomonic for enterovesical fistula.[41]

Clinical evaluation should include assessment for features of the underlying etiology. Older adult patients with chronic constipation, rectal bleeding, sensation of incomplete evacuation, recurrent left lower quadrant discomfort, and fever should prompt consideration of diverticular disease.[42] Colorectal malignancy presents with altered bowel habits, rectal bleeding, spurious diarrhea, abdominal pain, anorexia, and weight loss.[43]

Crohn's disease manifests with recurrent abdominal pain, diarrhea, fever, and constitutional symptoms, often accompanied by extraintestinal manifestations including arthritis, uveitis, and dermatologic conditions.[44] Complex perianal fistulas may coexist with enterovesical fistulas in patients with Crohn disease or tuberculosis, and concurrent enteroenteric, enterocolic, enterouterine, or enteroureteric fistulas should be suspected.[45][46] Radiation enteritis presents with recurrent abdominal pain, intestinal obstruction, malabsorption, and weight loss.[47]

Physical Examination

Physical examination requires a thorough abdominal, perineal, digital rectal, and vaginal assessment. The general examination should evaluate for pallor, lymphadenopathy, clubbing, and edema, which may indicate underlying malignancy, inflammatory bowel disease, or tuberculosis. Suprapubic tenderness is common in patients with enterovesical fistulas. Abdominal distention with generalized tenderness and guarding suggests intra-abdominal sepsis from diverticular perforation, tumor perforation, fistulizing Crohn disease with abscess formation, or ileocecal tuberculosis with obstruction. Perineal and digital rectal examination are essential for evaluating perianal Crohn's disease and locally advanced low rectal cancers with potential bladder infiltration.

Evaluation

The primary objectives in evaluating colovesical and enterovesical fistulas are to confirm the diagnosis, characterize the fistula site and complexity, identify the underlying pathology, and plan optimal management. Diagnosis is often challenging, as no consensus algorithm exists. Evaluation incorporates laboratory studies, imaging, and interventional modalities.

Laboratory Studies

The following laboratory studies are frequently recommended in the evaluation of colovesical and enterovesical fistulas:

• Complete blood count: Assessment for anemia secondary to chronic disease or occult blood loss and leukocytosis indicating infection or inflammatory process. Thrombocytosis may suggest underlying malignancy or chronic inflammation.

• Comprehensive metabolic panel: Evaluation of renal function is essential, as chronic or recurrent urinary tract infections and urosepsis may compromise kidney function. Electrolyte abnormalities and hypoalbuminemia may indicate malnutrition, particularly in patients with Crohn's disease or malignancy.

• Urinalysis and urine culture: Urinalysis typically demonstrates pyuria, bacteriuria, and occasionally fecal debris or undigested food particles. Urine culture characteristically grows polymicrobial enteric organisms, including Escherichia coli and mixed bowel flora, which should raise suspicion for enterovesical communication in patients with recurrent urinary tract infections.[1]

• Tumor markers: Carcinoembryonic antigen (CEA) should be obtained when colorectal malignancy is suspected. Additional markers may be indicated based on clinical suspicion for other primary malignancies.

• Inflammatory markers: Erythrocyte sedimentation rate and C-reactive protein may be elevated in inflammatory conditions, including Crohn's disease, diverticulitis, and infectious etiologies. Fecal calprotectin helps monitor inflammatory bowel disease activity.

Imaging Studies

Computed tomography

Computed tomography (CT) is the preferred initial imaging modality, with diagnostic accuracy of 90% to 100%.[48] The preferred protocol involves administering oral and rectal contrast before intravenous contrast to visualize the passage of enteric contrast into the bladder.[48][2] Characteristic CT findings include intravesical air (the most sensitive sign), passage of oral or rectal contrast into the bladder lumen, focal bladder wall thickening adjacent to the fistula site, thickening of the involved bowel segment, and extraluminal mass with air foci, suggesting abscess formation.

CT also identifies underlying etiologies, including sigmoid diverticulitis with pericolic inflammation, colorectal carcinoma with luminal narrowing and lymphadenopathy, inflammatory bowel disease with mural stratification and mesenteric fat proliferation, and radiation enteritis with diffuse bowel wall thickening. Fistula location on CT provides etiologic clues: diverticulitis and rectosigmoid malignancies typically involve the left and posterior bladder wall, while Crohn's disease, ileal tuberculosis, and appendiceal pathology affect the right lateral or anterior bladder wall.[48] False-positive results for intravesical air may occur following recent bladder instrumentation, in patients with indwelling urinary catheters, or with urinary tract infections caused by gas-forming organisms.[3][48]

Magnetic resonance imaging

Magnetic resonance imaging (MRI) offers superior soft-tissue resolution, multiplanar imaging capability, and approaches 100% sensitivity and specificity for colovesical fistulas.[49][50] The use of intravenous gadolinium and short-tau inversion recovery (STIR) sequences further improves detection rates. Characteristic MRI patterns include a visible fistula tract, intervening abscess cavity, and loss of fat plane between the bowel and bladder walls.[50] MRI is the gold standard for rectovesical and rectovaginal fistulas and is particularly valuable for complex fistulas in Crohn's disease.[51] However, higher costs and limited availability restrict its use in emergency settings.[49]

Ultrasonography

Ultrasonography has limited diagnostic value as a primary modality, although some studies report good diagnostic yield.[52] The characteristic beak sign demonstrates a connection between peristaltic bowel loops and the bladder lumen.[53] Transrectal and transvaginal ultrasonography may help identify fistula tracts in select cases and are useful adjuncts when cross-sectional imaging is inconclusive.

Barium studies

Barium enema and small bowel follow-through have largely been replaced by cross-sectional imaging, with a diagnostic accuracy of only approximately 30%.[3] These studies may occasionally demonstrate contrast extravasation into the bladder or outline an associated abscess cavity, but are rarely used as primary diagnostic tools.

Cystography

Cystography demonstrates contrast extravasation outside the bladder but has similarly low diagnostic accuracy of 20% to 30%.[3] This modality may be helpful when CT is contraindicated or unavailable; however, cystography provides limited information regarding the underlying etiology.

Interventional Studies

Cystoscopy

This consists of a videoendoscopic examination of the urethra, bladder, and ureteric orifices. Cystoscopy provides the highest diagnostic yield for colovesical and enterovesical fistulas but can have a failure rate of up to 89%, with findings often nonspecific when the primary etiology involves the bowel.[30] Common cystoscopic findings include mucosal erythema, edema, erosions, and localized bullous changes at the fistula site. Direct visualization of the fistula opening is uncommon unless the tract is large. Cystoscopy also allows biopsy of suspicious bladder lesions to exclude primary bladder malignancy.

Colonoscopy

Colonoscopy is the gold-standard investigation for diagnosing colorectal pathology, but it has low sensitivity for detecting fistulas, ranging from 8.5% to 55%.[40] Colonoscopy cannot visualize enterovesical fistulas proximal to the terminal ileum. Despite these limitations, colonoscopy remains essential since 10% to 20% of fistulas are secondary to colorectal malignancy, and tissue diagnosis is critical for treatment planning.[30] Endoscopic findings may include mucosal inflammation, ulceration, stricture, or mass lesions, depending on the underlying etiology. A biopsy should be performed for histopathologic confirmation of suspected malignancy or inflammatory bowel disease.

Double-balloon enteroscopy and capsule endoscopy

Double-balloon enteroscopy and capsule endoscopy modalities are reserved for suspected Crohn's disease when colonoscopy is nondiagnostic. Antegrade double-balloon or push enteroscopy visualizes the proximal jejunum, while retrograde enteroscopy examines the entire ileum with the added advantage of biopsy capability.[54] Capsule endoscopy is less invasive and helpful for detecting fistula location, but it cannot obtain tissue samples and carries a risk of capsule retention in patients with stricturing disease.[55]

Poppy seed test

The poppy seed test is a noninvasive, cost-effective screening tool with diagnostic accuracy approaching 100%, particularly useful in resource-constrained settings.[56] The test involves ingestion of 35 to 50 g of poppy seeds, followed by visual inspection of urine for seeds within 48 hours; their presence confirms an enterovesical communication. This test provides no information regarding fistula characteristics, anatomic location, or underlying etiology and serves only as a preliminary investigation to initiate appropriate referral pathways.[57]

Treatment / Management

Management of colovesical and other enterovesical fistulas depends on symptomatology, complications, and primary etiology. In patients with long-standing fistulas and recurrent urinary tract infections, initial management focuses on optimizing physiology by treating urosepsis and addressing nutritional deficiencies. Urine culture results should guide antibiotic selection and duration of therapy.

Conservative Management

Conservative management is a favorable option in patients with enterovesical fistulas secondary to Crohn's disease or tuberculosis, where medical therapy is the cornerstone of treatment. This approach is indicated in patients who are poor surgical candidates due to advanced age, significant comorbidities, or limited life expectancy.

Conservative treatment includes bowel rest, total parenteral nutrition in acute settings, broad-spectrum antibiotics, and continuous bladder drainage.[58] For Crohn's disease, immunomodulators including corticosteroids, thiopurines, and biologic agents such as anti-tumor necrosis factor therapy are employed.[59] Antitubercular treatment is initiated for confirmed or suspected intestinal tuberculosis.

Colovesical fistulas seldom respond to conservative management alone. However, studies demonstrate similar outcomes in terms of complications and mortality between conservative and surgical treatment for benign conditions.[60] In patients who are surgical candidates, particularly those with malignancy, a conservative approach is associated with higher mortality rates and complications.[61](B2)

Endoscopic Management

Endoscopic management benefits patients who are unfit for or have contraindications to conventional surgical treatment. This approach is beneficial in patients with radiation enteritis and peritoneal carcinomatosis-related enterovesical fistulas, where surgical intervention is often challenging and associated with high morbidity.

Endoscopic techniques include over-the-scope clips (OTSC) or through-the-scope clips (TTSC) for mechanical closure of the fistula tract.[62] These techniques have an initial success rate of approximately 80% and a long-term success rate of 50%.[63] Endoscopic injection of fibrin glue offers a safe and minimally invasive alternative in selected patients.[64] Covered self-expanding metal stents placed in locally advanced colorectal cancers can palliate symptoms and bridge patients through neoadjuvant therapy, thereby avoiding the morbidity of complex surgical resection in the acute setting.[65](B2)

Surgical Management

Operative management of colovesical and enterovesical fistulas depends on the primary etiology, fistula site and complexity, the involved bowel segment, and the patient's condition. The primary surgical objectives are adequate delineation of the fistulous communication, excision of the fistula tract, and resection of involved bowel and bladder segments.[1] Interposition of an omental flap between the bladder and intestine improves healing and reduces fistula recurrence when feasible.[66](A1)

The underlying etiology determines the extent of resection. Inflammatory conditions, including diverticulitis, Crohn's disease, and ulcerative colitis, typically require segmental bowel resection with bladder cuff excision. Malignant etiologies necessitate radical resection to achieve oncologically safe margins, including anterior resection for rectosigmoid tumors, radical sigmoid colectomy for primary sigmoid cancers, low anterior resection or abdominoperineal excision for rectal tumors, depending on location, and partial or total cystectomy as indicated.[67]

The surgery may be performed via an open or minimally invasive (laparoscopic or robotic) approach, depending on the patient's condition and the availability of expertise. Studies demonstrate that minimally invasive techniques are feasible in stable, well-selected patients but carry a higher risk of conversion to open surgery.[68]

Staged procedures

Additionally, operations may be performed as 1-, 2-, or 3-stage procedures depending on the etiology, patient condition, and extent of resection required.

One-stage procedure

The diseased bowel segment and bladder are excised, with primary bowel anastomosis and bladder repair performed without fecal diversion. This approach minimizes patient morbidity by avoiding reoperation risks, including adhesions, anesthesia-related complications, and wound morbidities such as incisional and parastomal hernias.[69] Prerequisites for 1-stage repair include a thorough knowledge of fistula anatomy and etiology, absence of intraperitoneal abscess or phlegmon, and exclusion of locally advanced or unresectable cancers, radiation enteritis, and peritoneal carcinomatosis. Complication rates range from 8% to 49%, including anastomotic leak, bladder leak, and need for reoperation, with overall mortality up to 63%.[1](A1)

Two-stage procedure

The 2-stage approach is indicated for patients with inoperable colorectal cancers, extensive intra-abdominal sepsis, or immunosuppressed states. The first operation involves creating a diversion stoma, with or without primary resection, anastomosis, and bladder repair. The stoma may be an end colostomy (Hartmann procedure) or diverting ileostomy. The subsequent surgery involves stoma reversal and completion of any remaining resection, anastomosis, or bladder repair.[70]

Three-stage procedure

Rarely, patients require a 3-stage approach consisting of an index diverting ileostomy, followed by primary resection with anastomosis and bladder repair, and finally stoma closure.[70]

Palliative diversion

A purely diverting ostomy to redirect the fecal stream away from the colovesical fistula is not recommended unless definitive surgical treatment is not possible, eg, in patients with radiation enteritis or peritoneal carcinomatosis-related fistulas. In these cases, diversion is performed solely to reduce morbidity related to urosepsis.[3]

Differential Diagnosis

Characteristic features of colovesical and enterovesical fistulas, eg, pneumaturia, fecaluria, dysuria with tenesmus, and suprapubic pain, have very few differential diagnoses. When these symptoms are isolated or accompanied by other nonspecific features (eg, fever, altered bowel habits, anorexia, and weight loss), these other differentials should be considered, including:

• Diverticulitis: Clinical features include older age, chronic constipation, altered bowel habits, rectal bleeding, fever, and abdominal pain. CT scan and colonoscopy are diagnostic.

• Locally advanced colon cancer: These can produce urinary symptoms when there is local infiltration of the prostate in males and the vagina in females. Diagnosis is confirmed by colonoscopy, and an MRI scan can help rule out a colovesical fistula. 

• Recent instrumentation of the bladder: This can present with pneumaturia and urinary tract infections, and can be determined with a detailed history.

• Urinary tract infection (UTI) with gas-forming organisms (emphysematous cystitis): Increased risk in people with diabetes and patients with urinary tract outflow obstruction. Imaging will show intravesical air, and the urine culture will be diagnostic. 

• Inflammatory bowel diseases: Both Crohn's disease and ulcerative colitis can have lower abdominal pain, tenesmus, and fever. A colonoscopy and CT scan will show the characteristic features. 

• Primary bladder cancers: They can present with hematuria, dysuria, suprapubic pain, and urinary tract infections. CT scan and cystoscopy are diagnostic.[71]

• Radiation enteritis: They can form adhesions with the bladder and present with nonspecific urinary symptoms accompanied by typical features, eg, recurrent intestinal obstruction and malabsorption. CECT is helpful in the diagnosis. 

• Gastrointestinal tuberculosis: Ileocaecal and peritoneal tuberculosis can present with chronic abdominal pain, fever, anorexia, and weight loss. Urinary symptoms are unusual unless the bladder is involved.[72]

• Genitourinary tuberculosis: Dysuria, urinary hesitancy, and frequency are common and are accompanied by other constitutional symptoms of tuberculosis.[73]

Prognosis

The prognosis of colovesical and other enterovesical fistulas is primarily determined by the underlying etiology, the involved intestinal segment, the complexity, and the morbidity related to surgery and to complications from recurrent urosepsis.

The most common cause of colovesical fistula, diverticular disease, has a favorable prognosis. Studies have shown that conservative approaches are comparable to surgical management in patients with diverticulitis-associated colovesical fistulas.[74] When surgery is performed, the procedure is often curative and has a negligible chance of recurrence. Similarly, the prognosis after a successful repair is good in other benign conditions, eg, inflammatory bowel disease, appendicular lesions, tuberculosis, and trauma. However, malignant colorectal neoplasms causing colovesical fistula represent an advanced stage of disease with higher chances of harboring metastatic potential and local recurrence. Therefore, they carry a poor prognosis. Similarly, radiation enteritis-related enterovesical fistulas pose a complex surgical challenge and have a higher chance of recurrence.[3]

Complications

The complications of colovesical and enterovesical fistulas, when left untreated, can result in renal failure secondary to recurrent urosepsis. The primary etiology plays a prominent role in the disease-related and treatment-related complications. The overall treatment-related morbidity, mortality, and recurrence rates are 8% to 49%, 0% to 63%, and 1.2%, respectively.[1] 

Benign conditions, eg, diverticulitis and inflammatory bowel diseases, are associated with fewer complications. However, patients with malignant colovesical fistulas have higher complications since they require extensive surgeries, including pelvic exenteration.[75] 

Postoperative complications in patients with colovesical and enterovesical fistulas due to benign conditions include wound infection, anastomotic leak, pelvic collection, and ileus, most of which can be managed conservatively. The long-term complications include incisional and parastomal hernias.[75] Due to skip lesions, Crohn's disease involves longer segments requiring repeated resection of multiple intestinal loops.[75]

In patients undergoing surgical treatment for malignant colovesical and enterovesical fistulas, the early postoperative complication rate is significantly higher than that of benign causes. Pelvic collection, anastomotic leak, wound dehiscence, and thromboembolism are the common postoperative complications.[1][75] Similarly, the complications are higher in patients with radiation-induced colovesical and enterovesical fistulas, as no clear planes between the involved segments of the intestine and the bladder are present, resulting in incomplete excision of the fistula and higher chances of iatrogenic bowel injury.[3]