Overview
Definition:
An enterovesical fistula is an abnormal connection between the small or large intestine and the urinary bladder
In Crohn's disease, these fistulas typically arise from transmural inflammation and transmural necrosis leading to a breach in the intestinal and bladder walls.
Epidemiology:
Enterovesical fistulas are the most common type of internal fistula in Crohn's disease, occurring in 2-15% of patients
They are more prevalent in patients with long-standing disease and extensive small bowel involvement
Risk factors include prior surgery, stricturing disease, and immunosuppressive therapy.
Clinical Significance:
Enterovesical fistulas significantly impact patient quality of life, causing recurrent urinary tract infections, pneumaturia, fecaluria, suprapubic pain, and potential renal compromise
Accurate diagnosis and appropriate surgical management are crucial for symptom relief, preventing complications, and improving long-term outcomes.
Clinical Presentation
Symptoms:
Recurrent urinary tract infections (UTIs), often resistant to standard antibiotic therapy
Pneumaturia (passage of gas in the urine)
Fecaluria (passage of stool in the urine), though less common than pneumaturia
Suprapubic pain and discomfort
Dysuria
Increased urinary frequency and urgency
Abdominal pain, particularly in the lower quadrants
Fever and malaise in cases of active infection.
Signs:
Tenderness on suprapubic palpation
Signs of sepsis in complicated cases
Digital rectal examination may reveal perianal disease or tenderness
Abdominal distension or a palpable mass in severe cases.
Diagnostic Criteria:
Diagnosis is typically confirmed by a combination of clinical suspicion, imaging studies, and sometimes cystoscopy with biopsy
No specific formal diagnostic criteria exist beyond the presence of an abnormal communication between the bowel and bladder confirmed by objective methods.
Diagnostic Approach
History Taking:
Detailed history focusing on the onset and progression of urinary symptoms, especially pneumaturia and recurrent UTIs
History of known Crohn's disease, its extent, and previous treatments
Prior abdominal surgeries
Medications, particularly immunosuppressants and biologics
Any history of abdominal trauma or radiation therapy.
Physical Examination:
General assessment for signs of inflammation or sepsis
Thorough abdominal examination for tenderness, masses, or distension
Digital rectal examination to assess for perianal disease or palpable fistulous tract extension
Pelvic examination in females to rule out gynecological causes
Assess for signs of malnutrition or dehydration.
Investigations:
Urinalysis: showing pyuria, bacteriuria, and potential fecaluria
Urine culture and sensitivity: to identify pathogens and guide antibiotic therapy
Complete blood count (CBC): may show leukocytosis or anemia of chronic disease
Inflammatory markers: ESR and CRP are often elevated in active Crohn's disease
Imaging: CT scan with oral and IV contrast is the preferred initial imaging modality, demonstrating bowel wall thickening, inflammation, and potential tract visualization
MRI: offers better soft tissue characterization and can be useful for delineating fistula tracts and their relationship to adjacent structures
Cystography: instilled contrast into the bladder to visualize the fistula
Voiding cystourethrogram (VCUG): may show contrast entering the bowel
Colonoscopy: to assess the extent and activity of Crohn's disease in the colon and terminal ileum
Cystoscopy: direct visualization of the bladder mucosa for inflammation, ulceration, or direct signs of fistula opening
Enteral contrast studies (e.g., small bowel follow-through): may demonstrate fistulous tracts in the small bowel.
Differential Diagnosis:
Diverticular disease with bladder involvement
Post-surgical fistulas (e.g., after pelvic surgery)
Radiation-induced enterovesical fistulas
Pelvic abscesses with secondary bladder involvement
Malignancy (e.g., bladder cancer, colorectal cancer invading the bladder)
Tuberculosis of the genitourinary tract
Crohn's disease without fistula, presenting with cystitis symptoms.
Management
Initial Management:
Medical management should be optimized to control inflammation and infection
Broad-spectrum antibiotics covering enteric organisms are essential to manage UTIs and any associated abscess
Nutritional support and hydration are critical, especially in malnourished patients
Urinary diversion may be considered in severe, unmanageable cases to protect renal function.
Medical Management:
High-dose corticosteroids for acute flares of Crohn's disease
Immunomodulators (e.g., azathioprine, 6-mercaptopurine)
Biologic therapy (e.g., anti-TNF agents like infliximab, adalimumab)
Antibiotics: tailored to urine culture and sensitivity, typically broad-spectrum initially
Probiotics may be considered as adjunctive therapy.
Surgical Management:
Surgical intervention is indicated for unresolving or complicated enterovesical fistulas, particularly those with symptoms unresponsive to medical therapy, recurrent infections, or suspicion of malignancy
The goals are to resect the diseased bowel segment involved in the fistula and to close or excise the fistulous tract with appropriate urinary diversion if necessary
Preoperative optimization of nutritional status and control of inflammation are paramount
Common surgical approaches include: Resection of the involved bowel segment (e.g., ileocecal resection for ileovesical fistulas) with primary anastomosis or stoma formation
Excision of the fistula tract from the bladder wall
Partial cystectomy may be required if there is significant bladder wall involvement or scarring
In complex cases with extensive disease, a temporary diversion (e.g., ileostomy, colostomy) may be necessary
Ureteric reimplantation might be required if the ureter is involved.
Supportive Care:
Aggressive fluid resuscitation and electrolyte correction
Pain management with appropriate analgesics
Nasogastric decompression if bowel obstruction is present
Stricture surveillance and management
Psychological support for patients dealing with chronic illness and potential stoma care.
Complications
Early Complications:
Anastomotic leak or dehiscence
Intra-abdominal abscess formation
Sepsis
Hemorrhage
Urinary tract infection
Damage to adjacent organs (e.g., ureter, rectum, female reproductive organs).
Late Complications:
Fistula recurrence
Stricture formation at the anastomosis or within the bowel
Malabsorption and nutritional deficiencies
Infertility
Adhesions leading to bowel obstruction
Incisional hernia
Development of malignancy within chronic inflammatory tracts.
Prevention Strategies:
Aggressive medical management of Crohn's disease to achieve and maintain remission
Careful surgical technique to minimize bowel trauma and ensure tension-free anastomoses
Prompt recognition and management of intra-abdominal infections
Adequate nutritional support
Close monitoring of patients post-operatively and long-term surveillance for recurrence or complications.
Prognosis
Factors Affecting Prognosis:
Extent and severity of Crohn's disease
Presence of complicating factors such as abscesses or strictures
Patient's nutritional status and overall health
Response to medical therapy
Technical success of surgical intervention
Development of complications post-operatively
Smoking status.
Outcomes:
With optimal medical and surgical management, many patients achieve significant symptom relief and improved quality of life
However, recurrence rates can be substantial, especially in patients with extensive disease or those who fail to achieve sustained remission
Long-term follow-up is essential.
Follow Up:
Regular clinical assessments to monitor for recurrence of symptoms
Serial laboratory investigations including inflammatory markers
Imaging studies (CT or MRI) may be performed periodically to assess for disease activity or complications
Colonoscopy or other endoscopic evaluations may be indicated
Nutritional monitoring and supplementation as needed.
Key Points
Exam Focus:
Enterovesical fistulas are the most common internal fistula in Crohn's
Pneumaturia and recurrent UTIs are hallmark symptoms
CT with IV/oral contrast is the initial imaging of choice
Surgical management involves resection of diseased bowel and fistula tract excision
Medical optimization is crucial pre- and post-operatively.
Clinical Pearls:
Always consider enterovesical fistula in a Crohn's patient with persistent or recurrent UTIs
Do not underestimate the impact of pneumaturia
it is a strong indicator
Aggressive medical management can sometimes lead to fistula closure or improve surgical outcomes significantly
Meticulous dissection and secure closure of the bladder wall are vital during surgery to prevent recurrence
Consider multidisciplinary team input (gastroenterology, colorectal surgery, urology).
Common Mistakes:
Delaying surgical intervention when indicated
Inadequate pre-operative medical optimization
Failure to resect the entire inflamed segment of bowel contributing to the fistula
Incomplete excision of the fistulous tract from the bladder
Underestimating the risk of anastomotic leak or abscess formation
Inadequate post-operative surveillance.