An enterovesical fistula (EVF) is an abnormal passage that forms between the intestine and the bladder. This specific type of fistula creates a communication channel, most commonly between the colon and the bladder, allowing intestinal contents to leak into the urinary tract. This condition is relatively uncommon but represents a serious complication of underlying disease and requires prompt medical evaluation and treatment.
Identifying the Symptoms
The symptoms of an enterovesical fistula are often distinct and primarily involve the urinary tract, as the bladder becomes contaminated by contents from the bowel. The most telling sign patients report is the passage of gas or air during urination, a condition known medically as pneumaturia. This occurs because gas produced by intestinal bacteria travels through the abnormal connection and is expelled during voiding. This symptom is present in over half of all confirmed cases, making it a strong indicator of the condition.
Patients may also notice fecaluria, which is the presence of fecal matter or debris in the urine. This manifests as a cloudy, brownish tint or the presence of visible vegetable matter and small particles. Intestinal contents leaking into the bladder introduce bacteria into the sterile urinary environment. This process directly leads to recurrent and persistent urinary tract infections (UTIs) that are difficult to treat.
These infections often involve common intestinal bacteria, such as Escherichia coli and other coliforms, which are not usually found in the urinary tract. Beyond these symptoms, patients frequently experience general lower urinary tract irritation. This includes painful urination (dysuria), a sudden urge to urinate, and increased urinary frequency. General abdominal discomfort, specifically suprapubic pain, and malodorous urine are also commonly reported.
Primary Causes of the Fistula
The formation of an enterovesical fistula is almost always the result of an underlying inflammatory or neoplastic disease process in the abdomen or pelvis. The most frequent cause is complicated diverticulitis, which accounts for over two-thirds of all cases. In this scenario, an inflamed pouch in the colon, called a diverticulum, can develop a localized abscess that erodes through the adjacent bladder wall, creating the abnormal passageway.
Inflammatory Bowel Diseases (IBD), particularly Crohn’s disease, represent another significant cause, contributing to approximately 10% of enterovesical fistulas. The chronic inflammation characteristic of Crohn’s disease can lead to tissue breakdown and the subsequent formation of a connection, most often between the small intestine (ileum) and the bladder.
Malignancy and Other Causes
Malignancy, primarily colorectal or bladder cancer, is the second most common underlying cause. Tumor growth can spread and destroy the tissue separating the two organs. Other less common but significant causes include prior abdominal or pelvic surgery, which can inadvertently lead to fistula formation as an iatrogenic injury. Radiation therapy delivered to the pelvic area for cancer treatment can also damage the intestinal and bladder walls, leading to tissue necrosis and fistula development.
Medical Confirmation and Testing
The diagnostic process begins with a detailed patient history, as the presence of pneumaturia or fecaluria is highly suggestive of a fistula. A physician then proceeds with specialized imaging to confirm the presence and pinpoint the location of the abnormal tract. Computed Tomography (CT) scanning of the abdomen and pelvis is considered the most sensitive imaging method for detecting this condition.
The CT scan can visualize small pockets of air within the bladder and will also show localized thickening of the bladder wall adjacent to the thickened bowel. To enhance visualization, the patient may be given oral or rectal contrast material, which can sometimes be seen leaking into the bladder, confirming the connection. Magnetic Resonance Imaging (MRI) is used when CT results are inconclusive, as it provides better soft tissue detail, particularly in complex cases or those involving Crohn’s disease.
Cystoscopy, a procedure where a thin, lighted tube is inserted into the urethra to examine the bladder interior, is often performed. While the opening itself is not always visible, the procedure frequently reveals a localized area of inflammation, redness, or bullous edema on the bladder wall where the fistula tract enters. Urine analysis is also informative, as the presence of mixed bacteria and fecal debris in the sample supports the clinical suspicion.
Repair and Management
For most patients, surgical intervention is necessary to definitively treat an enterovesical fistula and prevent ongoing contamination of the urinary tract. The main goal of treatment is to isolate and remove the diseased segment of the bowel that caused the fistula, along with the abnormal tract. For fistulas caused by diverticulitis, this involves resecting the affected portion of the colon and immediately reconnecting the healthy bowel ends in a single-stage procedure.
The defect created in the bladder wall is usually repaired with sutures, or if the opening is tiny, it may be left to heal spontaneously. Following the repair, a urinary catheter is placed to continuously drain the bladder for one to two weeks, allowing the bladder wall to rest and heal without tension. If the underlying cause is Crohn’s disease, medical therapy to control inflammation is often attempted first, but surgery is indicated if symptoms persist or if severe complications occur.
In situations involving severe infection, such as a large abdominal abscess, or in patients who are medically unstable, a staged surgical approach may be required. This can involve a temporary diversion of the fecal stream, such as a colostomy, to allow inflammation to subside before the final repair. Management of the underlying disease, whether through surgical resection or medical therapy, is a fundamental component of the treatment plan to minimize the risk of recurrence.