Enterovesical Fistula 

Normally, the urinary system is completely separated from the alimentary canal. Connections may result from (1) incomplete separation of the two systems during embryonic development (eg, failure of the urorectal septum to divide the common cloaca), (2) infection, (3) inflammatory conditions, (4) cancer, (5) trauma or foreign body, or (6) iatrogenic causes (presenting either postoperatively or as a treatment complication). In the general practice of medicine, bowel disease that occurs adjacent to the bladder and erupts into it is the most common cause of misconnection of the two systems. Fistulae from the bowel to the ureter and the renal pelvis are also possible but uncommon in the absence of trauma, chronic infection, or surgical interventions. This article focuses on the more common causes, presentations, and treatments of enterovesical fistulae.^[1]

For excellent patient education resources, visit eMedicine's Cancer and Tumors Center and Kidneys and Urinary System Center. Also, see eMedicine's patient education articles Bladder Cancer and Bladder Control Problems.

As early as the second century AD, Rufus of Ephesus described fistulae between the bowel and the bladder. The common causes of acquired vesicoenteric fistulae have shifted from diseases of the past (eg, typhoid, amebiasis, syphilis, tuberculosis) to diverticulitis, malignancy, Crohn disease, and iatrogenic causes.

Treatments have also evolved. In 1888, some suggested that colovesical fistulae "might be cured by a course of Bristol water and ass's milk."^[2] Although more invasive, certainly less colorful, and possibly more palatable, a single-stage surgical approach is more commonly used today.

A fistula is an abnormal communication between two epithelialized surfaces. Vesicoenteric fistulae, also known as enterovesical or intestinovesical fistulae, occur between the bowel and the bladder. Vesicoenteric fistulae can be divided into 4 primary categories based on the bowel segment involved, as follows: (1) colovesical, (2) rectovesical (including rectourethral), (3) ileovesical, and (4) appendicovesical fistulae. Colovesical fistula is the most common form of vesicointestinal fistula and is most commonly located between the sigmoid colon and the dome of the bladder.

Rectourethral and rectovesical fistulae are observed in the postoperative setting, such as after prostatectomy, as a consequence of chronic infection or tissue destruction that accompanies massive decubiti, or in the setting of acute infections such as Fournier gangrene.

Frequency

Colovesical fistulae are the most common type of fistulous communication between the urinary bladder and the bowel. The relative frequency of colovesical fistulae is difficult to ascertain because of the numerous potential etiologies, including multiple disease processes and surgical procedures.^[3]

The incidence of fistulae in patients with diverticular disease, the most common cause of colovesical fistula, is accepted to be 2%, although some referral centers have reported higher percentages. Only 0.6% of carcinomas of the colon lead to fistula formation.^[4]

Colovesical fistulae are more common in males, with a male-to-female ratio of 3:1. The lower incidence in females is thought to be due to interposition of the uterus and adnexa between the bladder and the colon. In women, other types of fistulae (typically iatrogenic, such as enterovaginal, ureterovaginal, and vesicovaginal) are more common than colovesical fistulae.^[4] Women who present with colovesical fistulae are commonly older and/or have a history of hysterectomy. Uterine atrophy or absence may be predisposing etiologies.

Fistula formation is believed to evolve from a localized perforation that has an adherent adjacent viscus. The pathologic process is almost always intestinal. Pathologic processes characteristic of particular intestinal segments cause those segments to adhere to the bladder. Therefore, the location of the segment can suggest intestinal pathology.

Fistulae may be either congenital or acquired (eg, inflammatory, surgical, neoplastic). Congenital vesicoenteric fistulae are rare and are often associated with an imperforate anus.

Inflammatory pathophysiology

Diverticulitis accounts for approximately 50%-70% of vesicoenteric fistulae, almost all of which are colovesical. A phlegmon or abscess is a risk factor for fistula formation.^[5] This complication occurs in 2%-4% of cases of diverticulitis, although referral centers have reported a higher incidence.^[6]

Crohn disease accounts for approximately 10% of vesicoenteric fistulae and is the most common cause of an ileovesical fistula. Ileovesical fistulae develop in 10% of patients with regional ileitis. The transmural nature of the inflammation characteristic of Crohn colitis often results in adherence to other organs. Subsequent erosion into adjacent organs can then give rise to a fistula. The mean duration of Crohn disease at the time of first symptoms of fistula formation is 10 years, and the average patient age is 30 years.^[7]

Less-common inflammatory causes of colovesical fistulae include Meckel diverticulum,^[8] genitourinary coccidioidomycosis,^[9] and pelvic actinomycosis.^[10] In addition, case reports have described appendicovesical fistulae as a complication of appendicitis.^{[11, 12, 13, 14]} Enterovesical fistula formation due to lymphadenopathy associated with Fabry disease has been reported.^[15]

Rarely, the bladder is the origin of the inflammatory process, as noted in a case report from Spain of bladder gangrene that caused a colovesical fistula in a patient with diabetes mellitus.^[16] Additional case reports have demonstrated fistula formation in the setting of chronic outlet obstruction due to benign hypertrophy with the formation of a large bladder stone and recurrent infections.^[17]

Malignant pathophysiology

Malignancy accounts for up to 20% of vesicoenteric fistulae and is the second most common cause of enterovesical fistula. Rectovesical fistula is the most common presentation, as rectal carcinoma is the most common colonic malignancy resulting in fistula formation.^[18] Transmural carcinomas of the colon and rectum may adhere to adjacent organs and may eventually invade directly, causing development of a fistula. Transitional cell carcinoma of the bladder is the next most common malignancy-related pathology.^[19] Occasionally, carcinomas of the cervix, prostate, and ovary are implicated, and incidents involving small-bowel lymphoma have been reported.^[20]

Although malignancy is the second most common cause of enterovesical fistula formation, such an event is uncommon today because most carcinomas are diagnosed and treated prior to this advanced stage.

Iatrogenic pathophysiology

Iatrogenic fistulae are usually induced by surgical procedures, primary or adjunctive radiotherapy, and/or postprocedural infection. Surgical procedures, including prostatectomies, resections of benign or malignant rectal lesions, and laparoscopic inguinal hernia repair, are well-documented causes of rectovesical and rectourethral fistulae.^{[21, 22]} Unrecognized rectal injury at the time of radical prostatectomy is an uncommon but well-documented etiology of rectourethral fistula.

External beam radiation or brachytherapy to bowel in the treatment field can eventually lead to fistula development. Radiation-associated fistulae usually develop years after radiation therapy for a gynecologic or urologic malignancy. The incidence of radiation-induced fistula associated with gynecological cancers (most commonly cervical cancer) is approximately 1%, many of which are rectovaginal or vesicovaginal.^[23]

Fistulae develop spontaneously after perforation of the irradiated intestine, with the development of an abscess in the pelvis that subsequently drains into the adjacent bladder. Radiation-associated fistulae are usually complex and often involve more than one organ (eg, colon to bladder). Because of improvements in radiotherapy techniques, the incidence of this complication is decreasing. Although rare, fistulae due to cytotoxic therapy have been reported in a patient undergoing a CHOP (cyclophosphamide, doxorubicin, vincristine, prednisolone) regimen for non-Hodgkin lymphoma.^[24]

Traumatic pathophysiology

Urethral disruption caused by blunt trauma or a penetrating injury can result in fistulae, but these fistulae are typically rectourethral in nature. Penetrating abdominal or pelvic trauma, such as a gunshot wound, may result in fistula formation between both small and large bowel, including the rectum with the bladder. In a recent review of complications of penetrating rectal and bladder injuries, fistula formation occurred only in the presence of bowel and bladder injuries.^[25] Foreign bodies in the bowel (eg, swallowed chicken bones or toothpicks) and peritoneum (eg, lost gallstone during laparoscopic cholecystectomy) have been reported as a cause of colovesical fistulae.^{[26, 27, 28, 29, 30]}

The presenting symptoms and signs of enterovesical fistulae occur primarily in the urinary tract. Symptoms include suprapubic pain, irritative voiding symptoms, and symptoms associated with chronic urinary tract infection (UTI). The hallmark of enterovesical fistulae may be described as Gouverneur syndrome, namely, suprapubic pain, frequency, dysuria, and tenesmus. Other signs include abnormal urinalysis findings, malodorous urine, pneumaturia, debris in the urine, hematuria, and UTIs.^[31]

The severity of the presentation also varies. Chronic UTI symptoms are common, and patients with enterovesical fistula frequently report numerous courses of antibiotics prior to referral to a urologist for evaluation. Urosepsis may be present and can be exacerbated in the setting of obstruction. It has been demonstrated in dog models that surgically created colovesical fistulae are tolerated well in the absence of obstruction.^[32]

Pneumaturia and fecaluria may be intermittent and must be carefully sought in the history. Pneumaturia occurs in approximately 50%-60% of patients with enterovesical fistula but alone is nondiagnostic, as it can be caused by gas-producing organisms (eg, Clostridium species, yeast) in the bladder, particularly in patients with diabetes mellitus (ie, fermentation of diabetic urine) or in those undergoing urinary tract instrumentation. Pneumaturia is more likely to occur in patients with diverticulitis or Crohn disease than in those with cancer. Fecaluria is pathognomonic of a fistula and occurs in approximately 40% of cases. Patients may describe passing vegetable matter in the urine. The flow through the fistula predominantly occurs from the bowel to the bladder. Patients very rarely pass urine from the rectum.^[18]

Symptoms of the underlying disease causing the fistula may be present. Abdominal pain is more common in patients with Crohn disease, but an abdominal mass is discovered in fewer than 30% of patients. In patients with Crohn disease who have a fistula, abdominal mass and abscess are more common.^[18]

The documented presence of a fistula that is causing symptoms or adversely affecting quality of life is an indication for surgical intervention in patients with enterovesical fistulae. Fistulae should be repaired in patients with abdominal pain, dysuria, malodorous urine, incontinence, urinary outlet obstruction, recurrent UTIs, bouts of sepsis, and/or pyelonephritis. Patients at high surgical risk may be treated with medical therapy and catheter drainage but may ultimately require at least diverting surgery if symptoms persist. Patients with terminal cancer are often better treated conservatively or with simple diversions.

Fistula formation is believed to evolve from a localized perforation to which an adjacent viscus adheres. The pathologic process is almost always intestinal and characteristic to particular intestinal segments that adhere to the bladder. The segments most commonly in proximity to the bladder include the rectum, sigmoid colon, ileum, jejunum, and appendix. Furthermore, the segment of bowel that is involved can suggest the intestinal pathology.

Colovesical fistulae primarily result from sigmoid diverticular disease. Ileovesical fistulae are most likely associated with Crohn disease. Rectovesical fistulae are more commonly due to trauma, surgery, or malignancy. Appendicovesical fistulae tend to be associated with a history of appendicitis.

Poor overall general health, inability to tolerate general or regional anesthesia, and terminal cancer are contraindications to aggressive management to cure a fistula. Patients with these contraindications may be served better with medical therapy or less-invasive diversions (eg, colostomy, ureterostomy, percutaneous drainage).