Diverticular fistulas

INTRODUCTION — 

Fistula formation is one of the complications of diverticulitis, accounting for 17 to 27 percent of surgically treated cases of diverticular disease [1]. Here we describe the symptoms, diagnosis, and treatment of the most common types of diverticular fistulas. These fistulas may also be caused by etiologies other than diverticulitis (eg, Crohn disease, obstetrical trauma, malignancy, or radiation), which are discussed in the following topics:

●(See "Colovesical fistulas".)

●(See "Enterocutaneous and enteroatmospheric fistulas".)

●(See "Rectovaginal and anovaginal fistulas".)

●(See "Surgical approach to radiation enteritis".)

General discussion of colonic diverticulitis and its treatment can be found in the following topics:

●(See "Clinical manifestations and diagnosis of acute colonic diverticulitis in adults".)

●(See "Acute colonic diverticulitis: Triage and inpatient management".)

●(See "Acute colonic diverticulitis: Outpatient management and follow-up".)

●(See "Acute colonic diverticulitis: Surgical management".)

EPIDEMIOLOGY — 

Diverticulitis in Western countries usually involves the sigmoid colon, and fistulization most frequently arises from this segment. The most common types of fistulas are colovesical (65 percent) and colovaginal (25 percent) fistulas, followed by coloenteric (7 percent), colouterine (3 percent), and colocutaneous fistulas [1]. However, a fistula can develop from the sigmoid colon to any adjacent organ or sites in the pelvis (image 1) [2]. Fistulization to multiple pelvic organs has also been reported in 10 percent of patients [1].

●Diverticulitis is the most common cause of colovesical fistulas, accounting for 40 to 90 percent of cases [3-5]. A colovesical fistula is found in 3 to 4 percent of patients who have surgery for diverticulitis [6]. Although diverticulitis occurs with a slight female predominance, colovesical fistulas secondary to diverticulitis have a distinct (2:1 to 3:1) male predominance [7]. It is likely that the uterus protects the bladder from the inflamed sigmoid colon; this hypothesis is supported by the observation that most female patients with colovesical or colovaginal fistulas have a prior hysterectomy [1,8].

Fewer than half of patients with a diverticular colovesical fistula have a history of prior treatment for diverticulitis; in the remainder, diverticular disease is initially diagnosed when the fistula becomes clinically evident [4,9]. Alternative causes of colovesical fistulas include Crohn disease and colorectal or bladder malignancies. (See "Colovesical fistulas".)

●Colovaginal fistulas are the most common diverticular fistulas to a female genital organ and most commonly occur in older individuals with a prior hysterectomy [10]. Only one-fourth to one-third of patients with a diverticular colovaginal fistula report a history of diverticulitis [10,11]. Diverticulitis is the most common cause of colovaginal fistulas, comprising 80 to 90 percent of the cases in most series [11,12]. Other causes include Crohn disease and colonic and gynecologic malignancies.

●Coloenteric fistulas only comprise 3 to 7 percent of all diverticular fistulas [1,13].

●Colouterine fistulas due to diverticulitis are rare and described in case reports only. Most affected patients are in their 70s and 80s. Alternative etiologies of colouterine fistulas are more common and include spontaneous rupture of a gravid uterus, obstetric trauma, pelvic malignancy, and radiation side effects [14].

CLINICAL FEATURES — 

Although the origin of diverticular fistulas is the colon, many patients present with extragastrointestinal symptoms.

●Colovesical fistula – Patients typically present with urinary symptoms including dysuria or recurrent/recalcitrant urinary tract infections (100 percent), pneumaturia (71 percent), and fecaluria (51 percent) [4,15]. Other symptoms occurring in fewer than 50 percent of patients include crampy abdominal pain, diarrhea, hematuria, and micturition per rectum. Rarely do patients present with an acute abdomen. Physical examination is frequently unremarkable. Occasionally, an abdominal or pelvic mass is palpable (<30 percent), which represents a thickened colon or a phlegmon [1]. A urinalysis is invariably abnormal, often with polymicrobial growth on urine culture.

●Colovaginal fistula – Most patients report discharge of flatus or feces from the vagina; about half report abdominal pain [1,10]. On vaginal speculum examination, a fistulous opening may be identified at the apex of the vagina in 30 to 87 percent of patients, most commonly on the left side [1,10,11]. In some patients, a flexible sigmoidoscopy may be used to perform the vaginal examination. (See "Rectovaginal and anovaginal fistulas", section on 'Evaluation and diagnosis'.)

●Coloenteric fistula – Diarrhea is the most prevalent symptom. The presence of a coloenteric fistula should be suspected when a patient with known diverticular disease suddenly develops severe, watery diarrhea [16]. Other symptoms include abdominal pain and weight loss, often chronic [1]. An abdominal mass is the most common abnormal physical finding reported in the literature, representing the sequela of chronic inflammation [1].

●Colouterine fistula – Patients typically present with foul-smelling, hemorrhagic, purulent, or feculent vaginal discharge that becomes a recurring complaint. Some may also present with lower abdominal pain [17]. The acuity of the initial presentation may vary widely from no fever or other constitutional symptoms to florid sepsis [18]. Physical examination may be unrevealing or only demonstrate a pelvic mass. Vaginal speculum examination typically reveals abnormal vaginal discharge per cervical os. This differs from colovaginal fistulas, which typically drain from an opening at the apex (most often left-sided) of the vagina. Vaginal or cervical cultures usually show polymicrobial growth. Although colouterine fistulas may have a similar initial presentation to that of a colovaginal fistula, the latter almost always occurs after hysterectomy. It is presumed that the thick uterine wall is a deterrent to fistulization.

DIAGNOSIS — 

Diverticular fistulas should be suspected in patients with a history of diverticulitis who present with abnormal urinary or vaginal discharges.

●Colovesical fistulas should be suspected in patients who present with pneumaturia or fecaluria. The diagnosis is typically established by identifying air within the urinary bladder on imaging studies, in the absence of recent urinary tract instrumentation.

●Colovaginal fistulas should be suspected in patients reporting passage of flatus or feces through the vagina. The diagnosis is typically confirmed by identifying a fistulous opening at the apex of the vagina, most often on the left side, supported by imaging studies and, in some cases, operative findings.

●Coloenteric fistulas should be suspected when a patient suddenly develops severe, watery diarrhea. The diagnosis is confirmed by imaging studies.

●Colouterine fistulas should be suspected in postmenopausal patients who present with persistent or recurring symptoms of a foul-smelling, hemorrhagic, purulent, or feculent vaginal discharge. The diagnosis is confirmed by imaging studies showing air and debris within the uterus.

DIAGNOSTIC EVALUATION — 

An abdominopelvic computed tomography (CT) with oral and intravenous contrast is the appropriate initial evaluation for a suspected diverticular fistula. Prior to surgical repair, a colonoscopy should be performed to exclude colon cancer. Some patients may require separate evaluation of other involved pelvic organs (eg, bladder, vagina, uterus).

●Abdominopelvic CT – The diagnosis is usually made by the findings of:

•Local colonic thickening adjacent to an area of thickened bladder, vagina, or uterus, indicating inflammation.

•Air in bladder, vagina, or uterus with no recent instrumentation of those organs. This findings is highly sensitive and specific for a diverticular fistula [19].

•Occasionally, the CT contrast could extravasate into a pelvic organ or outline the fistula; however, this is rare.

•CT also provides information regarding the presence of a fluid collection, phlegmon, or abscess. These should be addressed prior to surgical repair of the fistula.

●Colonoscopy – Most importantly, colonoscopy permits the entire colon and rectum to be surveilled. Findings of colorectal cancer will alter the operative plan significantly. The direct yield of colonoscopic visualization of a diverticular fistula is low (0 to 3 percent) [9,20]. Often, multiple sigmoid diverticula are seen, but the internal fistula orifice may be difficult to identify. However, there may be abnormalities suggestive of the diagnosis in up to 25 percent of endoscopies, such as diverticula and mucosal erythema [20].

●Selected evaluation of other pelvic organs – A cystoscopy should be performed if there is a concern for a malignant bladder fistula based on clinical or imaging findings. Cystoscopy, as with other diagnostic modalities, is unlikely to directly visualize the fistula. The diagnosis is suggested by localized inflammation and bullous edema of the bladder mucosa in up to 96 percent of patients [20]. In these cases, cystoscopy provides information about the location of the bladder lesion in relation to the ureteral orifices. Many consider such findings too nonspecific, and thus find cystoscopy to be useful in only approximately 40 percent of cases [1,9].

Because of the presence of vaginal discharge in a postmenopausal individual, most patients with colouterine fistulas are evaluated with endovaginal ultrasound, which may show pyometrium, which is consistent with fistulization. Cervical dilation may be performed to improve uterine drainage in the presence of pyometrium [21].

Conventional barium enema, vaginography, cystogram, and intravenous urography have very low sensitivity in detecting fistulas and add little information already gathered from CT [1,9,10]. However, some patients with a diverticular fistula may have a distal sigmoid colonic stricture, which is well demonstrated on a contrast enema [16].

TREATMENT — 

Surgery is the only definitive treatment for a diverticular fistula. In appropriate surgical candidates, we suggest operative management rather than observation or medical management. Diverticular fistulas rarely spontaneously close; a long-standing fistula can cause disturbing symptoms, recurrent infections (eg, urinary tract infection or pyelonephritis), and eventual end-organ damage in some cases (eg, kidney injury complication of colovesical fistula). Patients with minimal symptoms and poor surgical candidates are managed medically or symptomatically.

Operative management — Surgical treatment of diverticular fistulas involves identification and division of the fistula, resection of the involved portion of the colon, and repair of the involved pelvic organs if necessary. A primary colorectal anastomosis is typically appropriate. Repair should be performed electively and is amenable to a minimally invasive approach [6,22-28]. (See "Acute colonic diverticulitis: Surgical management", section on 'Open versus minimally invasive approach'.)

Colon resection — The segment of the colon where the fistula originates (usually the sigmoid colon) should be completely resected in the same manner as when diverticular surgery is performed for other indications. Incomplete resection of the sigmoid colon at the distal margin or simple division of the fistula without colon resection will lead to unacceptably high recurrence rates [29]. (See "Acute colonic diverticulitis: Surgical management", section on 'Operative considerations'.)

The presence of a diverticular fistula is rarely an indication for urgent surgical intervention (2 percent [1]). Thus, an elective, one-stage procedure with resection and primary anastomosis should be feasible in the majority of patients (84 percent [6]). In this setting, the complication rate of a primary anastomosis is comparable to rates associated with sigmoidectomy for other indications [30,31]. A one-stage procedure is associated with decreased morbidity and length of hospital stay [20]. If conditions are suboptimal due to extensive inflammation, operation in two stages (eg, proximal diversion or Hartmann procedure) may be necessary [6].

A drain is not required from the standpoint of colon resection or the creation of a coloproctostomy; if a bladder resection and closure is performed, a urologist will often request that a drain be placed to assist with identifying a urine leak. Placement of localizing ureteral stents, while not mandatory, may be helpful since the degree of inflammation encountered is often moderate to severe.

Pelvic organ repair — The management of other involved pelvic organs should primarily depend on the specific organ and the size of the defect.

●Bladder – In most patients with a colovesical fistula, the colon can be "pinched off" the bladder with either no visible defect or a very small defect in the bladder; management in this setting ranges from merely leaving an indwelling bladder catheter for 7 to 10 days, to the addition of sutures over the fistula site in the bladder. With a larger bladder defect, suture closure is usually adequate; resection of the bladder for benign colonic disease is rarely necessary. Mobilization of an omental pedicle flap interposed between the colorectal anastomosis and the bladder is unproven to prevent a recurrent fistula, but is performed by some surgeons to help prevent this complication [32].

Traditionally, bladder drainage via a urethral catheter is continued for a minimum of seven days [1]. However, this length of time is not a mandatory minimum. Most studies report an average catheter duration of 7 to 14 days, with up to 5 percent of patients developing urinary complications [6]. In one report, the authors advocated intraoperative methylene blue bladder instillation and suggested that the urinary catheter can be removed earlier when there is no methylene blue extravasation, without risking a bladder leak [6].

Postoperative cystogram prior to removal of the bladder catheter is commonly performed but remains a point of debate. In some series, postoperative cystogram was positive in none of the patients [33]. In other studies, it detected bladder leaks after a complex bladder repair [6] In the absence of high-quality evidence, the use of a postoperative cystogram should be directed by clinical indications and surgeon preference; most surgeons obtain a cystogram prior to removing the bladder catheter.

●Vagina – In patients with a colovaginal fistula, the colon can either be "pinched off" or resected off the vagina with a colpotomy. The management of the vagina usually only requires separation of this organ from the colon. The fistula is rarely large enough to warrant suture closure of the vaginal fistula site. Following surgery, patients should be instructed to refrain from sexual intercourse or insertion of anything into the vagina for at least six weeks to ensure complete healing of the vagina.

●Small intestine – In patients with a coloenteric fistula, the segment of small bowel involved in a diverticular coloenteric fistula is most commonly the terminal ileum; however, jejunal fistulas have also been described [16]. Either way, colon and small bowel resection, both with primary anastomosis, are typically performed to manage this type of fistula [1].

●Uterus – The colouterine fistula usually involves the fundus of the uterus and the sigmoid colon [21]. After colon resection, the management of the uterus varies. In cases where a malignant etiology cannot be excluded, or where the colon and uterus cannot be separated because of chronic inflammation, the uterus should be removed en bloc with the colon by performing a hysterectomy [17,21]. On the other hand, if the colon can be easily dissected off the uterus and the suspicion for a malignant process is low, the uterine fistulous opening can be closed, and the uterine cavity drained via the cervical os [14]. Since diverticular colouterine fistulas tend to occur in older patients, the latter approach may be less morbid and better tolerated; however, some gynecologists favor hysterectomy because it may be very difficult to drain the uterus due to cervical stenosis, which is common in postmenopausal patients.

Nonoperative management — Nonoperative management of a diverticular fistula is feasible but should only be offered to older patients with minimal symptoms or those who are otherwise poor operative candidates [6]. In the absence of a pelvic abscess, the risk of overwhelming sepsis is low [34,35].

SOCIETY GUIDELINE LINKS — 

Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Colonic diverticular disease".)

INFORMATION FOR PATIENTS — 

UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Beyond the Basics topics (see "Patient education: Diverticular disease (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●Epidemiology – Fistula formation is one of the complications of diverticulitis, accounting for about 20 percent of surgically treated cases of diverticular disease. The major types of fistulas are colovesical (65 percent) and colovaginal (25 percent) fistulas, followed by coloenteric (7 percent) and colouterine (3 percent) fistulas. (See 'Introduction' above.)

●Clinical features and diagnosis – Although the origin of a diverticular fistula is the colon, patients typically present with extragastrointestinal symptoms. Diverticular fistulas should be suspected in patients with a history of diverticulitis who present with abnormal urinary or vaginal discharges. (See 'Diagnosis' above.)

•Colovesical fistulas should be suspected in patients who present with pneumaturia or fecaluria. The diagnosis is typically established by identifying air within the urinary bladder on imaging studies, in the absence of recent urinary tract instrumentation.

•Colovaginal fistulas should be suspected in patients reporting passage of flatus or feces through the vagina. The diagnosis is typically confirmed by identifying a fistulous opening at the apex of the vagina, most often on the left side, supported by imaging studies and, in some cases, operative findings. These almost always occur after hysterectomy.

•Coloenteric fistulas should be suspected when a patient suddenly develops severe, watery diarrhea. The diagnosis is confirmed by imaging studies.

•Colouterine fistulas should be suspected in postmenopausal patients who present with foul-smelling, hemorrhagic, purulent, or feculent vaginal discharge that becomes a recurring complaint. The diagnosis is confirmed by imaging studies showing air and debris within the uterus.

●Diagnostic evaluation – We perform an abdominopelvic CT with oral and intravenous contrast as the initial evaluation for a suspected diverticular fistula. Prior to surgical repair, a colonoscopy should be performed to exclude colon cancer. Some patients may require separate evaluation of other involved pelvic organs (eg, bladder, vagina, uterus). (See 'Diagnostic evaluation' above.)

●Treatment – Surgery is the only definitive treatment for a diverticular fistula. Diverticular fistulas rarely spontaneously close; a long-standing colovesical fistula can cause disturbing symptoms, recurrent infections (eg, pyelonephritis), and eventual end-organ damage (eg, kidney injury from renal parenchymal scarring) in some cases. Patients with minimal symptoms or poor surgical candidates are managed medically or symptomatically. (See 'Treatment' above.)

Surgical treatment of colovesical fistulas involves identification and division of the fistula, resection of the involved portion of colon, and repair of any involved pelvic organs (eg, bladder, vagina, uterus) as necessary. A primary colorectal anastomosis is typically appropriate. Repair should be performed electively and is amenable to a minimally invasive approach.

ACKNOWLEDGMENT — 

The UpToDate editorial staff acknowledges John H Pemberton, MD, who contributed to earlier versions of this topic review.