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]. 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 fistulas (65 percent) and colovaginal fistulas (25 percent), followed by coloenteric (7 percent), colouterine (3 percent), and colocutaneous fistulas [1]. However, a fistula can form to any adjacent organ or structure and has been described in many unexpected sites (image 1) [2]. Fistulization to multiple pelvic organs has also been reported in 10 percent of patients [1].

Here we describe the symptoms, diagnosis, and treatment of the four 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: Medical management".)

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

DIVERTICULAR COLOVESICAL FISTULA — 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 to 3:1) male predominance [1,7]. It is likely that the uterus protects the bladder from the inflamed sigmoid colon; this hypothesis is supported by the observation that the majority of women with colovesical or colovaginal fistulas have had a previous hysterectomy [1,3,8].

Fewer than half of patients with a diverticular colovesical fistula have a history of diverticulitis; in the remainder, diverticular disease is diagnosed when the fistula becomes clinically evident [5,7]. Alternative causes of colovesical fistulas include Crohn disease and colorectal or bladder malignancy. (See "Colovesical fistulas".)

Clinical manifestations — Although the origin of colovesical fistula is the colon, patients typically present with urinary symptoms including dysuria or recurrent/recalcitrant urinary tract infections (100 percent), pneumaturia (71 percent), and fecaluria (51 percent) [1,3,5,7]. Other symptoms occurring in fewer than 50 percent of patients are crampy abdominal pain, diarrhea, hematuria, and passage of urine per rectum [1,7]. Rarely do patients present with an acute abdomen.

Physical examination is frequently unremarkable. Occasionally an abdominal or pelvic mass is palpable (<30 percent) [1]. The urinalysis is invariably abnormal, and urine cultures reveal the nonspecific finding of polymicrobial growth.

Diagnosis — Colovesical fistulas should be suspected in patients who present with pneumaturia or fecaluria. The diagnosis is made by imaging studies in some and operative findings in the remainder.

Diagnostic evaluation — Computed tomography (CT), contrast enema, colonoscopy, cystoscopy, and intravenous urography (IVU) have all been employed for the diagnosis of colovesical fistula. The diagnostic yield of each modality varies widely in different hands. There is no gold standard test.

Our approach is to perform abdominopelvic CT with oral or rectal contrast (but not intravenous [IV] contrast) to diagnose a colovesical fistula and to perform colonoscopy to exclude a malignancy. It is prudent to add cystoscopy to address any concern for a malignant bladder fistula.

●Although the fistula itself is opacified in some CT scans, the diagnosis is usually made by the combination of local colonic thickening adjacent to an area of thickened bladder, associated diverticula, and oral contrast material or air in the bladder (prior to instrumentation of the urinary tract); this constellation of findings is highly sensitive and specific for colovesical fistula from diverticular disease [9]. CT not only predicts the presence of a fistula more accurately than contrast enema or colonoscopy but also provides information regarding extraluminal inflammation, particularly the relationship between a phlegmon and the ureters.

●The direct yield of colonoscopic visualization of a colovesical fistula is low (0 to 3 percent) [3,7]. Often, multiple sigmoid diverticula are seen, but the actual site of fistulization may be difficult to identify. However, there may be abnormalities suggestive of the diagnosis in up to 25 percent of endoscopies [3]. More importantly, colonoscopy permits the entire colon and rectum to be surveilled. Findings of a colorectal cancer, whether etiologic or incidental to the fistula, will alter the operative plan significantly to an oncologic resection.

●Cystoscopy is highly recommended by some authors. As with the other diagnostic modalities, direct visualization of the fistula is uncommon. However, the diagnosis is suggested by localized inflammation and bullous edema of the bladder mucosa in up to 96 percent of patients [3]. In these cases, cystoscopy provides information about the location of the bladder lesion in relation to the ureteral orifices. Others, however, consider such findings too nonspecific and find cystoscopy to be useful in only approximately 40 percent of cases [1,7].

Intravenous urography is rarely useful [1,7]. Conventional radiographic cystogram and barium enema (image 2) also have very low sensitivity in detecting colovesical fistulas and do not add much to that already gathered from the combination of CT, colonoscopy, and possibly cystoscopy.

The poppy seed test, which is largely historical, involves oral ingestion of 50 grams of poppy seeds mixed in a beverage followed by visual inspection of urine samples during the next 48 hours and is highly sensitive (94.6 percent), inexpensive, and safe and therefore is advocated by some to be the initial test for a suspected colovesical fistula [10]. However, it does not provide any anatomical details of the fistula or hint at its etiology (diverticular versus malignant). Thus, the diagnostic evaluation consisting of CT, colonoscopy, and possibly cystoscopy is still required despite the poppy seed test.

Treatment — Diverticular fistulas do not generally close spontaneously. Therefore, we suggest operative management in appropriate surgical candidates.

Operative management — Surgical treatment of colovesical fistulas involves identification and division of the fistula, resection of the involved portion of colon, and bladder repair if necessary.

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 diverticula-laden sigmoid colon or simple division of the fistula without colon resection will lead to unacceptably high recurrence rates [11].

The presence of a diverticular colovesical 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 no higher than that of a Hartmann's procedure [12,13]. The one-stage procedure is associated with decreased morbidity and length of hospital stay [3]. If possible, the colonic anastomosis should be separated from the area of inflammation (eg, by interposed omentum) [1]. If conditions are suboptimal due to extensive inflammation, operation in two stages may be necessary (12 percent proximal diversion, 4 percent Hartmann’s procedure [6]). (See "Acute colonic diverticulitis: Surgical management".)

We routinely leave a peritoneal drain at the time of surgery. We also perform preoperative ureteral stenting if the fistula site is near the trigone or if the inflammatory mass persists until the time of the operation. Ureteral stents help identify and protect the trigone in difficult cases.

Management of the bladder aspect depends upon the size of the defect and surgeon preference. In most patients, 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 additionally placing a few sutures over the site in the bladder, to leaving a closed suction drain behind the bladder. With a larger bladder defect, simple closure is usually preferred to formal resection and repair, which is almost never necessary. The local induration will resolve once the inciting cause (ie, colon) has been removed [14]. Mobilization of an omental pedicle flap may be useful to interpose between the colorectal anastomosis and the bladder, allowing for healthy noninflamed tissue to separate the two structures.

Traditionally, bladder drainage via a urethral catheter is continued for a minimum of seven days [1]. However, the practice is not standardized and is evolving. Most studies report an average catheter duration of 7 to 14 days with up to 5 percent 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 via the catheter before removal is commonly performed but widely debated. In some series, postoperative cystogram was positive in none of the patients [15]. In other studies, it detected bladder leaks after a complex bladder repair [6]. In the absence of high-quality evidence, the use of postoperative cystogram should be directed by clinical indications and surgeon preference.

For average patients undergoing diverticular colovesicular fistula repair, we leave the urethral catheter for three to four days after a simple bladder repair and 7 to 10 days after a complex bladder repair. We perform a cystogram before removing the catheter after complex repairs and in complicated clinical situations.

Laparoscopic treatment of colovesical fistulas due to complicated colonic diverticular disease is gaining acceptance because of increasing experience and improved instruments [6,16,17]. In some series, laparoscopic surgery was carried out in the majority of patients [17]. Although it is safe, no study has demonstrated that laparoscopic surgery is superior to open surgery in treating diverticular fistulas [18]. It is important that such complex cases only be performed by surgeons experienced in minimally invasive gastrointestinal surgery.

Nonoperative management — Although surgical intervention is usually recommended for colovesical fistula because of disturbing symptoms (eg, pneumaturia, fecaluria, recurrent urinary tract infections), nonoperative management can be offered to asymptomatic patients who are poor operative candidates [6]. One small series described six patients who underwent observation for 3 to 14 years, being treated only with prophylactic antibiotics [19]. There were no significant complications, such as impairment of renal function or urosepsis. In another series, there was only one death from urosepsis in 26 men managed conservatively for three years; the mortality rate was not different from that of a concurrent group of men who underwent surgery [20]. However, long-term nonoperative management invariably requires repeated courses of antibiotics and indwelling urinary catheters and potentially risks bladder outlet obstruction. Long-term suppressive antibiotic use can lead to the development of antibiotic-resistant organisms and/or Clostridioides difficile colitis complicating further medical management.

DIVERTICULAR COLOVAGINAL FISTULA — Colovaginal fistulas are the most common diverticular fistulas to a female genital organ and most commonly occur in older women with a prior hysterectomy [21]. Only one-quarter to one-third of patients with a diverticular colovaginal fistula report a history of diverticulitis [21,22].

Diverticulitis is the most common cause of colovaginal fistulas, comprising 80 to 90 percent of the cases in most series [22,23]. Other causes include Crohn disease and colonic or gynecologic malignancies.

Clinical manifestations — Most women report discharge of gas or feces from the vagina; about half report abdominal pain [1,21].

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 [1,21,22]. In some patients, a flexible sigmoidoscopy may be used to perform the vaginal examination. (See "Rectovaginal and anovaginal fistulas", section on 'Evaluation and diagnosis'.)

Diagnosis — A colovaginal fistula should be suspected in a patient who complains of gas or feces passage from the vagina. The diagnosis is made by vaginal examination or imaging studies in some patients and operative findings in the remainder.

Diagnostic evaluation — CT, contrast enema, colonoscopy, and vaginography have all been employed for the diagnosis of colovaginal fistula. The diagnostic yield of each modality varies widely in different hands.

Our approach is to perform abdominopelvic CT to diagnose a colovaginal fistula and the presence of diverticulosis and to perform colonoscopy to exclude a malignancy. Even in patients who have an identifiable fistulous opening on the vaginal examination, this evaluation will provide information about the anatomy and possible etiology of the fistula, which may influence operative planning.

●CT imaging is relatively insensitive in detecting the actual fistula but can reveal additional complications of diverticulitis, such as intra-abdominal or pelvic abscesses, which should be drained prior to definitive fistula repair.

●Similarly, although colonoscopy is also insensitive in detecting the actual fistula, it can detect colorectal malignancies, which need to be treated with an oncologic resection, even pelvic exenteration.

●The utility of contrast enema is controversial. In some studies, Gastrografin or barium enemas are highly sensitive in detecting colovaginal fistulas (80 percent) [21], but in other studies, the sensitivity is much lower (30 to 40 percent) [1].

●Anorectal and vaginal examination under anesthesia (with or without gynecology support) may be required to define the anatomy.

Treatment — For the majority of women with a colovaginal fistula, the symptoms are intolerable. Thus, surgical repair is indicated regardless of whether a fistula tract is demonstrated on vaginal examination or imaging studies.

Operative management — Surgical repair of a colovaginal fistula is typically performed electively, rather than urgently. Thus, a one-stage colon resection is feasible in most cases. The procedure is performed transabdominally.

The sigmoid colon is first mobilized. Once the colovaginal fistula is identified, the colon can either be "pinched off" or resected off the vagina with a colpotomy. The segment of the colon involved in the fistulization is then resected. A primary anastomosis is performed unless there is excess inflammation or sepsis in the surrounding tissue or other extraneous conditions, in which case the anastomosis is either protected by a loop ileostomy, or a Hartmann's procedure is performed. (See "Acute colonic diverticulitis: Surgical management".)

The management of the vagina varies by surgeon preference. If a fistulous opening is present, it can be sutured closed with absorbable suture, left open, or covered by an omental patch [21]. The fistula tract invariably closes with very low recurrence rate. Laparoscopic treatment has been reported by experienced surgeons [24,25].

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.

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

DIVERTICULAR COLOENTERIC FISTULA — Coloenteric fistulas only comprise 3 to 7 percent of all diverticular fistulas [1,26].

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 [27]. 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 [1].

Abdominopelvic CT is most commonly performed to diagnose a suspected coloenteric fistula [28]. Prior to surgical repair, colonoscopy should be performed to exclude a malignant fistula. Some patients may have a distal sigmoid colonic stricture, which is best demonstrated on a barium enema [27].

The segment of small bowel involved in a diverticular coloenteric fistula is most commonly the terminal ileum; however, jejunal fistulas have also been described [27]. Either way, colon and small bowel resection, both with primary anastomosis, are typically performed for management of the fistula [1].

DIVERTICULAR COLOUTERINE FISTULA — Colouterine fistulas due to diverticulitis are so rare that the literature only consists of case reports. Most 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 [29]. 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.

All patients present with foul-smelling, hemorrhagic, purulent, or feculent vaginal discharge that lasts for days to months. Some may also present with lower abdominal pain [30]. The acuity of the initial presentation may vary widely from no fever or other constitutional symptoms to florid sepsis [31].

Physical examination may be unrevealing or only demonstrate a pelvic mass. Vaginal speculum examination typically reveals the aforementioned vaginal discharge per os. This differs from colovaginal fistulas, which typically drain from an opening at the apex (most often left) of the vagina. Vaginal or cervical cultures usually show polymicrobial growth, for which patients should be treated with broad-spectrum antibiotics.

Because of the presence of vaginal discharge in a postmenopausal woman, most women with colouterine fistulas are evaluated with endovaginal ultrasound and/or dilation and curettage with hysteroscopy to exclude malignancy. Ultrasound may show pyometrium; curettage may show acute and/or chronic inflammation, both consistent with fistulization. Cervical dilation is indicated to improve uterine drainage in the presence of pyometrium [32]. Abdominopelvic CT may show air and debris within the uterus, another strong indication of colouterine fistula, and diverticulosis/diverticulitis. Colonoscopy should be performed to identify diverticular disease and exclude a distal stricture or malignancy prior to surgery. In case reports, hysterosalpingograms [29], magnetic resonance imaging, hysteroscopy [33], and charcoal challenge tests [34] have been used to diagnose the fistula.

Surgery is the only definitive treatment for colouterine fistula. The fistula usually involves the fundus of the uterus and the sigmoid colon [32]. As the origin of the fistula, the sigmoid colon should be resected, with or without fecal diversion depending on the clinical situation. 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 [30,32]. 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 os [29]. Since diverticular colouterine fistulas tend to occur in older women, 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 in a postmenopausal woman.

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

●Prevalence – 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 fistulas (65 percent) and colovaginal fistulas (25 percent), followed by coloenteric (7 percent) and colouterine fistulas (3 percent). (See 'Introduction' above.)

●Colovesical fistula – Patients with a colovesical fistula typically present with urinary symptoms such as dysuria/urinary tract infection, pneumaturia, and fecaluria; fewer than one-half report a history of diverticulitis. We perform abdominopelvic CT with oral or rectal contrast (but not intravenous [IV] contrast) to diagnose a colovesical fistula and colonoscopy to exclude a malignancy. A cystoscopy can be added if there is any concern for a malignant fistula.

Most patients undergo surgical treatment, which involves identification and division of the fistula, resection of the involved portion of colon with or without primary anastomosis, and bladder repair if necessary. After surgery, we suggest draining the bladder with a urethral catheter (Grade 2C). We generally remove the urethral catheter in three to four days after a simple bladder repair and 7 to 10 days after a complex bladder repair. After complex repairs and in complicated clinical situations, we suggest performing a cystogram before removing the catheter. (See 'Diverticular colovesical fistula' above.)

●Colovaginal fistula – Colovaginal fistulas are the most common diverticular fistulas to a female genital organ and most commonly occur in older women with a prior hysterectomy. Patients report discharge of gas or feces from the vagina, and many have an identifiable fistulous opening at the apex of the vagina, most often on the left side, on vaginal speculum examination. Our approach is to perform abdominopelvic CT to diagnose a colovaginal fistula and to perform colonoscopy to exclude a malignancy.

For the majority of women with a colovaginal fistula, the symptoms are intolerable, so that surgery is indicated. An elective colon resection with primary anastomosis is feasible in most cases with the vagina either "pinched off" the colon or released with a colpotomy. If a vaginal fistulous opening is present, it can be sutured closed with absorbable sutures, left open, or covered by an omental patch. (See 'Diverticular colovaginal fistula' above.)

●Coloenteric fistula – Coloenteric fistulas are rare, and diarrhea is the most common symptom. The presence of a coloenteric fistula should be suspected when a patient with known diverticular disease suddenly develops severe watery diarrhea. Other symptoms include abdominal pain and weight loss. Abdominopelvic CT is most commonly performed to diagnose a suspected coloenteric fistula. Prior to surgical repair, colonoscopy should be performed to exclude a malignant fistula. The segment of small bowel involved in a diverticular coloenteric fistula is most commonly terminal ileum. Colon and small bowel resection, both with primary anastomosis, are typically performed to correct the fistula. (See 'Diverticular coloenteric fistula' above.)

●Colouterine fistula – Colouterine fistulas are rare and mostly occur in older women in their 70s and 80s. Patients present with foul-smelling, hemorrhagic, purulent, or feculent vaginal discharge that lasts for days to months. Vaginal speculum examination typically reveals vaginal discharge per os. Because of the vaginal discharge, patients typically undergo endovaginal ultrasound and/or dilation and curettage to exclude a uterine malignancy. Colonoscopy is performed prior to surgery to exclude colorectal cancer. The fistula usually involves the fundus of the uterus and the sigmoid colon.

Surgery is the only definitive treatment for colouterine fistula, which mandates colon resection with or without diversion. The management of the uterus varies from fistula repair with drainage per os to hysterectomy depending on the clinical situation. (See 'Diverticular colouterine fistula' above.)