Radiological Category GastrointestinalGenitourinary Principal Modality 1 Computed Tomography

Case History 53 -year-old man with dull lower abdominal pain and fever for a

Radiological Presentations LPO Hypaque enema LPO Cystogram

Test Your Diagnosis Which one of the following is your choice for the appropriate

Findings and Differentials Findings: Coronal CT images show markedly thickened sigmoid colon bowel wall

Discussion • Crohn’s disease is a common cause of many types of fistulas. The

Discussion • Diverticulitis is an inflammation of diverticula and can be associated with perforation

Discussion • Colon carcinoma is the second most common cause of colovesical fistula. Many

Diagnosis Diverticulitis with colovesical fistula.

References Brant WE. Abdomen and Pelvis. In: Brant WE, Helms CA. Fundamentals of Diagnostic

References Ravichandran S, Ahmed HU, Matanhelia SS, Dobson M. Is There a Role for

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Radiological Category: Gastrointestinal/Genitourinary Principal Modality (1): Computed Tomography Principal Modality (2): Fluoroscopy Case Report 704 Submitted by: Craig E Cook, M. D. Faculty reviewer: Verghese George, M. D. The University of Texas Medical School at Houston Date accepted: 13 April 2010

Case History 53 -year-old man with dull lower abdominal pain and fever for a few weeks.

Radiological Presentations

Radiological Presentations LPO Hypaque enema LPO Cystogram

Test Your Diagnosis Which one of the following is your choice for the appropriate diagnosis? After your selection, go to next page. • Crohn’s disease with colovesical fistula • Diverticulitis with colovesical fistula • Cystitis with vesicocolonic fistula • Colon carcinoma with colovesical fistula

Findings and Differentials Findings: Coronal CT images show markedly thickened sigmoid colon bowel wall with multiple diverticula and significant pericolonic fat stranding. An area of soft tissue density extending from the sigmoid to the bladder with locules of air internally is concerning for colovesical fistula. There is a focal area of bullous edema/thickening in the bladder wall in the area concerning for fistula. The terminal ileum is normal. Cystogram does not demonstrate fistula. However, a clinical diagnosis of fistula was made when fecal material drained from the Foley catheter with the contrast. Hypaque enema shows contrast passing freely into the sigmoid colon with multiple diverticula and luminal narrowing secondary to bowel wall thickening. The bladder fills with contrast and drains via Foley catheter. A fistulous tract is demonstrated between the sigmoid colon and urinary bladder. Differentials: • Crohn’s disease with colovesical fistula • Diverticulitis with colovesical fistula • Cystitis with vesicocolonic fistula • Colon carcinoma with colovesical fistula

Discussion • Crohn’s disease is a common cause of many types of fistulas. The most common fistulas are enterocutaneous, enterovesical and rectouterine/vaginal. Colovesical fistulas are less commonly caused by Crohn’s than other causes. Crohn’s disease in the acute phase is typically characterized by minimal luminal narrowing and classically the “target sign, ” representing an enhancing mucosa and muscularis propria and intervening relative hypoattenuation of the thickened and edematous submucosa. Chronically, there is typically increased luminal narrowing and inflammatory changes without the “target sign. ” This particular inflammatory bowel disease can have ulceration and wall thickness anywhere from the mouth to the anus, usually with skip lesions. The most common location to see disease is the terminal ileum/cecum. This patient does not demonstrate the “target sign” and the terminal ileum is normal. • Cystitis does not commonly cause fistulas, but can easily mimic a fistula. Gasforming bacterial infections in the urine or bladder can give the appearance of a fistula with the colon. The typical appearance of cysitis is bullous edema of the bladder mucosa in the acute phase and a contracted, irregular thick-walled bladder in the chronic phase. A potentially serious complication of cystitis is gas in the bladder wall and/or lumen, known as emphysematous cystitis.

Discussion • Diverticulitis is an inflammation of diverticula and can be associated with perforation and intramural or localized pericolic abscess. Diverticulitis is the most common cause of colovesical fistula. While colovesical fistula is the most common type of fistula associated with diverticulitis, other common types of fistula include colovaginal and coloenteric. Fistulas result from paracolic abscess extension into adjacent structures and complicate 2 -20% of patients with diverticular disease. The most common presenting symptoms are abdominal pain, dysuria, fecaluria, hematuria, weight loss and pneumaturia. The vast majority of these patients will have at least laboratory evidence of a urinary tract infection as well. The mainstays of diagnosis were excretory urography, cystography, barium enema and cystoscopy prior to the advent of CT and MR. However, CT and MR remain imperfect at proving a fistulous tract. CT is very accurate at predicting the correct location of a fistula, but poor at actually demonstrating a fistulous tract. The CT findings suggesting fistula are repeatedly demonstrated in the literature as presence of air within the bladder (provided there’s been no prior instrumentation), focal bladder wall thickening, focal bowel wall thickening, extravesical soft-tissue mass, direct adherence of bowel wall to bladder and presence of orally or rectally administered contrast material within the bladder (provided there’s no intravenous contrast). Other studies have tried to prove that MR is better at demonstrating a fistula, but the current expense and lack of emergent availability and MR-related research prevent widespread use of MR for diagnosis.

Discussion • Colon carcinoma is the second most common cause of colovesical fistula. Many of the CT findings of diverticulitis with fistula (focal wall thickening with surrounding inflammation, extracolonic/vesical soft tissue mass) can be seen in the setting of colon carcinoma with fistula. Therefore, in the setting of colovesical fistula suspected secondary to diverticulitis, colonoscopy following the acute phase of disease is recommended to rule out malignancy. Moreover, the sigmoid colon is the most common place to find both diverticulitis and colon carcinoma, further complicating the diagnosis of one versus the other. Fistulae caused by colon carcinoma and diverticulitis also share many of the same clinical characteristics, including abdominal pain, weight loss and dysuria. The most definitive way to confirm the diagnosis is by colonoscopy.

Diagnosis Diverticulitis with colovesical fistula.

References Brant WE. Abdomen and Pelvis. In: Brant WE, Helms CA. Fundamentals of Diagnostic Radiology. Philadelphia: Lippincott Williams and Wilkins; 2007: 858 -860, 904. Goldman SM, Fishman EK, Gatewood OMB, Jones B, Siegelman SS. CT in the Diagnosis of Enterovesical Fistulae. American Journal of Roentgenology. June 1985; 44: 1229 -1233. Jarrett TW, Vaughan ED Jr. Accuracy of Computerized Tomography in the Diagnosis of Colovesical Fistula Secondary to Diverticular Disease. The Journal of Urology. January 1995; 153: 44 -46. Nuño-Guzmàn CM, Hernàndez-Carlìn JM, Almaguer FI. Colovesical, coloenteric, colocutaneous fistula and hip septic arthritis secondary to sigmoid diverticulitis [letter to the editor]. Int J Colorectal Dis. 17 November 2009. Pickhardt PJ, Bhalla S, Balfe DM. Acquired Gastrointestinal Fistulas: Classification, Etiologies and Imaging Evaluation. Radiology. 2002; 244(1): 9 -23.

References Ravichandran S, Ahmed HU, Matanhelia SS, Dobson M. Is There a Role for Magnetic Resonance Imaging in Diagnosing Colovesical Fistulas? Urology. 2008; 72(4): 832 -837. Weissleder R, Wittenberg J, et al. Primer of Diagnostic Imaging. 4 th ed. Philadelphia: Mosby Elsevier; 2007: 197 -206. Stat. Dx