Colovesical Fistula: An Uncommon Cause of Hematuria and Rectal Bleeding

Colovesical fistula is an infrequent complication of diverticular disease that presents with pneumaturia, fecaluria, dysuria and, rarely, hematuria or hematochezia. Here we present a case of concurrent hematuria and rectal bleeding arising from a diverticular bleed traversing a previously undiagnosed colovesical fistula. Other causes of colovesical fistula include Crohn's disease, radiation, and malignancy, though it is most commonly caused by complicated diverticulitis as in this case. Computed tomography (CT) imaging, cystoscopy, and gastrograffin enema have been described as high-yield diagnostic tests. Interestingly, colonoscopy is only successful in diagnosing colovesical fistula in approximately 55% of cases. Management often requires surgical intervention, as in this case, given limited success with conservative management. Colovesical fistula should be considered in patients presenting with fecaluria, pneumaturia, and dysuria as well as in cases of hematuria.


Introduction
Colovesical fstula is an uncommon complication of complicated diverticular disease with an estimated prevalence between 2% and 23% [1]. Patients with a colovesical fstula commonly present with pneumaturia, fecaluria, recurrent urinary tract infection (UTI), and symptoms of urinary frequency, though they can rarely present with hematuria. Other etiologies of colovesical fstula include fstulizing Crohn's disease, malignancy, or history of radiation [2]. Here we describe an individual presenting with both hematuria and hematochezia who was found to have a colovesical fstula in the setting of complex diverticular disease.

Case Report
A 66-year-old man presented to the emergency department with acute-onset gross hematuria and rectal bleeding. His medical history was notable for sigmoid and descending colon diverticulosis seen on colonoscopy in 2019 and benign prostatic hyperplasia (BPH), for which he underwent greenlight laser transurethral resection of the prostate 5 months prior. His postoperative course was notable for urinary tract infection, acute urinary retention, and persistent pneumaturia.
Computed tomography (CT) of the abdomen and pelvis revealed sigmoid and bladder wall thickening, intravesicular gas, and a previously undiagnosed colovesical fstula (shown in Figure 1). Te CT was also notable for abnormal prostatic enhancement, iliac lymphadenopathy, and difuse osseous metastatic disease suggestive of metastatic prostate adenocarcinoma which was later confrmed on prostate biopsy.
Colonoscopy showed old blood, sigmoid diverticulosis, and an area of indurated tissue 20 centimeters from the anal verge concerning for the fstula (shown in Figure 2). His presentation was consistent with a diverticular bleed that traversed the fstula, causing both hematuria and rectal bleeding. Te etiology of the fstula was likely a prior episode of diverticulitis given his sigmoid diverticulosis; the location of the fstula was far from the site of any recent urologic instrumentation. Te urine culture from admission grew Escherichia coli, for which he was treated with cephalexin.
After discharge, he underwent robotic sigmoid colectomy with colorectal anastomosis and colovesical fstula takedown.
Tis case highlights a unique presentation of complicated diverticular disease with concurrent hematuria and rectal bleeding caused by diverticular bleeding traversing a colovesical fstula. As in this case, management of diverticular disease complicated by fstulas relies on multidisciplinary discussion including colorectal surgery and urology given bladder involvement. While colovesical fstula rarely presents with hematuria, it should be considered, particularly in patients with known diverticulosis.

Discussion
In this patient, his colovesical fstula most likely stemmed from a prior episode of diverticulitis which is consistent with the sigmoid diverticula seen on his colonoscopy. While diverticular disease accounts for approximately two-thirds of cases of colovesical fstula, other etiologies include malignancy including bladder and colon cancer, radiation, and fstulizing Crohn's disease [2]. Tese patients most commonly presented with pneumaturia, urinary frequency, dysuria, fecaluria, or with fecaluria and terminal pneumaturia considered to be pathognomonic [3]. Interestingly, these patients are rarely found to have leukocytosis or fever [1]. In a retrospective chart review of 39 patients with colovesical fstula, two patients (5%) presented with rectal bleeding, and only one patient (2%) presented with hematuria [2]. Presentation with concurrent hematuria and rectal bleeding has not been described in the existing literature.
Complicated diverticulitis refers to diverticular disease associated with obstruction, abscess, perforation, fstula, or stricture [4]. Tese patients typically present with left lower quadrant pain, changes in bowel movements, and low-grade fever. Uncomplicated diverticulitis can often be managed conservatively with antibiotics and bowel rest. However, recurrent uncomplicated disease or complicated diverticulitis often requires surgical consultation.
Diverticulitis complicated by fstula remains a difcult entity to manage. Approximately 2/3 of diverticular fstulas are colovesical and these most commonly afect the sigmoid colon, as in the patient described above [5]. Te pathogenesis includes rupture of the diverticulum or erosion of a diverticular abscess into the bladder [1]. Men are twice as likely to have a colovesical fstula than women due to the anatomical barrier of the uterus [5]. Other manifestations of diverticulitis complicated by fstula include enterocolonic fstulas which present primarily with diarrhea, and colovaginal fstulas which present with passing stool through the vagina [4].
Diagnosis of colovesical fstula in this case was made with CT imaging with contrast, though demonstrating the fstula radiographically can be challenging. Te literature describes other diagnostic modalities that can be considered. In a study of 39 patients with a colovesical fstula, the diagnosis was made with CT imaging in 80% of cases. Other high-yield diagnostic modalities include cystograms, gastrografn enema, and cystoscopy. Interestingly, the literature estimates the rate of successfully diagnosing a colovesical fstula via colonoscopy at 0% to 55%. Of note, oral charcoal administration and visualization of charcoal per urethra diagnosed colovesical fstula in all fve cases when it was used [2]. Te literature recommends surgical resection given the low likelihood of disease resolution with conservative management [4]. A recent meta-analysis demonstrated a shorter hospital length of stay with similar operating time, postoperative complication rates, and mortality rates in laparoscopic compared to open repair [6].
Tis case highlights an unusual presentation of colovesical fstula in a patient with sigmoid diverticulosis. Colovesical fstula should be considered in patients presenting with pneumaturia, fecaluria, or recurrent urinary tract infection.

Data Availability
No data were used to support this study.

Ethical Approval
Informed consent was obtained from the patient for the publication of their information and imaging.   Case Reports in Gastrointestinal Medicine