Seminal vesicle-rectal fistula is a rarely encountered complication in patients. The reported causes of this condition are Crohn's disease,^1,2 diverticulitis,^3–6 operative complications of the prostate,^7,8 direct invasion of rectal cancer,⁹ congenital anomalies,¹⁰ iatrogenic perforation by transrectal aspiration or seminal vesicle abcess,¹¹ secondary vesiculitis,¹² and anastomotic leakage after low anterior resection (LAR) of the rectum.^2,13–18 We could find only 9 reported cases of seminal vesicle-rectal fistula after LAR in the PubMed database.

Here, we present a case of a seminal vesicle-rectal fistula that developed after LAR in a patient and review the clinical manifestation, radiographic findings, and treatment procedure for this condition.

Case Report

A 53-year-old man was admitted to our hospital for an operation for rectal cancer. The patient had no history of health disorders. He had occasional melena and was diagnosed with adenocarcinoma in the rectum above the peritoneal reflection (Ra) on colonoscopy (Fig. 1a) and barium enema examinations (Fig. 1b). Additionally, computed tomography (CT) indicated that the preoperative diagnosis was adenocarcinoma located in the Ra, invading the muscularis propria without lymph node involvement and distant metastases (Fig. 1c). The patient underwent LAR of the rectum with D3 lymph node dissection, which was performed in the manner usually employed in Japan. A double-stapling technique using a 28-mm circular stapler was employed. The tissue rings were completely intact, and the anastomosis was noted to be airtight at the time of the operation. We placed a drainage tube near the anastomotic site. The postoperative pathologic diagnosis was a well-differentiated adenocarcinoma invading the muscularis propria without lymph node involvement and liver metastasis (T2, N0, M0, Stage I).

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The patient's condition was stable in the immediate postoperative period; however, on postoperative day (POD) 4, his body temperature rose to 38.3°C without symptoms such as abdominal pain and purulent drainage. Although we could not detect any infectious causes, the antibiotic was changed from flomoxef to meropenem on suspicion of surgical-site infection. The patient's fever reduced rapidly and was then allowed oral intake on POD 6, and the drainage tube was removed on POD 9. The patient was expected to be discharged, but he had diarrhea from POD 10 and had a high fever on POD 12. He was suspected to have cholecystitis or cholangitis because of mild epigastralgia, elevated levels of transaminase and biliary tract enzymes on biochemical blood tests, and debris in the swollen gallbladder on ultrasonographic examination. Further, he was treated with cefoperazone-sulbactam under fasting conditions. Diarrhea and fever initially improved but relapsed despite continuing the antibiotic treatment. Moreover, the patient developed pneumaturia on POD 16. CT scan showed emphysematous findings in the right seminal vesicle (Fig. 2a). At that time, the patient tested positive for fecal Clostridium difficile toxin. Therefore, he was diagnosed with antibiotic-associated colitis. We considered that an anastomotic leakage induced a seminal vesicle-rectal fistula with antibiotic-associated colitis. The patient had no severe symptoms and underwent conservative therapy with total parenteral nutrition and metronidazole intake. Diarrhea, pneumaturia, and fever rapidly improved with metronidazole therapy. After 10 days of metronidazole therapy, the emphysematous finding in the right seminal vesicle disappeared completely on a CT scan (Fig. 2b). Moreover, rectoscopy revealed a possible site of anastomotic leakage (Fig. 3a), and we confirmed that the fistula was already closed by Gastrografin contrast study (Fig. 3b). Therefore, the patient was allowed to start oral intake. Since then, he had no pneumaturia but had a cloudy urine and occasional low-grade fever. He was therefore treated with minomycin targeting the enterococcal infection in the bladder and was cured within several days. Finally, he was discharged on POD 41.

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Discussion

The anastomotic site in LAR is located close to the seminal vesicles in male patients and close to the vagina in female patients. Rectal-vaginal fistula is a well-known complication of LAR, whereas seminal vesicle-rectal fistula is a rarely encountered complication. We could find only 9 reported cases of this condition in the PubMed database (Table 1). This complication is characterized by a late onset, as compared with usual anastomotic leakage after LAR. In the reported cases, the earliest onset was at 1 week after surgery and the latest onset was at 9 weeks. Placer¹⁵ reported an atypical case with the latest onset. The patient underwent LAR with cover ileostomy and stoma closure 9 weeks later. On POD 10 of stoma closure the patient developed seminal vesicle-rectal fistula with pneumaturia and fecaluria. Pneumaturia was a characteristic symptom of the seminal vesicle-rectal fistula in 6 of the 8 described reports, and CT and contrast enema examinations were the most useful diagnostic modalities. The key diagnostic findings were emphysematous seminal vesicles on CT and a fistula from the rectum to the seminal vesicles on contrast enema examinations.

Table 1 Reported cases of the seminal vesicle-rectal fistula after low anterior resection of the colon

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Seven patients were treated with surgical procedures, whereas the other 2 patients were successfully treated with conservative therapy. In the present case, the patient's general condition was good, and his CT scan showed localized emphysema without peripheral abscess formation and inflammatory findings. Consequently, the patient chose to undergo conservative therapy, and he was successfully cured.

In many reports, a pelvic abscess rupture was considered as the cause of the seminal vesicle-rectal fistula. If this is true, then we can easily understand the reason underlying the late onset of this complication and the intractable nature of this fistula, similar to that of a perianal abscess or anal fistula. However, in the present case, the CT scan did not show the presence of an abscess or remains of an abscess in the pelvic cavity. We hypothesized the pathogenic process of this condition as follows: Antibiotic-related colitis caused inflammation of the anastomotic site. The weak, inflamed anastomotic site was perforated by frequent bowel movements, leading to the formation of the seminal vesicle-rectal fistula. The patient recovered after metronidazole treatment without using common antibiotics, and we believe that the antibiotic-associated colitis induced this complication.

This complication mostly induces localized inflammation and rarely induces panperitonitis or severe systemic inflammation. Therefore, patients with this complication have enough time to choose between surgical and conservative therapies. Our report provides valuable information regarding the use of conservative therapy for the successful treatment of this complication in a patient.