Challenges in the initial diagnosis of colon carcinoma from symptoms of a bladder and colon fistula: a case report.

INTRODUCTION AND IMPORTANCE: Sigmoid colon adenocarcinoma usually causes gastrointestinal complaints such as hematochezia or altered bowel habits. Urinary symptoms typically appear only in advanced disease. We describe an unusual case in which vesical fecaluria was the first and main symptom, mimicking recurrent urinary tract infection and risking delayed recognition of its colorectal origin. CASE PRESENTATION: A 62-year-old man presented with more than 6 months of urinary frequency, dysuria, recurrent fever, and vesical fecaluria, which had repeatedly been treated as a urinary tract infection. He had no abdominal pain, hematochezia, or change in bowel habits. CT showed loss of the fat plane between the sigmoid colon and the bladder. Laparoscopic en bloc sigmoidectomy with partial cystectomy removed a pT4bN0M0 adenocarcinoma invading the bladder and small bowel. At 1-year follow-up, symptoms had resolved, with no recurrence. CLINICAL DISCUSSION: Unlike typical sigmoid colon adenocarcinoma, which begins with bowel symptoms and later forms a colovesical fistula, this tumor primarily invaded outward into the bladder with minimal intraluminal growth; therefore, no bleeding or obstruction occurred. Infection obscured endoscopy and delayed diagnosis. MDT-led control of sepsis, plus en bloc laparoscopic R0 resection, was achieved, demonstrating that the combination of fecaluria and recurrent UTI warrants colorectal evaluation. CONCLUSION: Vesical fecaluria may be the first sign of sigmoid colon cancer. With early colorectal cancer suspicion, MDT-guided en bloc minimally invasive resection can achieve good short-term control without recurrence.