Background Intestinal tuberculosis (ITB) most commonly involves the ileocecal region. Isolated sigmoid colonic tuberculosis complicated by a colovesical fistula is extremely rare and may closely mimic colorectal malignancy or Crohn's disease (CD). Case presentation A 73-year-old man presented with subacute diarrhea, fever, and lower urinary tract symptoms. Laboratory tests showed markedly elevated inflammatory markers and anemia. Cross-sectional imaging demonstrated segmental thickening of the s