Colovesical fistula - malignant

Case contributed by Assoc Prof Frank Gaillard


Altered bowel habit.

Patient Data

Age: 50 years
Gender: Male

CT abdomen and pelvis

Poor contrast opacification is the result of partial extravasation of contrast. 

Approximately a 10 cm long segment of the proximal sigmoid colon (approximately 25 to 30 cm from the anal verge) demonstrates irregular marked thickening, with adjacent stranding of the fat, and a direct communication with the dome of the bladder, which contains a small amount of gas.

In the mesentery immediately above this segment is a 3 cm diameter partially calcified mass with some retraction along with multiple other small mesenteric lymph nodes. 

The liver contains multiple ill-defined regions of low attenuation of the throughout most segments, the largest of which is located in segment 8, near the hepatic hilum, and measures 3 cm in diameter.

The spleen, kidneys and adrenal glands appear unremarkable, other than an incidental splenunculus noted below the inferior tip of the spleen. No focal osseous lesion identified.

Chest (not shown): Four pulmonary nodules are demonstrated, two in the right base one in the left lingula and one in the apical segment of the left upper lobe (the latter being be largest and measuring 7 mm in diameter). The heart, great vessels and mediastinum are unremarkable. No focal osseous lesion identified.

Annotated image

Annotated image

Colorectal cancer (blue dotted line) communicating with the bladder (red *)  which contains urine (yellow dotted line) and gas (not shown on this image). Above the mass a nodal metastasis is present (orange dotted line). 

This patient went on to have an en-bloc resection. 

MACROSCOPIC DESCRIPTION: A segment of bowel, 158mm in length. Tethered to the anterior serosa of the specimen, is a full thickness segment of bladder wall, including mucosa. 54mm from the proximal resection margin, there is a sessile tan tumour with an indurated centre and raised irregular edges, measuring 43mm in axial length and 47mm transversely, occupying the full luminal circumference with stenosis.  The tumour invades through the full thickness of the bowel wall into the pericolic fat.  Anteriorly, the tumour invades into the detrusor muscle of the bladder wall. Posteriorly, involvement of vessels by tumour is seen, creating a deposit 8mm in maximum dimension, that extends to abut the serosa.  Uncomplicated diverticular disease is seen.  

MICROSCOPIC DESCRIPTION: Sections of the colon show features of moderately differentiated adenocarcinoma.  The tumour forms complex glandular structures, surrounded by desmoplasia.  The tumour cells have enlarged vesicular nuclei, prominent nucleoli and moderate amounts of eosinophilic cytoplasm.  Tumour-infiltrating lymphocytes are inconspicuous.  The tumour is seen to extend through the full thickness of the bowel wall into the adjacent attached bladder.  The tumour invades into the detrusor muscle but not involving the urothelium.  It is surrounded by abundant active chronic inflammation with microabscess formation.  In some areas, the tumour is seen to involve the serosa and there is also tumour in the pericolic fat.  Scattered foci of vascular invasion are seen including involvement of lymphatics and veins.  Perineural invasion is also identified.  The tumour is completely excised with clear proximal, distal and radial resection margins.  The bladder resection margins are also clear. 8 out of 38 lymph nodes show metastatic carcinoma including extranodal spread. 

Final diagnosis

Moderately differentiated adenocarcinoma, with local invasion:

  • tumour extends through the full thickness of bowel wall into detrusor muscle of the bladder, forming colovesical fistula
  • tumour seen on serosa of the colon and in pericolic fat


  • Dukes stage D
  • AJCC stage IVB 
  • TNM: T4 N2 M1

Case Discussion

Although the most common cause of gas in the bladder in a hospitalized patient is catheterization, when seen in the absence of a catheter careful inspection of the bladder is needed to ensure a fistula is not present. 

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Case information

rID: 15031
Published: 16th Sep 2011
Last edited: 22nd Mar 2021
Inclusion in quiz mode: Included