What is the likely diagnosis? Is there a differential?
Colorectal carcinoma. Given the mesenteric, liver and lung (not shown) changes there is no realistic differential diagnosis. If evidence of metastatic disease was absent diverticulitis could be entertained.
What is the cause of the gas in the bladder?
Malignant fistula between the colorectal malignancy and the bladder (colovesical fistula).
What is the cause of the mesenteric nodule above the cancer appearing somewhat spiculated?
Desmoplastic reaction induced by nodal metastasis.
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.