Differential Diagnosis
- Single most likely diagnosis
- Colorectal cancer: The patient's age, smoking history, and long-standing constipation are risk factors for colorectal cancer. The CT finding of colon narrowing is also consistent with a tumor causing luminal obstruction.
- Other Likely diagnoses
- Diverticulitis: Although the patient can pass gas, diverticulitis can cause narrowing of the colon and obstructive symptoms. The patient's age and constipation history are also risk factors for diverticular disease.
- Benign colonic stricture: A benign stricture, possibly due to chronic diverticulitis or ischemia, could cause narrowing of the colon and obstructive symptoms.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Colonic volvulus: Although less likely, a volvulus could cause obstruction and narrowing of the colon. If missed, it could lead to ischemia and perforation, which would be life-threatening.
- Intussusception: Intussusception is a rare cause of colonic obstruction in adults, but it can be life-threatening if not diagnosed promptly.
- Rare diagnoses
- Inflammatory bowel disease (IBD): Although IBD is less likely in a patient with a long history of mild constipation, it could cause narrowing of the colon and obstructive symptoms.
- Lymphoma or other rare tumors: These would be rare causes of colonic narrowing and obstruction, but should be considered in the differential diagnosis.