Differential Diagnosis
- Single most likely diagnosis
- Colorectal cancer: The patient's symptoms of left lower quadrant pain, changes in bowel habits, and the presence of a bulky, necrotic, circumferential mass-like thickening in the distal transverse colon on CT scan are highly suggestive of colorectal cancer. The mass's size, location, and characteristics, including severe luminal narrowing and possible contained perforation, support this diagnosis.
- Other Likely diagnoses
- Diverticulitis: Although the CT scan suggests a mass rather than inflammation, diverticulitis could cause similar symptoms, especially if there's a complication like an abscess. However, the absence of fever and the specific findings on the CT scan make this less likely.
- Intestinal obstruction: The patient's symptoms and the CT findings of severe luminal narrowing could suggest an obstruction, but the presence of a mass and the lack of complete obstruction symptoms (like vomiting) make this less likely as a primary diagnosis.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Perforated viscus: The CT scan suggests possible contained perforation, which is a medical emergency. Even though the patient does not currently exhibit symptoms like fever or severe abdominal tenderness, the potential for peritonitis and sepsis necessitates careful monitoring and possibly urgent intervention.
- Mesenteric ischemia: This condition can present with abdominal pain out of proportion to physical findings and can lead to bowel infarction if not promptly treated. Although the CT scan does not directly suggest ischemia, the presence of a mass and potential for compromised blood flow to the bowel makes this a consideration.
- Rare diagnoses
- Gastrointestinal stromal tumor (GIST): Although less common, GISTs can present as bulky masses in the gastrointestinal tract and could cause similar symptoms. The CT findings would need to be correlated with biopsy results to confirm this diagnosis.
- Lymphoma: This could also present as a bulky mass in the abdomen, but the specific location and characteristics of the mass, along with the patient's overall clinical presentation, make this a less likely consideration without further diagnostic evidence.