Differential Diagnosis for Abdominal Pain
The patient presents with cramping abdominal pain, constipation, and a shift in pain from the left to the right side, with a normal CT abdomen scan. Here's a categorized differential diagnosis:
Single most likely diagnosis
- Irritable Bowel Syndrome (IBS): The patient's symptoms of abdominal cramping, constipation, and the absence of blood in the stool, along with a normal CT scan, make IBS a plausible diagnosis. The shift in pain location can also occur in IBS.
Other Likely diagnoses
- Inflammatory Bowel Disease (IBD): Although the CT scan is normal, IBD (including Crohn's disease and ulcerative colitis) can present with similar symptoms. The initial left-sided pain could suggest ulcerative colitis, while the shift to right-sided pain might indicate Crohn's disease.
- Intestinal obstruction: Early or partial obstruction could cause constipation and cramping pain without significant findings on a CT scan, especially if the obstruction is not complete.
- Gastroenteritis: An infectious cause could lead to these symptoms, although the absence of diarrhea and the presence of constipation make this less likely.
Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Appendicitis: Although the CT scan is normal, appendicitis can sometimes be missed, especially if it's early or atypical. The shift from left to right-sided pain could suggest appendicitis, as the appendix is usually located in the right lower quadrant.
- Mesenteric ischemia: This condition involves insufficient blood flow to the intestines and can present with abdominal pain out of proportion to physical findings. A normal CT scan does not rule out early mesenteric ischemia.
- Ectopic pregnancy (in a female patient, but considered here for completeness): Though the patient is male, in a female patient, ectopic pregnancy could present with similar symptoms and would be a critical diagnosis not to miss.
Rare diagnoses
- Intussusception: A condition where a part of the intestine slides into an adjacent part, which can cause obstruction and ischemia. It's rare in adults but can occur.
- Malrotation with volvulus: A rare condition where the intestine twists around its base, cutting off blood supply. It's more common in children but can occur in adults.
- Chronic intestinal pseudo-obstruction: A rare condition characterized by recurrent episodes of intestinal obstruction without any physical blockage.