Differential Diagnosis for a 62-year-old male with left hypochondrial pain, normal colonoscopy, and few pus and blood cells in stool

• Single most likely diagnosis:
  • Diverticulitis: This condition is characterized by inflammation of the diverticula in the colon, which can cause left lower quadrant or hypochondrial pain, especially in older adults. The presence of pus and blood cells in the stool supports an inflammatory process, and diverticulitis is a common cause of such symptoms in this age group, even with a normal colonoscopy if the diverticula are not visualized or if the procedure was not recent.
• Other Likely diagnoses:
  • Ischemic colitis: This condition occurs when there is an interruption of blood flow to the colon, leading to inflammation. It can present with abdominal pain and bloody stools. Although less common than diverticulitis, it is a plausible diagnosis given the symptoms and the patient's age.
  • Crohn’s disease: While Crohn's disease can present at any age, it is less common in new diagnoses among older adults. However, it can cause chronic inflammation of the gastrointestinal tract, leading to symptoms like abdominal pain, diarrhea, and blood in the stool. The normal colonoscopy might not entirely rule out Crohn's, especially if the disease is limited to the small intestine or if the colonoscopy was not diagnostic.
• Do Not Miss diagnoses:
  • Infectious colitis (e.g., Bacillary dysentery): Although less likely given the clinical context, infectious causes of colitis (such as Shigella, Salmonella, or Campylobacter) can present with similar symptoms, including abdominal pain and bloody stools. These conditions require prompt diagnosis and treatment to prevent complications.
  • Colon cancer: Even with a recent normal colonoscopy, the possibility of a missed lesion or a newly developed lesion cannot be entirely excluded, especially if the symptoms persist or worsen. However, this would be less likely given the recent normal colonoscopy.
• Rare diagnoses:
  • Microscopic colitis: This condition involves inflammation of the colon that can only be seen with a microscope. It typically presents with chronic, watery diarrhea but can occasionally cause abdominal pain. It's less likely given the presence of blood and pus in the stool but remains a consideration in the differential diagnosis of chronic gastrointestinal symptoms.
  • Eosinophilic colitis: A rare condition characterized by eosinophilic infiltration of the colon, which can cause a variety of gastrointestinal symptoms, including abdominal pain and bloody stools. It is much less common and would be considered only after other diagnoses have been ruled out.