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 and must be considered, especially if the patient has been exposed to potential pathogens or has recently traveled. Missing an infectious cause could lead to delayed treatment and potentially severe complications.
  • Colon cancer: Even though the colonoscopy was normal, if it was not recent or if there were technical issues with the procedure, colon cancer could still be a consideration, especially with symptoms like blood in the stool. However, the presence of pus might be less typical for cancer.
• Rare diagnoses:
  • Microscopic colitis: This condition involves inflammation of the colon that can only be seen under a microscope. It typically presents with chronic, watery diarrhea but can occasionally cause abdominal pain and, less commonly, blood in the stool. It's a diagnosis of exclusion and might be considered if other tests are negative.
  • Intestinal lymphoma or other rare malignancies: These are less common causes of gastrointestinal symptoms but could present with a similar constellation of symptoms, including abdominal pain and alterations in bowel habits. They would be considered if initial evaluations for more common causes are negative.