Differential Diagnosis for Mild Infiltration of the Fat in the Perirectal Region with Blood in the Stool

• Single Most Likely Diagnosis
  • Diverticulitis: This condition is characterized by inflammation of a diverticulum in the wall of the colon, which can lead to blood in the stool and mild infiltration of the fat in the perirectal region due to the spread of the inflammation.
• Other Likely Diagnoses
  • Rectal Cancer: Although less common, rectal cancer can cause blood in the stool and infiltration of the perirectal fat due to tumor invasion.
  • Proctitis: Inflammation of the rectum can lead to blood in the stool and changes in the perirectal fat, especially if the inflammation is severe or chronic.
  • Abscess: An abscess in the perirectal region can cause mild infiltration of the fat and blood in the stool if it communicates with the rectum or if there is associated inflammation.
• Do Not Miss Diagnoses
  • Perforated Visculitis (e.g., due to vasculitis like Wegener's granulomatosis): Although rare, this condition can lead to severe complications if missed, including severe bleeding and sepsis.
  • Rectal Lymphoma: Lymphoma involving the rectum can cause a range of symptoms including blood in the stool and changes in the perirectal region.
• Rare Diagnoses
  • Actinomycosis: A rare bacterial infection that can cause chronic inflammation and abscesses in the perirectal region, leading to blood in the stool and changes in the perirectal fat.
  • Tuberculosis: Although more commonly associated with pulmonary symptoms, abdominal tuberculosis can involve the rectum and perirectal region, causing a range of symptoms including blood in the stool.