Differential Diagnosis for Anal Bleeding

• Single most likely diagnosis
  • Hemorrhoids: This is the most common cause of anal bleeding, especially in adults. Hemorrhoids can be internal or external and are often associated with straining during bowel movements, constipation, or prolonged sitting.
• Other Likely diagnoses
  • Anal fissure: A tear in the lining of the anus can cause painful bleeding during and after bowel movements. This condition is also common and can be related to constipation, diarrhea, or anal sex.
  • Diverticulitis: Inflammation of diverticula in the colon can lead to bleeding, although it more commonly presents with left lower quadrant pain and changes in bowel habits.
  • Inflammatory bowel disease (IBD): Conditions like Crohn's disease and ulcerative colitis can cause rectal bleeding, along with diarrhea, abdominal pain, and weight loss.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Colorectal cancer: Although less common than other causes, colorectal cancer is a critical diagnosis to consider, especially in older adults or those with a family history. It can present with rectal bleeding, changes in bowel habits, and weight loss.
  • Gastrointestinal infection: Certain infections, such as those caused by Salmonella or Shigella, can lead to rectal bleeding, especially in immunocompromised individuals or during outbreaks.
  • Angiodysplasia: Vascular malformations in the colon can cause bleeding, often in older adults, and may be associated with aortic stenosis or other cardiovascular conditions.
• Rare diagnoses
  • Rectal ulcers: These can be caused by a variety of factors, including ischemia, infection, or trauma, and are less common than other causes of anal bleeding.
  • Rectal varices: Enlarged veins in the rectum, often associated with liver cirrhosis and portal hypertension, can cause bleeding.
  • Intussusception: A condition where a part of the intestine slides into another, which can cause bowel obstruction and bleeding, is rare in adults but more common in children.
  • Vasculitis: Inflammation of blood vessels can affect the gastrointestinal tract and cause bleeding, although this is a rare condition.