Differential Diagnosis for Anal Bleeding

When considering the symptom of anal bleeding, it's crucial to approach the diagnosis systematically to ensure that all potential causes are considered. The differential diagnosis can be organized into the following categories:

• Single Most Likely Diagnosis

  • Hemorrhoids: This is often the most common cause of anal bleeding, especially in adults. Hemorrhoids can be internal or external and may bleed due to increased pressure, straining during bowel movements, or other factors.

• Other Likely Diagnoses

  • Anal Fissures: These are small tears in the lining of the anus, which can cause bleeding and pain during and after bowel movements.
  • Diverticulitis: Although more commonly associated with left lower quadrant abdominal pain, diverticulitis can cause rectal bleeding if the affected diverticula are located in the sigmoid colon.
  • Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis can cause chronic inflammation of the gastrointestinal tract, leading to symptoms including anal bleeding.
  • Rectal Prolapse: This condition, where the rectum loses its normal attachments inside the body, allowing it to protrude out through the anus, can cause bleeding due to the strain on the rectal mucosa.

• Do Not Miss Diagnoses

  • Colorectal Cancer: Although less common than other causes, colorectal cancer is a critical diagnosis not to miss. It can present with rectal bleeding, especially in older adults or those with a family history of the disease.
  • Gastrointestinal Infections: Certain infections, such as those caused by Salmonella or Shigella, can lead to rectal bleeding, especially if they cause significant inflammation or ulceration of the rectal mucosa.
  • Angiodysplasia: These are vascular malformations of the gastrointestinal tract that can cause bleeding. They are more common in the elderly and can be a source of significant blood loss.

• Rare Diagnoses

  • Rectal Varices: Enlarged veins in the rectum, often associated with portal hypertension, can cause bleeding.
  • Solitary Rectal Ulcer Syndrome: This condition involves the presence of one or more ulcers in the rectum, which can bleed.
  • Lymphogranuloma Venereum (LGV): A sexually transmitted infection that can cause rectal bleeding and pain, especially in individuals with high-risk sexual behaviors.
  • Rectal Trauma: Physical injury to the rectum, which can be due to various causes including sexual assault, can result in bleeding.

Each of these diagnoses has a different set of risk factors, symptoms, and diagnostic approaches. A thorough medical history, physical examination, and appropriate diagnostic tests (such as endoscopy, imaging studies, or stool tests) are essential for determining the underlying cause of anal bleeding.