Differential Diagnosis for External Hemorrhoid vs Perirectal Abscess

• Single most likely diagnosis:
  • External hemorrhoid: This is the most likely diagnosis due to the common presentation of pain, swelling, and a palpable mass in the anal region, which are typical symptoms of an external hemorrhoid.
• Other Likely diagnoses:
  • Perirectal abscess: Although less common than external hemorrhoids, perirectal abscesses can present with similar symptoms, including pain and swelling, but are often accompanied by signs of infection such as fever and purulent discharge.
  • Anal fissure: This condition can cause severe pain during and after defecation and may be confused with the pain associated with external hemorrhoids or perirectal abscesses.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):
  • Necrotizing fasciitis: Although rare, this is a life-threatening condition that can arise from an infected perirectal abscess or other infections in the anal region. Early recognition and treatment are crucial.
  • Rectal cancer: While less likely, rectal cancer can cause a range of symptoms including pain, bleeding, and a palpable mass, and missing this diagnosis could have severe consequences.
• Rare diagnoses:
  • Pilonidal sinus or cyst: These can become infected and present with symptoms similar to a perirectal abscess, including pain and swelling, but are located near the tailbone.
  • Hidradenitis suppurativa: This chronic skin condition can cause painful, inflamed lesions in the groin and anal areas, which might be confused with external hemorrhoids or perirectal abscesses.