Perianal abscess — USMLE Step 3 MCQ

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HardSurgery (post-operative, follow-up)Perianal abscessUSMLE Step 3

A 29-year-old has perianal pain, fever, and a tender fluctuant mass lateral to the anus. Which diagnosis best explains this presentation?

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Correct answer: E — An acute anorectal abscess

Fever, focal perianal tenderness, and fluctuation support an acute anorectal abscess. Fissure and hemorrhoidal disease do not usually produce this fluctuant febrile mass; prompt drainage is needed after surgical assessment.

Reference: American Society of Colon and Rectal Surgeons: Abscess and Fistula: https://fascrs.org/Web/Web/Patients/Diseases-and-Conditions/A-Z/Abscess_and_Fistula.aspx