Short answer

Rectal pain splits between two worlds, STI proctitis (gonorrhea, chlamydia/LGV, herpes, syphilis) and anorectal conditions (fissures, hemorrhoids, abscess, IBD), that share every symptom but diverge completely in treatment.

Pain character alone can’t distinguish them: anal exposure history plus rectal swabs decide, which is why the most important diagnostic step is a sentence (“I’ve had anal exposure”) rather than a description of the pain.

Continue with Testicular Pain and Possible Infections and Pelvic Pain and Possible STIs for the directly connected guidance.

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STI patterns with their signatures

  • Gonococcal/chlamydial proctitis: urgency, aching, discharge, bleeding. Often with concurrent genital infection.
  • LGV: severe pain with bleeding and discharge mimicking Crohn’s disease; the great mimicker of gastroenterology, diagnosed by exposure history plus LGV typing.
  • Herpes: severe anorectal pain with visible ulcers, sometimes with urinary difficulty or retention.
  • Syphilis: painless chancre or mucous patches, easily overlooked without examination.

Non-STI patterns with their signatures

  • Anal fissures: sharp tearing pain specifically with bowel movements plus bright-red blood on tissue. The classic benign pattern.
  • Thrombosed hemorrhoids: sudden tender lump at the anal verge.
  • Perianal abscess or fistula: fever with fluctuant swelling. A surgical urgency, not a clinic-next-week problem.
  • IBD flares: chronicity, systemic features, weight loss.
  • Colorectal malignancy: older patients, persistent bleeding, altered bowel habits. Age-appropriate screening applies.

Evaluation sequence

Anoscopy with rectal NAAT swabs for STI patterns, syphilis and HIV serology alongside, stool studies where IBD is suspected, surgical examination for fluctuant swelling (abscess drainage can’t wait for lab results), and LGV typing for severe or MSM-associated proctitis.

Genital-only testing never substitutes. Urine tests cannot see the rectum.

When to seek care

Promptly for rectal pain with exposure, discharge, or bleeding.

Urgently for fever with swelling (abscess until proven otherwise), severe pain with urinary retention (herpes proctitis pattern), heavy bleeding, or rapidly worsening pain of any pattern.