Short answer
Rectal discharge, mucus or pus from the rectum, means an inflamed rectum, and the two leading explanations could hardly differ more in management: STI proctitis (antibiotics plus partner care) versus inflammatory bowel disease (gastroenterology, immunosuppression, surgery in severe cases).
Rectal swabs plus exposure history separate them fast, which is why honest anal-exposure disclosure and site-specific sampling decide outcomes more than any symptom description.
Continue with Unusual Genital Discharge: Causes and Testing and Penile Discharge: When to Seek Testing for the directly connected guidance.
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See Tests & Prices →STI causes with their signatures
- Gonococcal proctitis: purulent discharge, urgency, bleeding. Often with concurrent genital infection.
- Chlamydial proctitis including LGV: mucoid to bloody discharge; LGV strains cause severe pain mimicking Crohn’s disease so closely that rectal LGV is frequently misdiagnosed as inflammatory bowel disease without exposure history.
- Herpetic proctitis: severe anorectal pain with ulcers, sometimes with urinary difficulty.
- Syphilitic chancre: painless ulcer exudate, easily missed.
HIV and syphilis serology accompany every workup regardless of presentation.
Non-STI causes with their signatures
- Ulcerative colitis and Crohn’s proctitis: chronic bloody-mucous discharge with systemic features (weight loss, extraintestinal manifestations) and no exposure pattern.
- Radiation proctitis: history of pelvic radiation.
- Solitary rectal ulcer: straining-associated.
- Colorectal neoplasia: older patients, persistent bleeding, weight loss. Age-appropriate cancer screening applies.
When STI workups return negative with absent exposures, gastroenterology takes over without delay rather than repeating STI panels.
Diagnosis that distinguishes
Anoscopy with rectal NAAT swabs (the test genital-only panels never perform), LGV molecular typing for severe or MSM-associated cases, syphilis and HIV serologies, stool studies and inflammatory markers where IBD is suspected, colonoscopy for chronic or atypical presentations.
Disclose anal exposures explicitly. Clinicians can’t sample sites they don’t know about, and rectal infections are usually silent until discharge appears.
Treatment by cause
Organism-directed antibiotics (extended courses for LGV), abstinence until resolution, partner evaluation and treatment, and retesting per schedules.
IBD findings refer to gastroenterology immediately. Mesalamine, immunomodulators, or biologics per severity, never prolonged antibiotics for non-infectious inflammation.
When to seek care
Promptly for any rectal discharge with exposure history.
Urgently for severe pain, fever, or heavy bleeding. Abscess and severe LGV need same-day assessment.