Tenesmus tells you where; history and mucosa tell you why.
Primary diagnostic imageProctitis is confined to rectal mucosa, which explains tenesmus, rectal pain, urgency, and distal bleeding.National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health / NIDDK, NIH (Public domain). SourcePublic domain
Use sexual and exposure history without assumptions
Choose anoscopy, site-specific pathogen testing, and endoscopy
Distinguish infectious treatment from IBD induction and maintenance
Key distinctions
Separate the closest diagnoses
The figure compares the nearest alternatives and highlights the finding that separates them.
Quick check
A man with receptive anal exposure has rectal pain, tenesmus, bloody discharge, and mucosal exudate on anoscopy.
Which diagnostic study should be obtained next?
Reason it through
What exposure localizes infection?Receptive anal exposure.
What symptoms localize inflammation?Tenesmus, rectal pain, and discharge.
What should happen before results return?Test and provide indicated empiric STI therapy.
Take the sexual history without judgment; it changes both tests and treatment.
Empiric STI treatment has triggers
Treat syndrome while preserving diagnostic precision.
When acute sexually acquired proctitis has exudate, polymorphonuclear leukocytes, or a compatible presentation and anoscopy is unavailable, CDC guidance supports presumptive treatment while tests are pending.
Ceftriaxone plus seven days of doxycycline covers gonorrhea and chlamydia; extend doxycycline to 21 days when rectal chlamydia accompanies bloody discharge, ulcers, or tenesmus suggesting LGV.
Painful ulcers warrant HSV evaluation and empiric antiviral coverage when clinically indicated.
Select the accurate rule.
One symptom cluster, four causes
Tenesmus localizes; history identifies the lane.
Proctitis causes rectal pain, tenesmus, urgency, discharge, and bleeding because inflammation is confined to the distal rectum.
Sexually acquired infection includes gonorrhea, chlamydia including LGV, HSV, and syphilis; CMV becomes important in severe immunosuppression.
Ulcerative, radiation, and rare ischemic proctitis are distinguished by chronic inflammatory history, pelvic radiation latency, or an acute low-flow event.
Compare etiologic fingerprints.
Acute pain, discharge, exposure, ulcers or exudate
Chronic relapsing urgency and blood with continuous rectal inflammation
Prior pelvic radiation; acute diarrhea or delayed bleeding and telangiectasias
Abrupt pain and blood after profound low flow or vascular injury
Escalate by depth and host risk
A small anatomic segment can cause major disease.
Mild urgency without systemic illness can be evaluated promptly as an outpatient, but severe pain, fever, immunosuppression, heavy bleeding, peritoneal signs, or toxicity require urgent escalation.
CMV should be considered in immunosuppressed patients with large ulcers or refractory symptoms.
Proctitis is limited to the rectum; proctocolitis extends proximally and adds diarrhea or abdominal cramps.
Ulcers suggest HSV, syphilis, LGV, CMV, trauma, or inflammatory disease; exudate supports infection but is not pathogen-specific.
Continuous circumferential inflammation beginning at the anal verge favors ulcerative proctitis, while sharply demarcated dusky tissue suggests ischemia.
Map finding to implication.
Vesicles, ulcers, fissures, chancres, or warts
Anoscopy reveals exudate, ulcers, blood, and friability
Tenesmus dominates; consider infectious or ulcerative proctitis
Diarrhea and cramps suggest proctocolitis
Provide context for ischemic or radiation injury
History, look, swab, then direct
Do not skip the rectal examination.
Ask about receptive anal, oral-anal, and digital exposure; barrier use; partners; prior STIs; HIV status; immunosuppression; inflammatory bowel disease; radiation; and vascular events.
Inspect perianal skin, perform digital examination when safe, and use anoscopy or proctoscopy to identify exudate, ulcers, friability, vesicles, or a mass.
Obtain rectal NAAT for gonorrhea and chlamydia, test lesions for HSV, obtain syphilis and HIV testing, and use stool or endoscopic testing when proctocolitis, enteritis, CMV, IBD, or malignancy is plausible.
Order the workup.
Localize
Tenesmus, rectal pain, discharge, bleeding
Elicit exposure
Sexual, inflammatory, radiation, immune, and vascular history
Examine
Perianal inspection, digital exam, anoscopy or proctoscopy
Test
Site-specific NAAT and lesion or serologic testing
Treat and prevent recurrence
Cause-directed therapy, partner care, abstinence interval, and follow-up
Cause-directed treatment has phases
Induction is not maintenance.
Acute infectious proctitis is treated for the identified or strongly suspected pathogen, with partner evaluation, testing at other exposed sites, and temporary sexual abstinence until treatment is complete and symptoms resolve.
Mild to moderate ulcerative proctitis is commonly induced with rectal mesalamine; after response, maintenance mesalamine reduces relapse rather than stopping all therapy.
Radiation proctopathy treatment depends on acute versus chronic injury and bleeding severity; ischemic proctitis requires perfusion support and urgent surgical assessment when necrosis is suspected.
Reveal the treatment lane.
Acute STI syndrome
Empiric ceftriaxone plus doxycycline when criteria are met, then tailor
LGV pattern
Doxycycline for 21 days
HSV ulcers
Antiviral therapy
Ulcerative proctitis
Topical mesalamine induction followed by maintenance
Severe radiation or ischemic injury
Endoscopic, hyperbaric, vascular, or surgical specialist care based on depth and bleeding
Decisive finding
Pick the discriminator
Choose the finding that separates the closest competing diagnoses.
Which diagnostic study should be obtained next?
Key finding. A man with receptive anal exposure has rectal pain, tenesmus, bloody discharge, and mucosal exudate on anoscopy.
Answer. Rectal pathogen testing plus empiric ceftriaxone and doxycycline
Why. The CDC acute sexually acquired proctitis syndrome warrants NAAT-based evaluation and empiric gonorrhea/chlamydia coverage when exudate or a compatible presentation is present.
Board rule. Take the sexual history without judgment; it changes both tests and treatment.
2Elicit exposureSexual, inflammatory, radiation, immune, and vascular history
3ExaminePerianal inspection, digital exam, anoscopy or proctoscopy
4TestSite-specific NAAT and lesion or serologic testing
5Treat and prevent recurrenceCause-directed therapy, partner care, abstinence interval, and follow-up
Clinical takeaway
Why it mattersObtain rectal NAAT for gonorrhea and chlamydia, test lesions for HSV, obtain syphilis and HIV testing, and use stool or endoscopic testing when proctocolitis, enteritis, CMV, IBD, or malignancy is plausible.
RememberTake the sexual history without judgment; it changes both tests and treatment.
Separate the competing diagnoses
The shortest GI segment demands one of the broadest histories.
Cross out mimics and highlight the finding that separates the diagnoses. Shuffle to compare a new case order.
A 24-year-old with a new receptive anal partner develops acute rectal pain, tenesmus, and mucopurulent discharge. Anoscopy shows diffuse inflamed mucosa without vesicles; rectal NAAT results are pending.
Which initial testing and treatment approach is appropriate now?
Reason it through
Which history changes the infectious differential?Receptive anal exposure raises concern for sexually transmitted proctitis.
Which samples should be obtained?Rectal testing should evaluate likely bacterial pathogens while examination looks for ulcerative causes.
Why begin empiric therapy before results return?A compatible acute syndrome warrants coverage for gonorrhea and chlamydia while targeted results are pending.
Acute sexually associated proctitis needs rectal pathogen testing and empiric gonorrhea-chlamydia coverage when the syndrome is convincing.
new receptive anal partnerrectal pain, tenesmus, and mucopurulent discharge
Which history changes the infectious differential?Receptive anal exposure raises concern for sexually transmitted proctitis.
Which samples should be obtained?Rectal testing should evaluate likely bacterial pathogens while examination looks for ulcerative causes.
Why begin empiric therapy before results return?A compatible acute syndrome warrants coverage for gonorrhea and chlamydia while targeted results are pending.
Rectal chlamydia NAAT is positive in a patient with bloody discharge, ulcers, and tenesmus.
How should doxycycline therapy change?
Reason it through
Which pathogen is detected?Rectal Chlamydia trachomatis.
Which features suggest invasive serovars?Blood, ulcers, and tenesmus.
What is the duration shift?Doxycycline for 21 days.
Rectal chlamydia plus ulcers or tenesmus means think LGV.
Which pathogen is detected?Which features suggest invasive serovars?
Which pathogen is detected?Rectal Chlamydia trachomatis.
Which features suggest invasive serovars?Blood, ulcers, and tenesmus.
What is the duration shift?Doxycycline for 21 days.
A patient with ulcerative colitis has inflammation limited to the rectum, urgency, tenesmus, and blood but negative pathogen testing.
What is appropriate induction therapy?
Reason it through
Is infection demonstrated?No.
Where is inflammation confined?Rectum.
What delivers anti-inflammatory drug directly?Topical mesalamine.
For ulcerative proctitis, distinguish induction from relapse-preventing maintenance.
Is infection demonstrated?Where is inflammation confined?
Is infection demonstrated?No.
Where is inflammation confined?Rectum.
What delivers anti-inflammatory drug directly?Topical mesalamine.
Years after pelvic radiotherapy, a patient has chronic rectal bleeding and friable telangiectatic mucosa.
What cause is most likely?
Reason it through
What is the remote exposure?Pelvic radiation.
What is the latency?Years.
What mucosal lesion explains bleeding?Radiation-associated telangiectasia.
Radiation injury can arrive long after the cancer treatment.
What is the remote exposure?What is the latency?
What is the remote exposure?Pelvic radiation.
What is the latency?Years.
What mucosal lesion explains bleeding?Radiation-associated telangiectasia.
An older hypotensive patient develops sudden rectal pain and bleeding; endoscopy shows sharply demarcated dusky rectal mucosa.
Which mechanism is most concerning?
Reason it through
Was onset abrupt?Yes.
What systemic trigger occurred?Hypotension.
What does dusky demarcated mucosa imply?Ischemia.
The rectum is protected, not invulnerable.
Was onset abrupt?What systemic trigger occurred?
Was onset abrupt?Yes.
What systemic trigger occurred?Hypotension.
What does dusky demarcated mucosa imply?Ischemia.
Rapid review
Three questions to check
Which diagnostic study should be obtained next?
Rectal pathogen testing plus empiric ceftriaxone and doxycycline. The CDC acute sexually acquired proctitis syndrome warrants NAAT-based evaluation and empiric gonorrhea/chlamydia coverage when exudate or a compatible presentation is present.
Which history changes the infectious differential?
Receptive anal exposure raises concern for sexually transmitted proctitis.
Which samples should be obtained?
Rectal testing should evaluate likely bacterial pathogens while examination looks for ulcerative causes.
Resident physician and founding medical reviewer at Bone Wizardry, focused on clinical accuracy, clear diagnostic reasoning, and practical board-oriented teaching across the curriculum.
