MKSAP Quiz: 2-week history of bright red blood per rectum
A 55-year-old man is evaluated for a 2-week history of intermittent bright red blood per rectum and pain with defecation. He has marked anorectal discomfort with wiping, and blood is visualized in the toilet water and on toilet paper. Following inspection of the perianal region, what is the most likely diagnosis?
A 55-year-old man is evaluated for a 2-week history of intermittent bright red blood per rectum and pain with defecation. He has marked anorectal discomfort with wiping, and blood is visualized in the toilet water and on toilet paper. His stools are firm and brown with bloody streaks. He also has chronic constipation treated with over-the-counter psyllium fiber supplement.
Inspection of the perineum reveals no thrombosed external hemorrhoid; however, while gently spreading the buttocks for inspection of the perianal region, the patient experiences exquisite pain.
Findings on screening colonoscopy 2 years ago were normal.
Which of the following is the most likely diagnosis?
A. Anal fissure
B. Angiodysplasia
C. Internal hemorrhoids
D. Rectal cancer
MKSAP Answer and Critique
The correct answer is A. Anal fissure. This content is available to MKSAP subscribers as Question 46 in the Gastroenterology and Hepatology section. More information about MKSAP is available online.
The most likely diagnosis is an anal fissure (Option A). Anal fissures are longitudinal mucosal tears in the anal canal characterized by anorectal pain worsened by bowel movements. Rectal bleeding with bowel movements or wiping is frequently reported. Anal fissures are idiopathic or result from trauma due to the passage of hard stool; receptive anal intercourse; or the insertion of a foreign body, such as an enema or endoscope. In this patient, the marked anorectal pain with attempted inspection of the perianal area in the context of painful defecatory bleeding is nearly diagnostic of anal fissure. A digital rectal examination is not needed in patients with severe anal pain, particularly when a thrombosed external hemorrhoid is excluded (as in this patient), because the likely diagnosis is an anal fissure. Acute anal fissures generally resolve within a few weeks with the use of sitz baths, psyllium, and bulking agents. For persistent symptoms despite these initial measures, topical vasodilators, including calcium channel blockers (preferred because of their more favorable adverse effect profile) or nitroglycerin can be used. Topical anesthetics and anti-inflammatory agents can be considered to address pain or bleeding, but their use is not required to promote fissure healing. Botulinum toxin injection of the internal sphincter or lateral internal sphincterotomy are considerations for chronic anal fissures that do not respond to conservative measures.
Angiodysplasia (Option B) can occur throughout the colon but is most common in the right colon. Angiodysplasia-related bleeding is typically painless and causes bleeding episodes that are unrelated to defecation. Because this patient has pain with defecation, angiodysplasia is not a likely cause of his symptoms.
Hemorrhoids (Option C) are submucosal, arteriovenous sinusoids that are part of normal anorectal anatomy and are believed to play an important role in anal canal function. Age-related changes can cause the hemorrhoid beds to slide back and forth during defecation, resulting in mucoid anal discharge, as well as perianal wetness, soiling, irritation, and/or pruritus. Hemorrhoidal bleeding is most often associated with painless defecation. The presence of pain (as in this patient) should raise suspicion for an alternative diagnosis, such as anal fissure.
Rectal cancer (Option D) should always be considered in a patient with new-onset rectal outlet bleeding. However, painful defecation typically does not occur with rectal cancer. In this patient, the presence of pain with defecation and the history of normal findings on screening colonoscopy 2 years previously make rectal cancer unlikely.
Key Points
- Anal fissures are longitudinal mucosal tears in the anal canal characterized by anorectal pain worsened by bowel movements.
- Marked anorectal pain with attempted inspection of the perianal area in the context of painful defecatory bleeding is nearly diagnostic of anal fissure.