A 32-year-old woman presents to the office with complaints of intense anal pain every time she has a bowel movement. The pain has been present for the past 4 weeks, and it is dull and throbbing in nature. It is associated with mild bright red bleeding from the rectum that is aggravated during defecation. She has no relevant past medical history. When asked about her sexual history, she reports practicing anal intercourse. The vital signs include heart rate 98/min, respiratory rate 16/min, temperature 37.6°C (99.7°F), and blood pressure 110/66 mm Hg. On physical examination, the anal sphincter tone is markedly increased, and it's impossible to introduce the finger due to severe pain. What is the most likely diagnosis?

Rectal prolapse and paradoxical contraction of the puborectalis muscle

One day after giving birth to a 4050-g (8-lb 15-oz) male newborn, a 22-year-old woman experiences involuntary loss of urine. The urine loss occurs intermittently in the absence of an urge to urinate. It is not exacerbated by sneezing or coughing. Pregnancy was uncomplicated except for two urinary tract infections that were treated with nitrofurantoin. Delivery was complicated by prolonged labor and severe labor pains; the patient received epidural analgesia. Her temperature is 36.2°C (97.2°F), pulse is 70/min, and blood pressure is 118/70 mm Hg. The abdomen is distended and tender to deep palpation. Pelvic examination shows a uterus that extends to the umbilicus; there is copious thick, whitish-red vaginal discharge. Neurologic examination shows no abnormalities. Which of the following is the most likely cause of this patient's urinary incontinence?

Current urinary tract infection

Recurrent urinary tract infections

A 62-year-old man presents to the office because of painless rectal bleeding for the past 3 months. He describes intermittent streaks of bright red blood on the toilet paper after wiping and blood on but not mixed within the stool. Occasionally, he has noted a small volume of blood within the toilet bowl, and he associates this with straining. For the past 2 weeks, he has noticed an 'uncomfortable lump' in his anus when defecating, which goes away by itself immediately afterwards. He says he has no abdominal pain, weight loss, or fevers. He is a well-appearing man that is slightly obese. Digital rectal examination shows bright red blood on the examination glove following the procedure. Anoscopy shows enlarged blood vessels above the pectinate line. Which of the following is the most likely cause?

Thrombosed external hemorrhoids

A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?

"Can you tell me more about the symptoms you have been experiencing?"

"Does the diarrhea typically precede the constipation, or vice-versa?"

"Is the diarrhea foul-smelling?"

"Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"

"Are the symptoms worse in the morning or at night?"

A 65-year-old patient presents with acute left lower quadrant abdominal pain and is diagnosed with diverticulitis. Which of the following is most likely to have prevented this patient's condition?

Different antibiotic regimen for bronchitis

Sitz baths and nifedipine suppositories

A 62-year-old man presents to the emergency department concerned about a large amount of blood in his recent bowel movement. He states he was at home when he noticed a large amount of red blood in his stool. He is not experiencing any pain and otherwise feels well. The patient has a past medical history of diabetes and obesity. His temperature is 98.9°F (37.2°C), blood pressure is 147/88 mmHg, pulse is 90/min, respirations are 13/min, and oxygen saturation is 98% on room air. Physical exam reveals a non-distressed man. His abdomen is non-tender, and he has normoactive bowel sounds. Stool guaiac test is positive for blood. The patient is started on IV fluids and kept nil per os. His next bowel movement 4 hours later appears grossly normal. Which of the following interventions will most likely reduce future complications in this patient?

Increase fiber and fluid intake

Ciprofloxacin and metronidazole

Anorectal disorders for USMLE Step 3: High-Yield Internal Medicine Lessons

Hemorrhoids - Piles of Problems

Anorectal Anatomy with Hemorrhoid Plexus and Dentate Line

Dilated submucosal veins in the anorectal canal.

Internal: Above dentate line (visceral afferents) → painless bright red bleeding. Graded I-IV.
External: Below dentate line (somatic nerves) → painful, especially if thrombosed.
Risks: Constipation, straining, pregnancy, portal HTN.

⭐ Acute, severe anorectal pain plus a tender, bluish nodule at the anal verge points strongly to a thrombosed external hemorrhoid.

Anal Fissures - Tears for Fears

Definition: Longitudinal tear in the anoderm, distal to the dentate line.
Etiology: Trauma from hard stool, local ischemia. Most common in the posterior midline.
Clinical: Severe, tearing pain with defecation; bright red blood on toilet paper.
- Acute: < 6 weeks; superficial tear.
- Chronic: > 6 weeks; may have a sentinel pile (skin tag) and hypertrophied anal papilla.

Chronic Anal Fissure with Hypertrophied Papilla and Skin Tag

Management:
- Conservative: High-fiber diet, stool softeners, sitz baths.
- Medical: Topical vasodilators (nifedipine, nitroglycerin) to ↓ sphincter pressure.
- Surgical: Lateral internal sphincterotomy (LIS) for refractory cases.

⭐ Exam Favorite: Fissures located off the midline should raise suspicion for secondary causes like Crohn's disease, HIV, syphilis, or tuberculosis.

Anorectal Abscess & Fistula - Tracts of Trouble

Anorectal Abscess: Arises from an infected anal crypt gland. Presents with acute, severe, constant perianal pain and swelling. Fever is common.
- Causative Organisms: E. coli, Bacteroides, Staphylococcus.
- Management: Crucial first step is incision and drainage (I&D). Antibiotics are secondary.
Fistula-in-Ano: A chronic complication in ~50% of abscesses; an epithelialized tract connecting the abscess source to the perianal skin, causing persistent drainage.

Perianal Abscess Locations

⭐ Goodsall's Rule predicts fistula tract anatomy. Anterior external openings connect via a simple, straight radial tract. Posterior openings follow a complex, curved path to the posterior midline before entering the anal canal.

Fecal Incontinence - Leaky Logic

Etiology: Most commonly due to obstetric trauma (pudendal nerve injury, sphincter laceration). Other causes: neurogenic (diabetes, spinal cord injury), overflow (impaction), or iatrogenic.
Initial Management: Conservative approach first.
- Dietary modification (bulk-forming agents like psyllium).
- Pelvic floor exercises (Kegel exercises).
- Anti-diarrheal agents (loperamide).

⭐ Exam Favorite: Fecal incontinence presenting years after childbirth is often due to delayed pudendal nerve neuropathy. The nerve is stretched during delivery, leading to a progressive decline in sphincter function over time.

High‑Yield Points - ⚡ Biggest Takeaways

Anal fissures cause tearing pain with defecation, typically at the posterior midline. A lateral fissure suggests Crohn's disease or other systemic illness.

Internal hemorrhoids manifest with painless, bright red rectal bleeding. In contrast, external hemorrhoids are acutely painful when thrombosed.

An anorectal abscess is a painful emergency requiring incision and drainage; it may evolve into a fistula-in-ano, strongly associated with Crohn's disease.

Proctitis from STIs or IBD presents with tenesmus and discharge.

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