NBME Medicine 3 — Questions and Answers
Question 1: A 28-year-old woman presents with bloody diarrhea, tenesmus, and crampy abdominal pain for 3 weeks. Colonoscopy shows continuous mucosal inflammation from the rectum to the splenic flexure. Which feature best distinguishes this condition from Crohn disease?
- Presence of granulomas on biopsy
- Involvement of the terminal ileum
- Continuous colonic involvement starting at the rectum (Correct answer)
- Transmural inflammation
Correct answer: Continuous colonic involvement starting at the rectum
Ulcerative colitis characteristically shows continuous inflammation beginning at the rectum and extending proximally, unlike the skip lesions and transmural involvement seen in Crohn disease.
Question 2: A 55-year-old man with diabetes and hypertension is found to have creatinine of 3.8 mg/dL (baseline 1.1 mg/dL) after starting an NSAID 5 days ago. Urinalysis shows muddy brown casts. What is the most likely mechanism of injury?
- Prerenal azotemia from volume depletion
- Acute tubular necrosis (Correct answer)
- Acute interstitial nephritis
- Post-renal obstruction
Correct answer: Acute tubular necrosis
Muddy brown granular casts are pathognomonic of acute tubular necrosis, which can be caused by NSAIDs reducing renal perfusion in patients with marginal renal blood flow.
Question 3: A 35-year-old vegetarian woman presents with fatigue and pallor. Labs: Hgb 9.2, MCV 110, hypersegmented neutrophils on smear. Serum B12 is low. Which additional finding would suggest pernicious anemia as the cause?
- Positive anti-intrinsic factor antibodies (Correct answer)
- Elevated serum ferritin
- Low reticulocyte count
- Elevated homocysteine only
Correct answer: Positive anti-intrinsic factor antibodies
Anti-intrinsic factor antibodies are highly specific for pernicious anemia, distinguishing it from dietary B12 deficiency.
Question 4: A 52-year-old obese man with heartburn for 10 years undergoes upper endoscopy showing salmon-colored mucosa replacing squamous epithelium in the distal esophagus. Biopsy confirms specialized intestinal metaplasia. What is the primary concern warranting surveillance?
- Esophageal squamous cell carcinoma
- Esophageal adenocarcinoma (Correct answer)
- Peptic ulcer disease
- Esophageal motility disorder
Correct answer: Esophageal adenocarcinoma
Barrett esophagus (intestinal metaplasia of the distal esophagus) is a premalignant condition that increases risk of esophageal adenocarcinoma.
Question 5: A 60-year-old diabetic presents for routine labs. eGFR is 28 mL/min/1.73m², K+ is 5.6 mEq/L, HCO3 is 18 mEq/L, and phosphorus is elevated. Which medication requires dose reduction or avoidance in this patient?
- Amlodipine
- Atorvastatin
- Metformin (Correct answer)
- Lisinopril
Correct answer: Metformin
Metformin is contraindicated when eGFR falls below 30 mL/min/1.73m² due to risk of lactic acidosis from impaired renal clearance.
Question 6: A 48-year-old woman with cirrhosis due to hepatitis C presents with confusion and asterixis. Ammonia level is 180 μmol/L. She is not taking any sedatives. What is the most appropriate initial treatment?
- Fresh frozen plasma
- Lactulose orally (Correct answer)
- Rifaximin IV
- Neomycin IV
Correct answer: Lactulose orally
Lactulose is first-line treatment for hepatic encephalopathy; it traps ammonia in the gut by acidifying the colon and promoting its excretion as ammonium.
Question 7: A 25-year-old woman presents with fatigue and jaundice. CBC shows Hgb 8.5, reticulocyte count 9%, and spherocytes on peripheral smear. Direct Coombs test is positive. What is the most likely diagnosis?
- Hereditary spherocytosis
- Autoimmune hemolytic anemia (Correct answer)
- G6PD deficiency
- Microangiopathic hemolytic anemia
Correct answer: Autoimmune hemolytic anemia
A positive direct Coombs test confirms autoantibodies coating the red cells, consistent with autoimmune hemolytic anemia.
NBME Medicine 3
A 28-year-old woman presents with bloody diarrhea, tenesmus, and crampy abdominal pain for 3 weeks.
Colonoscopy shows continuous mucosal inflammation from the rectum to the splenic flexure.
Which feature best distinguishes this condition from Crohn disease?