A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.
A 72-year-old female presents to the emergency department complaining of severe abdominal pain and several days of bloody diarrhea. Her symptoms began with intermittent bloody diarrhea five days ago and have worsened steadily. For the last 24 hours, she has complained of fevers, chills, and abdominal pain. She has a history of ulcerative colitis, idiopathic hypertension, and hypothyroidism. Her medications include hydrochlorothiazide, levothyroxine, and sulfasalazine.
In the ED, her temperature is 39.1°C (102.4°F), pulse is 120/min, blood pressure is 90/60 mmHg, and respirations are 20/min. On exam, the patient is alert and oriented to person and place, but does not know the day. Her mucus membranes are dry. Heart and lung exam are not revealing. Her abdomen is distended with marked rebound tenderness. Bowel sounds are hyperactive.
Serum:
Na+: 142 mEq/L
Cl-: 107 mEq/L
K+: 3.3 mEq/L
HCO3-: 20 mEq/L
BUN: 15 mg/dL
Glucose: 92 mg/dL
Creatinine: 1.2 mg/dL
Calcium: 10.1 mg/dL
Hemoglobin: 11.2 g/dL
Hematocrit: 30%
Leukocyte count: 14,600/mm^3 with normal differential
Platelet count: 405,000/mm^3
What is the next best step in management?
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A
Abdominal CT with IV contrastIncorrect. CT with IV contrast can demonstrate toxic megacolon but is not first-line; plain film is faster, available at bedside, and avoids contrast in a hemodynamically unstable patient.
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B
Plain abdominal radiographCorrect. Plain abdominal radiograph is the first step to diagnose toxic megacolon (transverse colon > 6 cm) in a UC patient with severe colitis. It is fast, bedside, and avoids perforation risk.
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C
ColectomyIncorrect. Colectomy is the definitive treatment if medical management fails or if there is perforation, but diagnosis must first be confirmed and an attempt at medical management is appropriate.
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D
Contrast enemaIncorrect. Contrast enema is CONTRAINDICATED in suspected toxic megacolon due to high risk of colonic perforation.
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E
Colonoscopy with biopsyIncorrect. Colonoscopy is CONTRAINDICATED in suspected toxic megacolon due to high perforation risk from insufflation. Plain abdominal radiograph is the safe first-line diagnostic test.
↑ Tap an answer to reveal the reasoning
Answer: B. This patient with ulcerative colitis presents with severe bloody diarrhea, fever, tachycardia, hypotension, abdominal distention, and rebound tenderness--findings highly suspicious for toxic megacolon, a life-threatening complication of UC. The diagnostic criteria for toxic megacolon are: (1) radiographic evidence of colonic dilation > 6 cm, AND (2) at least 3 of: fever > 38C, HR > 120, neutrophilic leukocytosis > 10,500, anemia; PLUS at least 1 of: dehydration, altered mental status, electrolyte derangement, hypotension. This patient meets all criteria except imaging confirmation.
The first imaging test for suspected toxic megacolon is a PLAIN abdominal radiograph (KUB), which shows the diagnostic colonic dilation (transverse colon > 6 cm). A plain film is fast, bedside-available, and avoids the contrast/manipulation risk of CT enterography or contrast enema.
CT with IV contrast can show toxic megacolon but is not the FIRST step--plain film is faster and avoids contrast in a hemodynamically unstable patient. Contrast enema is CONTRAINDICATED in toxic megacolon due to perforation risk. Colectomy is the definitive treatment if medical management fails (steroids, bowel rest, decompression), but diagnosis must be confirmed first. The order: plain film -> medical management -> colectomy if no improvement in 24-72 hours or if perforation occurs.
**Why each option:**
**A.** CT with IV contrast can demonstrate toxic megacolon but is not first-line; plain film is faster, available at bedside, and avoids contrast in a hemodynamically unstable patient.
**B.** Correct. Plain abdominal radiograph is the first step to diagnose toxic megacolon (transverse colon > 6 cm) in a UC patient with severe colitis. It is fast, bedside, and avoids perforation risk.
**C.** Colectomy is the definitive treatment if medical management fails or if there is perforation, but diagnosis must first be confirmed and an attempt at medical management is appropriate.
**D.** Contrast enema is CONTRAINDICATED in suspected toxic megacolon due to high risk of colonic perforation.