A 72-year-old woman is evaluated in the intensive care unit for sudden clinical deteriorat… — USMLE Step 2 CK

A $72$ -year-old woman is evaluated in the intensive care unit for sudden clinical deterioration. She was admitted $10$ days ago for a severe chronic obstructive pulmonary disease exacerbation, which was treated with systemic glucocorticoids and levofloxacin. Three days ago, she developed profuse, watery diarrhea. This morning, her diarrhea abruptly ceased, but she became increasingly lethargic and developed severe abdominal pain. Her temperature is $39.4^\circ\text{C}$ ( $102.9^\circ\text{F}$ ), pulse is $132\text{/min}$ , blood pressure is $78/45\text{ mm Hg}$ , and respirations are $24\text{/min}$ . Physical examination reveals a lethargic patient. The abdomen is markedly distended and tympanic with absent bowel sounds. Diffuse rigidity, guarding, and rebound tenderness are present.

Laboratory studies show:
Leukocyte count: $38,000/\text{mm}^3$ ( $90\%$ neutrophils, $5\%$ bands)
Serum lactate: $5.2\text{ mmol/L}$

Arterial blood gas (room air):
pH: $7.22$
$\text{PaCO}_2$ : $30\text{ mm Hg}$
$\text{HCO}_3^-$ : $12\text{ mEq/L}$

An upright chest and abdominal radiograph demonstrates a $10\text{-cm}$ dilation of the transverse colon, loss of colonic haustrations, and a prominent crescent of radiolucency beneath the right hemidiaphragm.

Which of the following is the most appropriate next step in management?

Emergent subtotal colectomy with end ileostomyAnswer
B
Enteric administration of vancomycin and intravenous metronidazole
C
Computed tomography of the abdomen and pelvis with intravenous contrast
D
Endoscopic decompression of the colon
E
Intravenous sodium bicarbonate infusion

Answer

Emergent subtotal colectomy with end ileostomy

The correct answer is emergent subtotal colectomy with end ileostomy. This patient has developed fulminant Clostridioides difficile colitis, progressing to toxic megacolon (indicated by the

10\text{-cm}

colonic dilation and abrupt cessation of diarrhea) and subsequent colonic perforation. The presence of a rigid, board-like abdomen with rebound tenderness, combined with the radiographic finding of a radiolucent crescent beneath the right hemidiaphragm (pneumoperitoneum), definitively confirms a perforated viscus. In the setting of a perforated viscus and hemodynamic instability (septic shock), immediate surgical exploration and source control are required to prevent death.

Step-by-Step Solution

Identify the primary underlying infection

The patient's recent levofloxacin use, hospitalization, and initial profuse watery diarrhea strongly suggest Clostridioides difficile infection.

Recent broad-spectrum antibiotic use is the primary risk factor for C. difficile.

Analyze the sudden clinical deterioration

The abrupt cessation of diarrhea coupled with worsening shock, a rigid abdomen, and a leukemoid reaction (

38,000/\text{mm}^3

) indicates progression to toxic megacolon.

Loss of colonic tone leads to distension and cessation of stool output, masking the severity of fluid sequestration.

Interpret the radiographic and examination findings

The radiograph shows a severely dilated colon (

10\text{ cm}

) and free air under the diaphragm (radiolucent crescent). The physical exam shows peritonitis (rigidity, rebound tenderness).

Free intraperitoneal air and a rigid abdomen confirm colonic perforation.

Determine the definitive management

An emergent subtotal colectomy with end ileostomy is required.

Medical therapy is insufficient for a perforated viscus; source control via emergent surgery is life-saving in hemodynamically unstable patients with peritonitis.

Key Concept

Management of fulminant Clostridioides difficile colitis complicated by toxic megacolon and perforation.

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