While rounding in the intensive care unit, a physician evaluates a 68-year-old woman whose… — USMLE Step 2 CK

While rounding in the intensive care unit, a physician evaluates a $68$ -year-old woman whose clinical status has acutely deteriorated. She was admitted $10$ days ago for severe community-acquired pneumonia and was treated with a course of intravenous levofloxacin. Five days into her hospitalization, she developed profuse, watery diarrhea and was subsequently diagnosed with a *Clostridioides difficile* infection. She was immediately started on oral vancomycin therapy. Over the past $12$ hours, the patient reports that her diarrhea has completely ceased, but she has developed agonizing abdominal pain and progressive bloating. Her temperature is $39.2^\circ\text{C}$ ( $102.6^\circ\text{F}$ ), blood pressure is $82/50\text{ mm Hg}$ , and pulse is $132\text{/min}$ . Physical examination reveals a markedly distended, tympanic abdomen with diffuse, severe tenderness and absent bowel sounds. Laboratory studies show a leukocyte count of $32,000\text{/mm}^3$ and a serum lactate of $5.2\text{ mmol/L}$ . An upright abdominal radiograph demonstrates a transverse colon diameter of $10\text{ cm}$ with a loss of haustral markings and no free air under the diaphragm. Which of the following is the most appropriate next step in the management of this patient?

A
Computed tomography scan of the abdomen and pelvis
Immediate surgical explorationAnswer
C
Addition of intravenous meropenem and observation
D
Intravenous sodium bicarbonate infusion
E
Nasogastric tube decompression and conservative observation

Answer

Immediate surgical exploration

This patient presents with classic signs of toxic megacolon complicating a severe *Clostridioides difficile* infection (CDI). Toxic megacolon is characterized by colonic dilation (diameter

>6\text{ cm}

) accompanied by systemic toxicity (fever, tachycardia, hypotension, and marked leukocytosis). A major clinical clue is the sudden cessation of diarrhea in a patient with active CDI, which paradoxically signals developing colonic dysmotility rather than clinical improvement. Given her hemodynamic instability (shock), massive dilation (

10\text{ cm}

), and elevated lactate indicating bowel ischemia, medical management has definitively failed. The life-saving intervention is immediate surgical exploration, typically requiring a subtotal colectomy with an end ileostomy.

Step-by-Step Solution

Analyze the patient's history and acute presentation.

The patient has a known C. difficile infection. The sudden cessation of diarrhea combined with worsening pain, severe distension, and signs of systemic toxicity (fever, hypotension) is highly suspicious for a complication rather than improvement.

Sudden cessation of diarrhea in severe colitis often indicates colonic dysmotility and the development of toxic megacolon.

Interpret the laboratory and radiographic findings.

Leukocytosis (

32,000\text{/mm}^3

) and elevated lactate (

5.2\text{ mmol/L}

) indicate severe systemic inflammation and probable bowel ischemia. The radiograph confirms toxic megacolon (transverse colon

>6\text{ cm}

with loss of haustra).

Objective data are required to confirm the diagnosis and severity of the condition.

Determine the most appropriate management based on the patient's hemodynamic status.

Because the patient is in shock (

82/50\text{ mm Hg}

) and medical therapy (vancomycin) has failed to prevent progression, urgent definitive source control is needed.

In fulminant C. difficile colitis complicated by toxic megacolon and shock, delaying surgery increases mortality rates; immediate subtotal colectomy is the standard of care.

Key Concept

Management of toxic megacolon complicating Clostridioides difficile infection

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