An 81-year-old male is transferred to the intensive care unit due to rapid clinical deteri… — USMLE Step 2 CK

An $81$ -year-old male is transferred to the intensive care unit due to rapid clinical deterioration. He was initially admitted to the general medical ward six days ago for an acute exacerbation of chronic obstructive pulmonary disease and was appropriately treated with systemic glucocorticoids and levofloxacin. On his fourth day of hospitalization, he developed profuse, watery stools and diffuse abdominal cramping. Stool assays returned positive for *Clostridioides difficile* toxins A and B, prompting the initiation of oral vancomycin. Today, he is increasingly lethargic and minimally responsive. His temperature is $39.4^\circ\text{C}$ ( $102.9^\circ\text{F}$ ), blood pressure is $82/50\text{ mmHg}$ , pulse is $128/\text{min}$ , and respiratory rate is $28/\text{min}$ . Physical examination reveals a markedly distended, tympanitic abdomen with severe generalized tenderness, rebound guarding, and absent bowel sounds.

Laboratory analysis reveals:
* Leukocytes: $38,000/\text{mm}^3$
* Serum bicarbonate: $10\text{ mEq/L}$
* Arterial blood gas (room air): pH $7.22$ , pCO2 $24\text{ mmHg}$ , pO2 $68\text{ mmHg}$

A supine abdominal radiograph demonstrates a transverse colon diameter of $8.5\text{ cm}$ with distinct loss of haustral markings, thumbprinting, and no evidence of pneumoperitoneum. After initiating aggressive fluid resuscitation, which of the following is the most appropriate next step in the management of this patient?

Surgical consultation for immediate subtotal colectomy and end ileostomyAnswer
B
Transition to systemic vancomycin therapy to address the fulminant infection
C
Nasogastric tube insertion and watchful waiting with serial abdominal examinations
D
Sodium bicarbonate infusion to correct concurrent metabolic and respiratory acidosis
E
Noninvasive positive pressure ventilation and diuresis for cardiopulmonary failure

Answer

Surgical consultation for immediate subtotal colectomy and end ileostomy

The correct answer is surgical consultation for immediate subtotal colectomy and end ileostomy. This patient has fulminant *Clostridioides difficile* infection (CDI) complicated by toxic megacolon (transverse colon >

6\text{ cm}

with loss of haustral markings) and peritonitis (rebound guarding, absent bowel sounds). While initial therapy for severe CDI includes oral vancomycin and intravenous metronidazole, the development of hemodynamic instability, massive leukocytosis (

38,000/\text{mm}^3

), and peritonitis are absolute indications for emergent surgical intervention. Subtotal colectomy with end ileostomy is the procedure of choice to remove the source of sepsis and prevent fatal bowel perforation.

Step-by-Step Solution

Identify the primary acute diagnosis and its severity.

The patient has fulminant Clostridioides difficile infection (CDI) complicated by toxic megacolon and shock.

He presents with severe sepsis, massive leukocytosis (

38,000/\text{mm}^3

), and an abdominal radiograph showing transverse colon dilation >

6\text{ cm}

with loss of haustral markings.

Evaluate the patient's acid-base status to rule out secondary complications.

Primary metabolic acidosis with adequate respiratory compensation.

Using Winter's formula (

1.5 \times 10 + 8 = 23 \pm 2

), the expected pCO2 range is

21-25\text{ mmHg}

, matching the measured

24\text{ mmHg}

. This confirms appropriate compensatory tachypnea (Kussmaul breathing) rather than respiratory failure.

Determine the definitive intervention based on the clinical examination.

Immediate surgical intervention is required.

The presence of peritonitis (rebound guarding), shock, and toxic megacolon indicates impending or actual perforation, making medical therapy alone insufficient and mandating immediate surgical source control.

Key Concept

Indications for surgery in fulminant Clostridioides difficile infection

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