A 26-day-old male infant, born at 28 weeks gestation, is evaluated in the neonatal intensi… — USMLE Step 2 CK

A 26-day-old male infant, born at 28 weeks gestation, is evaluated in the neonatal intensive care unit due to an acute clinical decline. The infant had been successfully advancing on enteral feedings with fortified maternal breast milk. Over the past 8 hours, he has developed temperature instability, marked abdominal distension, and bilious emesis. Vital signs reveal a temperature of $35.4^\circ\text{C}$ ( $95.7^\circ\text{F}$ ), heart rate of $190\text{ /min}$ , respiratory rate of $68\text{ /min}$ , and blood pressure of $38/20\text{ mm Hg}$ . Physical examination demonstrates a tense, erythematous abdomen with absent bowel sounds. Capillary refill time is 5 seconds.

Laboratory results are as follows:

Test	Value
Leukocyte count	$2,500/\text{mm}^3$ ( $10\%$ neutrophils, $30\%$ bands)
Platelet count	$42,000/\text{mm}^3$
Arterial pH	$7.18$
pCO $_2$	$34\text{ mm Hg}$
Bicarbonate	$12\text{ mEq/L}$
Lactate	$6.5\text{ mmol/L}$

An anteroposterior abdominal radiograph demonstrates widespread pneumatosis intestinalis and a continuous band of radiolucency across the upper abdomen clearly outlining the falciform ligament.

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

A
Immediate transport for computed tomography of the abdomen
B
Bowel rest, broad-spectrum intravenous antibiotics, and serial radiographs
C
Continuous infusion of intravenous sodium bicarbonate
Urgent exploratory laparotomyAnswer
E
Administration of intravenous furosemide and continuous positive airway pressure

Answer

Urgent exploratory laparotomy is the most appropriate next step due to evidence of intestinal perforation.

The correct answer is urgent exploratory laparotomy. This premature infant presents with classic signs of necrotizing enterocolitis (NEC), including temperature instability, abdominal distension, bilious emesis, and pneumatosis intestinalis. The critical radiographic finding is the visualization of the falciform ligament, which is normally unseen on a plain radiograph. When surrounded by massive free intraperitoneal air, it becomes visible as a linear opacity in the upper abdomen (the 'football sign'). The presence of pneumoperitoneum confirms intestinal perforation. In the setting of NEC, perforation is an absolute indication for surgical intervention (exploratory laparotomy or, in extremely low birth weight infants, primary peritoneal drainage) to resect necrotic bowel and achieve source control.

Step-by-Step Solution

Identify the primary diagnosis based on the clinical presentation and initial imaging.

Necrotizing enterocolitis (NEC).

The premature infant presents with feeding intolerance, bilious emesis, abdominal erythema, and pneumatosis intestinalis on radiography, which is pathognomonic for NEC.

Evaluate the clinical status and radiographic findings for severe complications.

Intestinal perforation complicated by septic shock.

The radiograph demonstrates a visible falciform ligament (the 'football sign'), which indicates massive free intraperitoneal air (pneumoperitoneum). The patient also exhibits hemodynamic instability, leukopenia with a left shift, and severe lactic acidosis.

Determine the definitive management for the identified complication.

Urgent surgical intervention.

Pneumoperitoneum is an absolute indication for surgery (exploratory laparotomy or primary peritoneal drainage) in patients with NEC, rendering medical management alone insufficient.

Key Concept

Surgical management of perforated necrotizing enterocolitis

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