A male preterm neonate, born at 28 weeks gestation and currently on day 12 of life, is eva… — USMLE Step 2 CK

A male preterm neonate, born at $28$ weeks gestation and currently on day $12$ of life, is evaluated in the neonatal intensive care unit for new-onset lethargy and temperature instability. He had been tolerating gradually increasing volumes of fortified expressed breast milk via an orogastric tube. Vital signs show a temperature of $35.8^\circ\text{C}$ ( $96.4^\circ\text{F}$ ), heart rate of $175/\text{min}$ , respiratory rate of $68/\text{min}$ , and blood pressure of $52/34\text{ mmHg}$ . Physical examination reveals a mottled, hypoactive infant. The abdomen is markedly distended and visibly erythematous. The bedside nurse reports aspirating $15\text{ mL}$ of bilious residual fluid from the feeding tube. A scattered cutaneous eruption of $1\text{-}$ to $2\text{-mm}$ yellow pustules on an erythematous base is noted on the infant's thighs; a previous Wright stain of these lesions demonstrated a predominance of eosinophils.

Laboratory evaluation reveals:

Parameter	Result
Leukocytes	$3,200/\text{mm}^3$
Platelets	$65,000/\text{mm}^3$
Arterial pH	$7.22$
pCO $_2$	$37\text{ mmHg}$
Bicarbonate	$14\text{ mEq/L}$

An anteroposterior abdominal radiograph demonstrates dilated loops of bowel, linear radiolucencies within the bowel wall, and branching radiolucencies overlying the hepatic shadow. No free intraperitoneal air is visualized.

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

Cessation of enteral nutrition, nasogastric suctioning, and initiation of empiric antimicrobial therapyAnswer
B
Immediate transfer to the operating room for an exploratory laparotomy
C
Administration of systemic ceftriaxone and metronidazole
D
Transport to radiology for a diagnostic water-soluble contrast enema
E
Implementation of contact isolation and administration of acyclovir therapy

Answer

Cessation of enteral nutrition, nasogastric suctioning, and initiation of empiric antimicrobial therapy

This preterm neonate presents with classic signs of necrotizing enterocolitis (NEC), including feeding intolerance (bilious aspirates), a distended erythematous abdomen, and pathognomonic radiographic findings of pneumatosis intestinalis (linear radiolucencies in the bowel wall) and portal venous gas. The profound metabolic acidosis, leukopenia, and thrombocytopenia reflect severe systemic inflammation and impending shock. Because there is no free intraperitoneal air, the bowel is not yet perforated (Bell's Stage IIB). The cornerstone of initial management for unperforated NEC is strict bowel rest (cessation of enteral feeds), gastrointestinal decompression via a sump tube, intravenous fluid resuscitation, and initiation of empiric broad-spectrum antimicrobial therapy.

Step-by-Step Solution

Interpret the clinical and radiographic findings.

The combination of feeding intolerance, bilious residuals, abdominal distention, and radiographic evidence of pneumatosis intestinalis with portal venous gas confirms the diagnosis of necrotizing enterocolitis (NEC).

Accurate diagnosis is required before selecting a management pathway.

Assess for indications of surgical intervention.

The radiograph shows no free intraperitoneal air (pneumoperitoneum), indicating the bowel has not yet perforated.

Determines whether the patient requires immediate surgery or conservative medical management.

Evaluate the cutaneous findings.

The pustular rash with eosinophils on a Wright stain is identified as erythema toxicum neonatorum.

Differentiates a benign incidental finding from an infectious etiology like neonatal herpes simplex virus.

Select the optimal medical management for unperforated NEC.

The patient requires immediate bowel rest, gastric decompression, and safe neonatal antibiotics, explicitly avoiding contraindicated agents like ceftriaxone.

Medical management is the gold standard for NEC prior to perforation.

Key Concept

The initial management of unperforated necrotizing enterocolitis includes bowel rest, gastric decompression, and broad-spectrum antibiotics, while surgical intervention is reserved for bowel perforation.

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