A 7-month-old boy is brought to the pediatric emergency department due to a 24-hour histor… — USMLE Step 2 CK

A $7$ -month-old boy is brought to the pediatric emergency department due to a $24$ -hour history of high fever, lethargy, and foul-smelling, explosive diarrhea. According to his parents, the patient has had severe constipation since birth, often requiring glycerin suppositories to pass stool. His first meconium was passed approximately $36$ hours after birth. On presentation, his temperature is $39.2^\circ\text{C}$ ( $102.6^\circ\text{F}$ ), pulse is $175/\text{min}$ , respirations are $55/\text{min}$ , and blood pressure is $72/45\text{ mmHg}$ . Physical examination reveals a lethargic, ill-appearing infant with dry mucous membranes. The abdomen is markedly distended and tympanitic. Digital rectal examination is followed by a sudden expulsion of foul-smelling liquid stool and flatus. Laboratory studies show a leukocyte count of $22,000/\text{mm}^3$ with $15\%$ bands. An abdominal radiograph demonstrates significantly dilated loops of bowel with multiple air-fluid levels, but no free air under the diaphragm. Which of the following is the most appropriate next step in management?

Intravenous fluid resuscitation, broad-spectrum antibiotics, and rectal irrigationAnswer
B
Immediate exploratory laparotomy and bowel resection
C
Water-soluble contrast enema
D
Rectal suction biopsy
E
Administration of oral polyethylene glycol and discharge with close follow-up

Answer

The most appropriate next step is initiating intravenous fluid resuscitation, broad-spectrum antibiotics, and rectal irrigation.

The correct sequence of management involves intravenous fluid resuscitation, broad-spectrum antibiotics, and rectal irrigation. This patient's history of delayed meconium passage and chronic constipation points to Hirschsprung disease. The acute onset of fever, shock, abdominal distension, and explosive diarrhea on rectal exam is the classic presentation of Hirschsprung-associated enterocolitis (HAEC). HAEC is a life-threatening complication resulting from intestinal stasis, bacterial overgrowth, and bacterial translocation. Because there is no free air on the radiograph to suggest perforation, the immediate priority is aggressive medical stabilization. This consists of IV fluids for shock, broad-spectrum antibiotics for sepsis, and serial warm saline rectal irrigations to mechanically decompress the retained stool and gas from the dilated colon.

Step-by-Step Solution

Analyze the patient's history and baseline presentation.

The history of delayed meconium passage (

>24

hours) and chronic constipation requiring suppositories suggests an underlying diagnosis of Hirschsprung disease.

Identifying the baseline chronic condition is necessary to contextualize the acute presentation.

Evaluate the acute clinical deterioration.

The acute onset of fever, lethargy, hemodynamic instability, abdominal distension, and explosive foul-smelling diarrhea after digital rectal exam (squirt sign) indicates Hirschsprung-associated enterocolitis (HAEC).

HAEC is a potentially fatal complication caused by stasis-induced bacterial overgrowth and mucosal inflammation in the dilated colon proximal to the aganglionic segment.

Determine the optimal acute management for this condition.

The patient is in shock without radiographic evidence of intestinal perforation. The priority is medical stabilization with IV fluids, broad-spectrum antibiotics to treat bacterial translocation, and serial rectal irrigations to decompress the toxic bowel.

Definitive diagnostic tests (biopsy) and definitive surgical correction must be deferred until the acute enterocolitis is fully treated.

Key Concept

Hirschsprung-Associated Enterocolitis (HAEC) requires prompt recognition and aggressive medical management including fluid resuscitation, broad-spectrum antibiotics, and bowel decompression via rectal irrigation prior to any definitive surgical or diagnostic interventions.

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