An 8-week-old male infant is brought to the emergency department by his parents due to a 2… — USMLE Step 2 CK

An 8-week-old male infant is brought to the emergency department by his parents due to a 24-hour history of severe abdominal distension, lethargy, and multiple episodes of explosive, foul-smelling diarrhea. His mother notes he has been feeding poorly and had two episodes of nonbilious emesis this morning. The patient's past medical history is notable for delayed passage of meconium, which required glycerin suppositories during his first week of life, and he has suffered from chronic constipation since discharge. His temperature is $38.9^\circ C$ ( $102^\circ F$ ), blood pressure is $65/35\text{ mm Hg}$ , pulse is $188/\text{min}$ , and respirations are $62/\text{min}$ . On physical examination, the infant appears mottled and lethargic. The abdomen is markedly distended and tense, with sluggish bowel sounds. Digital rectal examination produces a sudden, high-pressure expulsion of liquid stool and gas. A plain abdominal radiograph demonstrates markedly dilated loops of bowel with multiple air-fluid levels, but no free air is visible under the diaphragm. Which of the following is the most appropriate next step in management?

Intravenous fluids, broad-spectrum antibiotics, and rectal irrigationAnswer
B
Immediate exploratory laparotomy with diverting colostomy
C
Intravenous fluids and water-soluble contrast enema
D
Oral rehydration solution and oral metronidazole
E
Urgent needle decompression of the peritoneal cavity

Answer

The most appropriate next step in management is intravenous fluids, broad-spectrum antibiotics, and rectal irrigation.

The patient's clinical presentation—explosive foul-smelling diarrhea, toxic appearance, marked abdominal distension, and a history of delayed meconium passage—is highly suspicious for Hirschsprung-associated enterocolitis (HAEC). HAEC is a potentially fatal complication resulting from stasis and bacterial overgrowth proximal to the aganglionic segment. The initial step in managing HAEC, provided there is no evidence of bowel perforation (as confirmed by the lack of free air on the radiograph), involves rapid stabilization. This includes intravenous fluid resuscitation to correct shock, empiric broad-spectrum antibiotics to treat translocating enteric organisms, and mechanical decompression of the colon using warm saline rectal irrigations. This combination prevents further toxic dilation and prepares the patient for a definitive pull-through procedure at a later, safer time.

Step-by-Step Solution

Identify the clinical syndrome based on the presentation.

The infant has delayed meconium passage, chronic constipation, fever, toxic appearance, and explosive stool upon digital rectal examination.

These findings are classic for Hirschsprung-associated enterocolitis (HAEC), a life-threatening complication of Hirschsprung disease.

Evaluate the patient's hemodynamic stability and radiographic findings to determine the severity.

The patient is in shock (hypotension, tachycardia) but the abdominal radiograph confirms there is no pneumoperitoneum.

The absence of free air means gross bowel perforation has not yet occurred, which dictates medical rather than immediate surgical intervention.

Select the appropriate initial management for this specific stage of the disease.

The patient requires immediate stabilization with intravenous fluid resuscitation, broad-spectrum antibiotics, and mechanical decompression via rectal irrigation.

Medical decompression and resuscitation must be attempted first; surgery is reserved for patients who have perforated or fail to improve with conservative management.

Key Concept

Hirschsprung-associated enterocolitis (HAEC) presents with fever, distension, and explosive diarrhea in an infant with undiagnosed Hirschsprung disease. In the absence of perforation, initial management consists of fluid resuscitation, intravenous broad-spectrum antibiotics, and bowel decompression via rectal irrigation.

Estimated Time:1m 30s

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