A 7-month-old male infant is brought to the emergency department due to intermittent episo… — USMLE Step 2 CK

A $7$ -month-old male infant is brought to the emergency department due to intermittent episodes of inconsolable crying over the past $6$ hours. During these episodes, the infant intensely draws his knees to his chest and appears visibly distressed. Between episodes, he becomes uncharacteristically lethargic. His parents report one instance of non-bilious emesis and note that his last diaper contained dark red, mucoid stool. Vital signs reveal a heart rate of $165$ /min, respiratory rate of $40$ /min, temperature of $37.8$ °C ( $100$ °F), and blood pressure of $85/50$ mm Hg. Physical examination is notable for dry mucous membranes and a palpable, slightly tender, sausage-shaped mass in the right upper quadrant. The abdomen is otherwise soft without involuntary guarding.

Arrange the following steps in the most appropriate chronological sequence for the management of this patient.

1Establish intravenous access and administer an isotonic fluid bolus
2Perform an abdominal ultrasonography
3Obtain a pediatric surgery consultation
4Perform a fluoroscopy-guided pneumatic enema
5Proceed to an exploratory laparotomy

Answer

The correct sequence is: Establish intravenous access and administer an isotonic fluid bolus, followed by abdominal ultrasonography, pediatric surgery consultation, fluoroscopy-guided pneumatic enema, and finally exploratory laparotomy if non-operative reduction fails.

The management of uncomplicated intussusception follows a standardized protocol designed to maximize safety and success rates. Initial presentation often includes dehydration secondary to emesis and third-spacing, making intravenous fluid resuscitation the indispensable first step. Once the patient is stabilized, the diagnosis is confirmed non-invasively using abdominal ultrasonography. Crucially, before attempting therapeutic radiologic reduction (such as a pneumatic enema), a pediatric surgery consultation is required. This is because enema reduction carries a risk of bowel perforation and may ultimately fail, necessitating immediate operative intervention. Only after surgical backup is secured should the pneumatic enema proceed. Finally, an exploratory laparotomy is appropriately positioned as the last step, reserved exclusively for cases where radiologic reduction fails or complications arise.

Step-by-Step Solution

Identify the clinical presentation as highly suspicious for intussusception.

The patient exhibits the classic triad of colicky abdominal pain, lethargy, and 'currant jelly' stool, alongside a palpable right upper quadrant mass.

Recognizing the pathology dictates the clinical urgency and specific sequence of required diagnostic and therapeutic interventions.

Determine the initial resuscitation requirements.

The patient's tachycardia and dry mucous membranes necessitate immediate intravenous fluid resuscitation prior to any diagnostic workup.

Hemodynamic stabilization is paramount and always takes precedence over achieving a definitive diagnosis.

Select the appropriate diagnostic imaging modality.

Abdominal ultrasonography is chosen to definitively confirm the diagnosis.

Ultrasound is the most sensitive and specific non-invasive test for intussusception, rapidly confirming the pathology without exposing the infant to ionizing radiation.

Sequence the pre-intervention and radiologic intervention steps.

A pediatric surgical consultation is ordered prior to attempting the pneumatic enema.

Radiologic reduction carries approximately a

1\%

risk of bowel perforation. A surgical team must be notified and ready to intervene should the reduction fail or a complication occur.

Key Concept

The management of intussusception requires a strict stepwise approach: initial hemodynamic stabilization, ultrasound confirmation, mandatory surgical consultation to prepare for potential complications, therapeutic radiologic reduction, and operative intervention as a definitive last resort.

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