Diagnostics Questions for the CPEN Exam — Practice Free

The diagnostic priority is a Venous Blood Gas (VBG) and urinalysis. To confirm Pediatric Diabetic Ketoacidosis (DKA), criteria include: Blood glucose >200 mg/dL, venous pH <7.3 or bicarbonate <15 mmol/L, and ketonemia/ketonuria. Exam Strategy: BCEN often tests the differentiation between DKA and simple hyperglycemia. Remember that cerebral edema is the leading cause of mortality in pediatric DKA; watch for sudden changes in AMS during fluid resuscitation. Initial fluid boluses should be conservative (10-20 mL/kg) unless the patient is in frank shock.

Gold standard: Air or Contrast Enema (diagnostic and often therapeutic). Ultrasound finding: Target or Donut sign (concentric rings of bowel-in-bowel). Clinical Pearl: Currant jelly stool is a late finding indicating mucosal ischemia. BCEN emphasizes recognizing the intermittent nature of the pain between which the child may appear entirely normal.

A clear aspirate is inconclusive and does not rule out an Upper GI Bleed (UGIB). Up to 15% of patients with an active UGIB (especially post-pyloric/duodenal) may have a clear NG aspirate if the pylorus is closed or not refluxing. Clinical Pearl: If the aspirate is bilious (yellow/green) AND non-bloody, a UGIB is much less likely as the bile indicates the tube has sampled the duodenum. BCEN focuses on the fact that NG lavage lacks sensitivity for ruling out bleeds but is highly specific if blood is found.

Grade IV. This grade is characterized by lacerations involving segmental or hilar vessels that produce major devascularization (>25% of the spleen). Grade V is reserved for a completely shattered spleen or total hilar vascular exhaustion (devascularization). Clinical Pearl: Grade IV and V injuries in children still prioritize non-operative management (NOM) unless there is hemodynamic instability refractory to fluid/blood resuscitation. BCEN emphasizes that Grade does not equal Surgery.

Serial Physical Examinations. While CT is standard for initial trauma screening, serial abdominal exams by the same provider are superior for detecting the evolving signs of HVI (increasing tenderness, guarding, rebound). BCEN Distractor: FAST exams are often unreliable for HVI as they primarily detect large volumes of hemoperitoneum, not the small amounts of fluid or air associated with early bowel perforation. If the question asks for the most reliable ongoing assessment, choose serial exams.