In a 12‑year‑old male presenting with acute lower abdominal (hypogastric) pain, tenderness, a positive renal punch test, dark urine containing bilirubin and trace ketones, and no fever or vomiting, what is the next step in management?

Immediate Renal Imaging with Ultrasound or Non-Contrast CT

The next step is urgent renal imaging—preferably renal ultrasound as the initial modality in this 12-year-old—to evaluate for urolithiasis, hydronephrosis, or alternative diagnoses such as subcapsular hematoma, given the positive kidney punch test, dark urine, and hypogastric pain following strenuous activity. 1, 2

Clinical Reasoning

This presentation strongly suggests acute urolithiasis (kidney stone) based on several key features:

• Positive kidney punch test (renal tenderness) is a highly significant predictor of renal colic 3
• Dark urine with trace protein and ketones suggests concentrated urine and possible hematuria (though frank blood wasn't documented, microscopic hematuria supports stone disease) 3
• Pain pattern: hypogastric pain worsened by sitting but relieved by standing/walking is consistent with lower urinary tract involvement 1
• Timing: onset after prolonged outdoor activity suggests dehydration as a precipitating factor 2
• Age: while less common than in adults, pediatric urolithiasis is increasingly recognized and often underdiagnosed 2

Imaging Strategy

First-Line: Renal Ultrasound

• Ultrasound is the preferred initial imaging in children with suspected urolithiasis because it avoids radiation, can identify stones, hydronephrosis, and alternative diagnoses like subcapsular hematoma 2, 4
• Ultrasound has excellent sensitivity and specificity for many pediatric abdominal conditions and is particularly well-suited for children 4
• Can detect urinary tract anomalies and acute obstruction 2

If Ultrasound is Inconclusive: Non-Contrast CT

• Non-contrast CT is more sensitive for detecting stones and should be obtained if ultrasound is negative but clinical suspicion remains high 1, 2
• The ACR Appropriateness Criteria support CT for definitive stone diagnosis when needed 1

Critical Alternative Diagnosis to Exclude

Page kidney (subcapsular hematoma) must be considered given:

• Recent strenuous physical activity (potential trauma) 5
• Flank pain and dark urine mimicking nephrolithiasis 5
• This can cause secondary hypertension and requires different management 5

Concurrent Management Steps

While arranging imaging:

• Check vital signs including blood pressure (to exclude shock, infection, or secondary hypertension from Page kidney) 1, 5
• Obtain proper urinalysis with microscopy to confirm hematuria (>10 RBCs strongly supports renal colic) 3
• Assess for fever to exclude obstructive pyelonephritis, which would require urgent intervention 1, 3

Important Caveat About the Bilirubin Finding

The presence of bilirubin in the urine is unusual in this clinical context and warrants attention:

• Bilirubinuria typically indicates conjugated hyperbilirubinemia from hepatobiliary disease, not renal pathology 6, 7, 8
• This finding may represent a false positive or suggest concurrent liver pathology requiring separate evaluation
• However, the dominant clinical picture points to renal pathology, so proceed with renal imaging first 2, 4

Timeline for Imaging

• Imaging should be obtained within 7 days of symptom onset for optimal diagnostic accuracy 1
• Given the patient is currently ambulatory without fever or signs of obstruction, outpatient fast-track imaging is appropriate 1
• If pain worsens, fever develops, or the patient cannot ambulate, immediate hospital evaluation is required 1

Post-Imaging Management

Once imaging is complete, all pediatric stone patients require:

• Metabolic workup to identify underlying causes (primary hyperoxalurias, hypercalciuria, cystinuria) as metabolic disorders are frequent in children 2
• Determination of stone size and location to guide conservative versus interventional management 1
• Increased fluid intake and urine straining to capture any passed stones 1