Ordering Renal Ultrasound for Suspected Kidney Stones in a 9-Year-Old
Order a renal and bladder ultrasound as the initial imaging study for suspected kidney stones in a 9-year-old child. 1
Primary Imaging Recommendation
Ultrasound of the kidneys and bladder is the appropriate first-line imaging modality for evaluating suspected nephrolithiasis in pediatric patients, avoiding radiation exposure while providing adequate diagnostic information in most cases. 1, 2, 3
How to Order the Study
Order the study as: "Ultrasound kidneys and bladder" or "Renal and bladder ultrasound" with the indication "rule out nephrolithiasis" or "suspected kidney stones." 1
- Ensure the bladder is adequately distended with urine during the examination to optimize assessment, as this improves visualization of the entire urinary tract. 1
- The examination should include evaluation of both kidneys for stones, hydronephrosis, and any anatomic abnormalities, as well as bladder assessment. 1
Clinical Context Matters
If the Child Has Painful Hematuria
- Ultrasound remains the initial imaging choice even when urolithiasis is strongly suspected. 1
- Be aware that ultrasound has limited sensitivity for detecting stones, finding approximately 75% of all urinary tract stones but only 38% of ureteral stones specifically. 1
- If ultrasound is negative but clinical suspicion remains high (persistent pain, hematuria, strong family history), consider low-dose unenhanced CT as the next step, as CT has sensitivity and specificity both well above 90% for stone detection. 1
If Asymptomatic or Painless Hematuria
- Ultrasound is highly appropriate as it can also evaluate for other causes of hematuria including renal masses, anatomic abnormalities, and bladder lesions. 1
- Unenhanced CT may be considered after a negative ultrasound if there is strong suspicion for asymptomatic nephrolithiasis. 1
Important Caveats and Pitfalls
Avoid ordering CT as the first imaging study unless there are exceptional circumstances, as children with kidney stones are at high risk for recurrence and multiple imaging studies throughout their lifetime, significantly increasing cancer risk from cumulative radiation exposure. 4
- Despite guidelines recommending ultrasound first, studies show CT is inappropriately used as the initial study in 63% of pediatric cases in some regions—this practice should be avoided. 4
- Ultrasound limitations include difficulty detecting small stones, obscuration by bowel gas, and operator dependence, but these drawbacks are outweighed by the safety profile in children. 1, 4
- Plain radiography (KUB) has limited utility due to small stone size and obscuration by bowel contents in children. 1
When to Escalate Imaging
Consider low-dose unenhanced CT in these specific scenarios: 1
- Negative ultrasound with persistent symptoms and high clinical suspicion
- When stone detection would directly impact treatment decisions
- Poor response to conservative management
Modern CT techniques with iterative reconstruction algorithms can achieve radiation doses lower than traditional IVU, making it a reasonable second-line option when necessary. 1
Follow-Up Considerations
After confirming stone disease, metabolic evaluation is essential as metabolic factors (hypercalciuria, hypocitraturia, genetic diseases) are frequent causes in children and require identification to prevent recurrence and long-term morbidity. 2, 5