PEDIATRIC UROLOGY

Diagnosis of pediatric urolithiasis: role of ultrasound and computerized tomography
Palmer JS, Donaher ER, O’Riordan MA, Dell KM
Division of Pediatric Urology, Rainbow Babies and Children’s Hospital, Cleveland, Ohio 44106, USA
J Urol. 2005; 174 (4 Pt 1): 1413-6

• Purpose: Pediatric urolithiasis is believed to be uncommon, and may present without the classic symptoms of renal colic. The objectives of this study were to describe the presenting features and radiographic evaluation of pediatric urolithiasis, and to determine the accuracy of ultrasound and unenhanced computerized tomography (CT) in detecting urolithiasis.
• Materials and Methods: We retrospectively reviewed the charts of children 0 to 18 years old with urolithiasis. Data collected included age, sex, race, presenting symptoms, radiographic studies performed during initial evaluation, calculus location and family history of urolithiasis.
• Results: A total of 75 patients had complete data for analysis. Of these patients 54 (72%) had urolithiasis symptoms (flank pain, gross hematuria or both). Patients with urolithiasis symptoms were older at diagnosis (median age 11.9 years vs 1.0 years, p < 0.001) and were more likely to have a family history of urolithiasis (54% vs 14%, p = 0.002). The 39 CTs performed were accurate in detecting calculi in children with urolithiasis symptoms (96% to 100%) and in those without symptoms (100%). The 36 ultrasounds performed had more variable accuracy in children with urolithiasis symptoms (33% to 100%) vs those without symptoms (89%). Ultrasound failed to detect urolithiasis in 41% of the patients with urolithiasis symptoms, compared to 5% with CT. CT was also highly accurate regardless of calculus location (89% to 100%), whereas ultrasound was again more variable (kidney 90%, kidney and ureter 75%, ureter alone 38%).
• Conclusions: Ultrasound failed to detect calculi in 41% of the children with urolithiasis symptoms, whereas CT was highly accurate in all situations. Unenhanced CT should be performed in all children with persistent urolithiasis symptoms and nondiagnostic ultrasound.
  
  
• Editorial Comment
  The authors reviewed their experience with diagnosing urolithiasis in children. In this series, 75 patients were diagnosed with stones over a period of about 18 months. 54 patients had symptoms including 48 with pain and the others, hematuria. The most interesting group for comparing diagnostic modalities was the symptomatic patients. Of the 54 with symptoms, ultrasound made the diagnosis in 10/17 patients (59%) and CT made the diagnosis in 36/37 (97%). Ultrasound was more accurate in patients with renal stones alone (90%) and patients with renal and ureteral stones (75%), but only diagnosed 38% of those with ureteral stones. In contrast, CT was accurate in 89% of kidney stones alone, but in 100% of those cases of ureteral stones (including 6 with both renal and ureteral stones).
  Non-contrast CT has largely replaced IVP (and ultrasound) in the evaluation of adults with symptoms consistent with urinary tract calculi. In contrast, most practitioners workup children with symptoms suggestive of calculi using ultrasound. This is primarily because of fears of radiation exposure in children. This series demonstrates that the diagnostic accuracy of ultrasound is unfortunately limited. Of course, in contrast to CT scans, ultrasound is much more operator dependent. It is unclear from this retrospective study where the ultrasounds were performed. Would truly expert pediatric sonographers have done better? If they did not see a ureteral stone, would they have seen enough hydronephrosis to suggest some form of ureteral obstruction that required further evaluation? This is unknown. However, even if so, when a patient is symptomatic in a local emergency department in a community hospital, it is impractical to have an expert pediatric ultrasonographer involved.
  Considering that radiation exposure in children is a real issue (and non-contrast CT scans with thin cuts from the top of the kidneys all the way through the pelvis do expose children to a fair amount of radiation), it is still reasonable to obtain an ultrasound initially in a child with a probable calculus by history. However, this study teaches us that, if the ultrasound is negative and the symptoms are suggestive, a non-contrast CT is appropriate.

Dr. Barry A. Kogan
Chief and Professor of Urology and Pediatrics
Albany Medical College
Albany, New York, USA