Purpose or Case Report: Ultrasound (US) of the kidneys is one of the most frequently performed imaging examination in the pediatric population. Conventionally, curvilinear probes (6-10MHz) are used for initial assessment. Liner high-resolution probes (HRP) (>15MHz) have been reported to improve the visualization of renal pyramid pathology. At our institution, we have implemented the use of HRP (15 or 18MHz) in addition to the lower-resolution probes (LRP) to the renal US protocol. This is a study to investigate whether the routine utilization of HRP can increase the detection and confidence in the diagnosis of nephrocalcinosis.
Methods & Materials: We performed a retrospective search of our database for patients referred for renal US between June and September 2024, with the keyword “nephrocalcinosis” and an age of <18 years. All US studies were performed on Siemens Sequoia (probes 1-5C1, 10L4 and 18L6) or GE LOGIQ E10 (probes C2-9 and ML6-15) systems. The images were reviewed by 2 radiologists (21 years and 13 years of experience), who were blinded to the final diagnosis of nephrocalcinosis. We defined nephrocalcinosis as the presence of hyperechoic foci in the renal medulla according to the patterns previously published by Patriquin and Robitaille (1986). Confidence in the diagnosis for each probe was graded 1-5 (1=low, 5=high confidence).
Results: Out of 1407 renal US referrals, 49 patients met the inclusion criteria. 39/49 had the US performed with both LRP (up to 10MHz) and HRP (15 or 18MHz). 18/39 (46%) had US findings consistent with nephrocalcinosis on both LRP and HRP. 11/39 (28%) had no US findings of nephrocalcinosis on LRP but calcium deposition in the pyramids were noted with HRP. 10/39 (26%) had no US findings of nephrocalcinosis on both LRP and HRP. The mean values for confidence grading for LRP images were 3.3 and 3.4 respectively for each observer; with mean values increased to 4.4 and 4.5 for HRP images. The confidence grading of diagnosis increased in 28/39 (71.8%) patients for the first observer and increased in 26/39 (66.7%) patients for the second observer. In 5 patients, incidental cortical anomalies were noted only with the HRP.
Conclusions: Ultrasound with HRP is helpful for the detection of nephrocalcinosis in children, which is sometimes difficult to diagnose with LRP alone. HRP utilization increases confidence in the diagnosis of nephrocalcinosis and may improve the detection of other cortical or medullary anomalies.