Renal Papillary Mapping and Quantification of Randall's Plaque in Pediatric Calcium Oxalate Stone Formers.

Randall's plaque (RP) with attached stones is recognized as a primary mechanism for stone formation in adult calcium oxalate stone formers (CaOx SF). The role of RP in pediatric stone pathogenesis is unknown, with no reported studies to date. The purpose of this study is to investigate renal papillary abnormalities and quantify RP in pediatric CaOx SF.

8 pediatric CaOx SF underwent ureteroscopy for symptomatic urolithiasis. The collecting system was mapped using a digital ureteroscope. Video for each patient was then reviewed using a retrograde pyelogram to confirm the location of each papilla. A single investigator (NLM) reviewed the video to quantify RP. Each papilla was graded as having mild , moderate, or severe amount of RP. Patient history was recorded.

An average of 9 papillae were mapped per patient. RP was present in 100% of patients and in 88.8% (64/72) of all papillae examined. When present, RP was uniformly distributed throughout the kidney without preferential distribution to a region or pole. The amount of RP on the papillae was graded as mild in 60%, moderate in 20.8%, and severe in 8.3%. The mean fractional RP coverage ranged from 0.39-9.34%. No correlation was found between the amount of plaque and age at first stone or number of prior stones (p= 0.84). Attached stones were rare (1/8 patients). The two patients with severe RP had a small amount of calcium phosphate in their stone analysis.

RP is common in pediatric CaOx SF. Compared to adult CaOx SF where up to 75% of stones are found attached to RP, attached stones were rare. The significance of these findings in the pathogenesis of pediatric stone formation remains unclear and will require longer term follow up.

Journal of endourology. 2019 Aug 13 [Epub ahead of print]

Anne L Darves-Bornoz, Tracy Marien, Gabriel E Fiscus, Douglass B Clayton, John Brock, John Thomas, Nicole Miller

Vanderbilt University Medical Center, 12328, Urology, A-1302 Medical Center Dr, Nashville, Tennessee, United States, 37232-2102; ., Vanderbilt University Medical Center, 12328, Urology, Nashville, Tennessee, United States; ., Vanderbilt University Medical Center, 12328, Urology, A-1302 Medical Center North, Nashville, Tennessee, United States, 37232-2102., Vanderbilt University Medical Center, 12328, Urology, Nashville, Tennessee, United States; ., Vanderbilt University Medical Center, 12328, Urology, Nashville, Tennessee, United States; ., Vanderbilt University Medical Center, 12328, Urology, Nashville, Tennessee, United States; ., Vanderbilt University Medical Center, 12328, Urology, Nashville, Tennessee, United States; .