Transient renal enlargement in pediatric hematopoietic cell transplant recipients

Age‐dependent renal length tables are routinely used when interpreting pediatric ultrasound. Standard renal length tables may not be accurate for HCT patients due to treatment effects on kidney size. The purpose of this study was to determine whether renal size changes from expected lengths based on age after HCT in the absence of other markers of renal disease. Four hundred and fifty renal measurements were made on 101 patients who underwent HCT between 2006 and 2010. Renal length was measured at 1–90 days pre‐HCT and at 0–30, 31–90, 91–180, and 181+ days post‐HCT. Values were compared with normal renal length tables. Average post‐HCT renal lengths were greater than established normative renal length data within every age group. Age‐adjusted average renal lengths measured at 0–30 and 31–90 days post‐transplantation were significantly larger than pre‐HCT renal lengths, with relative increases of 6.9% (4.5, 9.4; p < 0.001) and 3.9% (1.4, 6.4; p = 0.003), respectively. Average renal length did not differ significantly after 90 days post‐transplantation. HCT patients may have larger kidneys in the absence of renal disease. Awareness of the potential phenomenon of transient renal enlargement following HCT can prevent misdiagnosis and eliminate unnecessary diagnostic evaluations, interventions, anxiety, resource allocation, and financial costs.