Correlation Between Renal Medullary Pyramidal Thickness, Parenchymal Thickness, and Differential Renal Function in Hydronephrotic Kidneys

The study investigates the relationship between renal medullary pyramidal thickness (PT), parenchymal thickness, and differential renal function (DRF) in children with unilateral hydronephrosis, particularly focusing on cases with a PT of 3 mm or less, which is often linked to increased risk for ureteropelvic junction (UPJ) obstruction and pyeloplasty. Conducted as a retrospective review of ultrasound and nuclear renal scans (MAG3) in 98 children with grade 3 and 4 unilateral hydronephrosis, the research aimed to evaluate how these ultrasound measurements correlate with the renal function as determined by the MAG3 scan. The results indicate that no kidneys with a PT greater than 3 mm or a parenchymal thickness above 5 mm exhibited a DRF below 40%, with significant findings highlighting that 17% of kidneys with a PT of 3 mm or less and 18% with a parenchymal thickness of 5 mm or less demonstrated a DRF <40%. Additionally, a weak positive correlation was identified between the ratio of PT in the hydronephrotic kidney compared to the non-hydronephrotic kidney and its corresponding DRF, suggesting that these ultrasound metrics could be beneficial in selecting patients for further renal scanning. The study concludes that maintaining a PT above 3 mm and a parenchymal thickness above 5 mm is associated with preserving a relative renal function greater than 40%, thus supporting the utility of ultrasound assessments in pediatric patients with hydronephrosis while minimizing unnecessary radiation exposure from nuclear imaging.