A Decrease in Longitudinal Length of Kidney is a Reliable Tool to Predict the Success of Pyeloplasty in Children.

Objectives: The renal pelvis anteroposterior diameter (RPAPD) is an important parameter used in the indication and follow-up of ureteropelvic junction obstruction (UPJO). We hypothesized that kidney dimensions, namely longitudinal length (LL) and transverse width (TW), may have an easier similar validity to RPAPD measurement in the diagnosis of UPJO and follow-up after pyeloplasty.

Methods: Children who underwent pyeloplasty (January 2012-January 2024) were retrospectively evaluated. Exclusion criteria included megaureter, vesicoureteral reflux, urinary stones, duplicated systems, abnormal contralateral kidneys, secondary interventions, and incomplete data. The RPAPD, hydronephrosis grade, LL, and TW measured by ultrasound (US) before and 6 months after pyeloplasty were compared.

Results: Forty-nine children (14 girls, 35 boys; age range: 6 months to 17 years) who underwent pyeloplasty were studied. A significant reduction in RPAPD (29 to 18 mm) and LL (99 to 95 mm) was observed in affected kidneys 6 months after pyeloplasty compared to preoperative US measurements (p < 0.0001 and p = 0.005, respectively) but not in TW (p = 0.19). Similarly, the ratio of LL of the affected kidney to contralateral kidney (1.2 to 1.12 mm) significantly decreased after pyeloplasty (p = 0.026) but not the ratio of TW (p = 0.357). A positive correlation between RPAPD and LL is revealed (correlation coefficient = 0.619, p < 0.001).

Conclusions: The present study indicates that LL was elevated in affected kidneys compared to contralaterals and significantly decreases after pyeloplasty. We suppose that the decrease in LL may be an alternative, straightforward, and reliable measurement to assist in the follow-up after pyeloplasty.