# Paediatric multicystic dysplastic kidney disease in Cape Town, South Africa

## TL;DR

This study examines the characteristics and outcomes of pediatric multicystic dysplastic kidney disease in South Africa, highlighting the need for long-term follow-up and standardized guidelines.

## Contribution

The study identifies a distinctive pattern of contralateral kidney abnormalities in MCDK cases in South Africa, previously unreported in this region.

## Key findings

- Unilateral MCDK was found in 6.2% of congenital kidney cases, with left-sided involvement in 57.1%.
- Contralateral kidney abnormalities occurred in 17.3% of cases, with duplex kidney being the most common.
- Initial kidney size ≤ 5.0 cm was the sole predictor of MCDK involution.

## Abstract

Multicystic dysplastic kidney disease (MCDK) is a notable congenital anomaly of the kidney and urinary tract, with potential risk for chronic kidney disease, yet data from sub-Saharan Africa remain scarce. This study examined the pattern of MCDK, associated contralateral kidney abnormalities, determined the predictors of MCDK involution and assessed short-term outcomes in children followed beyond one year in South Africa.

This retrospective study involved children under 13 years of age with suspected unilateral MCDK, confirmed on kidney ultrasound and [99mTc]Tc-MAG3 scans at the Red Cross War Memorial Children’s Hospital between January 1, 2014, and December 31, 2023. Demographic, clinical, and radiologic data were obtained. The Log-rank test and Cox Proportional Hazards regression analyses were used to identify predictors of MCDK involution.

Among 1,581 new cases, 98 (6.2%) had unilateral MCDK. 50% were male, and 57.1% had left-sided involvement. Median follow-up was 60 months (IQR: 12–72). Contralateral kidney abnormalities occurred in 17 (17.3%), most commonly duplex kidney (35.3%) and ureteropelvic junction obstruction (29.4%), but no vesicoureteric reflux was noted. Of 81 children followed beyond a year, 80.2% demonstrated contralateral hypertrophy, and 69.1% exhibited involution of the affected kidney. Initial kidney size ≤ 5.0 cm was the sole predictor of involution (Hazard Ratio: 2.42, 95% CI: 1.31–4.48). Urinary tract infections occurred in 18.5%, proteinuria in 2.5%, hypertension in 1.2%, and 2.5% developed chronic kidney disease related to contralateral dysplasia. One nephrectomy was performed, and no malignancies or deaths. At last follow-up, 28.4% were lost to follow-up, and 12.3% had transitioned to adolescent clinics.

All MCDK cases were unilateral, with duplex kidney being the most common contralateral abnormality, a distinctive finding previously unreported. Follow-up into adolescence may be beneficial, as progression of chronic kidney disease is rare in those without contralateral anomalies. Multicentre long-term studies are needed to provide standardised follow-up guidelines.