Prenatal compensatory renal growth in unilateral renal agenesis

Multicystic Dysplastic Kidney: Prenatal Compensatory Renal Growth Pattern

OBJECTIVES

To assess the prenatal growth pattern of the normal kidney contralateral to a multicystic dysplastic kidney (MCDK).

METHODS

A retrospective study was conducted in a single referral center over 4 years. Cases diagnosed prenatally as MCDK and confirmed postnatally constituted the study group. For creation of nomograms, only isolated cases of MCDK were included.

RESULTS

Sixty-one fetuses had a diagnosis of an MCDK during the study period. After exclusion of cases with associated malformations, 47 fetuses remained, providing 94 measurements for creation of nomograms. The growth pattern of the normal kidney contralateral to an MCDK was linear throughout gestation (percentile = 20.01 + 1.5 gestational age; linear R²  = 0.753; r = 0.868) and was significantly higher during the third trimester (29-38 weeks' gestation) compared to the second trimester (22-28 weeks' gestation; P < .001). A comparison of the growth pattern of the normal kidney contralateral to the MCDK to the growth pattern of a solitary kidney revealed a significant higher compensatory trend during the third trimester (P < .0001). The mean kidney lengths at 22 and 38 weeks' gestation correlated with the 52nd and 88th and with the 84th and 90th percentiles for the normal kidney contralateral to the MCDK and a solitary kidney, respectively.

CONCLUSIONS

According to our study, the normal kidney contralateral to an MCDK has a unique growth pattern during intrauterine life, with dominant growth during the third trimester. The exact mechanism for this pattern, in comparison to early renal hypertrophy shown in solitary kidneys, is currently not clear. These data provide relevant information for the multidisciplinary prenatal counseling of future parents regarding the future renal outcome.

Renal growth slope in children with congenital and acquired solitary functioning kidneys

Purpose

This study aimed to analyze the renal growth slope in children with congenital and acquired solitary functioning kidneys.

Methods

This retrospective study included all renal ultrasonography examinations performed in children in the agenesis, multicystic dysplastic kidney (MCDK), or nephrectomy group between September 2002 and February 2019. We reviewed the images and recorded the contralateral kidney size only when there was no focal lesion. Linear mixed model or piecewise linear mixed model analyses with a time point of 24 months of age were performed.

Results

There were 132 patients, including 26 patients in the agenesis group, 35 in the MCDK group, and 71 in the nephrectomy group. The nephrectomy group showed the largest baseline kidney size (7.4 cm vs. 5.3 cm in the agenesis group [P<0.001] and 5.2 cm in the MCDK group [P<0.001]) and the smallest overall growth slope (0.04 cm/mo vs. 0.06 cm/mo in the agenesis group [P=0.004] and 0.07 cm/mo in the MCDK group [P<0.001]). However, considering the time point of 24 months for reaching adult renal function, there were significant changes in slope, from 0.1 cm/mo before 24 months of age to 0.03 cm/mo after 24 months of age in all three groups (P<0.001), without a significant difference among the groups.

Conclusion

Significant changes were found in the renal growth slope before and after 24 months of age, with no significant difference between congenital and acquired solitary functioning kidneys.

Is renal scintigraphy really a necessity in the routine diagnosis of congenital solitary kidney?

BACKGROUND

For a definitive diagnosis of congenital solitary kidney, renal scintigraphy is suggested as being the gold standard of ruling out ectopic functioning renal tissue, possibly missed by ultrasound. The aim of our study was to test ultrasonography precision in comparison with renal scintigraphy on a larger cohort of congenital solitary kidneys.

METHODS

We performed a retrospective unicenter study of children with congenital solitary kidney with no contralateral tissue, who were treated in the period from 1980 to 2017. The findings in children who underwent both abdominopelvic ultrasound and nuclear renal scintigraphy were compared and the accuracy of ultrasound was assessed.

RESULTS

99 children met the inclusion criteria of congenital solitary kidney confirmed with abdominopelvic ultrasound and nuclear renal scintigraphy. The children were predominantly male (61.6%), and the congenital solitary kidney was largely right-sided (55.5%). In 97 cases (98%), ultrasound correctly predicted the absence of functional renal tissue on one side in the renal fossa or in an ectopic location (pelvis or ipsilateral side). The calculated accuracy of abdominopelvic ultrasound in diagnosing congenital solitary kidney was therefore 98%.

CONCLUSIONS

Our findings confirm that abdominopelvic ultrasound alone is accurate enough to diagnose congenital solitary kidney. It gives enough information for consideration if further radiological evaluation is still needed.

Analysis of renal blood flow and renal volume in normal fetuses and in fetuses with a solitary functioning kidney

OBJECTIVE

To evaluate renal blood flow and renal volume for the prediction of postnatal renal function in fetuses with solitary functioning kidney (SFK).

METHODS

Seventy-four SFK fetuses (unilateral renal agenesis [12], multicystic dysplastic kidney [36], and severe renal dysplasia [26]) were compared with 58 healthy fetuses. Peak systolic velocity (PSV), pulsatility index (PI), and resistance index (RI) of the renal artery (RA) were measured; 2D and 3D (VOCAL) volumes were calculated. Renal length and glomerular filtration rate (GFR) were obtained in SFK children (2 years).

RESULTS

Compared with the control group, the PSV RA was significantly lower in nonfunctioning kidneys and significantly higher in SFK. Volume measurements indicated a significantly larger volume of SFK compared with healthy kidneys. All but 4 children had GFR above 70 mL/min/1.73 m² , and compensatory hypertrophy was present in 69% at 2 years. PSV RA and SFK volume correlated with postnatal renal hypertrophy. No correlation between prenatal and postnatal SFK volume and GFR at 2 years was demonstrated.

CONCLUSION

Low PSV RA might have a predictive value for diagnosing a nonfunctioning kidney in fetuses with a SFK. We demonstrated a higher PSV RA and larger renal volume in the SFK compared with healthy kidneys.