Renal Parenchymal Area Growth Curves for Children 0 to 10 Months Old

Ultrasound-Based Renal Parenchymal Area and Kidney Function Decline in Infants With Congenital Anomalies of the Kidney and Urinary Tract

Congenital anomalies of the kidney and urinary tract are the leading cause of chronic kidney disease in children. Noninvasive imaging biomarkers that predict chronic kidney disease progression in early infancy are needed. We performed a pilot study nested in the prospective Chronic Kidney Disease in Children cohort study to determine the association between renal parenchymal area (RPA) on first post-natal renal ultrasound and change in estimated glomerular filtration rate (eGFR) in children with congenital anomalies of the kidney and urinary tract. Among 14 participants, 78.6% were males, the median age at the time of the ultrasound was 3.4 months (interquartile range, 1.3-7.9 mo), and the median total RPA z-score at baseline was -1.01 (interquartile range, -2.39 to 0.52). After a median follow-up period of 7.4 years (interquartile range, 6.8-8.2 y), the eGFR decreased from a median of 49.4 mL/min per 1.73 m² at baseline to 29.4 mL/min per 1.73 m², an annual eGFR percentage decrease of -4.68%. Lower RPA z-scores were correlated weakly with a higher annual decrease in eGFR (Spearman correlation, 0.35; 95% confidence interval, -0.25 to 0.76). This pilot study shows the feasibility of obtaining RPA from a routine ultrasound and suggests that a lower baseline RPA may be associated with a greater decrease in eGFR over time. Further studies with larger patient cohorts are needed to confirm this association.

Study of the renal Parenchymal volume during the human fetal period

Objective:

To evaluate the renal parenchymal area in human fetuses, providing a descriptive analysis on the renal area development by demographic factors during the second gestational trimester.

Material and Methods:

We analyzed 84 fetuses (44 males and 40 females), for a total of 168 renal units evaluated in terms of longitudinal length, superior pole width, inferior pole width and thickness. Renal volume was calculated by ellipsoid formula. After renal pelvis dissection, length and width were evaluated; as pelvis is free of urine, we considered thickness as 1mm. Renal pelvis volume was also calculated by ellipsoid formula. Renal parenchymal area was assessed by excluding the volume of the renal pelvis from the total renal volume. We performed the statistical analysis by simple linear regression assessing the association between the variables analyzed with the fetal age.

Results:

Gestational age ranged from 12 to 23 weeks post conception. Mean renal parenchymal area of the right kidney was 666.22mm³ (45.86 to 2375.35mm³) and for the left kidney was 606.76mm3 (68.63 to 2402.57mm³). No statistical difference was observed between the sides (p-value = 0.3456) or genders (p-value = 0.07429). Linear regression between renal parenchymal volume and gestational age was positive for right kidney (y = 133.74x-1479.94 / r² = 0.4009) and left kidney (y = 149.53x-1761.59 / r² = 0.4591).

Conclusions:

The linear regression analysis indicated that renal parenchymal area correlated significantly and positively with fetal age, weight and crown-rump length with no statistical differences between gender or laterality. These growth curves provide a reference for functional volume of the kidney during fetal period.

Predicting and Modifying Risk for Development of Renal Failure in Boys with Posterior Urethral Valves

PURPOSE OF REVIEW

The purpose of this review is to bring the reader up to date on the current risk factors for the development of renal deterioration in the boys with posterior urethral valves (PUV) and approaches to modify this risk.

RECENT FINDINGS

Renal bladder ultrasound (RBUS) is routinely performed in boys with PUV and recent advancements allow imaging processing that can more accurately quantify renal parenchyma and correlate this with risk for renal loss. Refinement of urine studies may improve our ability to stratify patients into renal loss categories. Use of videourodynamics (VUDS) allows refined assessment of the valve bladder to identify those who might benefit from secondary procedures and/or the addition of targeted pharmacotherapy to improve bladder emptying or dangerous storage pressures. All boys with a history of PUV are at a significant long-term risk of renal deterioration. The literature suggests that several technical advances have improved our ability to predict this risk, although there needs to be further refinement and validation before widespread use. Utilization of close follow-up, VUDS, pharmacotherapy, and bladder drainage provide the best methods to improve care to this group of patients and if more studies confirm their utility, adoption of these as part of standard of care protocols may be warranted.

Parenchyma-to-hydronephrosis Area Ratio Is a Promising Outcome Measure to Quantify Upper Tract Changes in Infants With High-grade Prenatal Hydronephrosis

OBJECTIVE

To explore the value of renal parenchyma-to-hydronephrosis area ratio (PHAR) in detecting trends of hydronephrosis (HN) improvement or worsening and response to surgical intervention.

METHODS

Initial and follow-up sagittal renal ultrasound images of patients entered into a prenatal HN database from 2008 to 2016, with baseline Society for Fetal Urology (SFU) grades III and IV HN and without vesicoureteral reflux, were evaluated using National Institutes of Health-sponsored image-processing software. Renal parenchymal area, hydronephrosis area (HA), PHAR, anteroposterior diameter (APd), and SFU grade were captured at baseline and most recent visit. Data were analyzed based on the need for surgical intervention to address obstruction.

RESULTS

Out of 193 infants (159 boys; 135 left side), 58 (30%) underwent surgery. Patients managed surgically compared with those managed nonsurgically had worse baseline HN severity markers: SFU grade (3.6 ± 0.5 vs 3.1 ± 0.4; P <.001), urinary tract dilation classification (2.7 ± 0.5 vs 2.2 ± 0.4; P <.001), APd (20.3 ± 10.1 vs 12.8 ± 8.0; P <.001), HA (10.0 ± 6.6 vs 4.7 ± 2.8; P <.001), and PHAR (1.3 ± 1.0 vs 3.0 ± 2.9; P <.001); but both patient groups had similar renal parenchymal area (9.4 ± 3.5 vs 9.7 ± 2.8; P = .5). At last follow-up, the following discrepancies persisted: SFU grade (2.3 ± 1.0 vs 1.7 ± 1.0; P <.001), urinary tract dilation classification (1.5 ± 0.7 vs 1.0 ± 0.7; P <.001), APd (11.7 ± 8.0 vs 7.7 ± 5.7; P <.001), and HA (6.4 ± 5.1 vs 3.6 ± 2.7; P <.001); however, PHAR was equalized for both groups (7.2 ± 14.0 vs 7.1 ± 6.1; P = .9).

CONCLUSION

By concurrently considering changes in renal parenchyma and degree of HN, we found that PHAR appears to be a promising parameter that reflects similarities between patients managed surgically and those managed nonsurgically, despite initial discrepancies. Our data suggest that this variable may provide reassurance and a more objective assessment of improvement after surgery compared with other traditional ultrasound outcome measures.

Renal Parenchyma to Hydronephrosis Area Ratio (PHAR) as a Predictor of Future Surgical Intervention for Infants With High-grade Prenatal Hydronephrosis

OBJECTIVE

To explore the potential value of an objective assessment, renal parenchyma to hydronephrosis area ratio (PHAR), as an early predictor of surgery.

METHODS

Initial sagittal renal ultrasound (US) images of patients prospectively entered into a prenatal hydronephrosis database from January 2008 to January 2016 with baseline Society for Fetal Urology (SFU) grades III and IV prenatal hydronephrosis, without vesicoureteral reflux, were evaluated using the National Institutes of Health-sponsored image processing software. PHAR, anteroposterior diameter, SFU grade, and urinary tract dilation risk categories were contrasted with nuclear scan data (differential renal function and drainage time [t_1/2]) and analyzed for predictive value in determining the decision to proceed with surgery by drawing receiver operating characteristic curves.

RESULTS

Out of 196 infants (162 male; 138 left sided hydronephrosis), 58 (30%) underwent surgery to address obstruction. Surgical patients compared with those managed conservatively had longer t_1/2 (60 vs 18 min; P < .01) and lower differential renal function (46 vs 50%; P = .01). Of the initial US parameters, PHAR (area under the curve = 0.816; P < .001) had a better predictive performance than anteroposterior diameter, SFU grade, or urinary tract dilation classification. PHAR values correlated with subsequent parameters obtained on nuclear scan.

CONCLUSION

PHAR is a promising parameter that can be estimated on presentation US to help predict future need for surgery in newborns with high-grade hydronephrosis.