A renal size nomogram for the patient with myelomeningocele

Diagnostic Test Characteristics of Ultrasound Based Hydronephrosis in Identifying Low Kidney Function in Young Patients with Spina Bifida: A Retrospective Cohort Study

PURPOSE

Kidney dysfunction in spina bifida is usually detected by low estimated glomerular filtration rate or ultrasound based hydronephrosis. We assessed the diagnostic test characteristics of hydronephrosis for detecting low estimated glomerular filtration rate, hypothesizing that hydronephrosis has low sensitivity compared to cystatin C based estimated glomerular filtration rate.

MATERIALS AND METHODS

We conducted a single center, retrospective cohort study, including patients with spina bifida from 2012-2017 with 2 kidneys and complete data needed to calculate estimated glomerular filtration rate via multiple pediatric (age 1-17.9 years) or adult (age ≥18 years) estimating equations. We evaluated the association of hydronephrosis status (high grade, low grade or none) with estimated glomerular filtration rate, adjusting for small kidney size and scarring, and calculated diagnostic test characteristics of hydronephrosis for low estimated glomerular filtration rate.

RESULTS

We analyzed 247 patients (176 children and 71 adults). Mean±SD age was 13.7±6.6 years, and 81% of patients had myelomeningocele. Hydronephrosis (77% low grade) was found in 35/176 children and 18/71 adults. Hydronephrosis was associated with low estimated glomerular filtration rate in stepwise fashion, independent of kidney size and scarring. However, across cystatin C based pediatric equations, any hydronephrosis (compared to none) had 23%-48% sensitivity, and high grade hydronephrosis (compared to none or low grade) had 4%-15% sensitivity for estimated glomerular filtration rate <90 ml/min/1.73 m2, which remained unchanged after excluding small kidneys and scarring. Across cystatin C based adult equations, any and high grade hydronephrosis had 55%-75% and 40%-100% sensitivity, respectively, for estimated glomerular filtration rate <90 ml/min/1.73 m2, although with wide confidence intervals. Specificity was higher with high grade vs any hydronephrosis. Sensitivities were higher for estimated glomerular filtration rate <60 ml/min/1.73 m2.

CONCLUSIONS

Hydronephrosis was associated with low estimated glomerular filtration rate but had poor sensitivity for cystatin C based estimated glomerular filtration rate <90 ml/min/1.73 m2, especially among children with spina bifida.

Renal function in children with congenital neurogenic bladder

AIMS

Preservation of renal function in children with congenital neurogenic bladder is an important goal of treatment for the disease. This study analyzed the evolution of renal function in patients with congenital neurogenic bladder.

METHODS

We reviewed the records of 58 pediatric patients with respect to the following attributes: gender, age, etiology of neurogenic bladder, reason for referral, medical/surgical management, episodes of treated urinary tract infections, urodynamics, DMSA scintigraphy, weight, height, blood pressure, glomerular filtration rate, microalbuminuria and metabolic acidosis. Statistical analysis was performed, adopting the 5% significance level.

RESULTS

The mean age at presentation was 4.2 ± 3.5 years. Myelomeningocele was the most frequent etiology (71.4%). Recurrent urinary tract infection was the reason for referral in 82.8% of the patients. Recurrent urinary tract infections were diagnosed in 84.5% of the patients initially; 83.7% of those patients experienced improvement during follow-up. The initial mean glomerular filtration rate was 146.7 ± 70.1 mL/1.73 m²/min, and the final mean was 193.6 ± 93.6 mL/1.73 m²/min, p = 0.0004. Microalbuminuria was diagnosed in 54.1% of the patients initially and in 69% in the final evaluation. Metabolic acidosis was present in 19% of the patients initially and in 32.8% in the final assessment.

CONCLUSIONS

Patient referral to a pediatric nephrologist was late. A reduction in the number of urinary tract infections was observed with adequate treatment, but microalbuminuria and metabolic acidosis occurred frequently despite adequate management.

The effect of obesity on kidney length in a healthy pediatric population

Over the past decade, the percentage of children who are obese has rapidly increased. As weight has been shown to correlate strongly with the size of various organs, we have observed that obese children have larger kidneys than their normal-weight counterparts. This study sought to quantify this observation by establishing the normal limits of renal length for this population. We examined 204 healthy patients seen for benign hematuria between January 2000 and May 2008. Both right and left kidney lengths significantly correlated with age, height, weight, body mass index and body surface area in our obese patients (n = 59). Height was also found to be a significant predictor of kidney length, in the obese group, by multiple linear regression analysis and was used to create renal length nomograms for the obese pediatric population (P < 0.01). According to this analysis, obese patients had significantly larger kidneys than those of normal-weight patients (P < 0.01). By defining the normal limits of renal length for this group, unnecessary evaluation for nephromegaly will be avoided.