Predictors of Renal Compromise in the Young Spina Bifida Population
Gina N. Tundo, MD; Lael Reinstatler, MD; Adam R. Weinstein, MD; Bridget A. Logan, APRN; Frank J. Penna, MD
Dartmouth Hitchcock, Lebanon, NH
Long-term renal function preservation in the spina bifida population is one of the primary goals of pediatric urologists and nephrologists caring for patients with this condition. There are inherent limitations in assessing renal function in this unique demographic. Use of creatinine (Cr) to estimate glomerular filtration rate (GFR), the standard marker for renal function, is limited due to decreased lean body mass in this population. Moreover, little data exists elucidating which parameters increase the risk of renal deterioration over time. We therefore sought to identify these risk factors.
A retrospective review was performed of all patients between birth and 30 years of age with the diagnosis of "spina bifida" who were treated at our institution. Five parameters were used to screen for renal compromise, including (1) a sustained increase in serum creatinine of 0.2 mg/dL over two subsequent lab draws, (2) hypertension, (3) a size discrepancy of >1 cm between renal units on renal ultrasound (US), (4) presence of renal scarring or cortical thinning on US, and (5) significant proteinuria (100+ protein on at least 2 consecutive spot urine samples or elevated urine protein/Cr ratio defined as a sustained increase of 0.2 g/g over two subsequent samples). If at least one of these criteria were met, the patient was determined to have evidence of renal compromise. We then examined a variety of other patient factors to determine which were significantly correlated with renal compromise.
There was a total of 140 patients initially identified; 55 were excluded due to a diagnosis of spina bifida occulta, and an additional 14 were excluded because they received their urologic care elsewhere, leaving a total of 71 patients. Of the 71 patients, 27 had at least one marker of renal compromise (38%). These patients had a higher rate of obesity (42% vs 30%, p=0.3075), were more likely to have had a history of recurrent febrile urinary tract infections (UTI) [37% vs 13%, p=0.022], were more likely to exhibit hydronephrosis on US (15% vs 4%, p=0.1890), were more likely to have vesicoureteral reflux (VUR) demonstrated on either voiding cystourethrogram (VCUG) or a fluoro-urodynamic study (f-UDS) [22% vs 9%, p=0.1643], and were more likely to have elevated bladder pressures (greater than or equal to 30 cm water) on f-UDS (43% vs 23%, p=0.1478). Additionally, four of the patients with renal compromise had a solitary kidney, versus none of the patients with no markers of renal compromise.
In the young spina bifida population, the prevalence of obesity, recurrent febrile UTI, hydronephrosis, VUR and elevated bladder pressures are higher among patients who go on to develop renal compromise. These specific parameters should be assessed regularly, and treatable markers of renal dysfunction such as proteinuria and blood pressure elevation should be screened for in these patients in order to preserve long-term renal function.
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