Variation in Definitions of Kidney Abnormality in Patients with Spina Bifida: A Systematic Scoping Review

Purpose: We systematically reviewed the variability in definitions of kidney abnormality (KA) outcomes in individuals with spina bifida (SB). Materials and Methods: A systematic scoping review was conducted using MEDLINE, Embase(R), Cochrane Library, CINAHL, PsycInfo(R), Web of Science(TM) and ClinicalTrials.gov for articles from time of database inception to September 2020. No language or patient age restrictions were applied. Primary research articles involving individuals with SB where KA was assessed as an outcome were included. Means of assessing KA and defining KA severity were abstracted. Results: Of 2,034 articles found, 274 were included in the review. Most articles were published after 1990 (63.5%) and included pediatric-only populations (0e18 years; 60.5%). KA outcomes were identified by imaging-based anatomical outcomes (84.7%), serum-based outcomes (44.9%), imaging-based functional outcomes (5.5%), urine-based outcomes (3.3%) and diagnoses of end-stage kidney disease (2.6%) or chronic kidney disease otherwise unspecified (1.8%). Hydronephrosis was the most commonly used specific outcome (64.6%, 177/274) with 19.8% (35/177) of articles defining hydronephrosis severity. Hydronephrosis was used more frequently in articles with pediatric-only populations. Creatinine and cystatin-C were used in 82.1% (101/123) and 17.9% (22/123) of articles reporting serum-based outcomes, respectively, with 32.7% and 50.0% of articles defining estimated glomerular filtration rate (GFR) severity. Serum-based outcomes were more common in articles including adults >18 years. Measured GFR was assessed in 9.9% (27/274) of articles, with 44.4% (12/27) of articles defining GFR severity. Conclusions: Significant variability exists in how authors define KA with few specifically defining KA severity. Consensus and consistency in defining KA outcomes are needed.