The antenatal urinary tract dilation classification system accurately predicts severity of kidney and urinary tract abnormalities

Summary Background Urinary tract dilation (UTD) is a commonly diagnosed prenatal condition; however, it is currently unknown which features lead to benign and resolving or pathologic abnormalities. A consensus UTD classification system (antenatal UTD classification, UTD-A) was created by Nguyen et al. in 2014, but has not yet been validated. Objective To evaluate the ability of the UTD-A system to identify kidney and urinary tract (KUT) abnormalities, assess whether UTD-A can predict severity of KUT conditions, and perform a cost analysis of screening ultrasound (US). Methods A retrospective single-center study was conducted at an academic medical center. Inclusion criteria were: neonates in the well or sick nursery who had a complete abdominal or limited renal US performed in the first 30 days of life between January 01, 2011 and December 31, 2013. Data were collected on prenatal US characteristics from which UTD-A classification was retrospectively applied, and postnatal data were collected up to 2 years following birth. Results A total of 203 patients were identified. Of the 36 abnormal postnatal KUT diagnoses, 90% were identified prenatally as UTD A1 or UTD A2-3. The remaining 10% developed postnatal KUT abnormalities due to myelomeningocele, such as VUR or UTD, which were not evident prenatally. Overall sensitivity and specificity of the UTD-A system was 0.767 (95% CI 0.577, 0.901) and 0.836 (95% CI 0.758, 0.897), respectively, when resolved UTD was counted as a normal diagnosis. Postnatal diagnoses differed by UTD-A classification as shown in the Summary fig. Of all the obstructive uropathies, 90.9% occurred in the UTD A2-3 class and none occurred in UTD-A Normal. Rate of postnatally resolved UTD was significantly higher in the UTD A1 group (78%) compared with UTD A2-3 (31%) or UTD-A Normal (12%, all P