Fetal hydronephrosis: does adding an extra parameter improve detection of neonatal uropathies?

Area of Science:

• Fetal medicine
• Pediatric nephrology
• Medical imaging

Background:

• Fetal pyelectasis, or renal pelvis dilatation, is a common finding during prenatal ultrasound.
• Accurate assessment of fetal renal pelvis dimensions is vital for predicting neonatal outcomes and guiding management.
• Existing criteria for diagnosing fetal pyelectasis vary, necessitating evaluation of their diagnostic accuracy.

Purpose of the Study:

• To assess the correlation between fetal renal pelvis diameters (antero-posterior, transverse, longitudinal) and neonatal outcomes.
• To compare the diagnostic performance of different antero-posterior renal pelvis (ARP) measurement thresholds for identifying uropathies requiring surgery.

Main Methods:

• Retrospective evaluation of 612 fetuses with suspected pyelectasis diagnosed between May 1997 and March 2006.
• Fetal pyelectasis was categorized as mild (ARP ≥ 5-<10 mm), moderate (ARP ≥ 10-<15 mm), and severe (ARP ≥ 15 mm).
• Comparison of ARP measurements with established criteria (Corteville criteria: AP ≥ 7 mm; AP ≥ 10 mm) and analysis of likelihood ratios and post-test probabilities for neonatal surgical intervention.

Main Results:

• 73 (11.9%) infants required postnatal surgery, with the highest proportion in the severe hydronephrosis group (8.2%).
• An ARP ≥ 5 mm detected more uropathies and surgical indications compared to AP ≥ 10 mm.
• Using AP ≥ 10 mm would have missed 5.1% of cases, while the Corteville criteria (AP ≥ 7 mm) would have missed 1.8%.

Conclusions:

• An average renal pelvis (ARP) measurement of ≥ 5 mm in pregnancy offers improved detection of fetal uropathies and surgical indications compared to an AP of ≥ 10 mm.
• The ARP ≥ 5 mm threshold demonstrates comparable results to the Corteville criteria (AP ≥ 7 mm) for third-trimester assessments.
• Utilizing ARP measurements aids in better risk stratification for neonatal renal anomalies.