Ultrasound score: a new method to differentiate fetal physiological and pathological hydronephrosis

To determine whether the prenatal ultrasound (US) score can effectively differentiate fetal physiological and pathological hydronephrosis.

158 fetuses (198 kidneys) with hydronephrosis (PAPD>or=10mm) were diagnosed by prenatal US in the third trimester. We measured and recorded three US parameters: renal pelvic anterior posterior diameter (PAPD), renal parenchyma thickness and pelvicaliceal morphology. They were graded with a score from 0 to 3 on the basis of severity of hydronephrosis, and the total US score of each kidney was obtained. According to the postnatal US and clinical diagnosis and management, all the cases were divided into two groups: physiological and pathological hydronephrosis. Using receiver operating characteristic curves analysis, we researched whether the US score was more accurate than each parameter and which was the best cut-off value for differential diagnosis of physiological and pathological hydronephrosis.

Of all the 198 hydronephrosis, 139 (70.20%) were physiological and 59 (29.80%) were pathological confirmed postnatally. Area under the curve of US score was 0.982, which was significantly larger than that of each parameter (P<0.05). The higher the score, the higher the possibility of pathological hydronephrosis was. Score 6 was the best cut-off value: the sensitivity, specificity, positive predictive value, negative predictive value, consistency rate and Youden's index were 89.83%, 94.24%, 86.89%, 95.62%, 92.93% and 0.8407, respectively.

Prenatal US score is easy to obtain by measuring some data of the kidney and can effectively differentiate fetal physiological and pathological hydronephrosis. It can also be used as a new quantitative method to evaluate the prognosis of fetal hydronephrosis so as to provide reference for prenatal intervention and more accurate information for the family of the fetus.