Antenatal Diagnosis of Upper Urinary Tract Dilation by Ultrasonography

Abstract

The criteria for the detection of fetal pyelectasis are still controversial. Prenatal and postnatal data from 2,170 consecutive pregnant women who underwent at least one antenatal ultrasound scan were prospectively studied. Fetal pyelectasis was defined on the basis of a mean renal pelvis dimension > 5 or 10 mm before or after 28 weeks of gestation, respectively. Pyelectasis was detected in 95 (4.4%) fetuses. Eighty-nine among them were explored after birth. In 13 (13.7%) cases, an obstructive urinary tract abnormality, a severe vesicoureteral reflux, or a megaureter were diagnosed postnatally. In 29 (30.5%) cases, pyelectasis was confirmed postnatally, while complementary investigations ruled out an obstruction of the urinary tract. The incidence of urinary tract malformations was thus 0.60%, while the positive predictive value was 13.7%. We recommend to use a value not < 10 mm of the renal pelvis mean dimension beyond 28 weeks of gestation as a threshold for detection of fetal upper urinary tract obstruction, in the absence of ureteric and/or bladder dilation. Any value between 5 and 10 mm measured during the 2nd trimester of gestation should be confirmed by a second ultrasound examination performed during the 3rd trimester, before being considered pathological.

Mild Fetal Renal Pelvis Dilatation—Much Ado About Nothing?

“…We would like to have seen information on changes in fetal RP size during the pregnancy, but reporting was inconsistent, and some studies actually excluded fetuses in whom RPD resolved before birth, which biases their results toward worse outcomes (23,24,26 -28), and few mentioned details such as calyceal dilation, which has been reported to be useful indicators of poorer prognosis (8). Timing of initial postnatal ultrasound may also be critical as babies become relatively dehydrated and oliguric for the first 48 h postnatally (39), but several studies did not mention excluding measurements during this period (18,29,30,33). Differences in measurement and interpretation of outcomes also varied.…”

“…Five hundred and six potentially relevant studies were identified, of which 18 met the inclusion criteria (17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34). Two studies reported overlapping patient cohorts but different outcomes (27,28).…”

“…The earliest reported fetal ultrasound was at 14 wk of gestation (21). Most studies reported that postnatal scans were not performed within 2 d after birth (17,20,22,23,(27)(28)(29)(30)(31), which may be important because newborns are initially oliguric and false-negative results are common at this time: 4 studies did not specify the earliest age at postnatal ultrasound assessment (18,29,30,33).…”

Mild Dilatation of Renal Pelvis in Term Neonates with Urinary Tract Infection

“…These infants were of no increased risk for urinary tract infections and did not need further postnatal investigations. Langer et al [11] recommended the use of a mean value of renal pelvis dimension of not less than 10 mm beyond 28 weeks of gestation as threshold for detection of fetal upper urinary tract obstruction in the absence of ureteric and/or bladder dilatation. They suggested that values between 5 and 10 mm found in the second trimester of pregnancy should be confirmed by a repeat scan in the third trimester and that postnatal investigations should be limited to those with antenatal pyelectasis of 110 mm.…”

Second‐trimester sonographic demonstration of retrognathia and bilateral pyelectasis in a fetus with a duplication of chromosome 10q24.1→qter

“…The anteroposterior (AP) diameters of renal pelves were 6 mm in the right kidney and 6.2 mm in the left kidney. An AP pelvic diameter > 5 mm defines pyelectasis in the second trimester 2,3 . The parents opted to terminate the pregnancy.…”