Maternal Physiologic Renal Pelvis Dilatation in Pregnancy: Sonographic Reference Data.
OBJECTIVE
The purpose of this study was to produce sonographic reference data for maternal renal pelvis dilatation in asymptomatic pregnant women.


METHODS
A prospective cross-sectional study was undertaken on pregnant women presenting for outpatient obstetric imaging. For each side, the renal length and axial anteroposterior diameter of the renal pelvis were measured. Maternal demographics, gravidity and parity, number of fetuses, and estimated fetal weight (when available) were recorded.


RESULTS
A total of 700 women enrolled, with 191 excluded. The 509 women analyzed included 465 singleton and 44 twin pregnancies. A total of 815 sonographic investigations were performed: 716 in singleton pregnancies and 99 in twin pregnancies. The gestational age range was 10 to 40 weeks. Charts depicting the anteroposterior renal pelvis diameter versus gestational age were constructed to determine normative sonographic reference data for maternal renal pelvis dilatation in singleton pregnancies. Although the mean renal pelvis diameter increased as pregnancy progressed, measurements of greater than 10 mm remained relatively uncommon, being identified in 9.7% of right and 2.1% of left kidneys in the third trimester. Only 4.1% of right and 0.4% of left third-trimester measurements exceeded 15 mm. Right renal pelvis measurements on average were greater than the left by 1.54 mm (95% confidence interval [CI], 1.20 to 1.87 mm). Twins had significantly larger renal pelvis measurements than singletons on average, measuring 2.11 mm (95% CI, 1.50 to 2.72 mm) larger on the right and 1.69 mm (95% CI, 0.73 to 2.65) on the left.


CONCLUSIONS
We present sonographic reference data for asymptomatic pregnancy-related renal pelvis dilatation in singleton pregnancies from a large cohort of women.
Department of Radiology, North Shore Hospital, Auckland, New Zealand sahan.wadasinghe@waitem-atadhb.govt.nz.
Sahan Udayanga
SU
Wadasinghe
Department of Radiology, National Women's Health, Auckland City Hospital, Auckland, New Zealand.
Louisa
L
Metcalf
Department of Statistics, University of Auckland, Auckland, New Zealand.
Patricia
P
Metcalf
Department of Radiology, National Women's Health, Auckland City Hospital, Auckland, New Zealand.
David
D
Perry
D000293:Adolescent; D000328:Adult; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007682:Kidney Pelvis / Q000000981:diagnostic imaging* / Q000502:physiology*; D008875:Middle Aged; D011247:Pregnancy; D011446:Prospective Studies; D012016:Reference Values; D016216:Ultrasonography, Prenatal; D055815:Young Adult
hydronephrosis; maternal; obstetric ultrasound; obstetrics; pelvicaliectasis; pregnancy; reference data; renal pelvis dilatation; sonography