The association between maternal hydronephrosis and acute flank pain during pregnancy: a prospective pilot-study

Purpose: Maternal hydronephrosis may cause flank pain during pregnancy. We aimed to investigate the association between maternal hydronephrosis and flank pain intensity.Methods: From 2014 to 2015, all consecutive women with singleton pregnancies, who presented at our tertiary center due to acute flank pain, were prospectively evaluated by renal ultrasonography and pain questionnaires. A visual analogue scale was used to assess pain intensity. The study had 90% power to detect a significant correlation between hydronephrosis and flank pain (Spearman's test).Results: A total of 51 consecutive women with left-sided (13.7%), right-sided (64.7%) or bilateral (21.6%) pain were enrolled. The mean gestational age of these women, who presented due to their pain, was 27.56.8 weeks at the time of consultation. The mean VAS score was 7.6 +/- 2.2. In 43/51 (84.3%) women, hydronephrosis was found on renal sonograms. No correlation was found between the grade of hydronephrosis and pain intensity (p = 0.466; r=-0.28). Women delivered at a mean gestational age of 38.1 +/- 2.4 weeks and their infants had a mean birthweight of 3138 +/- 677g.Conclusions: Hydronephrosis is a common finding among pregnant women with acute flank pain. The grade of hydronephrosis does not affect pain intensity. This study suggests normal pregnancy outcomes in these women.