Physiologic hydronephrosis as a cause of emergent right abdominal pain in pregnancy-truth or myth?

Abstract

Background: Physiologic hydronephrosis in pregnancy is usually asymptomatic, however, definitions of symptomatic hydronephrosis vary, pain being the only criterion in some cases. We found no literature validating physiologic hydronephrosis as a cause of emergent right abdominal pain. We aimed to evaluate whether the incidence of hydronephrosis is higher in patients with right abdominal pain and no other identifiable cause, as compared to asymptomatic pregnant women (APW).

Methods: A retrospective review of abdominal magnetic resonance imaging (MRI) was performed for acute abdominal pain (AAP) in pregnant patients with no identifiable cause, compared to MRI performed for fetal evaluation in APW. Two readers (R1/R2) performed qualitative evaluation of hydronephrosis and hydroureters, and quantitative measurement of ureteral maximal diameter. Inter-rater agreement was calculated.

Results: The study included 39 AAP and 162 APW patients, mean ages 31.0±4 and 31.7±5 years respectively. Quantitative and qualitative measurements showed no statistically significant differences between the groups. Right hydronephrosis was found in 33.3%/53.8% of AAP versus 43.8%/45.1% of APW (P=0.280/P=0.324, R1/R2 respectively). Right hydroureter was found in 28.2%/33.3% of AAP versus 28.4%/30.9% of APW (P=0.946/P=0.765, R1/R2 respectively). Inter-reader agreement showed good to excellent reliability in qualitative and quantitative measurements.

Conclusions: Emergent right abdominal pain in pregnant patients with no appendicitis or other identifiable causes was not related to a higher incidence of hydronephrosis or hydroureter, as compared to asymptomatic ambulatory pregnant patients. The findings suggest that emergent right abdominal pain in these patients is not necessarily attributable to physiologic hydronephrosis and alternative diagnoses should be carefully considered.