Dynamics of the renal pelvis size during normal preg- nancy

Kogan M.I., Ivanov A.G., Vorobyeva N.V., Belousov I.I.

1) Department of Urology and Human Reproductive Health (with a course of pediatric urology-andrology). Rostov State Medical University, Rostov-on-Don, Russia; 2) Department of Obstetrics and Gynecology No. 1. Rostov State Medical University, Rostov-on-Don, Russia

Objective. To evaluate changes in the anteroposterior renal pelvis diameter (APD) from the first to the third trimester in healthy primigravid women.
Materials and Methods. A prospective observational study was conducted from March 2021 to July 2022, involving 30 healthy pregnant women aged 18–40 years. Inclusion criteria were: primigravida, singleton pregnancy, absence of significant medical conditions, and no history of urinary tract infections. Renal ultrasound examinations was performed in the first (10–12 weeks), second (22–24 weeks) and third (34–36 weeks) trimesters. Statistical analysis was performed using nonparametric methods (Statistica 10, StatSoft).
Results. In 10 women, APD was not detectable throughout the pregnancy. In the right kidneys, the APD increased from the first to the second trimester in 40% of women, while in the left kidneys? in increased in 33.3%. From the first to the third trimester, an increase in APD was observed in 30% of women in the right kidneys and in 53.3% in the left kidneys. Significant differences in the APD were noted only in the left kidneys between the first and second trimesters (p=0.005) and the first and third trimesters (p=0.003). In the right kidneys, the changes approached significance (p=0.072 and p=0.075, respectively). Differences between the second and third trimesters were not statistically significant.
Discussion. The study results demonstrated that dilation of the renal pelvis in pregnant women can vary: some women exhibit no dilation, while others shou an increase or decrease. Notably, an increase in APD was more frequently observed in the left kidneys, which contradicts the common belief of a predominance of right-sided hydronephrosis. It is important to note that changes in the APD do not always correlate with clinical symptoms, making it difficult to distinguish between physiological and pathological dilation. These findings highlight the need for further research to refine diagnostic criteria and understand the factors influencing the progression of maternal hydronephrosis.
Conclusion. Dilation of the renal collecting system in healthy primigravid women may be absent, increase, or decrease during pregnancy. The most significant changes in the collecting system of the kidneys occur from the first to the second trimester, particularly in the left kidneys. These findings underscore the necessity for further studies to differentiate between physiological and pathological dilation of the upper urinary tract and to clarify their clinical significance.

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About the Authors

Corresponding author: M.I. Kogan – Dr.Med.Sci., Full Professor, Honored Scientist of the Russian Federation; Head of Department of Urology and Human Reproductive Health (with Pediatric Urology and Andrology Course) Federal State Budgetary Educational Institution of Higher Education «Rostov State Medical University». Rostov-on-Don, Russia; e-mail: dept_kogan@mail.ru