[Hydronephrosis in pregnancy. Ultrasonographic study].

Hydronephrosis is a common pathology during pregnancy and according to some authors affects between 80 and 90% of women in the third trimester. The right side is most frequently affected. Moreover, there appears to be no relation between parity and hydronephrosis or between previous infections of the urinary tract and hydronephrosis; however its presence, especially if severe, is associated with urinary infections with a frequency which is significantly greater than in patients with a urinary tract within normal limits. There are two pathogenetic hypotheses: one identifies the inhibitory effect of progesterone and prostaglandins on muscular tone and the peristalsis of smooth ureteral muscle, with consequent dilatation and anfractuosity of the excretory tract above the pelvic brim; the other is the mechanical hypothesis based on the possible compression of the ureter caused by the pregnant womb at the level of the pelvic brim at the intersection with the ilial and ovarian vessels. One hypothesis does not exclude the other, but on the contrary they complement each other and give added plausibility to a multifactorial pathogenesis. The study of hydronephrosis in pregnancy has made considerable progress since the introduction of echotomography in image diagnosis, a low-cost method which is easy to use and does not harm the product of conception. Echographs with 3.5 MHz probes were used to carry out a prospective study by examining the kidneys and excretory tract in 370 asymptomatic pregnant women during the first, second and third trimesters of gestation.(ABSTRACT TRUNCATED AT 250 WORDS)