Morphology of the fetal bladder during the second trimester: Comparing genders

Abstract

ObjectivesThe aim of the present study was to determine, by histological and stereological analysis, whether there are between-gender structural differences in the bladder in the second gestational trimester in human fetuses. Material and methodsForty bladders, which were obtained from 40 human fetuses (20 males and 20 females) ranging in age from 13 to 23 weeks post-conception (WPC), were studied. The fetuses were macroscopically well preserved, without anomalies of the urinary and genital systems; the cases with syndromes were abandoned. The bladders were dissected and embedded in paraffin, from which 5-μm thick sections were obtained and stained with: Masson's trichrome, to quantify connective and smooth muscle tissue; Weigert's resorcin fuchsin, to observe elastic fibers; picrosirius red with polarization, to observe collagen; and anti-beta III tubulin antibody, to observe the bladder nerves. The images were captured with an Olympus BX51 microscope and Olympus DP70 camera. The stereological analysis was performed with the Image Pro and Image J programs, using a grid to determine volumetric densities (Vv). Means were statistically compared using simple linear regression and the paired t-test (P < 0.05). ResultsThe fetuses weighed between 60 and 490 g, and had crown–rump lengths between 9.5 and 20.4 cm. No elastic system fibers were observed in any bladders. Quantitative analysis indicated no differences in the Vv of the smooth muscle cells in the male bladders (26.19–50.16%; mean = 35.66%) compared to the female ones (30.60–45.63%; mean = 38.73%) (P = 0.740) and there were also no differences in the Vv of the connective tissue in females (40.52–60.40%; mean = 50.69%) and males (38.84–70.16%; mean = 57.04%) (P = 0.0506). There were no differences observed in the distribution of the nerves and collagen between the genders. ConclusionThe histological analysis of the smooth muscle, collagen, nerves and connective tissue of the developing bladders revealed that there are no gender differences during weeks 13–23 of gestation.