Development of the fetal ureter: A fetal metric and histological study

Introduction: This study provides a description of development of various components of the human ureter at different gestational ages. Methods: Measurements of the length of the ureter from pelvi-ureteric junction to vesico-ureteric junction, length of its intravesicular portion and angle made by the ureter at the entry into the bladder with respect to the internal ureteric orifice were taken. Transverse sections of the ureter were taken at the upper end, close to the pelvi-ureteric junction, and at the midpoint between the pelvis of the kidney and the vesico-ureteric junction. These were subjected for processing and stained with Haematoxylin Eosin and Masson's Trichrome. They were then studied under the light microscope. Results: The length of the ureter from the pelvi-ureteric junction to the vesico-ureteric junction showed a highly positive correlation with the gestational age (GA). The angle of entry of the ureter to the bladder decreased as the GA increased. The microstructure of the ureter in both the sections showed development of transitional epithelium with an increase in layers by 33 weeks. At 18 weeks, the smooth muscle layer was in a single layer with an abundance of interspersed collagen fibers. By 33 weeks, the thickness of the wall increased significantly with a decrease in collagen. There was no trace of longitudinal muscle fibers even upto 33 weeks. Conclusion: Epithelial, muscular and connective tissue components displayed significant changes during intra uterine development.