Embryogenesis of the Kidneys and Ureters. Normal Development. Three excretory organs (pronephroi, mesonephroi, and metanephroi) develop from the intermediate mesoderm
A. A pair of cervical nephrotomes forms in each of five to seven cervical segments, but these quickly degenerate during the 4th week.
B The mesonephric ducts first appear on day 24
C. Mesonephric nephrotomes and tubules form in craniocaudal sequence throughout the thoracic and lumbar regions.
D. The mesonephroi contain functional nephric units consisting of glomeruli, Bowman's capsules, mesonephric tubules, and mesonephric ducts.
Ventral views of the abdominopelvic region of embryos and fetuses (sixth to ninth weeks), showing medial rotation and 'ascent' of the kidneys from the pelvis to the abdomen.
A. Unilateral renal agenesis.
B. Right side, pelvic kidney; left side, divided kidney with a bifid ureter
C. Right side, malrotation of the kidney; left side, bifid ureter and double kidney.
D. Crossed renal ectopia.
E. 'Pancake' or discoid kidney resulting from fusion of the kidneys while they were in the pelvis.
F. Supernumerary left kidney resulting from the development of two ureteric buds.
Diagnosed by IVU