Pregnancy Dilatation of the Urinary Tract

During intravenous urography, iliac artery sign is an oblique filling defect in the ureter at the pelvic brim produced by the ureter crossing the iliac artery. It delineates the lower limit of pregnancy dilatation, thereby characterizing all changes associated with pregnancy. Asymmetry of the iliac arteries and ureters at the pelvic brim accounts for the characteristic distribution of pregnancy dilatation. There are permanent subtle functional and anatomical changes in the ureter after the first pregnancy. Upper urinary tract infection during pregnancy produces persistent ureteric dilatation which may be the only evidence of upper urinary tract involvement in the adult.