What are bifid (duplicated) collecting systems?

These are the most common congenital variations of the ureter. They can be unilateral or bilateral. Two ureters may be separate throughout their length and have separate openings into the bladder. The ureter draining the upper moiety may drain outside the bladder (e.g., into the vagina or urethra). These ectopic ureters are frequently obstructed. The distal end of the dilated ureter may herniate through the bladder wall, causing a smooth filling defect in the bladder (ureterocele), which can have the appearance of a cobra head.