When two ureteric buds arise from the mesonephric duct, they can induce two portions of the same kidney. Two separate collecting systems will result. Because of the rotational incorporation of the distal mesonephric duct and associated ureter into the base of the bladder, the bud that arises more medial on the mesonephric duct will enter the bladder lateral to and cephalad. This ureter will drain the lower pole of the kidney. The upper pole of the kidney will be drained by the ureter that drains inferior to and medial.
When duplication occurs, the lower pole ureter is at increased risk of reflux.
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©David A. Hatch, M.D., 1996