IS Case 118: Duplicated Collecting System
Imaging Sciences URMC 2008
Publication Date: 2009-05-20
Duplicated right collecting system with moderate hydronephrosis of the upper pole moiety. Moderate to severe right hydroureter and no contrast excretion into this ureter is seen on delayed images. There is delayed contrast excretion from the right upper pole moiety parenchyma. Right lower pole moiety ureter and left ureter of normal caliber with normal contrast enhancement of the lower pole parenchyma of the right kidney and of the left kidney parenchyma. Insertion of ectopic right ureter into the bladder was not seen clearly on images.
Duplicated Collecting System
Duplication abnormalities of the kidneys are the most common congenital anomalies of the urinary tract. Ureteral duplication occurs when a second ureteral bud arises from the mesonephric duct causing compete ureteral duplication. This is seen in 0.2 % of live births with a two-to-one, female-to-male predominance. Fifteen to 40 percent are bilateral.
The Weigert-Meyer rule states that the upper moiety ureter inserts in an ectopic location inferior and medial to the lower moiety ureter below the trigone. The lower moiety ureter drains the lower pole and interpolar portion which enters the bladder at the trigone per this rule.
Ureteral obstruction of the upper moiety occurs at the ectopic ureteral insertion, ectopic ureterocele or any place where this ureter aberrantly crosses another structure. Renal dysplasia occurs as a result. In males, there is usually a suprasphincteric insertion low in the bladder, bladder neck, prostatic urethra, vas deferens, seminal vesicle or ejaculatory duct. Females have an infrasphincteric insertion in the distal urethra, vaginal vestibule, vagina, cervix, uterus, fallopian tube or rectum. The upper pole moiety has obstructive hydronephrosis.
The "drooping lily" sign is seen in cases of upper moiety obstruction. Inferolateral displacement of the functioning lower pole moiety and lateral displacement of superior calices of the lower pole collecting system by a non-opacified, hydronephrotic upper pole collecting system is seen. The lower pole collecting system resembles a lily that is wilting or drooping.
Vesicoureteral reflux commonly occurs in the lower pole moiety due to its shortened ureteral tunnel at the bladder insertion. The lower pole moiety atrophies in about half of cases secondary to chronic pyelonephritis from reflux nephropathy and resultant infection.
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