Urogenital ImagingDouble ureter
refers to the presence of two complete and separate ipsilateral ureters. It represents complete, rather than partial, ureteric duplication (see
duplication ureteric). The kidney on the affected side may have a duplicated pelvicaliceal system, or there may be two separate kidneys (see
supernumerary kidney). The ureteric orifices are characteristically inverted in relation to the
renal unit they drain, so that the
ureter of the lower
renal unit drains to the normal ureteric insertion and the
ureter of the upper
renal unit drains ectopically in the bladder,
urethra or elsewhere. This relationship is so consistent that it has been termed the Weigert Meyer law, after the original description by Weigert (1877) and subsequent modification by Meyer (1948). The ectopic
ureter is frequently associated with
stenosis or
ureterocoele. The orthotopic
ureter is
prone to vesicoureteric reflux. The reported incidence of complete duplication varies from 1 in 100 to 1 in 500. The contralateral
ureter in complete duplication is usually partially or completely duplicated.
Double ureter may be asymptomatic, but more frequently presents with recurrent urinary tract infections. Females may present with continuous dribbling due to the ectopic ureter. This does not occur in males, because the ectopic insertion is proximal to the external sphincter. An increasing number of cases have been diagnosed recently following the detection of fetal hydronephrosis on antenatal ultrasound (US).
The radiological findings in complete ureteric duplication are somewhat variable, depending on the presence or absence of obstruction to the upper moiety and vesicoureteric reflux in the lower moiety. In most cases, double ureters can be seen at intravenous urography. Sometimes, one renal moiety functions so poorly that it is not visualized. In such cases the diagnosis can be inferred from displacement of the visualized calices or ureter, or from the discrepancy between the amount of renal parenchyma and the relatively small number of visualized calices. The displaced appearance of the calices in the lower moiety when the upper moiety is obstructed has been termed the "drooping lily" sign. Reflux into the lower moiety may cause pyelonephritic scarring, and this may also be evident on intravenous urography. The presence of vesicoureteric reflux is best demonstrated by voiding cystourethrography, which may also demonstrate a ureterocele. An obstructed nonvisualized upper moiety can also be demonstrated by US, CT or MRI. Renal scintigraphy may also be helpful for estimating the degree of renal function.
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