Case No. :	73
Month :	January
Year :	2005
Contributor :	Dr. Nikhil Unune

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A 10-year-boy presented with pain off and on over the periumbilical region since six months. On examination, the child was moderately built and well nourished. His systemic examination revealed no abnormality. Routine blood and urine investigations were normal.

Ultrasonography of the abdomen showed a large left ureterocoele with dysplastic left lower moiety associated with a dilated ureter. The left upper moiety was normal. The right kidney and the urinary bladder were normal.

Fig. 1	Fig. 2	Fig. 3

Intravenous urography showed evidence of duplication with only one moiety (probably the upper) being seen on the left side. There was a well defined impression displacing the upper ureter medially. The right kidney was normal with a bifid renal pelvis.

Fig. 4	Fig. 5

Micturiting cystourethrography revealed no abnormality in the urinary bladder. There was no vesicoureteric reflux.

Fig. 6

CT scan of the abdomen showed a left duplex kidney with cysitc dysplastia of the lower moiety. The upper moiety was normal with normal course of the ureter which was opacified on delayed contrast scan. The ureter of the lower moiety was massively dilated and not opacified on delayed contrast scan. The urinary bladder was normal.

Fig. 7	Fig. 8
Fig. 9	Fig. 10

MR Urography confirmed.these findings and in addition exquisitely showed the dilated and tortuous ureter of the lower moiety ureter throughout its course without any intrinsic filling defects or extrinsic compression.

Fig. 11	Fig. 11A
Fig. 12	Fig. 13
Fig. 14	Fig. 15
Fig. 16	Fig. 17

Cystoscopy and left ascending pyelogram were done. Cystoscopy showed the bladder wall to be smooth with adequate closure of the bladder neck. There was no evidence of an ureterocele. There was a normal right ureteric orifice and a normal single left ureteric orifice.The left ascending pyelogram done through this orifice showed opacification of the upper moiety with two calyces .There was no dilatation of the pelvis .The upper 1/3 rd ureter was medially displaced .The course of the rest of the ureter was normal.

DTPA/DMSA scan revealed good perfusion and adequate cortical uptake in the right kidney. The upper moiety of the left kidney showed normal function and lower moiety was non functioning .

The child was operated - left lower pole heminephreoureterctomy was done. Intraoperative findings were duplex left kidney; cystic dysplastic lower moiety; the lower pole ureter was massively dilated. The upper pole kidney was normal and upper pole ureter was normal in size. The imaging features and post operative findings confirmed the diagnosis - Left duplex kidney with normal functioning upper moiety with normal course of ureter and cystic dysplastic nonfunctioning lower moiety with hydronephrosis and hydroureter.

DISCUSSION:

Duplex kidney is a congenital anomaly of kidney. In most of the cases of duplex kidney, according to the Weigert Meyer Law, the lower moiety ureter opens into the urinary bladder and upper moiety ureter open distal and medial to opening of upper moiety ureter. The upper moiety is more prone to obstruction and dysplastia and the lower moiety to vesicuureteric reflux. Discussion: Normal embryology of kidney and ureter.

If two ureteric buds arise from the mesonephric (Wolfian) duct, or if a single bud divides into two branches before it invades into the metanephrogenic blastema, a duplication occurs. Complete duplication results when two entirely separate ureters drain separate parts of the kidney. Partial duplication occurs when the two ureters join before reaching the bladder.

Complete ureteral duplication occurs when the mesonephric duct gives off a second ureteral bud. The ureteral bud closest to the urogenital sinus becomes the lower pole ureter and the bud further away becomes the upper pole ureter. As the common excretory duct is absorbed, the lower pole ureteral orifice migrates cephalad and laterally andthe upper pole ureteral orifice migrates caudally. Also, because the lower pole ureteral bud is absorbed more rapidly, the detrusor submucosal tunnel becomes short. This short submucosal tunnel predisposes the lower pole ureter to reflux. In contrast, the upper pole ureteral bud is absorbed slowly, resulting in a long submucosal tunnel. In males, the upper pole ureteral orifice may insert into the posterior urethra, prostatic utricle, seminal vesical, ejaculatory duct, or vas deferens. In females, the upper pole ureter may insert into the urethra, vestibule, vagina, cervix, uterus, Gartner's duct, or a urethral diverticulum. When two ureteric buds arise from the mesonephric duct, they can induce two portions of the same kidney. Two separate collecting systems will result.

A rare exception to the Weigert-Meyer law occurs when there is an early division of a single ureteral bud. Early fusion of the ureteral bud before it leaves the mesonephric duct to meet the metanephric blastema will result in a complete duplication. After the absorption of a common excretory duct, the common base will be absorbed into the urogenital sinus without rotation of ureteral orifices.

In this case, a left sided duplex kidney was present .The lower moiety was dysplastc and the lower moiety ureter dilated. The cause may be vesicoureteric reflux or intrinsic obstruction of ureter. The upper moiety was normal and upper moiety ureter was normal in its course and caliber. This case is one of the exceptions to Weigert Meyer Law.

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