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Saudi Journal of Kidney Diseases and Transplantation
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Year : 2013  |  Volume : 24  |  Issue : 4  |  Page : 773-776
Crossed fused renal ectopia with a single ureter: A rare anomaly

Department of Surgery, University College of Medical Sciences and GTB Hospital, University of Delhi, Delhi, India

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Date of Web Publication24-Jun-2013


A rare case of crossed fused renal ectopia is presented where the fused kidneys were present on the right side and there was a single ureter opening into the right side of the bladder. To the best of our knowledge, this variant of crossed fused ectopia has not been reported previously. This case challenges the embryological theory that deviation of one of the ureteric buds to the opposite side results in crossed fused renal ectopia.

How to cite this article:
Kaur N, Saha S, Mriglani R, Saini P, Gupta A. Crossed fused renal ectopia with a single ureter: A rare anomaly. Saudi J Kidney Dis Transpl 2013;24:773-6

How to cite this URL:
Kaur N, Saha S, Mriglani R, Saini P, Gupta A. Crossed fused renal ectopia with a single ureter: A rare anomaly. Saudi J Kidney Dis Transpl [serial online] 2013 [cited 2022 Oct 3];24:773-6. Available from: https://www.sjkdt.org/text.asp?2013/24/4/773/113881

   Introduction Top

Crossed fused renal ectopia is an unusual congenital anomaly in which both the kidneys lie on one side and are fused. Crossed fused renal ectopia is usually characterized by double pelvis and ureters that drain into both sides of the urinary bladder. [1] We encountered an unusual case of crossed fused renal ectopia with a single ureter and containing renal stones in both the kidneys. The patient underwent open pyelolithotomy for the renal stones as percutaneous nephrolithotomy was not considered a safe option in this case. This variant of crossed fused ectopia has not been described in the literature previously to the best of our knowledge.

   Case Report Top

A 22-year-old female presented with intermittent episodes of colicky pain in the right flank for eight months. The patient also had one episode of gross hematuria eight months back that resolved spontaneously. A 10 × 10 cm lump was palpable in the right lumbar area, which was moving with respiration. X-ray kidney, ureter and bladder (KUB) region showed multiple radio-opaque shadows in the right lumbar area [Figure 1]. The renal function test was within normal limits. An ultrasonogram of the abdomen revealed multiple calculi in all the calices of the right kidney. The left kidney was not seen in the normal anatomical position and it was present on the right side, below the right kidney, and contained multiple calculi.
Figure 1: Plain X-ray KUB showing multiple radio-opaque shadows.

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Intravenous pyelography (IVP) showed right kidney in the normal position with moderate hydronephrosis. No renal outline was seen in the left lumbar area. Another reniform shadow was seen in the right lumbar region below the right renal outline and appeared to be malrotated. Radio-opaque shadows seen on plain film appeared to be present in all the calyces of both the kidneys. Normal right ureter entering into the right side of the bladder was visualized; however, the left ureter was absent. Contrast-enhanced computed tomography (CECT) abdomen showed left kidney in the right lumbar region below the right kidney, and this appeared to be fused with the lower pole of the right kidney [Figure 2]. The right kidney was supplied by the right renal artery with origin from the aorta and ectopically placed inferior kidney (left kidney) was supplied from branch of right internal iliac artery. No vertebral or skeletal anomalies were detected in this patient. A cystoscopic examination of the patient also showed only one ureteric opening.
Figure 2: CECT showing fused kidneys on the right side.

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The patient underwent open pyelolithotomy for the renal stones by right lumbar subcostal incision. The left kidney was found to be fused to the lower pole of the right kidney and the collecting systems of both the kidneys were opening in a single pelvis [Figure 3]. Of a total of 11 stone shadows that were seen on X-ray, nine stones could be removed. However, three stones could not be traced despite all attempts. To access the remaining stones, nephroscopy after clamping the opened pelvis was also tried but the stones could not be visualized. This probably was due to stenosis of the calyceal necks due to chronic inflammation.
Figure 3: Intraoperative photograph showing fused kidneys with single pelvis and ureter (long arrow - ureter, short arrows – calices).

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The pelvis was closed over a DJ stent, which was removed three weeks later. The patient's post-operative course was uneventful.

   Discussion Top

Crossed fused renal ectopia is the second common fusion abnormality of the kidney after horse shoe kidney, with an incidence of approximately 1:1300-1:7500. In crossed fused ectopia, one of the kidneys crosses over to the opposite side and is fused to the other kidney.

Most commonly, the upper pole of the inferiorly positioned crossed ectopic kidney is fused to the lower pole of the superior normally placed kidney. The ureter of the ectopic kidney crosses the midline and enters the bladder on the opposite side. [1]

Six variations of crossed fusion have been described [Figure 4]. These are: type 1 - inferior crossed fused ectopia, type 2 - sigmoid or S-shaped kidney, type 3 - unilateral lump kidney, type 4 - unilateral disc kidney, type 5 - L-shaped kidney and type 6 - superior crossed fused ectopia. [2] In this classification, the pertinent feature is that the ureters are present on either side of the urinary bladder. The crossed fused renal ectopia in this case was unusual as there was a single ureter, and this type has not been described as per the literature searched.
Figure 4: Various types of crossed fused renal ectopia. (A) Type 1 - inferior crossed fused ectopia, (B) type 2 - sigmoid or S-shaped kidney, (C) type 3 - unilateral lump kidney, (D) type 4 - unilateral disc kidney, (E) type 5 - Lshaped kidney and (F) type 6 - superior crossed fused ectopia.

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Most cases of renal ectopia remain asymptomatic during life and are diagnosed incidentally. [3] When symptoms do occur, the most common symptoms reported are abdominal or flank pain, a palpable mass, hematuria and dysuria. Nephrolithiasis, ureteropelvic junction obstruction and hydronephrosis are associated with this anomaly. [1],[3],[4],[5],[6],[7] Signs or symptoms of urinary tract infection occur in 30% of the patients. In children, urinary tract infection is the most common presentation. Ureteropelvic junction obstruction causing significant hydronephrosis occurs in one-third of the individuals. Stones are thought to be due to associated hydronephrosis or ureteropelvic junction obstruction, causing stasis of urine. The most frequent anomalies associated with crossed ectopia are imperforate anus (4%), skeletal abnormalities (4%) and septal cardiovascular defects. [1]

Renal ultrasonography is a good radiological modality to demonstrate the presence of fused ectopia. The sonographic examination usually reveals absence of kidney in contralateral renal fossa or pelvis and fused kidneys on the ipsilateral side (with an anterior or posterior notch and different orientations of collecting systems). [8] IVP reveals the absence of kidney on the contralateral side and also gives the information regarding the origin, course and insertion of the ureters. However, IVP may not definitely confirm the fusion of kidneys. Computed tomography (CT) allows accurate diagnosis, provides good orientation about the anatomy of the kidneys and help in deciding the surgical approach. Renal scintigrahy can also give information about the functioning of the kidneys. [1],[9]

Renal cell carcinoma, transitional cell carcinoma and Wilm's tumor have been reported in crossed fused renal ectopia, which were managed by resection of the involved renal unit. [10],[11],[12] Renal angiography or CT angiography is essential in these cases to provide key information about the renal vasculature, which is essential for planning the surgical dissection and line of separation between the kidneys. [10]

The embryological basis of crossed renal ectopia has not been clearly established. The formation of kidneys depends on the presence of both the ureteric bud and the metanephric blastema. The ureteric bud arises from the lower portion of the Wulffian duct and the metanephric blastema is a mesoderm tissue. Both these tissues migrate toward each other and merge to form the kidney and the urinary tract. It is suggested that overbending and rotation of the caudal end of the embryo prevents the ureteric bud from merging with the ipsilateral metanephric blastema and it turns toward the more-closer contralateral side. The migrated and the normally placed ureteric bud induces the metanephric blastema twice to form two kidneys on one side. [13],[14] However, this explanation does not hold true in the present case as there was only one ureter that was draining both the kidneys. This case raises a question on the above theory and an embryological basis for crossed fused renal ectopia needs to be re-evaluated.

   References Top

1.Bauer SB. Anomalies of the upper urinary tract. In: Wein AJ, Kavoussi LR, Novick AC, Partin AW, Peterseds CA, eds. Campbell's urology, 9 th ed. Philadelphia: Saunders-Elsevier; 2007. p. 3269-304.  Back to cited text no. 1
2.Mcdonald JH, Mcclellan DS. Crossed renal ectopia. Am J Surg 1957;93:995-1002.  Back to cited text no. 2
3.Boyan N, Kubat H, Uzum A. Crossed renal ectopia with fusion: Report of two patients. Clin Anat 2007;20:699-702.  Back to cited text no. 3
4.Larré S, Carpentier X, Sèbe P, Tassart M, Cus-senot O, Traxer O. A report of unusual crossed fused renal ectopia and minimal invasive management of calculi. Surg Radiol Anat 2007;29:393-5.  Back to cited text no. 4
5.Amin MU, Khan S, Nafees M. Crossed fused renal ectopia with staghorn calculus and gross hydronephrosis. J Coll Physicians Surg Pak 2009;19:69-70.  Back to cited text no. 5
6.Kumar S, Panigrahy B. Laparoscopic management of complex ureteropelvic junction obstruction. J Laparoendosc Adv Surg Tech 2009; 19:521-8.  Back to cited text no. 6
7.Taweel W, Sripathi V, Ahmed S. Crossed fused renal ectopia with hydronephrosis. Aust N Z J Surg 1998;68:808-9.  Back to cited text no. 7
8.Goodman JD, Norton KI, Carr L, Yeh HC. Crossed fused renal ectopia: Sonographic diagnosis. Urol Radiol 1986;8:13-6.  Back to cited text no. 8
9.Muttarak M, Peh WC, Lerttumnongtum P. Clinics in diagnostic imaging (59). Crossed-fused renal ectopia. Singapore Med J 2001;42:139-41.  Back to cited text no. 9
10.Gur U, Yossepowitch O, Baniel J. Transitional cell carcinoma in a fused crossed ectopic kidney. Urology 2003;62:748.  Back to cited text no. 10
11.Davis CM, Rao MV, Flanigan RC, Quek ML. Renal cell carcinoma in two patients with crossed fused ectopic kidneys. Urol Int 2008; 81:370-2.  Back to cited text no. 11
12.Redman JF, Berry DL. Wilms' tumor in crossed fused renal ectopia. J Pediatr Surg 1977;12:601-3.  Back to cited text no. 12
13.Cook WA, Stephens FD. Fused kidneys: Morphologic study and theory of embryogenesis. Birth Defects Orig Artic Ser 1977;13:327-40.  Back to cited text no. 13
14.Marshall FF, Freedman MT. Crossed renal ectopia. J Urol 1978;119:188-91.  Back to cited text no. 14

Correspondence Address:
Sudipta Saha
Department of Surgery, University College of Medical Sciences and GTB Hospital, Dilshad Garden, Delhi - 110 095
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1319-2442.113881

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

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