Indian Journal of Urology
: 2015  |  Volume : 31  |  Issue : 3  |  Page : 264--265

Bilateral s-shaped kidneys: A rare congenital malformation

Nikhil Ranjan, Rana P Singh, Rohit Upadhyay, Vijoy Kumar 
 Department of Urology, Indira Gandhi Institute of Medical Sciences, Patna, India

Correspondence Address:
Dr. Nikhil Ranjan
Old MDH q 3/5, Indira Gandhi Institute of Medical Sciences (IGIMS), Patna


A bilateral S-shaped kidney is a rare anomaly in which both the kidneys are in their normal position, in contrast to the commonly reported S-shaped fusion anomaly, in which the contralateral kidney crosses the midline to fuse with opposite kidney leaving the ipsilateral renal fossa empty. Here we present the diagnosis and management of a case of bilateral S-shaped renal anomaly with associated left pelviureteric junction obstruction and nonfunctioning kidney and right renal stones. Left kidney was managed by open nephrectomy and right kidney by PNL.

How to cite this article:
Ranjan N, Singh RP, Upadhyay R, Kumar V. Bilateral s-shaped kidneys: A rare congenital malformation.Indian J Urol 2015;31:264-265

How to cite this URL:
Ranjan N, Singh RP, Upadhyay R, Kumar V. Bilateral s-shaped kidneys: A rare congenital malformation. Indian J Urol [serial online] 2015 [cited 2020 Sep 23 ];31:264-265
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Full Text


Unilateral S-shaped anomaly with a contra lateral normal kidney has been reported sparsely in the literature. Herein we present perhaps the first case of bilateral presentation with associated pelviureteric junction obstruction on the left and renal stones on the right side.

 Case Report

Sixteen-year-old male patient presented to us with left dull aching flank pain. Intravenous urogram (IVU) showed an excretory kidney on right side with three radiopaque shadows apparently outside the pelvicalyceal system [Figure 1]. The left renal moiety was non-visualized. A retrograde pyelogram showed an S-shaped kidney on the right side with the upper calyces pointing laterally and the medial calyces pointing medially [Figure 2]. On the left side a grossly hydronephrotic kidney was seen. Computed tomography scan showed bilateral S-shaped kidneys with the upper calyces pointing posterolaterally and the lower calyces pointing anteromedially. On the left side severe cortical thinning and non-excretion of contrast were noted [Figure 3]. A 99m-DTPA acid scan revealed right S-shaped renal anomaly with a non-functioning kidney on the left side. As the patient was symptomatic on the left side we proceeded with left renal exploration. The left kidney was found to have S-shaped renal anomaly with two separate set of calyces oriented in opposite directions with a common pelvis and ureter. Pelviureteric junction obstruction (PUJO) with severe parenchymal loss was present. A simple nephrectomy was done. After 1 month the right renal stones were treated by percutaneous nephrolithotomy.{Figure 1}{Figure 2}{Figure 3}


The common S-shaped kidney reported in the literature is a fusion anomaly where the contra lateral kidney crosses to fuse with its mate leaving the opposite renal fossa empty. This is theorized as a ureteral phenomenon with the developing ureteric bud wandering to the opposite side and inducing differentiation of the contra lateral nephrogenic analge. In contrast the S-shaped renal anomaly reported in our case has been reported in the literature albeit with a normal opposite kidney. [1],[2] As IVU denotes near normal course of distal ureter we do not consider the defect at the ureteral bud origin.

The CT urogram and RGP vividly demonstrate the collecting system anatomy in which the obtuse angulation of major calyces is noted, this could explain the near separation of two moieties and resultant development of this type of kidneys, so we propose a defect in the dichomotous branching of the ureteral bud as the cause of this anatomy in which the first ureteric division was at a greater angle then normal resulting in large spatial separation of the two units with subsequent normal branching, with spatial separation providing enough space for both the kidneys to develop. A similar embroyological hypothesis accounts for supernumeray kidneys. [3],[4] A second ureteral bud or a branching from the initial bud is considered a necessary step. Alternatively, the nephrogenic analge may divide into two metanephric tails, which separate entirely when induced to differentiate by the separate or bifid buds. The S-shaped renal anomaly may be at an earlier stage where complete separation does not occur.

A differential diagnosis of bilateral supernumerary kidney was considered but the presence of single pelvis and ureter ruled out the possibility. A concomitant PUJO caused renal loss on the left side and an association between the two conditions may be present. We believe this is the first reported case of bilateral S-shaped anomaly.


Dr. SK Singh, Professor of Urology, PGIMER, Chandigarh.


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2Agarwal MM, Singh SK, Mandal AK. Is s-shaped kidney always a fusion anomaly. Radiological diagnosis of a new anatomical variant of a single kidney. Indian J Urol 2009;25:541-2.
3Ellen S, Bauer SB, Chow JS. In: Anomalies of upper urinary tract. Campbell Walsh urology 10 th ed. Vol. 4. Philadelphia: Saunders; 2012. p. 3123-60.
4Weyrauch HM Jr. Anomalies of renal rotation. Surg Gynecol Obstat 1939;69:183.