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 .
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 ] .
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
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 .
ivu with right renal stones in s - shaped kidney retrograde pyelogram showing s - shaped kidney ct scan of bilateral s shaped kidneys
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 .
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 .
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 .
 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 . 
INTRODUCTION
CASE REPORT
DISCUSSION