ectopic kidney is a relatively rare renal anomaly however , an endourologist does encounter stone disease in an ectopic kidney occasionally .
factors such as anomalous blood vessels and tortuous ureter with high insertion can lead to poor drainage and predisposition to the formation of renal calculi in these patients .
the common management option for such stones is laparoscopy or ultrasound guided percutaneous nephrolithotomy ( pcnl ) .
we report our experience with the use the recently described micro - pcnl or  microperc  for two such cases .
two male patients , aged 57 and 60 years respectively , presented to us with calculi in ectopic pelvic kidneys .
the first patient had undergone a flexible ureterorenoscopy elsewhere during which the stone could not be reached due to difficult angulation and inflamed tissue leading to poor vision . computed tomography urogram revealed an ectopic malrotated left kidney lying over the sacrum .
there was a 13 mm  11 mm sized calculus in the renal pelvis [ figure 1a and b ] . in the second patient ,
computed tomography urogram revealed a normal right kidney and an ectopic malrotated left kidney lying over the sacrum .
there was an 18 mm  17 mm sized calculus ( 1232 hu ) in the pelvis and a 5 mm  4 mm sized calculus ( 423 hu ) in the lower calyx of the ectopic kidney [ figure 1c and d ] .
( a ) x - ray kub showing renal calculus in pelvis of pelvic ectopic kidney with double j stent in situ , ( b ) computed tomography urogram showing the pelvicalyceal system anatomy , ( c ) x - ray kub showing renal calculus ( yellow arrow ) in ectopic kidney , ( d ) computed tomography urogram showing the pelvicalyceal system anatomy ( location of pelvic stone - yellow arrow ; location of lower calyceal stone - red arrow ) both procedures were performed under general anesthesia . in lithotomy position ,
ureteric catheterization was carried out under cystoscopic guidance using 7 fr ureteric catheters over a 0.035 inch glidewire ( terumo , tokyo , japan ) .
the position was changed to supine - oblique with a sandbag under the ipsilateral hemipelvis to move the overlying bowel away from the kidney .
an ultrasound probe was pressed against the anterior abdominal wall to displace the bowel away from the line of access .
further , colour doppler was used to rule out any significant blood vessel in the path of needle puncture .
three - way connector was attached to the needle , allowing saline irrigation , passage of a 0.9 mm flexible microperc telescope , and a 272 m holmium : yttrium aluminum garnet ( ho : yag ) laser fiber [ figure 2 ] .
the stones were completely fragmented to dust with the laser . an x - ray and ultrasound
was obtained on the first post - operative day to document stone clearance and to rule out any fluid collection .
the urethral catheter was removed on the first post - operative day and the patient was discharged .
( a ) surface view of patient position and ultrasound guided percutaneous renal access , ( b ) intraoperative ultrasonography picture showing entry of puncture needle ( yellow arrows ) into lower calyx containing calculus ( red arrow ) , ( c ) confirmation of access into lower calyx by antegrade contrast study to delineate pelvicalyceal system , ( d ) intraoperative surface view showing microperc instruments , ( e ) puncture site at the end of the procedure ( yellow arrow ) , ( f ) post - operative x - ray kub showing complete clearance operating times were 30 and 35 min respectively .
in the first patient , ureteric catheter was left in situ for 1 day . in the second patient ,
ureteric catheter was replaced by a double - j stent at the end of the procedure .
visual analog pain scores ( 1 - 10 scale ) on first post - operative day were two and three respectively .
first post - operative day and 1 month follow - up x - ray and ultrasound kub revealed complete stone clearance and no evidence of fluid collection in the abdomen .
options for managing small renal calculi in pelvic ectopic kidney are shock wave lithotripsy ( swl ) , retrograde intrarenal surgery ( rirs ) , ultrasound or laparoscopy guided pcnl . since these kidneys are surrounded by bowel and bone ,
moreover , the clearance of fragmented stones is also impaired due to high insertion of ureter and impaired pyeloureteral motility due to surrounding fibrous bands .
rirs can be technically demanding due to abnormal and tortuous course of the ureter of a pelvic kidney .
this was exemplified by our first patient in whom the stone could not be reached with flexible ureteroscope and the procedure had to be abandoned .
the potential hazards in percutaneous access in an ectopic kidney are : ( 1 ) risk of injury to surrounding bowel , particularly if track dilatation is carried out through the bowel , ( 2 ) abnormal vasculature resulting in bleeding from tract dilatation and ( 3 ) spillage of fluid into peritoneal cavity .
microperc is a minimally invasive form of pcnl in which percutaneous renal access and stone fragmentation are achieved in a single - step using a 16 g needle . since dilatation is not performed , potential hazards associated with it are avoided .
fluid collection is less likely during puncture and at the end of the procedure since the needle puncture site closes quickly .
both our patients had rapid post - operative recovery , probably due to lack of fluid spillage and hence no paralytic ileus .
though laparoscopic guidance has been advocated for percutaneous access of an ectopic kidney , in experienced hands , ultrasound guidance can provide a safe entry into the appropriate calyx .
appropriate patient positioning to move bowel away from the kidney , placing a sand bag to push the kidney towards the anterior abdominal wall and compression with the ultrasound transducer allow safe access into the kidney .
further , the use of colour doppler rules out any significant blood vessel along the path of needle puncture . the hemoglobin drop in both of our patients was minimal , supporting the safety of this procedure . in laparoscopy guided pcnl , an abdominal drain may need to be left in situ for a prolonged period because of persistent urinary leakage .
the average hospital stay in a series of 15 patients who underwent laparoscopy guided pcnl was 4.8 days ( 4 - 11 days ) .
the patients in that series had sequential removal of nephrostomy tube , urethral catheter and abdominal drain , which lead to the prolonged post - operative stay .
thus , ultrasound guided microperc is a safe and efficient technique in the management of small renal calculi in ectopic kidneys and it is a minimally invasive procedure with short hospital stay .
 management of stone disease in an ectopic kidney is challenging . 
 laparoscopy or ultrasound guided percutaneous nephrolithotomy and retrograde intra - renal surgery are the preferred techniques for these stones . 
 we performed ultrasound guided microperc using a 16 g needle for the management of renal calculi in pelvic ectopic kidneys in two patients . 
 there was no intraoperative or post - operative complication . 
 both patients had complete stone clearance and were discharged on the first post - operative day . 
 ultrasound guided microperc is a safe and effective option for the management of small renal calculi in pelvic ectopic kidneys . 
INTRODUCTION
CASE REPORT
DISCUSSION