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solitary crossed renal ectopia ( scre ) is a congenital abnormality that occurs due to combination of unilateral renal agenesis and renal ectopia . most of the patients are asymptomatic and usually present with complaints related to genitourinary , cardiovascular , hematological or vertebral abnormalities .
we report a case of scre with an unusual presentation in neonatal age with vesico - ureteric reflux ( vur ) and impaired renal function .
a 15-day - old male neonate was brought to us by parents with an antenatal ultrasound scan suggestive of right sided hydronephrosis and hydroureter . at the time of presentation , the general and systemic examination of the neonate was normal .
his renal functions were deranged ( blood urea nitrogen ( bun ) : 16.2 mmol / l [ 8.0 - 16.4 mmol / l ] and serum creat : 331 mol / l 50 - 110 mol / l ] ) .
routine urine examination revealed plenty of pus cells and urine culture showed growth of escherichia coli .
ultrasound of abdomen showed right sided hydronephrosis with right upper hydroureter with non - visualization of the left kidney .
patient was catheterized perurethrally and urinary tract infection ( uti ) was treated with intravenous antibiotics .
renal radionucleotide scintigraphy , technetium-99m - l , l - ethylenedicysteine ( ec scan ) was done which was suggestive of absent left kidney and incomplete pelviureteric junction obstruction on the right side with adequate cortical function [ figure 1 ] .
ec scan showing absent left kidney and right puj obstruction after obtaining a sterile urine culture report , a voiding cystourethrogram ( vcug ) was done .
the vcug showed the ureter crossing the midline and entering the kidney on the right side [ figure 2a and b ] .
magnetic resonance urography , done to confirm the anatomy , revealed a solitary right kidney with the ureter crossing midline and opening on the left side of urinary bladder along with presence of hydroureteronephrosis [ figure 3 ] .
diagnostic cystoscopy revealed absent right ureteric orifice and a wide left ureteric orifice with left hemitrigone confirming the diagnosis of scre .
once renal functions improved ( bun : 8 mg / dl and serum creatine : 1.2 mg / dl ) , the patient was discharged on chemoprophylaxis .
however , in view of breakthrough utis with vur in a solitary functioning renal unit , ureteric reimplantation was done at 6 months of age .
( a ) voiding cystourethrogram anteroposterior view showing left to right renal ectopia , ( b ) voiding cystourethrogram lateral view showing left to right renal ectopia magnetic resonance urography showing solitary crossed renal ectopia
crossed renal ectopia is a condition in which kidney is located on side opposite from which its ureter inserts into bladder .
mcdonald and mcclellan classified renal ectopia into 4 types ( i ) crossed renal ectopia with fusion , ( ii ) crossed renal ectopia without fusion ; ( iii ) scre and ( iv ) bilaterally crossed renal ectopia .
renal agenesis of one side and contra lateral displacement of the ureter draining the only kidney is termed as scre .
the various embryological theories that have been proposed for renal ectopia are ( i ) the metanephros and ureter are displaced by pressure of the umbilical arteries , ( ii ) the ureter wanders to induce the contra lateral metanephros , ( iii ) strong forces attract a ureter to the opposite metanephros and ( iv ) deviation of the median axis of renal vasculature .
most of the cases reported in literature are associated with orthopedic deformities , genital abnormalities , hematological disorders and anorectal malformation .
the most common genital abnormality in the male is cryptorchidism or absence of the vas deferens ; in the female , it is vaginal atresia or a unilateral uterine abnormality .
most individuals with crossed ectopic anomalies are asymptomatic and are often discovered incidentally at autopsy , during routine perinatal ultrasound screening , or after bone scanning .
our case presented with impaired renal function in neonatal age with vur , which is an unusual presentation of scre .
scre can be diagnosed by ultrasonography and radionuclide scintigraphy using 99mtc- dimercaptosuccinic acid ( volkan et al . , 2003 ) in most of the asymptomatic cases .
excretory urography and multi - detector three - dimensional ( 3d ) computed tomography ( ct ) urography is excellent for delineating renal ectopia .
but in our patient , excretory urography and ct urography could not be done due to deranged renal functions .
vcug , magnetic resonance imaging urthogram and diagnostic cystoscopy confirmed the diagnosis of scre ( left to right ectopia ) in our patient .
our patient required treatment for uti , deranged renal function and then ureteric reimplantation for grade iv vur .
malignancy in scre is unusual and the incidence of renal cell carcinoma in the ct era in a solitary crossed ectopic kidney is approximately 1 in 22 million .
scre is very rare disorder and our patient is probably the 35 case to be reported in literature .
scre is often an incidental diagnosis but we report an unusual presentation of scre in neonatal age with impaired renal function , uti , and vur without any associated abnormality .
our patient required treatment initially for deranged renal function , uti and then ureteric reimplantation for persistent grade iv vur with breakthrough utis .
solitary crossed renal ectopia ( scre ) is an exceedingly rare anomaly of the urinary tract . 
 so far , only 34 cases have been reported in the literature . 
 it usually presents after infancy . 
 most of these cases are diagnosed incidentally while patients are undergoing evaluation for associated genitourinary , cardiovascular , hematological or vertebral abnormalities . 
 we report the first case of scre presenting in neonatal age with impaired renal function and vesico - ureteric reflux .