bulking agent injection is now a standard treatment for patients with grade 1 - 3 primary vesicoureteral reflux ( vur ) .
patients with higher grades and secondary types of vur show an unacceptably high failure rate when treated with injections of a bulking agent .
collagen has been used for many years as a bulking agent in ureterovesical orifice and bladder neck to treat vur and incontinence .
collagen , however , can get calcified in the tissue , a process that can cause a series of problems for patients .
we present a case of a patient in whom calcified injected collagen showed imaging features mimicking ureteral stone .
a 15-year - old girl presented with moderate degree of right flank pain for 2 weeks .
pain was localized on the right side , altered with change in position , and did not relate to any particular organ .
the patient had been treated successfully for bilateral grade 2 vur when she was 3 years old .
a kidney ureter bladder ( kub ) radiography was requested and the report indicated presence of bilateral ureteral stone [ figure 1 ] .
ultrasonography showed bilateral ureterovesical junction ( uvj ) stone and mild stasis in both kidneys , which was compatible with the findings of the non - enhanced spiral abdomino - pelvic computed tomography ( ct ) scan [ figure 2 ] .
however , diethylene triamine pentaacaetic acid ( dtpa ) scan with furosemide injection and radionuclide cystography ( rnc ) scan ruled out obstruction and relapse of vur .
calcification of bilateral intravesical collagen injected to treat her vur 12 years earlier was responsible for the positive findings on kub , ultrasonography , and spiral ct .
15-year - old female with bilateral flank pain , which was suspected to be due to stones in bilateral ureterovesical junction , later diagnosed as due to calcification of collagen used 12 years earlier to treat vesicoureteral reflux .
15-year - old female with bilateral flank pain , which was suspected to be due to stones in bilateral ureterovesical junction , later diagnosed as due to calcification of collagen used 12 years earlier to treat vesicoureteral reflux .
spiral ct scan of pelvis without intravenous and oral contrast shows bilateral uvj calcifications ( arrows ) .
endoscopic therapy for vur has gained popularity because of elimination of invasive surgical procedures in children .
in addition , it has an acceptable success rate and a low level of complications . although a transition has occurred in the material of choice from teflon to collagen and now to hyaluronic acid copolymers .
however , we do find patients who were treated with collagen now in the second decade of their life .
the injected material , being a foreign body , can induce inflammatory response that leads to tissue calcification .
this calcification has been reported to be symptomatic with some patients reporting episodes of stone passing , hematuria , and even obstruction .
this is the second case report of ureterovesical injection calcification presenting as a ureteral stone during differential diagnosis and the first report of its imaging .
unlike the first case report where the patient presented with renal colic and passing of stone , our patient was completely asymptomatic , except for positional non - related flank pain .
there is no difference between a ureteral stone and calcification of injected collagen , when viewed by different imaging modalities like kub [ figure 1 ] , ct scanning [ figure 2 ] , and also ultrasound examination .
this similarity is because of the place where the bulking agent is injected . in doubtful cases , as in our case , uvj obstruction can be ruled out by dtpa nuclear scan in which glomerular filtration of injected nuclear radioisotope reveals any obstruction in the upper urinary tract .
the diagnosis of uvj stone in the presence of uvj calcification , possibility of ureteral stone passing ( in a patient with renal colic ) after uvj injection therapy , and the probability of recurrent vur after ureteral intervention ( in which calcified ureteral orifice will tolerate dilatation to pass the ureteroscope ) remain to be studied .
vur can be assessed by rnc in which a radioisotope passing to the bladder via the urethral catheter reveals presence of vur .
the standard treatment for grade 1 and 3 primary vur is injection of a bulking agent into the uvj .
clinicians should be aware that calcification of bulking agent like collagen can occur and they need to differentiate this from ureterovesical stones on imaging findings .
 primary vesicoureteral reflux can be treated by injection of a bulking agent into the wall of the ureterovesical junction . over time , the bulking agent can get calcified . 
 radiological images of the area show findings that mimic those seen in ureterovesical junction calculi . in this report 
 , we present the imaging findings of this phenomenon and discuss its challenging aspects . 