urinary tract infection ( uti ) is the most common infection contracted by renal allograft recipients . in patients of autosomal dominant polycystic kidney disease ( adpkd ) , cyst infection presents a complex diagnostic and therapeutic challenge , especially in the post transplant period . consequently , early and reliable detection of infected renal cyst is crucial for optimal patient management , especially when initial antibiotic therapy has failed . it has been infrequently reported in the post transplant scenario or in the adpkd patients . we report a case of post transplant xpn in the native adpkd kidney presenting as relapsing uti . 18-fluorodeoxyglucose ( fdg)-positron emission computerized tomography ( pet / ct ) scan allowed the exact localization of the infection in the renal parenchyma and guided the therapeutic procedure with subsequent resolution of uti . a 53-year - old male of adpkd - ckd on maintenance hemodialysis since one and half years received a deceased donor renal transplant at our institute . his postoperative recovery was uneventful and he was discharged on tenth post transplant day with a serum creatinine of 1.2 mg / dl . he presented two weeks later with complains of fever , malaise and dysuria . on clinical examination , he was hemo - dynamically stable but febrile . laboratory parameters included hemoglobin 10.2 gm / dl , leukocytes 8,600/cmm , platelets 2.9 lacs / cmm , glucose 186 mg / dl , urea 18 mg / dl , serum creatinine 1.7 mg / dl , sodium 138 meq / l , potassium 4.3 meq / l . urine analysis showed , albumin 1 + , 40 - 50 leukocytes /high power field ( hpf ) , red cells 4 - 5/hpf , no casts , bacteria , acid fast bacilli or fungus were found . chest x - ray was normal , abdominal ultrasonography showed multiple hepatic and renal cysts in native kidneys , but was not suggestive of any infection , graft kidney was unremarkable . he was treated with antibiotics and responded well to the same and later discharged . over the next three months patient presented twice with symptoms of uti and the urine cultures on both occasions grew escherichia coli . he was evaluated with ultrasonography and unenhanced computerized tomography ( ct ) , which revealed a normal transplant kidney and multiple cysts without evidence of any infection , hemorrhage or calculi in native kidneys . subsequently , patient underwent cystoureteroscopy with bilateral selective urine sampling from native kidneys , however culture revealed no growth . in an attempt to localize the source of infection it showed hyper - metabolic lesion arising in postero - inferior part of right native kidney [ figure 1 ] . pet / ct guided aspiration reveled purulent fluid , culture of the same yielded heavy growth of e. coli . on the basis of these findings , patient was subjected to right native kidney nephrectomy . the cut section of the gross specimen showed xanthomatous area [ figure 2 ] and the histopathology was suggestive of xpn [ figure 3 ] . patient made a good recovery with s. creatinine returning to 1.3 mg / dl and urine culture being sterile on subsequent follow - up of three months . pet / ct scan showing strong fdg uptake into postero inferior part of right native kidney ( arrow ) gross section of right kidney showing xanthogranulomatous area ( arrow ) light micrograph showing an interstitial infiltrate composed of neutrophils , mononuclear cells , and , most characteristically , lipid - laden macrophages ( arrow ) . febrile illness owing to complicated uti 's secondary to renal or hepatic cyst infection is a common cause of graft dysfunction . if not localized early and redressed they can be a source of significant morbidity especially in an immuno - compromised host . it is characterized by replacement of renal parenchyma with diffuse or segmental cellular infiltrate of lipid laden macrophages called foam cells . here , we report a case of rare occurrence of xpn in native polycystic kidney of a renal allograft recipient . in the literature , xpn in adpkd either in transplant scenario or otherwise has been infrequently reported.[46 ] in our case , conventional ct scan was non - contributory , however fdg pet / ct scan was helpful in localizing the site of infection . as the patient was not responding to conservative management it was decided to proceed with nephrectomy of infected kidney . xpn was subsequently established on evaluation of gross specimen [ figure 2 ] and histopathology [ figure 3 ] . fdg pet / ct scan in the recent times has emerged as a valuable tool for the transplant physician in localizing of infections especially in adpkd patients . pet / ct can overcome interpretive challenges in identifying tissue infection , based on the high metabolic activity and increased uptake of the glucose - analogue fdg by inflammatory cells . post transplant , uti especially in the adpkd patients is challenging to the transplant physician . this case highlights the rare occurrence of xpn as a cause of post transplant uti , especially in the absence of obstruction or stone disease . fdg pet / ct imaging is a valuable tool in both localization and subsequent planning of therapeutic interventions for complicated utis associated with adpkd transplant patients .
urinary tract infection ( uti ) is the most common infection contracted by renal allograft recipients . in patients of autosomal dominant polycystic kidney disease ( adpkd ) 
 , cyst infection presents a complex diagnostic and therapeutic challenge especially in the post transplant period . 
 accurate diagnosis forms the cornerstone in salvaging the graft from potentially catastrophic outcome . 
 we describe a case of xanthogranulomatous pyelonephritis ( xpn ) in the native kidney in a patient of post transplant adpkd which presented as frequently relapsing uti with graft dysfunction where in accurate diagnosis was made possible with the aid of 18-fluorodeoxyglucose ( fdg ) - positron emission computerized tomography ( pet / ct ) .