bilateral renal lymphoma frequently presents as an acute kidney injury ( aki ) 3 . with systematic chemotherapy for renal lymphoma
however , in the case we describe herein , the patient 's kidney function greatly recovered after an open renal biopsy and before systematic chemotherapy . here , we review and discuss this unique case .
a 64yearold japanese man was referred to our clinic with gross hematuria , hypertension ( blood pressure 180/75 mmhg ) , and kidney insufficiency ( serum creatinine [ cr ] 2.17 mg / dl ) .
magnetic resonance imaging ( mri ) demonstrated multiple bilateral renal tumor lesions , with a low intensity on t1 and t2weighted images ( fig .
1 ) . the serum soluble interleukin2 receptor was elevated to 870 u / ml ( normal range 145519 u / ml ) . 

mri showing kidney enlargement and bilateral renal multiple tumors , with low intensity on t1 and t2weighted images .
2 ) . f2fluoro2deoxyglucose positron emission tomography / computed tomography ) fdgpet / ct showed intense uptake in bilateral kidneys , a paraaortic lymph node , and the right atrial appendage .
we suspected malignant lymphoma and performed an open right kidney biopsy for a histopathologic diagnosis .
the kidney was hard and massively swelled , and the tumor lesions could not be distinguished from the normal renal parenchyma .
we freed the entire kidney from gerota 's fascia and made 1cm incisions in the renal capsule and obtained first and secondcuneiform specimens which were insufficient for diagnosis because of the inadequate number of infiltrating lymphocytes .
the third tissue specimen enabled the diagnosis : nonhodgkin 's lymphoma ( diffuse large bcell lymphoma / barkitt lymphoma ) ( fig .
( a ) renal biopsy showed diffuse interstitial infiltration by lymphocytes ( hematoxylineosin stains [ he ] 100 ) , ( b ) diffuse immunoreactivity of lymphocytes to cd10 , ( c ) no immunoreactivity of lymphocytes to cd3 ( he 200 ) .
after the open renal biopsy , the aki was unexpectedly getting better and the patient was withdrawn from hemodialysis ( fig .
he was treated with doseadjusted systemic chemotherapy ( the rchop protocol : rituximab , cyclophosphamide , doxorubicin , vincristine , and prednisone ) .
the patient was discharged after the 1st cycle of chemotherapy , and the systemic chemotherapy was continued .
renal involvement is common in hematologic malignancies and lymphomas , and it is observed in approximately 34% of patients in advanced stages of these cancers 4 . however , primary renal lymphoma ( prl ) is relatively rare , with only a few welldocumented cases reports in the literature 1 , 2 . the term  prl  is usually defined as when the disease is limited to the renal parenchyma and has not invaded from an adjacent lymphomatous mass 2 .
therefore , the status of prl as a primary disease or the first manifestation of a rapidly progressive disease is controversial 2 .
proposed the following diagnostic criteria for prl : ( 1 ) renal failure as the initial presentation ; ( 2 ) enlargement of the kidneys without obstruction and without other organ or nodal involvement ; ( 3 ) the diagnosis is made only by renal biopsy ; ( 4 ) absence of other causes of renal failure ; and ( 5 ) the rapid improvement of renal function after radiotherapy or systemic chemotherapy 5 .
our patient 's case matched almost all of these criteria , but he could not be diagnosed as having prl due to the involvement of the lymph node and the right atrial appendage .
there is no difference in its gender distribution , and the patients ' ages at onset have ranged from 2 to 90 years 7 , 8 .
the symptoms of prl are abdominal pain , gross hematuria , fever , and weight loss 7 , 8 .
ultrasonography and ct show kidney enlargement and hypovascular tumors . according to cohan et al .
, four patterns of renal lymphoma can be identified on ct : ( 1 ) the singlemass type ; ( 2 ) the multiplemass type ; ( 3 ) invasion of the contiguous retroperitonealmass type ; and ( 4 ) the perinephricmass type 9 .
mri shows renal tumors with low or isointensity on t1weighted images and low intensity on t2weighted images 10 . in histopathologic sections of renal lymphoma ,
the prognosis of prl is usually poor , with a 1year mortality rate of 75% 11 .
many reported cases show renal insufficiency by lymphomatous infiltration of the kidney 3 , 5 , 6 , 12 . according to tornroth et al .
, 3 acute renal failure or nephroticrange proteinuria was the principal indication for percutaneous kidney biopsy in 48 ( 87% ) of their 55 patients with bilateral renal lymphoma .
they also proposed a mechanism of acute kidney injury in which an interstitial proliferation of lymphoma increases the interstitial pressure without much destruction of renal parenchymal elements 3 .
increased pressure , however , could cause renal insufficiency by tubular obstruction , compression of the peritubular capillaries with increased postglomerular vascular resistance , or modulation of the tubuloglomerular feedback mechanism 3 .
in many reports , renal insufficiency by lymphomatous infiltration recovered rapidly after treatment 3 , 11 , 12 , 13 , 14 . in our patient 's case ,
hemodialysis and multiple incisions of the renal capsule for biopsy may have led to his kidney function recovery ; the treatment also recovered his kidney function as described .
to the best of our knowledge , the recovery of kidney function before systematic chemotherapy for a lymphoma has not been reported . in our patient , the dissection of the renal capsule , by chance , may have decreased in the renal internal pressure
this case supported the theory of renal insufficiency by compression of the peritubular capillaries with increased postglomerular vascular resistance or moderation of the tubuloglomerular feedback mechanism by a lymphomatous infiltration of the kidney . both needle biopsies and open biopsies
are used for the diagnosis of renal lymphoma 1 , 12 . in our patient , since his aki worsened rapidly and the flow cytometry for the current precise diagnosis of lymphoma required a substantial amount of malignant cells , we chose an open biopsy .
in fact , we needed to cut out renal tissue specimens three times to obtain the final diagnosis , since lymphoma cells infiltrated heterogeneously into the renal parenchyma . based on these observations
, we recommended an open biopsy rather than a needle biopsy for the precise and accurate diagnosis if a renal lymphoma is suspected .
this case supported the theory that renal insufficiency by lymphomatous infiltration of kidney is caused by compression of peritubular capillaries with increased postglomerular vascular resistance , or modulation of the tubuloglomerular feedback mechanism .
rapid diagnosis and treatment initiation are essential to preserve renal function and improve the prognosis .
informed consent was obtained from the patient for publishing this case report and accompanying images .
we declare that there is no conflict of interests regarding the publication of this article .
 key clinical messagerenal lymphoma as an initial lesion is relatively rare . 
 bilateral renal lymphoma frequently presents as acute kidney injury . with systematic chemotherapy for the lymphoma 
 , patients usually recover their kidney function . 
 however , in the case we describe here , the patient 's kidney function recovered greatly after an open renal biopsy . here , we review and discuss this unique case . 
Background
Case Presentation
Discussion
Conclusions
Consent
Conflict of Interest