W712 AJR:201, November 2013 lymphatics) with subsequent spread to renal parenchyma [6–8]. Chronic inflammation is also reported to be a possible etiologic fac- tor [9, 10]. To avoid misdiagnosing second- ary renal involvement as PRL, investigators have reported that PRL should be diagnosed only in the following situations: disease lo- calized to the kidney without evidence of any other organ or nodal involvement; presenta- tion with renal failure in the absence of oth- er causes of renal impairment and rapid im- provement of renal function after treatment of lymphoma; or diagnosis confirmed by bi- opsy [11]. Histopathology shows infiltration of the interstitium with or without glomerular involvement. Pure intraglomerular infiltra- tion may also be present [12]. PRL is report- ed to occur more commonly in middle-aged men, and patients are usually symptomatic with flank pain, fatigue, or weight loss [13]. Hematuria, proteinuria, and renal failure are often present [14]. In contrast to PRL, SRL commonly oc- curs in patients with widespread disease. Al- though autopsy studies report an incidence as high as 30–60%, the imaging manifesta- tions of SRL occur in only 1–8% [15–17]. This discrepancy between autopsy and imag- ing studies may be explained by a high inci- dence of clinically silent cases that are diag- nosed only after microscopic examination of the kidneys. SRL occurs from either direct or hematogenous spread from disseminated dis- ease. SRL has been reported in both pediatric and adult patients [18]. Although any subtype of lymphoma can involve the kidneys, renal lymphoma (both Imaging of Primary and Secondary Renal Lymphoma Dhakshinamoorthy Ganeshan 1 Revathy Iyer Catherine Devine Priya Bhosale Erik Paulson Ganeshan D, Iyer R, Devine C, Bhosale P, Paulson E 1 All authors: Department of Diagnostic Radiology, Division of Diagnostic Imaging, Body Imaging Section, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd, Unit 1473, Houston, TX 77030-4009. Address correspondence to D. Ganeshan (dganeshan@mdanderson.org). Genitourinary Imaging • Review WEB This is a web exclusive article. AJR 2013; 201:W712–W719 0361–803X/13/2015–W712 © American Roentgen Ray Society R enal involvement in lymphoma commonly occurs in the presence of widespread nodal or extranodal lymphoma and is classified as secondary renal lymphoma (SRL). However, lymphoma may rarely involve the kidneys alone without evidence of disease elsewhere; then, it is termed “primary renal lymphoma” (PRL) [1, 2]. Although the diagnosis of renal lymphoma can be challenging, an awareness of the spectrum of imaging findings can help to differentiate lymphoma from other renal malig- nancies such as renal cell carcinoma (RCC) and can lead to appropriate recommendations for biopsy. An accurate diagnosis is critical be- cause renal lymphoma is treated by chemo- therapy whereas RCC is typically managed by surgery or ablation. On ultrasound, renal lymphoma is usual- ly hypoechoic or anechoic [3]. Diffuse neph- romegaly may also be seen. However, ultra- sound is less sensitive than contrast-enhanced CT for detecting renal lymphoma [3]. Further, sonographic appearances of renal lymphoma are usually nonspecific and lead to further in- vestigation with CT or MRI. This article re- views the CT and MRI patterns of renal lym- phoma and discusses the role of percutaneous biopsy in the diagnosis and management. PRL is exceedingly rare, accounting for fewer than 1% of extranodal lymphomas [2, 4, 5] (Figs. 1 and 2). The fact that the kid- neys lack lymphoid tissue has led many to question whether PRL truly exists [1]. Var- ious theories about the origin of PRL have been postulated including an origin of the re- nal capsule or perinephric fat (which has rich Keywords: CT, kidney, lymphoma, MRI DOI:10.2214/AJR.13.10669 Received January 28, 2013; accepted after revision February 19, 2013. OBJECTIVE. This article reviews the CT and MRI patterns of primary and secondary re- nal lymphomas and discusses the role of percutaneous biopsy in diagnosis and management. CONCLUSION. Renal lymphoma has a variable imaging spectrum and may mimic re- nal cell carcinoma. An awareness of the typical and atypical imaging features of both pri- mary and secondary renal lymphomas can help the radiologist to suggest these diagnoses and recommend biopsy when appropriate. Ganeshan et al. Primary and Secondary Renal Lymphoma Genitourinary Imaging Review Downloaded from www.ajronline.org by 52.73.204.196 on 05/17/22 from IP address 52.73.204.196. Copyright ARRS. For personal use only; all rights reserved