PICTORIAL ESSAY: Role of FDG PET/CT in imaging of renal lesions

Abstract

Focal incidental renal lesions are commonly encountered on positron emission tomography (PET)/computed tomography (CT) imaging. The vast majority of these lesions are benign. However, the interpretation of renal lesions can be problematic if the imaging criteria of simple cysts are not met. Limited literature exists on the characterisation of renal masses with metabolic imaging. The purpose of this article is to focus on the imaging features of benign and malignant renal masses with PET/CT. The lesions discussed include renal cyst, angiomyolipoma, oncocytoma, renal cell carcinoma, renal metastases and other infiltrating neoplastic processes affecting the kidney. Both the anatomical and metabolic features which characterise these benign and malignant entities are described. We emphasise the importance of viewing the CT component to identify the typical morphological features and discuss how to best use hybrid imaging for management of renal lesions. Metabolic imaging has a promising role in the imaging of renal lesions and can help prevent unnecessary biopsies and ensure optimal management of suspicious lesions.

Malignant Epithelioid Angiomyolipoma: Tumor and Metabolic Response to Everolimus as Evaluated With Positron Emission Tomography

“…18 Most published descriptions have documented AML as metabolically active on FDG PET. 19–21 Another group found that patients with AML did not have increased FDG uptake but did have increased 11C-acetate metabolism.…”

Extrarenal Retroperitoneal Angiomyolipoma Mimicking Metastatic Melanoma

“…8 A third report has described a renal AML that did not demonstrate increased FDG avidity. 1 In our case, a pathologically proven case of AML did demonstrate increased FDG avidity. Given the paucity of data, FDG PET cannot be reliably used in the evaluation of AML; however, it is important to recognize that AMLs can have variable metabolic activity on FDG PET.…”

“…AMLs are the most common benign renal tumors. 1 The incidence of AMLs has been found to be 0.1% in males and 0.2% in females in populations without tuberous sclerosis. 2 AMLs are most commonly asymptomatic; however, once a size of 4 cm is reached, symptoms may develop in up to 80% of patients and up to 60% present with hemorrhage.…”

The rationale and the role of lymph node dissection in renal cell carcinoma

“…Additional radiological features, such as nodal size and contrast uptake, lack of hilar fat, diffusion weighted images [34, 38-40] and lymphotrophic nanoparticle-enhanced MRI imaging [41], may have potential to increase the sensitivity and the specificity imaging, although final pathological evaluation remains the only accurate nodal staging procedure [42]. Positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) has been evaluated as a potential imaging technique for detecting primary renal lesions with disappointing [43], as well. Recently, studies combining FDG-PET with CT scanning in the detection of labelled antibodies against the carbonic anhydrase IX (CAIX) antigen have shown promise for imaging and as a diagnostic marker for the primary tumor in patients with clear cell RCC [44][45][46]; to date, this technology has not yet been tested in the detection of RCC lymph node metastases.…”