Sonographically Identified Echogenic Renal Masses Up to 1 cm in Size Are So Rarely Malignant They Can Be Safely Ignored

Abstract

chogenic renal masses in general are more often angiomyolipomas than carcinomas. Without regard to size, the chance of carcinoma in general is high enough that echogenic masses should not be ignored, and further workup is advocated. To this end, a recent review by Farrelly et al 1 concluded that "all noncalcified echogenic renal lesions detected with ultrasound need a CT to rule out a renal cell carcinoma." Another study further recommended computed tomography (CT) ORIGINAL RESEARCHObjectives-The purpose of this study was to determine whether small echogenic renal masses up to 1 cm in size incidentally detected by sonography are rarely malignant and thus do not need further workup.Methods-We reviewed approximately 13,600 reports of all abdominal sonographic examinations performed between November 2001 and October 2007 that identified a small echogenic mass in a kidney. Patients with known malignancy of any kind, tuberous sclerosis, lesions larger than 1.0 cm, lesions with heterogeneous echogenicity, and lesions with posterior ring-down artifacts or posterior acoustic shadowing were excluded. All patients without magnetic resonance imaging or computed tomographic scans that completely characterized the lesions were excluded unless a follow-up study (sonography, magnetic resonance imaging, or contrast-enhanced computed tomography) at least 5 years later was available for comparison to prove that the lesion was benign.Results-A total of 120 lesions in 111 patients satisfied the inclusion criteria. Lesion sizes were 0 to 5 mm (n = 16) and 6 to 10 mm (n = 104). Of these, 54 lesions were characterized as definitely benign (47 angiomyolipomas and 7 other benign entities: calcifications in stones or within a cyst or calyx and cysts that were either simple on follow-up studies or complicated with hemorrhagic or proteinaceous content). For the remaining 66 lesions, follow-up results after at least 5 years were normal in 24 cases (which meant that the lesion was no longer visible), and the remaining 42 lesions were stable in size. The mean duration of follow-up for these 66 lesions was 7.4 years.Conclusions-Small echogenic renal masses up to 1 cm in size that fulfill our study criteria are so likely to be benign that they can be safely ignored.

Can subcentimetre ultrasound detected angiomyolipomas be safely disregarded?

“…Itani et al found that subcentimetre echogenic renal lesions identified on US (containing fat or absence of growth for 5 years) were also likely benign enough not to require follow-up. 16 Further supporting evidence from Jinzaki et al demonstrated slow growth of AMLs at a rate of 5% or 19 mm per year, 7 a rate that was far slower in the present study population. Although the present study investigated definite reported AMLs, only 17 cases (0.01%) were found in which patients were suggested to have possible malignancies on their subsequent scans.…”

Etiology of Small Echogenic Renal Masses

“…Our smallest oncocytic variant was 1.2 cm (Figure 4). Our data is similar to that of Itani et al 3 who found no RCCs among 120 echogenic renal masses less than 1 cm. We found no RCCs among any of our echogenic renal masses less than 1 cm in diameter.…”

“…From this, we included only patients who had a follow‐up unenhanced computed tomography (CT), contrast‐enhanced CT or MR imaging, pathologically proven diagnosis, or lesions that were stable (showed no growth) on follow‐up ultrasound performed more than 5 years after the initial examination (Figure 1). Itani et al 3 used no growth for 5 years as a criterion for a benign lesion in 66 of 120 of their benign lesions. Exclusion criteria included patients less than 18 years of age, those ultrasounds with less than 5 years of follow‐up, lesions that were primarily cysts, and lesions with characteristic ultrasound findings for nephrolithiasis such as shadowing and twinkling artifact.…”

“…Furthermore, there has been controversy in how frequently small echogenic masses are AMLs versus other entities including RCC. Management of these small echogenic renal masses has become an area of controversy 3,4 . Itani et al 3 reviewed 120 echogenic renal masses, less than 1 cm in diameter, and found no RCCs in their series.…”

“…Management of these small echogenic renal masses has become an area of controversy 3,4 . Itani et al 3 reviewed 120 echogenic renal masses, less than 1 cm in diameter, and found no RCCs in their series. They concluded echogenic renal masses less than 1 cm in size is so unlikely malignant that they can be ignored.…”