The inability to detect kidney disease on the basis of echogenicity

Abstract

With the use of new sonographic technology, we have observed that the echogenicity of kidneys is often equal to that of the liver in patients in whom there is no evidence of renal disease; this observation conflicts with the generally accepted notion that a normal kidney is always less echogenic than the liver. In order to reassess renal echogenicity as an indicator of disease, three experienced radiologists blindly reviewed the sonograms of the right kidney and liver in 153 patients. The prevalence of renal disease was 26% (40/153). Accepted sonographic criteria for abnormal renal echogenicity (kidney echogenicity greater than or equal to liver) were neither sensitive (62%) nor specific (58%) for renal disease, with a positive predictive value of 35%. Most of these inaccuracies occurred because 43 (72%) of 60 patients in whom renal echogenicity was equal to that of liver had normal renal function. If stricter criteria for abnormality were adopted (kidney echogenicity greater than liver), specificity (96%) and positive predictive value (67%) rose; however, sensitivity was only 20%. We conclude that renal echogenicity equal to the echogenicity of liver is not a good indicator of disease. Use of stricter criteria (kidney echogenicity greater than liver) provides a specific but insensitive test.

Renal Relevant Radiology

“…For example, increased echogenicity was reported to have a 96% specificity (and 67% positive predictive value) for the presence of parenchymal kidney disease (3).…”

Intrarenal arterial Doppler sonography in patients with nonobstructive renal disease: correlation of resistive index with biopsy findings.

“…Kidneys were considered abnormally echogenic if the echo intensity of the cortex of the right kidney was greater than that of adjacent liver. Kidneys with echogenicity equal to that of the adjacent liver were not included as abnormal because our earlier work has shown that this criteria of abnormality includes too many normal kidneys [7].…”

Increased Echogenicity of Renal Cortex: A Transient Feature in Acutely Ill Children

“…A limitation of this study was the subjectivity of the evaluation of the cortical echogenicity. Few reports have stated that densitometric measurement of echogenicity is more reliable than naked eye evaluations [10,12,13]. However, in our institute these measurements are not made in regular practice.…”

“…Because previous articles [3,5] have shown that in healthy pediatric subjects (neonates and infants excluded) echogenicity of the renal parenchyma is not increased, we believe that hyperechogenicity of renal parenchyma can be a nonspecific finding, a sign of (abdominal) illness varying from appendicitis to ileocecitis, infectious gastroenteritis or otherwise, rather than an indicator of renal disease. Only one study reported that renal echogenicity equal to the liver parenchyma is a nonspecific finding and does not suggest renal disease; that study, however, included only adults [10]. The cause of increased renal cortex echogenicity remains unclear.…”