Relationship of diagnostic accuracy of renal cortical echogenicity with renal histopathology in dogs and cats, a quantitative study

Abstract

BackgroundRenal cortical echogenicity is routinely evaluated during ultrasonographic investigation of the kidneys. Both in dog and cat previous ex-vivo studies have revealed a poor correlation between renal echogenicity and corresponding lesions. The aim of this study was to establish the in-vivo relationship between renal cortical echogenicity and renal histopathology.ResultsThirty-eight dogs and fifteen cats euthanized for critical medical conditions were included in the study. Ultrasonographic images of both kidneys were acquired ante mortem at standardized ultrasonographic settings. The echogenicity was quantified by means of Mean Gray Value (MGV) of the renal cortex measured with ImageJ. A complete histopathological examination of both kidneys was performed. Five kidneys were excluded because histopathology revealed neoplastic lesions. Only samples affected by tubular atrophy showed statistically different values in dog, and histopathology explained 13% of the total variance. MGV was not correlated neither to the degeneration nor to the inflammation scores. However, significant differences were identified between mildly and severely degenerated samples. Overall, the classification efficiency of MGV to detect renal lesions was poor with a sensitivity of 39% and a specificity of 86%.In cats, samples affected by both tubular vacuolar degeneration and interstitial nephritis were statistically different and histopathology explained 44% of the total variance. A linear correlation was evident between degeneration and MGV, whereas no correlation with inflammation was found. Statistically significant differences were evident only between normal and severely degenerated samples with a sensitivity of 54.17% and a specificity of 83.3% and MGV resulted scarce to discriminate renal lesions in this species.ConclusionsRenal cortical echogenicity shows low relevance in detecting chronic renal disease in dog whereas it results worth to identify severe renal damage in cat.

Renal ultrasonographic abnormalities are associated with low glomerular filtration rate calculated by scintigraphy in dogs

“…In the recent years, qualitative and quantitative studies on the cortical echogenicity and the effect of artifacts on its intensity have been performed in healthy dogs. Two more recent publications have tried to eliminate patient and technical related biases, avoiding the comparison with other organs and analyzing the mean gray value in ex vivo and in vivo kidneys under standardized experimental conditions. However, the use of a mean gray scale and strictly standardized ultrasonographic settings was concluded to be poor in distinguishing between normal and pathological kidneys.…”

“…On account of its wide availability, low cost, and safety, ultrasound is often the first diagnostic imaging method used for investigation of kidney disease . Several studies have analyzed the sonographic features of the kidneys both in normal dogs and dogs with kidney disease . It is stated in the literature that morphologically abnormal kidneys may function normally, and that morphological alterations may be absent from functionally impaired kidneys, but studies on the association between structural and functional abnormalities are lacking.…”

“…12 Several studies have analyzed the sonographic features of the kidneys both in normal dogs [13][14][15][16][17][18][19][20][21][22][23] and dogs with kidney disease. [24][25][26][27] It is stated in the literature that morphologically abnormal kidneys may function normally, and that morphological alterations may be absent from functionally impaired kidneys, 3,11 but studies on the association between structural and functional abnormalities are lacking.…”

Correlation between separate findings in 60 dogs suffering from CKD in IRIS stage 1

“…kind or extent of sonographic abnormalities needed for inclusion in IRIS stage 1 and many seemingly healthy dogs show slight abnormalities of the kidneys in abdominal sonography (20), a scoring system was used in this study. As previous studies have already shown, there is a poor relation between single sonographic findings and kidney function in dogs(20,21,29) as well as in humans (30). Thus, patients in this study had to achieve at least two points to be included.…”

Correlation between separate findings in 60 dogs suffering from CKD in IRIS stage 1

“…While correlation of serum SDMA and GFR as the Gold standard for the evaluation of renal function has already been established, correlation between abnormalities in sonography of the kidneys and GFR is still inconclusive. Regarding ultrasonography, a scoring system considering several sonographic parameters of the kidneys was developed, since single criteria of the sonographic appearance of the kidneys have shown little correlation to kidney function in past studies (20)(21)(22)(23).…”