In vitro prediction of canine urolith mineral composition using computed tomographic mean beam attenuation measurements

Abstract

Determination of urolith mineral composition is critical for management of urolithiasis in dogs and cats. Using computed tomography, urolith physical density, and hence chemical composition, can be quantified using mean beam attenuation measurements (Hounsfield units; HU). This study was designed to establish in vitro reference ranges for three types of compositionally pure uroliths retrieved from dogs. Sixty-six canine uroliths (22 uric acid, 21 calcium oxalate, 14 struvite, nine mixed or compound) were placed in a phantom array. Uroliths were scanned at 120 kVp, 200 mA, and 80 kVp, 200 mA. The region of interest (ROI) for mean HU calculation was determined using two techniques, and reference ranges were calculated for each kVp using either ROI technique. HU for urolith types of pure composition were statistically different (Wilcoxon's two-sample test, P < 0.0083 [Bonferonni correction with six comparisons for total P < 0.05]) using both ROI techniques at either kVp. Struvite uroliths were not statistically different from mixed or compound uroliths. The accuracy for determination of composition of pure uroliths ranged from 86% to 93%; the prediction accuracy for each urolith mineral type and for all uroliths in general was highest when the ROI was hand-drawn just within the visible urolith border at 80 kVp. Technique of ROI determination and kVp that yielded the highest sensitivity, specificity, and positive and negative predictive values varied for each urolith type. Therefore, in this study, HU could be used to differentiate three types of uroliths of pure mineral composition in vitro. Further studies are needed to determine the predictive value of HU in vivo.

IMAGING DIAGNOSIS—ULTRASONOGRAPHIC AND CT FINDINGS IN A GRAY SEAL (HALICHOERUS GRYPUS) WITH HEPATIC CIRRHOSIS, PYELONEPHRITIS, AND NEPHROLITHIASIS

“…Secondary changes such as acquired porto‐caval shunts and splenomegaly can also be seen. Changes in the appearance of the liver in this gray seal were not seen, which could be explained by several reasons. First, the absence of intra‐abdominal fat prevented the clear delineation of the liver margins from other abdominal organs.…”

“…However, in human medicine, CT is considered to be superior to ultrasound to detect urinary calculi . The CT appearance of different uroliths, and especially their attenuation values, have been described in vitro in dogs and in vivo in humans . In this case, CT allowed full assessment of the extent of the nephrolithiasis.…”

Diagnóstico Da Urolitíase Em Felinos

“…A tomografia computadorizada (TC) têm se popularizado como melhor método no diagnóstico da litíase urinária em medicina, uma vez que apresenta 94% de sensibilidade na detecção dos cálculos, além de fornecer alternativas diagnósticas para dor lombar aguda (TÜRK et al, 2016;NYKAMP, 2017). Essa técnica permite facilmente a distinção de urólitos dos tecidos moles circundantes (PRESSLER et al, 2004). Em estudo realizado com felinos, a tomografia computadorizada foi capaz de diagnosticar cálculo ureteral em três pacientes, cujo urólitos não haviam sido observados na radiografia simples e ultrassonografia abdominal (KYLES et al, 2005).…”

“…Além da capacidade de detecção da presença de urólitos, outra aplicação do exame seria a possibilidade de predizer a composição dos cálculos com base nas diferentes densidades (PRESSLER et al, 2004;NYKAMP, 2017). A determinação da composição in vivo beneficia o tratamento médico ao facilitar a escolha terapêutica, quando não há possibilidade de remoção da pedra.…”

A review on urolithiasis in dogs and cats

“…A recent human study showed that non-contrast computed tomography could be used to predict the composition of uroliths on the basis of differences in radiodensity, measured in Hounsfield units. One in vitro study of uroliths removed from dogs showed the prediction of mineral content to be 75% to 88% accurate for pure uroliths, but mixed uroliths could not be accurately assessed (Pressler et al, 2004).…”