Assessment of feline chronic kidney disease (CKD) using ultrasound Diffusion Constant

Abstract

The indicator of kidney function, glomerular filtration rate is time and resource intensive, and blood and urine tests are insensitive. Hence, there is a need for non-invasive and sensitive methods to identify chronic kidney disease (CKD). Contrast enhanced ultrasound was used to measure the diffusion constant which is expected to change with changes in vascularization and microbubble population. Data was obtained on 43 cats (23 controls, 10 stage 1, 10 stages 2–4) after injection of 0.05 ml of Definity contrast agent. The inter-element response matrix was acquired by transmitting 5 MHz pulses with individual elements of a transducer array (L7-4) using a Verasonics Vantage system. The incoherent contribution (Iinc) to the backscattered intensity was extracted. The diffusion constant (D) was measured using the spatial growth of Iinc over time. A significant decrease (p = 0.0021) in D was observed in cats with stages 2–4 chronic kidney disease (mean D: 1.04 mm2/μs), compared to control (mean D: 1.69 mm2/μs), and stage 1 CKD cats (mean D: 1.77 mm2/μs). Smaller kidneys and presence of structural abnormalities could result in a denser vasculature, leading to more multiple scattering by the microbubbles and consequently lower D values for stage 2-4 CKD cases.