Assessment of glomerular filtration rate measurement in dogs using dynamic contrast CT compared to serum iohexol clearance

Abstract

Dynamic contrast CT with Patlak plot analysis can be used to determine the glomerular filtration rate (GFR). However, several studies have shown different GFR values and they are most likely less than the values by the standard techniques. The purpose of this prospective, experimental, and method comparison study was to evaluate the GFR using a CT technique (CT-GFR) in 12 healthy dogs compared to serum iohexol clearance (SIC-GFR). All dogs were anesthetized and placed in the right lateral recumbency position and the caudal part was lifted inside the CT gantry. A single-slice dynamic CT of the aorta and both kidneys was scanned sequentially every 2 s for 2 min after a bolus injection (3 mL/s) of iohexol (300 mg/kg). Time attenuation curves (TAC) were constructed and the GFR per volume of kidney was calculated using the Patlak plot analysis method based on 30-120 s time intervals, and results were compared to global GFR from SIC that was determined with eight blood samples for up to 240 min. The CT-GFR value (1.85 ± 0.48 mL/min/kg) was significantly less than the SIC-GFR value (3.40 ± 0.80 mL/min/kg; P < .05). The CT-GFR was correlated with SIC-GFR by the coefficient of correlation (r) at 0.61 (P = .046). In conclusion, the CT-GFR underestimated SIC-GFR and should be used carefully. We suggest that the GFR should be calculated using the equation derived from linear regression between CT-GFR and the standard GFR method. With its own particular parameters, each institute should have its own prediction equation.

Delayed non‐selective contrast‐enhanced CT can reveal spontaneous contrast enhancement of the lymphatic system in cats

“…The delayed enhancement of the lymphatic structures object of the study led to some considerations about the behavior of the contrast media moleculae. The new generation of radiopaque contrast media (iopamidol, iohexol, ioxaglate, iotrol, and iopromide) are eliminated mainly by glomerular filtration and serum or plasma iohexol clearance can be used for estimating Glomerular Filtration Rate in small animal practice 13,14 . In experimental models, extrarenal excretion of iodine‐based contrast media via bile and intestines increases in case of reduced/absent renal function 15 .…”

“…Imaging ance can be used for estimating Glomerular Filtration Rate in small animal practice. 13,14 In experimental models, extrarenal excretion of iodine-based contrast media via bile and intestines increases in case of reduced/absent renal function. 15 However, some studies in human and veterinary medicine described the vicarious excretion route of the new generation of contrast media also in non-nephropathic patients.…”