Chronic kidney disease is common in domestic rabbits (Oryctolagus cuniculus) and is often difficult to diagnose, especially during the early stages of the disease. In rabbits, nephrons are intermittently operative, and nephrons are never all active at any 1 time. When there is an incipient reduction in functional renal mass, the remaining glomeruli of dogs and cats enter a state of hyperfiltration to compensate, whereas rabbits recruit silent (inactive) glomeruli. Consequently, in rabbits, the early stages of CKD are characterized by the activation of previously inactive nephrons, which masks the signs of impaired renal function. In fact, rabbits with CKD can live for months to years without any clinical signs of the disease. However, once rabbits lose > 50% to 75% of renal function, they have a significant increase in serum creatine and SUN concentrations in a manner similar to that of dogs and cats with impaired renal function. Although abnormally increased serum creatinine and SUN concentrations are commonly used to identify rabbits with CKD, those 2 biomarkers are not very sensitive for that purpose because they can be affected by several extrarenal factors or pathological conditions such as gut stasis.1
Glomerular filtration rate is considered the best quantitative variable for assessment of overall renal function in both human and veterinary medicine.2–5 It is directly related to functional renal mass and is considered the most sensitive biomarker for early-stage kidney disease.6,7 The GFR can be determined by urinary or plasma Cl of an ideal filtration marker, which is defined as a substance that is freely filtered by the kidney, not reabsorbed or secreted by the renal tubules, not metabolized or bound to plasma proteins, and not nephrotoxic.5,6 Iohexol is a nonionic low-osmolarity contrast medium that is widely used in many species because of its low toxicity. In fact, plasma Cl of IOX is used to estimate GFR in humans8 and various animals, such as horses,2 donkeys,2 dogs,6,9 and cats.7,9
To our knowledge, estimation of the GFR by means of IOX Cl has not been evaluated in rabbits. Therefore, the aims of the study reported here were to evaluate GFR estimation by means of plasma IOX Cl in healthy domestic rabbits and to assess the accuracy of limited-sampling methods for GFR estimation.
Terminal slope of the concentration-time curve
Area under the concentration-time curve
Chronic kidney disease
Glomerular filtration rate
High-performance liquid chromatography
Limit of determination
Limit of quantification
Urine protein-to-creatinine ratio
ELISA, Medicago, Uppsala, Sweden.
Procyte DX, Idexx, Milano, Italy.
SLIM, Seac, Firenze, Italy.
STAT Profile pHOx Plus, GEPA, Milano, Italy.
VetLab UA, Idexx Europe BV, Hoofddorp, Netherlands.
Vet 360 refractometer, Reichert Technologies, Buffalo, NY.
Omnipaque 350, Nycomed Imaging AS, Oslo, Norway.
Pump Series 200, PerkinElmer Inc, Nashville, Tenn.
Series 200 variable UV detector, PerkinElmer Inc, Nashville, Tenn.
HAISIL HL, The Nest Group Inc, Southborough, Mass.
Turbochrom, PerkinElmer Inc, Nashville, Tenn.
VWR International, Milan, Italy.
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