Plasma biochemistry and urinalysis variables of koalas (Phascolarctos cinereus)with and without oxalate nephrosis
K. Natasha Speight1,2, Julie I. Haynes1, Wayne Boardman2, William G. Breed1, David A. Taggart3, Brian Rich4, Lucy Woolford2
1Discipline of Anatomy and Pathology, School of Medical Sciences, University of Adelaide, Adelaide, SA, Australia;
2School of Animal and Veterinary Sciences, University of Adelaide, Roseworthy, SA, Australia;
3Discipline of Ecology, Evolution and Landscape Science, School of Earth and Environmental Sciences, University of Adelaide, Adelaide, SA, Australia
4Royal Zoological Society of South Australia, Adelaide, SA, Australia
Background Oxalate nephrosis is a highly prevalent disease in the Mount Lofty Ranges koala population in South Australia, but associated clinicopathologic ﬁndings remain undescribed.
Objectives The aims of this study were to determine plasma biochemical and urinalysis variables, particularly for renal function and urinary crystal morphology and composition, in koalas with oxalate nephrosis.
Methods Blood and urine samples from Mount Lofty Ranges koalas with oxalate nephrosis were compared with those unaffected by renal oxalate crystal deposition from Mount Lofty and Kangaroo Island, South Australia and Moggill, Queensland. Plasma and urine biochemistry variables were analyzed using a Cobas Bio analyzer, and urinary oxalate by high-performance liquid chromatography. Urinary crystal composition was determined by infrared spectroscopy and energy dispersive X-ray analysis.
Results Azotemia (urea > 6.6 mmol/L, creatinine > 150 lmol/L) was found in 93% of koalas with oxalate nephrosis (n = 15). All azotemic animals had renal insufﬁciency (urine speciﬁc gravity [USG] < 1.035), and in 83%, USG was < 1.030. Koalas with oxalate nephrosis were hyperoxaluric compared with Queensland koalas (P < .01). Urinary crystals from koalas with oxalate nephrosis had atypical morphology and were composed of calcium oxalate. Mount Lofty Ranges koalas unaffected by renal oxalate crystal deposition had renal insufﬁciency (43%), although only 14% had USG < 1.030 (n = 7). Unaffected Mount Lofty Ranges and Kangaroo Island koalas were hyperoxaluric compared with Queensland koalas (P < .01).
Conclusions Koalas with oxalate nephrosis from the Mount Lofty Ranges had renal insufﬁciency, hyperoxaluria, and pathognomonic urinary crystals. The ﬁndings of this study will aid veterinary diagnosis of this disease.