Plasma biochemistry and urinalysis variables of koalas (Phascolarctos cinereus) with and without oxalate nephrosis.
BACKGROUND
Oxalate nephrosis is a highly prevalent disease in the Mount Lofty Ranges koala population in South Australia, but associated clinicopathologic findings remain undescribed.


OBJECTIVE
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 μmol/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.
Discipline of Anatomy and Pathology, School of Medical Sciences, University of Adelaide, Adelaide, SA, Australia; School of Animal and Veterinary Sciences, University of Adelaide, Roseworthy, SA, Australia.
K Natasha
KN
Speight
Julie I
JI
Haynes
Wayne
W
Boardman
William G
WG
Breed
David A
DA
Taggart
Brian
B
Rich
Lucy
L
Woolford
D000818:Animals; D001774:Blood Chemical Analysis / Q000662:veterinary; D002129:Calcium Oxalate / Q000378:metabolism*; D005260:Female; D006959:Hyperoxaluria / Q000473:pathology / Q000662:veterinary*; D007668:Kidney / Q000473:pathology; D008297:Male; D008855:Microscopy, Electron, Scanning / Q000662:veterinary; D009401:Nephrosis / Q000473:pathology / Q000662:veterinary*; D010070:Oxalates / Q000737:chemistry / Q000652:urine*; D048368:Phascolarctidae / Q000097:blood / Q000652:urine; D051437:Renal Insufficiency / Q000473:pathology / Q000662:veterinary*; D013021:South Australia; D016482:Urinalysis / Q000662:veterinary
D010070:Oxalates; D002129:Calcium Oxalate
Calcium oxalate; Phascolarctidae; hyperoxaluria; kidney; renal insufficiency