Using Voided Urine to Monitor Kidney Function in Felids at Taronga Zoo, Australia
Abstract
Chronic kidney disease (CKD) is a common cause of morbidity and mortality in zoo felids. Retrospective analysis (1973–2013) at Taronga (TZ) and Taronga Western Plains Zoos identified CKD as cause of mortality in 15 of 29 felids. Elevated serum creatinine and urea were late and insensitive markers for CKD, with time from onset of azotemia to death ranged from 0–15 months. Where prior urine specific gravity (USG) data were available (n=9), urine was inadequately concentrated (USG<1.035) for prolonged periods before onset of azotemia (median 1.6 yrs, range 0.2–9.9 yrs).
This prospective study was designed to investigate urine as an early screening tool for CKD. Fresh voided urine samples (n=101) were collected from night enclosures of all eleven TZ felids, requiring no human-felid contact. Urinalysis included USG (handheld refractometer); glucose, bilirubin, ketones, blood, pH, protein (reagent strip); urine protein:creatinine ratio and microalbuminuria immunoassaya.
Voided urine from clinically healthy TZ felids was highly concentrated (USG 1.066±0.008) and negative for microalbumin (Table 1). Two snow leopards (Uncia uncia) had high physiological proteinuria. Sequential sampling revealed urine parameters are consistent for individual felids, allowing reliable inferences to be made.
One clinically well 12yo female fishing cat (Prionailurus viverrinus) exhibits persistently inadequate urine concentration (USG 1.018–1.038), warranting further investigation of kidney function.
For large predatory felids, sequential voided urine collection from night dens is a simple, non-invasive, inexpensive tool. Continuation of this longitudinal study aims to demonstrate the value of monitoring urine parameters for earlier detection of CKD.
Endnote
a. Heska E.R.D.-HealthScreen® Feline Urine Tests, Heska Corporation, Loveland, CO, USA.
Acknowledgments
Sincere thanks go to the staff of Taronga Wildlife Hospital and Taronga Zoo Carnivore Department for 16 months of frequent urine collection and analysis, the Jenna Donley Memorial Fund for financial support of this ongoing study and the Morris Animal Foundation for their ongoing support of this research.
Table 1. Summary of USG and UP:C values of voided urine from 11 Taronga Zoo felids
|
|
Voided urine specific gravity
|
Urine protein creatinine ratio
|
|
|
Median
|
S.D.
|
Range
|
No. of samples
|
Median
|
Range
|
|
Snow leopard male
Uncia uncia
|
1.069
|
0.009
|
1.048–1.076
|
16
|
0.42
|
0.24–0.97
|
|
Snow leopard female
Uncia uncia
|
1.054
|
0.009
|
1.052–1.075
|
13
|
0.52
|
0.50–0.77
|
|
African lion female
Panthera leo senegalensis
|
1.064
|
0.007
|
1.054–1.072
|
6
|
0.049
|
0.036–0.057
|
|
African lion male
Panthera leo senegalensis
|
1.063
|
0.007
|
1.062–1.076
|
5
|
0.084
|
0.037–0.16
|
|
African lion female
Panthera leo senegalensis
|
1.069
|
0.007
|
1.056–1.073
|
8
|
0.050
|
0.038–0.20
|
|
Fishing cat female
Prionailurus viverrinus
|
1.031
|
0.005
|
1.018–1.038
|
16
|
0.18
|
0.13–0.26
|
|
Sumatran tiger male
Panthera tigris sumatrae
|
1.067
|
0.004
|
1.062–1.070
|
9
|
0.054
|
0.049–0.065
|
|
Sumatran tiger female
Panthera tigris sumatrae
|
1.071
|
0.010
|
1.051–1.073
|
13
|
0.069
|
0.051–0.11
|
|
Sumatran tiger young male
Panthera tigris sumatrae
|
1.064
|
0.009
|
1.055–1.080
|
13
|
0.11
|
0.082–0.19
|
|
Sumatran tiger young male
Panthera tigris sumatrae
|
1.071
|
0.000
|
1.071
|
1
|
0.29*
|
* Single sample by cystocentesis at end of general anaesthesia
|
|
Sumatran tiger young female
Panthera tigris sumatrae
|
1.063
|
0.000
|
1.063
|
1
|
0.27*
|