ELEVATED RENAL ENZYMES IN BIRMAN CATS

Danièlle Gunn-Moore

 For a number of years I have been interested in Birman cats and their kidneys. This started when it was noticed that blood samples from many apparently healthy Birman cats had elevated urea and creatinine levels. While increases in urea and creatinine usually indicate a significant degree of kidney damage the affected cats did not appear to be ill.

 Incidence of raised creatinine levels:

To investigate this further we performed a prospective survey of healthy Birman cats. The cats were recruited with the assistance of the Southern and South Western Birman Cat Club and via direct contact with a number of individual Birman breeders. Initially, 112 clinically healthy cats were blood sampled. They ranged in age from eight weeks to 12 years; 78% were less than six years of age, 18% were less than six months of age; 50% were entire females, 14% neutered females, 23% entire males, and 13% neutered males.  The cats came from 19 separate households. Only creatinine levels were assessed because urea is more inherently variable and can be altered by feeding.  

The study found statistically significant evidence of elevated creatinine levels in apparently healthy Birman cats. The incidence appeared to relate to age, with over 80% of Birmans of less than six months of age having creatinine levels above the normal range for that age, while 30% of adults appeared to be similarly affected.

 Prospective study:

Sixty-eight of the cats were then reassessed 18 months later. Information was available for all of these cats, but repeat samples were obtained from only 43. This was because some had moved to new homes, were unavailable on the day of sampling, or had died. Two of the cats had died from renal failure.

The study showed that in the majority of cats the raised creatinine changed little with time. The stability of the condition can also be seen when looking at a number of individual cats for which we have urea and creatinine levels over a long period of time. Table 1 shows details of two cats, Esther and Koska, both of whom were first sampled at nine years of age, and who, despite having raised urea and creatinine levels went on to live long and happy lives. Koska eventually died of kidney failure, aged nearly 16 years of age, while Esther is still well, aged 17 years!

 Interestingly, while in the majority of cases the raised kidney enzymes appeared to change little with time, the finding may still reflect underlying renal disease. In support of this, two of the cats (one aged 10 years, the other aged only eight weeks), while apparently healthy at the time of first testing, developed progressive kidney failure within a few months, and had to be euthanased.  In addition, I have seen several young Birmans with clinical renal failure; the most severely affected being under two years of age, with clinical signs often developing shortly after routine neutering. In some cases, entire families appear to be affected. For example, Figure 1 and Table 2 detail two related families. In one litter of four apparently healthy kittens three of the kittens were found to have raised kidney enzymes at eight weeks of age (a1, 3 and 4). When the kittens were neutered at six months of age, all four were given intravenous fluids and antibiotics. Two of the kittens recovered well (a2 and a4), while the other two other were slow to recover (a1 and a3), and one (a1) progressed to terminal renal failure within six months. A related cat (the dam’s sister) was mated to the same sire, and gave birth to a litter of three kittens; b1 and b2 developed acute renal failure within one month of being castrated. b2 failed to respond to supportive treatment and died two weeks later. b1 responded initially, but developed chronic renal failure and had to be euthanased at one year of age.  A second litter brother (b3) also had raised kidney enzymes, but was clinically healthy at the time of blood sampling.

 Summary:

This study suggests that many Birman cats may have some degree of renal dysfunction, which may or may not result in signs of ill-heath, and which may or may not progress with time.  It has not yet been possible to determine an underlying cause of disease in clinically affected cats, nor to draw any firm conclusions as to the nature of the defect within the breed as a whole. While the clinical significance of these findings therefore remains unclear, it seems appropriate to suggest that evidence of elevated kidney enzymes in an otherwise healthy Birman cat should not be over interpreted as evidence of severe or progressive disease. It would however, seem sensible to monitor affected cats, and to consider the possibility of renal dysfunction when undertaking anaesthesia, surgery or treatment in cats of this breed.

 Acknowledgements:

I would like to thank all of the owners who volunteered their cats for the survey, the Southern and South Western Birman Cat Club for their assistance, the veterinary surgeons who referred cases or sent blood samples, and members of the University of Bristol who helped in this study.

 Table 1. Long term serum urea and creatinine levels in two healthy Birman cats.

Normal adult range:      Urea  6.5-10.5 mmol/l             

Creatinine  80-150 mmol/l

Table 2.           Long term results for an individual family of Birman cats.

Normal range:   Urea                                                    6.5-10.5 mmol/l

                        Creatinine         2-5 months of age:         35-88 mmol/l

                                                        Adult:                           80-150 mmol/l  

 Danièlle Gunn-Moore,

BSc, BVM&S, PhD, MACVSc, MRCVS,

Ralston Purina Lecturer in Feline Medicine

R(D) SVS Hospital for Small Animals,

University of Edinburgh , Easter Bush Veterinary Centre, Roslin, Midlothian , Scotland EH25 9RG

Email: Danielle.Gunn-Moore@ed.ac.uk    Tel: 0131 650 7650     Fax: 0131 650 7652

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