Bull Terrier Autosomal Dominant Polycystic Kidney Disease (BTPKD)

BTPKD was first reported in 1994 in eight related dogs (Burrows et al). The mode of inheritance as an autosomal dominant form of polycystic kidney disease was identified by O’Leary et al (1999). In 150 clinically normal dogs, 39 were diagnosed to have BTPKD by renal ultrasound or necropsy. There was no sex predilection. Dogs positive for the disease should be identified with a view to eliminating the gene from the population. 

Diagnosis

Ultrasound examination of the kidneys is currently the method of choice for the antemortem diagnosis of  BTPKD.  BTPKD is characterised by at least 3 cysts distributed in the renal cortex and renal medulla between 2 kidneys (O’Leary et al, 1999). On ultrasonography these are seen as circular, anechoic structures with well defined, thin walls with a distinct far wall border and strong acoustic enhancement. In cases where fewer than 3 cysts were detected, or if only one kidney appeared affected, results were classified as equivocal and retesting was recommended in 6-12 months. Animals with equivocal results were regarded as likely to be affected if they had an affected first degree relative (O’Leary et al, 1999).  

Ultrasound examinations should be performed with the highest frequency transducer available (at least 7.5 MHz). Examination should include imaging the entire kidney in transverse and longitudinal planes. The cysts should not be confused with the normal medulla of the kidneys. The normal medulla is relatively hypoechoic when compared to the renal cortex and does not have acoustic enhancement beyond it.

In practice the sensitivity and specificity will be influenced by the operator experience and skill, the type of ultrasound machine and the frequency of the ultrasound transducer that is used.

Protocol for the examination

The dog should be appropriately identified from microchip.

The dog should be restrained for the examination and sedated if required.

The coat should be clipped and the skin wet with alcohol. Ultrasound coupling gel should be applied to the skin. 

The kidneys should be identified and examined in transverse and longitudinal planes. The entire kidney should be imaged.

Cysts are identified as circular, anechoic structures with well defined walls and a distinct far wall border. There should be obvious distal enhancement (through transmission) beyond the cyst.

An estimate of cyst numbers should be obtained and the diameter of the largest cyst measured.

The findings should be recorded and a certificate provided for each dog examined.

Dogs less than 6 months can be examined, however if negative, they should be re-examined in 6 to 12 months.

Certification

A national form of certification needs to be developed to assist Bull Terrier breeders in identifying positive dogs and thus being able to reduce the incidence of BTPKD in the breed. The form should be available to members of AAVDI to provide consistency in recording and certifying PKD negative and positive dogs.

Identification of Animals

The certificate should record the microchip number.

Breed Information

A register of BTPKD should be maintained by the Bull Terrier Club in each state.

Charge to Clients

Currently the charge to clients varies widely throughout Australia. Costs should be formulated to cover the time taken for examination and the cost of equipment used. However, costs should be kept at a reasonable level to assist breeders in their efforts to eliminate the disease. Multiple dogs examined in one visit may enable the fee to be lower for the owner.

References

Burrows A.K, Malik R, Hunt G.B et al Familial polycystic kidney disease in bull terriers Journal Small Animal Pract. 1994 35: 364-369

O’Leary C.A, MacKay B.M, Malik R, Edmondston J.E, Robinson W.F, Huxtable C.R  Polycystic kidney disease in Bull Terriers: an autosomal dominant inherited disorder Australian Veterinary Journal 1999 77:6,361-366

This document was drafted from the input of the following veterinarians -

Drs. Nia Tilley, Karon Hoffmann, Richard Malik and Sue Foster

 

 


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