Polycystic Kidney Disease

Polycystic kidney disease (PKD) is characterized by the abnormal growth of epithelial-lined cysts from the nephrons and collecting ducts of affected kidneys . PKD is associated with dramatic increases in kidney size, starting before birth, which results from the unrelenting growth of thousands of fluid-filled cysts, many undergoing massive enlargement. As cysts grow, they compress neighboring tubules and capillary circulation, causing kidney cell loss and promoting the development of fibrosis, destroying the surrounding kidney tissue.

Polycystic Kidney Disease (PKD) has been reported in many species. However, English Bull Terriers, Persian and Exotic cats, wild felids, humans and rats suffer from a very similar disease in terms of mode of inheritance, age of onset, clinical signs and renal pathology. In addition, cystic renal disease has been described in sheep, zebra fish, ferrets, rabbits, swine and cattle.

Cats affected by this potentially lethal congenital renal disorder have many cysts within the kidney filled with fluids. This enlages the kidney, reducing its ability to function properly. PKD is seen equally in males and females. The cysts gradually increase in size and crowd out the normal kidney tissue. The disease is usually fatal. Hepatic and pancreatic cysts also can be seen in cats with PKD. As cats age, additional renal (chronic tubulointerstitial nephritis) and hepatic lesions (hepatic fibrosis) occur. Renal failure in these cats has an average age of onset of 7 years and is associated with azotemia, hyperphosphatemia, isosthenuria, nonregenerative anemia, and metabolic acidosis.4

Polycystic Kidney Disease is caused by a defective gene in Persians and exotic short-haired breeds. PKD in Persians and Exotic breed is estimated at 30–38% worldwide. Every cat with the gene will have polycystic kidneys. Some of the clinical signs are depression, lack of or reduced appetite, excessive thirst, excessive urination, and weight loss.

It has been established that decreased intracellular calcium levels can transform normal cells into PKD-like cells.

Currently the only practical way to identify affected cats has been by ultrasound scanning of the kidneys when a kitten is at least 10 months old. At this age the screening has a 95% accuracy. Before that age, the cysts may be too small to accurately identify and a false clearance may be given. As the kidneys fail, only supportive measures can be provided to make the cat more comfortable and to try to slow down the progression of the disease through changes in the diet.

Because the Selkirk Rex is so closely related to the Persian breed family, diseases, such as hypertrophic cardiomyopathy, polycystic kidney disease, and problems associated with a more than moderate degree of brachycephalic, head shape should be monitored in the Selkirk Rex.3

References

  1. Genetic testing in domestic cats. Leslie A. Lyons Mol Cell Probes. 2012 Dec; 26(6): 224–230.
  2. Pathology in Captive Wild Felids at German Zoological Gardens. Johannes Junginger et al. PLoS One. 2015; 10(6): e0130573.
  3. Selkirk Rex: Morphological and Genetic Characterization of a New Cat Breed. Serina Filler, Hasan Alhaddad, Barbara Gandolfi, Jennifer D. Kurushima, Alejandro Cortes, Christine Veit, Leslie A. Lyons, and Gottfried Brem. J Hered. 2012 Sep-Oct; 103(5): 727–733.
  4. Cystic Renal Disease in the Domestic Ferret Courtnye N Jackson, Arlin B Rogers, Kirk J Maurer, Jennifer LS Lofgren, James G Fox,* Robert P Marini Comp Med. 2008 Apr; 58(2): 161–167.
  5. Polycystic Kidney Disease. Li X, editor. Codon Publications; 2015 Nov.




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