WHAT IS RENAL
Renal Dysplasia is a defect of the kidneys. It is found most
commonly in Shih Tzu, Soft Coated Wheaten Terriers and Lhasa Apsos.
The dog is born with relatively immature kidneys. This changes rapidly in the first six weeks of life. In many animals, immature nephrons (urine-forming units) exist until 6-10 weeks of age. But in this disease, these immature nephrons persist throughout life. Also, some nephron units do not develop and are replaced with fibrous tissue. Sometimes this fibrous tissue represents 20-50% of the kidney, and the kidneys are noticeably small and irregular.
evidence of RD includes diffuse interstitial fibrosis in the cortex and
medula (which seems quite peculiar to this disease), reduced numbers of
glomeruli (the filtering structure of the kidney where toxins, fluid and
electrolytes are removed from the blood), dilated and hypoplastic
tubules (through which the fluid or filtrate passes while being
transformed into final urine), and a variety of sizes of glomeruli. Some
glomeruli are 20-30% smaller than normal, some are normal size, and some
are embryonic. While mineralization of tubules can be seen in any
chronic renal disease, this mineralization is seen with JRD even in
young animals that have only moderate uremia. Researchers believe that
this mineralization is somehow an early component of this disease and is
related to the abnormal development of the nephrons. Dogs with RD have
had an embryonic arrest some time around birth. Hypertension does not
seem to be part of this disease.
poorly recognized because many animals are only slightly affected. They
show no clinical signs, and the presence of the disease may fail to be
detected by routine laboratory tests, including urinalysis, serum
creatinine, BUN, radiographs of renal size, and ultrasound. Many
moderately and slightly affected dogs will live normal life spans with
apparently normal renal function and can pass on the disease to their
offspring. Due to the nature of this disease it can go undetected for
many generations or be ignored by knowledgeable breeders because only a
small percentage of animals will die of renal failure. Without the
development of more effective tests than those presently available, the
disease is going to be with us for a long time because it is transmitted
in a very silent fashion by many animals that appear clinically normal.