Kidney disease. We all remember hearing about it, don't we.  But it hasn't happened to OUR dogs. has it?  So we don't worry about it. After all, if I haven't had it in 20 years of breeding, it can't be carried in my line.  This represents the thinking of almost everyone you talk to about kidney disease, except the few who have had pups die from it, and they aren't talking at all.

The facts are frighteningly different from our perceptions.  I recently contacted Dr. Ken Bovee, from the University of Pennsylvania, who had been doing research in this field for a number of years.  I wanted to know if he had any advice for breeders regarding the inherited problem. His response was "Breed Labradors."  He went on to say that though he had accumulated a good bit of data, including a number of test breedings, when he submitted it to the statisticians, they were unable to establish the mode of transmission.

If you think the problem will just go away, and does not concern your dogs, you may some day have a rude awakening.  It is possible to breed Lhasas for over 20 years without having a single puppy sick from kidney disease, and suddenly have an entire affected litter.  I know of such a case in a line which used mainly healthy older animals for breeding, and normally had large litters and very low infant mortality.  (The assumption was that such breeding stock was unlikely to produce any genetic "surprises".)  Renal biopsy of one healthy male from a previous litter from this bitch also revealed evidence of the typical lesion.  This dog will never become ill, because his kidneys are only minimally affected.  This diagnosis could only have been made by biopsy.  (The bitch who produced these affected pups was herself proven, by biopsy, to be free of the lesion.)

Shortly after the first few breedings of Tibetan imports, breeders began to notice the occurrence of puppies which, at the time of weaning, urinated pale urine, drank large quantities of water, and later went on to develop clinical signs of kidney failure, ultimately dying of uremia.  Letter from Marie Stillman  Over the past 40 years or so, efforts have been made to study this disease, and determine its causes. We have learned a few things.  Others remain a mystery.

The actual lesion of the kidney in familial kidney dysplasia is a failure of maturation of the fetal kidney.  In the dog, all pups are born with fetal kidneys, but by 8 or 10 weeks, normal puppies kidneys have differentiated further and resemble the adult kidney.  In pups affected with the familial kidney disease, parts of the kidney fail to fully differentiate.  The kidneys are smaller than normal, and often irregularly shaped, with variable cortical thickness. (see fig. 1) On microscopic section we find areas of fetal kidney interspersed with normal kidney tissue.  (see fig. 2)

Sick puppies exhibit the well known signs of renal failure: failure to concentrate urine, resulting in large amounts of dilute urine, excessive water intake, vomiting, weight loss, failure to thrive.  In older animals, among the symptoms of kidney failure are early tooth loss, poor condition, weight loss, malaise, and poor appetite.  However, many animals whose kidneys are affected show no sign of illness, nor are their blood or urine tests abnormal.  All young mammals have at least 4 times the kidney tissue they absolutely need, so that pups who have more than 25% of functioning kidney tissue appear normal and healthy often into advanced old age.

The latest studies indicate that familial nephrodysplasia is inherited as a somatic dominant gene, with incomplete penetrance. This means that it only takes one mutation to cause the defect, but having that gene does not always cause renal failure. In familial kidney dysplasia, the affected state is difficult to recognize unless the animal is clinically ill.  We believe that this is the case very infrequently, since over 75% of the kidney must be non-functional before the animal shows any recognizable signs of illness or abnormal test results in urine or blood.   In fact we think that only about a tenth of the dogs that have the defective gene actually show any signs of the disease.  Very recently a DNA test has been developed to test for the defective gene.  As soon as there is enough data available we will be able to say more about the incidence of the problem and what steps need to be taken by breeders.