Secondary Renal Hyperparathyroidism In A Dog at ThePetCenter.com

ThePetCenter.com presents an interesting case that relied greatly on modern laboratory techniques and data in order to establish a firm diagnosis. This 18 month old dog was presented to the veterinarian because of a swollen face and difficulty eating. The dog wasn't "acting quite right" over the previous three weeks according to the owners. He had been drooling and had difficulty chewing and would "pick up his food and drop it". Plus, the owners noticed that the dog was urinating "all over the house". Since they acquired the dog only three months prior, they knew little of his earlier medical history.

A very sick dog...

The 18 month old Golden Retriever mix male dog was slightly under weight, had a noticeably swollen muzzle and acted depressed although not in pain. The temperature was very slightly elevated at 102.6 degrees. The heart and lungs were normal sounding and no bony deformities were noticed other than the firm and enlarged maxilla (the bones that hold the upper teeth) and the jaw bone which seemed slightly pliable and not as rigid as a normal jaw bone.

The tentative diagnoses included three main possibilities:
1.) A bone cancer
2.) Hyperparathyroidism
3.) Kidney disease causing mineral loss

Since the history indicated that the patient was "urinating all over the house", obtaining a urine sample for analysis was of primary concern. Here are the results of the urinalysis:

Specific Gravity...   1.005 This measures how concentrated or dilute the urine is so this is very dilute!
Protein... +1 (This is not very significant. +3 or +4 would be remarkable.)
Blood... Trace   This is noteworthy but not alarming.
pH 5...   This means that the urine is very acid. Urine almost never is this acid normally!
Bilirubin...None (This means the liver's internal bile channels are not obstructed.)
Ketones... None (This would be positive in diabetics and starving animals.)

Sediment (This displays any solids that are a part of the urine sample. The solids settle to the bottom of a test tube that is spun in a centrifuge. The fluid portion is poured off leaving the solids for microscopic exam.)
White Blood Cells: 50+ per HPF This means High Power Field: The microscope is getting a really close look! Fifty white blood cells per HPF is significant and indicates inflammation or infection and possibly leukemia.
RBCs: 5 per HPF This refers to Red Blood Cells and there should be none seen in a normal urine sample.
Bacteria: 2+ (0 to 4+ scale) Rods Rods are a type of bacteria and a normal urine sample should have no bacteria present.
Epi cells: 2+ (0 to 4+ scale) Epi (epithelial) cells are cells that line the inside of the urinary tract. 2+ epi cells may or may not be significant.

The most significant data obtained from this urine sample is the very dilute nature of the urine. The urine has barely been concentrated any more than water which has a specific gravity of 1.000. For some reason this dog is not concentrating the urine. A normal and expected concentration would be 1.020 to 1.045. Also, this urine sample is very acid and indicates that the patient is trying to get rid of excess acid from his body.

Let's take an x-ray of the dog's skull and see what we can find out about those swollen gums and face. Lightly sedating the dog so that we can position him for the x-rays without motion that would blur the image, we entered the X-ray Room and after sending the exposed film through the automatic processor we viewed the x-rays moments later. (To view lots of other X-rays go to ThePetCenter' X-ray Room.)

You can see exactly what we saw:

The teeth are loose and seem to "float" in the gums.	The x-ray above shows very little bone density especially in the upper (maxillary) bone. (This condition is referred to as OSTEOMALACIA). Some of the teeth appear to be floating in the gum and not attached to any bone at all!
The side (lateral) view of the skull on the right reveals very uniformly thin bone. The outer edges of the jaw bone should be nearly as dense (white) as the teeth.

Well... now we can rule out cancer of the facial bones since no discrete tumor or empty spaces are observed.. There is evidence of widespread lack of density in all the facial bones which leads the veterinarian to believe there is a reabsorptive process going on. Since the owners indicated that this condition has become apparent fairly recently, the assumption is that the dog developed normally and then somehow began to reabsorb the calcium from his bones. The body has methods to preferentially keep the blood levels of calcium at normal concentrations in order to keep nerve and muscle activities functional. Too little calcium in the blood leads to dangerous seizures!!

What could be making the dog's body reabsorb calcium from the bones
to supply the blood stream with calcium ions?

Let's review: We've taken x-rays and determined that there is no evidence of cancer in the facial bones and we know from the urine sample that the kidneys are not working as they should. The next step is to have a Chemistry Profile done with a blood sample analysis. Let's just do a chemistry profile for kidney dysfunction since that is our primary organ under suspicion.

Blood Chemistry

Creatinine........6.4 (Normal is 1.5 or less) The creatinine level is extremely high and suggests irreversible kidney damage is present.

BUN...............217 (Normal is 15 to 30) Blood Urea Nitrogen measures the urea waste products in the blood stream and should not be more than 30 for a dog of this age. The BUN level here is about as high as it can get! This dog has an extremely acid condition in his body as a result of the kidneys not being able to eliminate the acid wastes.
NOTE: For BUN and Creatinine levels in the blood to rise this high we know that at least 75% of the total kidney function is lost!

Sodium..............156 This is slightly elevated.
Potassium.........4.2 This is in the normal range.
Calcium............10.9 This is slightly elevated above normal.
Glucose.............112 This is normal.
Total Protein.....6.3 This is normal
Albumin.............3.4 This is normal
Alkaline Phosphatase...148 This liver function test is insignificantly elevated.
Total Bilirubin......0.3 This is normal and tells us that the liver's bile system is not obstructed.
Total Cholesterol...297 This is nearly normal.
T4.........................0.5 This is a measure of the Thyroid gland's output. It is lower than normal but is due probably to the gland being poisoned by all the waste products building up in the dog's body. There are no real signs of hypothyroidism in this dog.

Hematology

Red Blood Cell Count... 2,100 This Red Cell Count is very low; it should be about 7,000 to 9,000. Since this dog is not bleeding (losing RBCs) the indication implies that red cells are not being produced. This is common with severe kidney disorders since the chemical called erythropoetin, produced in the kidneys, promotes red cell production; any kidney disease can diminish erythropoetin production.

Hemoglobin...................5.6 This is the Oxygen-carrying protein of the red blood cell. Since the numbers of red blood cells are very low we expect to see a lower Hemoglobin value... and this is the case here where the value is about one-third what it should be!

Hematocrit......................15.8% This is the percentage of cells in the entire blood sample. (Blood is composed of solids such as cells and protein elements AND the liquid portion called serum.) The Hematocrit is the percent of cells in the total volume of blood. Since blood is partially a fluid and partially cellular we find from this test that the percent of cells in the blood (red and white cells) is very low. The Hematocrit should be about 45% and again since we see no evidence of blood loss this low percentage must reflect a poor production level.

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To be quite honest, the lab tests that were run can be considered the bare essentials needed to make a diagnosis. There are a multitude of other tests that could be run to gain further data. In veterinary medicine, unlike human medicine, the veterinarian often is at the mercy of the owner's ability to pay for tests and procedures that would otherwise be standard in good human/veterinary medicine. All the veterinarian can do is recommend certain tests and procedures and hope the client agrees to pay for them. In this case the client was able to give permission for the essential lab and x-ray procedures required to come to a reasonably precise diagnosis.

There should be enough data now for the veterinarian to conclude what is wrong with our little patient. Here's what is known at this time:

1.) The patient is deteriorating quickly.
2.) The kidneys are in advanced failure even though lots of urine is being produced.
3.) The kidneys are not conserving minerals like they should and are loosing minerals and other elements that ordinarily would be kept in the body. Poisons are building up in the body to unsurvivable levels.
4.) Bone is being reabsorbed from the skeleton in order to keep the vital blood level of Calcium normal. Since the Calcium is conveniently available from the skeleton, this reabsorption is happening faster than the dog is able to replace Calcium from dietary sources.
5.) Anemia is present which further debilitates the dog. The anemia is another indicator of advanced kidney disease since the kidneys secrete Erythropoetin, a hormone that triggers cells in the bone marrow to produce Red Blood Cells.

In the dog there are actually four independent parts to this gland which are closely associated with the two lobes of the Thyroid gland at the base and front of the neck. The Parathyroid Gland closely regulates blood Calcium levels by secreting its hormone called Parathormone.

Without actually checking the Parathyroid gland's production of Parathormone, we can safely assume the Parathyroid gland is working overtime to keep the body's blood Calcium at safe levels. After all, the bones are being robbed of Calcium and this is a direct result of the Parathyroid gland doing exactly what it is told to do by chemical messages in the blood stream.

So... as a result of the kidney disease (also called Renal Disease) the dog is losing minerals and lots of other chemicals that should be conserved in the body. Because of this loss, the body sends messages to the Parathyroid gland to find more Calcium for the blood stream. The Parathyroid gland goes into "Hyperdrive"! The most readily available source, unfortunately for the dog, happens to be its own skeleton! This depletion of the skeleton of Calcium by a hyperactive Parathyroid gland eventually leads to soft, less dense bone and lots of discomfort for the dog. A good name for this condition, which sadly is a fatal disorder for the dog, is Hyperparathyroidism. But... there are a number of kinds of Hyperparathyroidism. This particular case happens to be Hyperparathyroidism caused by Kidney (Renal) Disease. So actually the Hyperparathyroidism is secondary to the primary problem which is Kidney Disease. To be most accurate, then, when we tell someone about this poor little dog and try to describe what is wrong with him, we need to say that he died of Renal Secondary Hyperparathyroidism.

Sadly for this little dog he was gently euthanized and his unhappy existence came to an end. Yes, this same condition can occur in humans. Kidney transplantation may be required.