New Assay May Improve Surgical Accuracy, Reduce Time

Veterinary surgeons could soon identify the location of abnormal parathyroid glands and ensure success before completing surgery on pets with hyperparathyroidism by using a test commonly used in human medicine

A surgical study underway at the University of Illinois Veterinary Teaching Hospital will gauge the efficacy of an assay used preoperatively to localize abnormal parathyroid glands with ultrasound. Once location of the malfunctioning gland is identified, doctors remove it and use the assay again to measure hormone levels in the blood. Once an over-productive gland is removed, hormone levels should return to normal within five to 10 minutes, said Kathleen Ham, DVM, a surgical resident at the University of Illinois Veterinary Teaching Hospital who initiated the canine study in June 2006. She is still accepting patients for the study and can be reached via email.

Hyperparathyroidism also affects cats, as addressed in a recent JAVMA article, and veterinary researchers may extend their study of this assay tool to include felids in the future, Ham said.

The rapid parathyroid hormone assay, a tool employed by human doctors, takes 10 to 20 minutes to gauge hormone levels in the body. Healthy dogs and humans have four glands that work in tandem to produce adequate hormone levels. In dogs with hyperparathyroidism one or more of those glands develop adenomas, benign tumors that trigger excess hormone production and do not respond to body signals to lower secretion.

Exact disease numbers are not known, but professionals suspect the a-symptomatic condition is underreported in pets and people. The disease is detected when excess levels of calcium are found in the blood so diagnosis is often accidental, Ham said. Common clinical signs are associated with signs of urinary tract infections and kidney stones, she added. More veterinary cases have been diagnosed recently because of a rise in pre-anesthetic blood work and routine blood screens, and the teaching hospital sees about 12 cases per year, she added.

Late sequela for hyperparathyroid dogs includes renal failure and skeletal problems caused by calcium build-up, Ham said. Neuromuscular affects such as weakness, tremors and mental dullness have also been reported.

Out of the four client dogs that underwent traditional surgery, the assay was used to assess blood from a jugular vein and identify abnormal glands before surgery. Hormone levels were higher on one side of the neck in three out of the four dogs, Ham said.

Determining which gland is hypersecretory is difficult because “there is no scientific proof to know which one is abnormal,” Ham said. However, studies show that affected glands are slightly larger – measuring at 6 millimeters versus 2 to 4 millimeters, she added. If the tumor is malignant the case is called adnocarcinoma; when multiple glands are affected the condition is called hyperplasia.

The cost of the 20 to 40 minute surgery is estimated at $2,000 in teaching hospitals and dogs stayed in the hospital for two to three days to measure levels of calcium. They were reevaluated 14 days after the surgery.

“Overall it’s not a bad disease to have since it’s curable with surgery,” Ham said. If the assay tool is effective, veterinarians could reduce surgery time and improve the outcome for dogs that have the disease, she added.

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