Parathyroid Tumors in Dogs and Cats

Article Written by Dr. Daniel A. Degner, Board-certified Veterinary Surgeon (DACVS)

Key Points

Parathyroid tumors usually are benign

Because these tumors produce excessive amounts of parathyroid hormone, the calcium level in the blood becomes abnormally elevated and has profound effects on other body systems

The most common early warning sign of a parathyroid tumor is increased thirst and increased urination

Surgery has been and still is an excellent form of treatment for these tumors. Other treatments are available and seem to work well

Prognosis is generally excellent following treatment

Introduction

Parathyroid tumors are uncommon in dogs and much less common in cats. These tumors usually are benign, meaning that they usually do not metastasize or invade into nearby tissues. They usually are very small tumors that raise a lot of havoc in the affected patient’s body, because they produce excessive amount of parathyroid hormone. Multiple parathyroid tumors are found in about 10% of affected patients. Breeds that most commonly develop this problem include Keeshonds, Labradors retrievers, and German shepherds.

Anatomy and Physiology

Both dogs and cats have four parathyroid glands, two on each side of the neck. The parathyroid glands are attached to the surface or are imbedded within the thyroid glands. One parathyroid gland is located on the top pole (end) of the thyroid and the other is located on the bottom pole. Normally these glands are about 2 to 3 mm in diameter and are tan colored. The glands produce parathyroid hormone which causes the calcium level in the blood to increase. Because many electrical systems of the body’s organs such as the kidneys, bowels, muscle, and brain are totally dependant on calcium, a change in the normal level of this important element in the blood can be very harmful to the pet. In addition, high calcium levels can cause stones to form in the urine.

Signs and Diagnosis

Signs of hyperparathyroidism develop as a result of abnormally high calcium levels in the blood. Most common signs of this condition include increased thirst and urination. Subsequently, lethargy, weakness, and poor appetite may be noted. Signs such as straining to urinate, passage of blood-tinged urine or the inability to pass urine may be caused by calcium-based stones. Cats can have diarrhea and vomiting as additional signs. Because the relatively small parathyroid tumors are located deeply within the neck in dogs, they usually cannot be palpated. In cats, however, these same tumors can be palpated along the side of the neck.

A complete blood count, chemistry profile and urine testing are completed in the initial stages of the evaluation. Blood tests showing an elevation of the calcium level may be due to a parathyroid tumor, however, there are many other diseases that may elevate the calcium in the blood. To confirm a diagnosis of a functioning parathyroid tumor, a parathyroid hormone level is measured from a blood sample. Ultrasound of the neck frequently can identify these small tumors within the neck. In addition, ultrasound is used to check the bladder and kidneys for stones. The blood work will also be evaluated to check for damage to internal organs that may have occurred from the high blood calcium levels.

The Day of Surgery

In preparation for surgery, your pet should be fasted starting at 10 PM the night before surgery, however water does not need to be with held. To help prevent heartburn after surgery, a single dose of Pepcid AC (10 mg tablet per 20 pounds of body weight) should be administered at 6 AM at home on the day of surgery. Our anesthesia and surgical team will prescribe a pain management program, both during and after surgery, that will keep your companion comfortable. This will include a combination of general anesthesia, injectable analgesics, and oral analgesics.

Treatment

Initial evaluation of the patient will determine if the kidneys, heart or nervous system are affected by the high calcium levels. If this is the case, treatment with medication and intravenous fluids may be needed prior to removal of the parathyroid tumor.

There are two treatment options available to ablate a parathyroid tumor. The least invasive technique is performed under ultrasound guidance and involves the destruction of the gland with an injection of alcohol or heat via a radiofrequency needle. The alcohol injection technique is successful with one injection in about 90% of the cases. The heat treatment is about 50% successful after one treatment. With these techniques, damage to surrounding vital structures such as the nerves that control the voice box have been reported to be temporary, however, permanent complications may be possible.

Surgery is another option in which an incision is made on the under side of the neck. The parathyroid tumor is removed with a relatively simple procedure. Although this does involve a more invasive approach, vital structures can be more carefully preserved versus with the minimally invasive techniques.

Aftercare and Results

After surgery, you can continue to give your pet a prescribed pain reliever to minimize discomfort. It’s also extremely important to limit your dog’s activity for 3 weeks after surgery.

About 50% of dogs that have a parathyroid tumor removed will develop a low calcium level in the blood. Dogs that have a high calcium level (>14 mg/dl) prior to surgery are much more prone to developing this problem. Left untreated, a low calcium level could be fatal in some patients. Warning signs of this problem may include rubbing the face, dilation of the pupils, twitching muscles, loss of appetite, weakness and seizures. If any of these signs are seen at home, please call us as soon as possible and bring your companion in for an evaluation. If blood tests show that the calcium level is low in your pet’s blood, medication will be prescribed for a few weeks until the remaining parathyroid glands start functioning again.

If your companion is recovering well following surgery and no complications develop, the healing process will be monitored by the surgeon with one follow-up exam scheduled two weeks after the surgery.

The overall prognosis for your pet should be favorable following treatment of a parathyroid tumor, as this disease can be cured, yet left untreated it can cause irreversible damage to internal organs.

Frequently Asked Questions After Surgery

When should my dog have the first bowel movement after surgery?

• Many dogs will not have a bowel movement for the first 4 to 5 days after surgery
• Reasons that a dog will not have regular bowel movements after surgery include:
  • The dog has been fasted prior to surgery
  • Dogs do not eat well during the hospital stay
  • They frequently do not eat well when they go home
  • They are fed highly digestible food that produces little stool
  • Pain medication that contain narcotics (such as morphine, fentanyl patches, and tramadol) can be constipating
• If a pet does not have a bowel movement on the 5th day of being home, a stool softener such as metamucil can be fed
  • Dose of metamucil is 1 tsp per 25 Kg mixed in with each meal (canned dog food); feed immediately after mixing, as the metamucil will gel the food and may make it less palatable

My pet had surgery and will not eat.  What can be done?

• Dogs
  • Most pets will not eat their regular dog food after surgery, especially if it is kibble.
  • Offer a cooked diet having a 1:1 ratio of a protein source and carbohydrate source.  The protein source can be any meat (example: chicken breast, turkey breast, lean hamburger) that is low in fat and should be cooked (drain off all fat after the meat has been cooked).   The carbohydrate can be pasta, potato or white rice.
  • Try canned dog food; to enhance the flavor sprinkle a very small amount of garlic powder or chicken or beef broth (Chicken-in-a- Mug^TM or Beef-in-a-Mug^TM products)
  • Try Gerber strained meats for babies such as the chicken, beef, turkey, or veal
  • Try Hill's A/D diet available at most veterinary hospitals
  • Hand feeding: place a small amount of food in the mouth so that your dog gets the flavor
  • Warm the food slightly in a microwave, as the food will be more aromatic; stir the food before feeding and test the temperature on the bottom side of your wrist; it should only be luke warm.
  • Remember that most pets will not eat the first day or two after they get home from surgery
• Cats
  • Offer smelly foods that contain fish such as tuna or smelly cat foods
  • Try Gerber strained meats for babies such as the chicken, beef, turkey or veal
  • Hand feeding:  with your finger place a small amount of food on the roof of your cat's mouth; use a syringe to get soft food into the mouth
  • Warm the food slightly in a microwave as the food will be more aromatic; remember to stir the food before feeding and test the temperature; it should be only luke-warm
  • Some cats will only eat dry food, try kibble if your cat normally has been fed that food
  • Petting and stroking your cat frequently will help to stimulate appetite
  • Remember that most pets will not eat the first day or two after they get home from surgery
  • Appetite stimulants such as cyproheptadine may be helpful
  • If your cat refuses to eat anything for 7 days a stomach tube or nasogastric tube should be placed to provide nutrition so that a serious liver problem (hepatic lipidosis) does not develop

My pet is vomiting.  What can be done?

• The first thing for you to discern is whether your pet is vomiting or regurgitating.  Both will result in fluid or food being brought up.  Vomiting always will have heaving or retching of the abdomen prior to expulsion of the vomitus.  Regurgitation is not associated with heaving and the pet usually just opens the mouth and fluid or food will be expelled.  Usually the regurgited material will be clear or brown colored fluid. 
• Next is to identify the cause of the vomiting or regurgitation.
• Causes and treatment of vomiting after surgery
  • When some pets return home after a stay in the hospital they may drink excessive amounts of water at one time and then vomit; if this appears to be the case, the water should be limited to frequent smaller amounts.
  • Medications such as antibiotics, narcotics or nonsteroidal anti-inflammatory medication commonly cause vomiting after surgery.  In order to see which medication is causing the problem, the administration of each drug should be separated 2 hours apart.  Usually the pet will vomit or appear nauseated (drooling and sick look) within 1 hour of administration of the medication that they are sensitive to.  The antibiotic in some cases may be changed to a different one, or may be discontinued. 
  • Stomach upset from anesthesia is a potential cause of vomiting and will pass within a couple of days. 
  • An uncommon cause of vomiting after surgery is internal organ failure.  Blood testing will confirm this problem. For this reason vomiting should not be ignored if it persists for more than 24 hours.
  • If your pet had surgery of the bowels or stomach, vomiting is always a concern, as it may indicate that infection of the abdominal cavity, called peritonitis, is present.  Do not ignore this sign.
  • Symptomatic treatment of vomiting involves withholding food for 12 to 24 hours, then introducing small amounts of bland food such as rice and lean cooked hamburger, if your pet does not vomit after that then gradually wean him/her back onto the regular diet after 3 days.  In order to decrease the acidity of the stomach, Pepcid AC 0.5 mg/kg can be given by mouth twice daily for 5 days.  Metoclopramide and Cerenia are good anti-vomiting medications for dogs and cats.  You should always consult a veterinary healthcare professional before administering medication.
• Causes and treatment of regurgitation after surgery
  • The most common cause of regurgitation is reflux of acid from the stomach into the esophagus while your pet is under anesthesia.  Acidic fluid from the stomach can cause a chemical burn of the esophagus and result in a bad case of heart burn, called esophagitis.  This results in poor motility of the esophagus, therefore water and food will accumulate in this structure.  In most cases, esphagitis is self-eliminating and will resolve within two or three days. 
  • If the esophagitis is severe the esophagus may develop one or more strictures.  A stricture is a narrowing or stenosis of the esophagus and does not allow passage of food down the esophagus, in regurgitation that lasts longer than one week.  This problem should be brought to the attention of your pet's doctor within the first two weeks so that it can be treated by ballooning the stricture (minimally invasive procedure, as it is done with the aide of an endoscope).  If an esophageal stricture is chronic surgery is needed.
  • Symptomatic treatment of regurgitation caused by esophagitis includes feeding bland food, and administering a coating agent (sucralfate) and an acid blocker (omeprazole or other).  Consult a veterinary health care professional if the regurgitation continues for more than a couple of days.

How do I know that my dog is in pain following surgery?

• Signs of pain include
  • crying
  • biting if you get near the surgical site
  • grimacing (lips are pulled back and the the dog looks anxious)
  • tragic facial expression
  • panting
  • restlessness and unable to sleep; pacing
  • if abdominal surgery was done the pet will not lie down on the incision, or will continually sit up in spite of appearing very tired
  • the worst pain will be for the first 2 to 3 days after surgery

What can I do to control my dog's pain?

• Narcotic medications that control pain: tramadol, butorphanol, Duragesic (fentanyl patch)
• Anti-inflammatories used to control pain: Deramaxx, Rimadyl, Previcox, or Etogesic
• If an orthopedic surgery has been done cold packing the surgical site may be helpful
  • A cold pack may be a pack of frozen peas, crushed ice in a Ziploc bag, or a cold gel pack; place a thin barrier between the skin and the cold pack.  An alternative to a cold pack is to freeze water in a styrofoam cup; after frozen cut the bottom of the styrofoam cup out. Cool the surgical site around the incision by rubbing the exposed ice directly on the skin in a circular pattern.  Cooling the surgical site helps to numb the area.

How do I know that my cat is in pain following surgery?

• Pain is more difficult to assess in cats versus dogs, as signs can be more subtle and they usually do not vocalize when in pain
• Signs of pain in a cat include the following:
  • biting if you get near the surgical site
  • growling or deep cry
  • not wanting to eat
  • hiding and not wanting to be near owner (remember that this could also be caused by the cat just being upset about leaving home and coming back)

What can be done for pain at home for my cat?

• Pain medication such as buprenorphine or a Duragesic (fentanyl) patch
• Tylenol will kill a cat as they lack abundant glutathione enzyme in the liver
• Anti-inflammatories can be used, but the dose is much less than dogs

Is it okay for my pet to lick the incision?

• If a dog licks the incision, the healing process may be delayed.
• Licking can remove stitches and cause the incision to open
• Licking can become a severe habit that is difficult to break
• Licking can cause infection as the mouth has many bacteria
• Dogs will frequently lick the incision when the owner is not watching such as at night time; if the skin looks red or excoriated the most common cause is from licking.
• To stop your pet from licking the following can be tried:
  • Elizabethan collar can be placed on the neck; this will not help stop your pet from scratching at the region
  • Cervical collar (bite not collar) is a less awkward device and can be effective at stopping a pet from licking the surgical site
  • A tee shirt can be used to cover an incision on the chest or front part of the abdomen; gather the waist of the shirt up over the dog's back and wrap an elastic band around this part of the shirt.
  • A bandage or sock can be used to cover an incision on a limb; fasten the top of the sock to the dog's limb with tape.
  • Bitter apple can be applied around the incision; many dogs will continue to lick  after application of this topical
  • Bitter Apple and Liquid Heet^TM (obtain this from a drugstore...it is used for sore muscles) mixed in a 2:1 ratio can be applied around the skin incision
  • Antipsychotic medication in some cases is needed

Board-certification by the American College of Veterinary Surgeons

What does it mean?

• Four years of advanced training in surgery beyond the Doctor of Veterinary Medicine Degree

• Experience in the development of new surgical treatments

• Rigorous examination by the American College of Veterinary Surgeons to ensure competency in advanced surgical techniques

• Assurance that a veterinarian is a surgical specialist