Adrenal Gland Tumors

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

Key Points

Adrenal gland tumors can secrete hormones that dramatically affect the well-being of the pet

Surgery is frequently the best option

Patients surviving the perioperative period have a good chance for long-term survival, providing that no evidence of spread is found


Adrenal gland anatomy

The name "adrenal" is translated "near kidney". The adrenal glands, therefore are glands that are located near the kidneys.

Adrenal glands are located adjacent to the left and right kidneys. The right adrenal gland is nestled between vena cava (largest vein that runs through the abdomen) and the muscles attached to the under side of the backbone. The draining vein of each adrenal gland joins directly onto the vena cava. A small artery branching directly off the abdominal aorta (great artery that runs through the abdomen) enters the top (dorsal) side of each adrenal gland.

The adrenal gland consists of an outer shell of tissue called the cortex and an inner core of glandular tissue called the medulla. The cortex has three layers called the zona reticularis, zona fasciculata, and zona glomerulosa and produce respectively, androgens, glucocorticoids, and mineralicorticoids. The cells in each layer have specific enzymes that will modify the steroid nucleus (originally cholesterol), thus producing their specific hormones. The adrenal gland is directly wired into the nervous system via a network of nerves.

 

Adrenal gland function

The adrenal glands are essential for life. They are needed for basic body regulation and to respond to stressful situations. They have five primary functions:

  1. control blood pressure
  2. water and salt balance
  3. carbohydrate balance
  4. immune system control
  5. sex hormones (after menopause in humans or post neutering)

Androgens are precursors to sex hormones such as estrogen and testosterone. In neutered animals, these hormones are only produced by the adrenals.

Glucocorticoids are produced from the cortex of the adrenal gland and the most important form of this hormone is cortisone. This hormone is essential for the regulation of glucose (sugar) metabolism, increases the blood vessels to respond better to adrenalin (blood pressure control), suppresses inflammation and immune responses, and controls function of the nervous system. The release of this hormone is controlled by another hormone called ACTH

Mineralicorticoids are also produced from the cortex and the most important hormone is called aldosterone. This hormone controls reabsorption of sodium and water by the kidney. Low blood pressure will increase the release of aldosterone from the adrenal gland (via the renin/angiotensin in the kidney).

 

Adrenal tumors

Adrenal gland tumors are uncommon in dogs and represent about 0.17 to 0.76% of all tumors in dogs. Tumors originating from the cortex are commonly adenomas or adenocarcinomas. These may produce sex hormones, cortisone, or aldosterone, which causes severe havoc to the body. Tumors originating from the medulla, called pheochromocytoma frequently secrete adrenalin, which causes episodic or continuous high blood pressure.

Malignant tumors can spread to other parts of the body with the liver, pancreas, and kidneys being most common. Metastasis to the lungs is relatively uncommon at the time of original diagnosis.

Adrenal tumors, especially pheochromocytomas, have a tendency to grow from the vein of the adrenal gland to the vena cava. This is called a tumor thrombus.

 

Signs

A nonfunctional (do not secrete hormones) tumor of the adrenal gland frequently does not cause the patient to have any clinical signs until it is sizeable or has spread to another organ. Pheochromocytomas commonly have vague clinical signs such as panting, rapid heart rate, seizures and weakness. More dramatic signs may include bleeding into the abdomen and collapse.

Warning signs of an adrenal tumor that produces excessive cortisone includes excessive thirst, muscle wasting, abdominal enlargement, hair loss, and paper-thin skin especially on the abdomen.

 

Diagnosis

The diagnosis of cortisone secreting adrenal tumors is based on screening tests such as the urine cortisol creatinine ratio, low dose dexamethasone suppression test and the ACTH stimulation test. Abdominal ultrasound or CT scan can confirm the presence of the tumor in the adrenal gland. Pheochomocytomas frequently have nonspecific signs such as agitation and panting due to excessive production of adrenalin. Diagnosis of this type of tumor is based on finding high blood pressure and a mass in the adrenal gland. Abdominal ultrasound or CT scan can confirm the presence of an adrenal mass.

Other tests done prior to surgery may include a complete blood count, blood chemistry profile, and urinalysis to check internal organ health. Chest x-rays and abdominal ultrasound are used to identify visible spread of the cancer; however, microscopic spread of cancer to other organs cannot be detected with x-rays and ultrasound. Ultimately a definitive diagnosis of the type of adrenal tumor is based on microscopic analysis of the tumor (histopathology).

 

Preparation for surgery

The pet should be fasted prior to surgery, as instructed by the surgical team. Water is usually permitted up to the time of admission to the hospital. The surgical team should be informed of any medications that your pet is currently receiving. Just prior to surgery, your pet will receive a sedative, have an intravenous catheter placed for the administration of intravenous fluids and intravenous medications, be induced under general anesthesia with medication(s), and have a breathing tube (endotracheal tube) placed to allow delivery of oxygen and gaseous anesthesia. If a ventral bulla osteotomy is to be performed, the surgical site will be clipped and cleansed with an anti-septic solution in preparation for surgery. While under general anesthesia, the pet's breathing will be assisted with a ventilator and vital parameters such as heart rate, respiratory rate, core body temperature, blood pressure, oxygenation of the blood (pulse oximetry), exhaled carbon dioxide (capnography), and heart rhythm (EKG) will be monitored to ensure the pet's well being. Pain will be controlled both during and after surgery with analgesics (pain-controlling medication). Please note that each surgical and anesthesia team may elect to chose a different, but effective analgesia protocol. If a pheochromocytoma has been diagnosed or suspected, a medication called phenoxybenzamine may prescribed for 2 weeks prior to surgery. Some veterinarians will also attempt to reduce the cortisone levels with a mediation called Trilostane to help reduce the risk of blood clots during the perioperative period.

 

Surgery

An incision is typically made along the midline of the abdomen to expose the offending adrenal tumor. In some cases, the gland may be exposed with an incision made on the pet's side. The blood supply to the tumor is tied off, the mass is dissected from its attachments and removed from the body; this is called an adrenalectomy. If the tumor has an extension (caval thrombus) into the great vessel called the vena cava, it is removed by opening this great vessel. This type of surgery is not to be taken lightly and should be done by experienced surgeons for optimal results. Complications may include anesthetic death, blood clots to the lungs, pneumonia, kidney failure, inflammation of the pancreas, wound infection and poor healing.

 

Results

In a study of 52 dogs that had surgical removal of adrenal tumors by Massari et al, factors found to negatively affect prognosis included size of the tumor being greater than 5 cm, metastasis (obviously), vein thrombosis and combining another abdominal procedure with adrenalectomy. The median survival time was 953 days with 65% of patients surviving greater than 1 year after surgery. The intraoperative mortality was 2% and the perioperative mortality rate was 13.5%. Dogs with large adrenal masses (>5 cm) had a median survival time of 156 days and were more malignant in behavior. Although this study showed a poorer outcome with caval tumor thrombosis, two other studies did not show this to be a negative prognostic factor (Kyles and Schwartz). Caval tumor thrombus is also associated more commonly with pheochromocytomas, right-sided adrenal gland tumors and large size seems to increase the incidence of thrombosis (according to Massari).

In a study of 40 dogs by Kyles, the short-term mortality rate was evaluated in regards to the presence of caval tumor thrombus. Reportedly, tumor thrombus was seen in 25% of all dogs. Eleven percent of adenocarcinomas had tumor thrombus and 55% of pheochromocytomas had tumor thrombus. As mentioned there was no difference in the perioperative death rate regardless of presence or absence of tumor thrombus. The perioperative death rate was 21% for adenocarcinomas and 18% for pheochromocytomas. Previously, pheochromocytomas patients have a high perioperative mortality rate, but the addition of protocols that include administration of high doses of phenoxybenzamine (as high as 2.5 mg/kg twice daily) have reduced the death rate.

Swartz summarized the prognostic factors and survival of 41 patients undergoing adrenalectomy for adrenal tumors and she reported a 22% perioperative mortality rate. Overall, the median survival time was 690 days. Factors influencing shorter survival times included perioperative weakness, lethargy, decreased platelet count, increased BUN, increased clotting times (PTT), increased AST (liver enzyme), low potassium level, profuse bleeding during surgery, and the need to have a kidney removed at the time of surgery.

The bottom line:

  1. If the patient leaves the hospital, there is a very good chance for long-term survival.
  2. Of those patients that die while in the hospital do not die during surgery, rather from complications after surgery (like throwing a blood clot to the lungs).
  3. Adding medication a few weeks prior to surgery to stabilize blood pressure in patients that have pheochromocytomas will reduce the mortality rate from about 48% to 13% (Herrera).
  4. Adding medication about 1 month prior to surgery to lower cortisol production (trilostane) may help reduce the risk of blood clots in the lungs in patients that have functional adenomas or adenocarcinomas (no scientific proof of this at the writing of this article - but that is what UC Davis folks are doing and they are are seeing a benefit).

 

References

  1. Assari F, Nicoli S, Romanelli G, et al. Adrenalectomy in dogs with adrenal gland tumors: 52 cases (2002-2008). J Am Vet Med Assoc 2011; 239:216-221.
  2. Kyles AE, Feldman EC, De Cock HE, et al. Surgical management of adrenal gland tumors with and without associated tumor thrombi in dogs: 40 cases (1994–2001). J Am Vet Med Assoc 2003;223:654–662.
  3. Schwartz P, Kovak JR, Koprowsky A, et al. Evaluation of prognostic factors in the surgical treatment of adrenal gland tumors in dogs: 41 cases (1999–2005). J Am Vet Med Assoc 2008;232:77–84.
  4. Herrera AM, Mehl PH, Kass, et al. Predictive factors and the effect of phenoxybenzamine on outcome in dogs undergoing adrenalectomy for pheochromocytoma. J Vet Intern Med 2008;22:1333–1339.

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- MugTM or Beef-in-a-MugTM 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 HeetTM (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

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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

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