Insulinoma

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

Animal Surgical Center of Michigan

5045 Miller Road

Flint, MI 48507

www.animalsurgicalcenter.com

Phone: 810-671-0088

Key Points

Low blood sugar and high insulin level is usually associated with an insulinoma

Surgical removal of the tumor frequently will extend the life of the patient but the prognosis is guarded as the tumor commonly metastasizes

Medical therapy is commonly needed to control signs of low blood sugar


Anatomy

The pancreas in dogs and cats have a left lobe, right lobe and body. The body contains ducts (channels) that connect to the small intestine. The pancreas has two major functional components: the exocrine pancreas and the endocrine pancreas. The exocrine pancreas is glandular tissue that secretes digestive enzymes into the intestine; these enzymes digest food. The endocrine pancreas is located in nests of tissue called the ilets of Langerhan. These produce a number of chemical messengers including insulin that are secreted directly into the blood stream. Insulin secretion is regulated by the blood sugar level; thus, when the sugar level is high insulin is secreted, but when the sugar level is low, insulin secretion is stopped.

Insulinoma

This type of tumor originates from the beta cells of the ilets of Langerhan and secrete uncontrolled amounts of insulin. These tumors are always malignant and invarialby spread to regional lymph nodes, liver and sometimes to the lungs

 

Signs

Predisposed breeds include Irish Setters, Golden Retriever, German Shepernds, Boxers and Standard Poodles; average age of affected dogs is about 9 to 10 years of age. Clinical signs are primarily due to low blood sugar and these include seizures, collapse, weakness, hindlimb weakness, depression, wobbliness when walking, muscle twitching, abnormal behavior, increased appetite, intolerance to exercise, shaking, weight gain, head tilt, head jerking, facial twitching, diarrhea, disorientation, episodes of blindness, hyperactivity and in some cases no clinical signs.

 

Diagnosis

A low blood sugar and a high insulin level in the blood are classic findings in a patient with insulinoma. Because the blood sugar level will fluctuate in patients with an insulinoma, it is important to measure the blood insulin levels when the blood sugar level is less than 60 mg/dl. Abdominal ultrasound may or may not show the mass within the pancreas, as this is dependant on the size of the tumor. In addition, lymph nodes, liver and other internal organs are imaged for evidence of gross metastatic disease. Chest x-rays rarely demonstrate spread of tumor to the lungs. Nuclear scintigraphy with radiolabled octreotide is sensitive to identify very small tumors.

 

Day of surgery

The anesthesia and surgical team will prescribe a pain management program, both during and after surgery that will keep your companion comfortable. This may include a combination of general anesthesia, injectable analgesics, and oral analgesics.

 

Surgery

Control of low blood sugar prior to surgery includes frequent meals, with a diet containing high protein and low sugar content. Prednisone, a corticosteroid, can be given to increase the blood sugar level. Side effects from this medication may include increased thrist, increased urination, increased appetite, restlessness behavioral changes, and weight gain. Diazoxide can also be prescribed to increase the blood sugar. Side effects include anorexia, vomiting, and diarrhea. These side effects can be minimized by reducing the dose and giving the medication with food. None of these medical therapies have any anti-cancer effect.

If a pet is found to be seizuring or comatosed at home, corn syrup can be put under the tongue to help increase the blood sugar level. You should seek immediate medical attention for your pet. At a veterinary hospital, a continual infusion of glucogon through an intravenous line is administered to for emergent control of low blood sugar. Intravenous dextrose (sugar) may also be required if the patient has severe neurological signs.

 

An incision is made into the abdomen to allow the surgeon to examine of the internal organs. A section of the pancreas with its associated tumor is removed. If the mass is located in the body of the pancreas, close to the important pancreatic ducts, the mass is gently dissected from the pancreatic tissue. These tumors may be small and difficult to see. A dye called new methylene blue can be administered to the patient to assist in identification of the mass.

Complications following surgery may include inflamation of the pancreas, continued low blood sugar or diabetes mellitus.

 

Aftercare

An analgesic medication may be required once the pet goes home. If the blood sugar returns to normal after surgery, a regular diet can be be fed. If the blood sugar still mildly decreased after surgery, a high protein diet with low carbohydrate content should be fed. In some cases, prednisone may still be needed. If the patient has too high of blood sugar, insulin may be needed for a short period of time.

 

Prognosis

Surgery does not cure patients with insulinoma, rather will help with clinical signs of low blood sugar for a period of time. Survival times with stage 1 tumors (isolated only to the pancreas) is 20 months with recurrence of hypoglycemia at 17 months. Survival time for stage 2 tumors (in the pancreas and the regional lymph nodes) is 10 months with recurrence of hypoglycemia at 2 months postop. Survival time for stage 3 tumors (in pancras, regional lymph nodes, and liver) is 6 months with recurrence of hypoglycemia at 1 to 2 months postop.

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

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

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