Insulinoma in a senior pit bull: Surgery perspective

Dr. Christian LatimerSurgical goals for insulinoma consist of confirming the diagnosis, staging the disease and removing as much gross disease as possible.1

Hypoglycemia must be controlled before surgery. Glucocorticoid therapy and intravenous fluids containing dextrose are often used for blood glucose normalization. In cases of severely intractable hyperinsulinemia, a glucagon CRI can also be used. The patient should not be fasted preoperatively and should ideally be fed a small meal two to three hours before surgery. Dextrose can stimulate insulin secretion, so blood glucose must be carefully monitored preoperatively and intraoperatively.

In surgery, the entire pancreas is palpated and visually inspected. Insulinomas are typically single, firm round nodules on the pancreatic surface and are more likely to be found on the right or left lobes of the pancreas compared to the pancreatic body.2 A partial pancreatectomy is performed via the blunt dissection or suture fracture techniques in order to remove the primary tumor.1 One study found that using a bipolar vessel-sealing device for partial pancreatectomy significantly decreased operative and hospitalization times for dogs with insulinomas compared with the suture fracture technique.3 Samples of the liver and regional lymph nodes should be taken and submitted for histopathology for staging purposes.

If unable to localize the pancreatic tumor, intraoperative intravenous infusion of methylene blue has been reported.1 Methylene blue stains normal pancreatic tissue differently than hyperfunctioning pancreatic tissue. This infusion is rarely performed because it can take up to 30 minutes for color changes to become obvious during surgery. Additionally, intravenous methylene blue infusion can lead to serious adverse effects for the patient, including Heinz body hemolytic anemia and acute renal failure. Intraoperative ultrasonography is another reported method for localizing the tumor in surgery.4

Potential complications of partial pancreatectomy include pancreatitis, persistent hypoglycemia and diabetes mellitus.5,6 Pancreatitis often results from manipulation of the organ during surgery, and persistent hypoglycemia postoperatively indicates incomplete removal of the tumor or that there are functional metastatic lesions remaining. Diabetes mellitus is often transient until the remaining healthy pancreatic beta cells regain their function.6

Surgery is unlikely to be curative in cases of canine insulinoma; however, it offers the best chance for prolonged survival as compared with medical management alone.7,8

References

1. Tobias K, Johnston S. Pancreas. In: Veterinary surgery: small animal. 1st ed. St. Louis: Elsevier, 2011.

2. Goutal CM, Brugmann BL, Ryan KA. Insulinoma in dogs: a review. J Am Anim Hosp Assoc 2012;48:151-163.

3. Wouters EG, Buishand FO, Kik M, et al. Use of a bipolar vessel-sealing device in resection of canine insulinoma. J Small Anim Pract 2011;52:139-145.

4. Goswami J, Somkuwar P, Naik Y. Insulinoma and anaesthetic implications. Indian J Anaesth 2012;56:117-122.

5. Trifonidou MA, Kirpensteijn J, Robben JH. A retrospective evaluation of 51 dogs with insulinoma. Vet Q 1998;20(Suppl 1):S114-S115.

6. Feldman EC, Nelson RW. Beta cell neoplasia: insulinoma. Canine and feline endocrinology and reproduction. 3rd ed. Philadelphia: WB Saunders Company, 2003.

7. Tobin RL, Nelson RW, Lucroy MD, et al. Outcome of surgical versus medical treatment of dogs with beta call neoplasia: 39 cases (1990-1997). J Am Vet Med Assoc 1999;215:226-230.

8. Polton GA, White RN, Brearley MJ, et al. Improved survival in a retrospective cohort of 28 dogs with insulinoma. J Small Anim Pract 2007;48:151-156.

Let's go back to the hall to check out another perspective.