Issue Description When a dog has insulinoma, a tumor is present
in the pancreas. This health condition causes insulin production to
increase, which can cause hypoglycemia in dogs. Although insulinoma
can affect breeds of all ages, older dogs are most likely to be
diagnosed. Insulinoma is a disease of middle-aged to older dogs, with
the mean age of affected dogs being 8.9 years (range: 3 to 15 years).
Causes Insulinomas most commonly affect middle-aged to
older dogs with no sex predilection. Unlike in humans, the majority of
insulinomas in dogs are malignant, with up to 50% or more of affected
dogs having metastasis at the time of diagnosis. Metastasis to the
regional lymph nodes, liver, and mesentery is most common.
Symptoms Hunger, behavior changes, muscle
fasciculations, weakness, ataxia, or seizures can be seen and are
often exacerbated by exercise and/or fasting. Eating can also result
in clinical signs because of excessive insulin release.
The typical presentation for a dog with
insulinoma is a large-breed dog with a history of weakness, ataxia, or
seizures, signs that may be exacerbated with exercise or fasting.
Physical examination findings are often within normal limits.
The most consistent laboratory abnormality is a fasting
Presumptive diagnosis is made with an abnormal insulin-glucose
pair, with normal to elevated insulin levels in the face of low
Abdominal ultrasonography may be useful to detect nodules in the
pancreas as well as metastatic disease in the abdomen. Intraoperative
ultrasonography may be useful if nodules cannot be detected by visual
Additional diagnostic tests may help support the diagnosis of
insulinoma but typically are not as sensitive as the insulin-glucose
pair and abdominal ultrasonography.
Clinical Staging System
Stage I: Insulinoma confined to the
Stage II: Insulinoma in the pancreas and regional lymph nodes
Stage III: Insulinoma with distant metastase
Treatment Surgery is the initial treatment of choice for
insulinoma. Blood glucose must be normalized before, during, and after
surgery. This is important because palpation of the nodules during
surgery can result in insulin release. Palpation allows localization
of the nodules in the majority of cases. Insulinomas tend to occur in
the right and left lobes of the pancreas with equal frequency.
Nondiscriminatory removal of pancreatic tissue is not recommended.
Removal of the nodules can be performed by nodulectomy or partial or
total pancreatectomy. Exploration with biopsy of suspicious areas in
the abdomen should be performed. Metastasis has been reported in 36%
to 51% of dogs at the time of initial surgery. Metastasis is most
common to the liver and lymph nodes but has also been reported in the
intestines, mesentery, spleen, and kidneys. Metastatic disease should
be debulked as much as possible, as this may provide significant
improvement in clinical signs.
Dogs with tumors confined to the pancreas(stage I) or to the pancreas
and regional nodes (stage II) have a median survival of approximately
1.5 years, while dogs that have metastasis beyond the nodes(stage III)
have a median survival of less than 6 months.
Pronosis Remission and survival in dogs with insulinoma
following surgery depend on the clinical stage at the time of
diagnosis. The median survival time of all affected dogs is
approximately 12 months.
Dogs with tumors confined to the pancreas
(stage I) have a longer remission time (defined as the period of
euglycemia) than dogs whose tumors have metastasized. Dogs with stage
I disease have a median remission time of approximately 14 months
versus approximately 1 month for stage II or III dogs.
Dogs with tumors confined to the pancreas (stage I) or to the
pancreas and regional nodes (stage II) have a longer survival time
than dogs with tumors that are metastatic beyond the nodes (stage
III). Dogs with stage I or II disease have a median survival of
approximately 1.5 years, while dogs with stage III disease have a
median survival of 6 months or less.
Partial pancreatectomy yields longer survival times than
Total pancreatectomy is associated with
high morbidity and mortality.
Tumors in the body of the pancreas are more difficult to remove
than tumors in the limbs of the pancreas.
Persistent postoperative hypoglycemia indicates that a residual
tumor (either primary or metastatic) exists.