VETgirl July 2025 BEAT e-Magazine

QUARTERLY BEAT / JULY 2025

VARIABILITY OF NEUROLOGIC SIGNS Now, you may wonder “Why do some dogs wag their tail with a blood glucose (BG) of 40 mg/dL (2.2 mmol/L) and others develop seizures?” The degree of neurologic impairment does not directly correlate with a specific blood glucose level. Individual responses will vary due to the following:

• magnitude of BG change • speed of BG change • duration of hypoglycemia

CANINE INSULINOMA:

With gradual or mild BG changes, as seen in episodic hypoglycemia, clinical signs tend be subtle behavioral changes (e.g. confusion, weakness) and often resolve as BG normalized. These dogs may present with normal or low-normal BG, but more commonly, they will be hypoglycemic, which can be confirmed by running a quick BG on your handheld glucometer or in-house analyzer.

Image courtesy of Dr. Heidi Fay

RECOGNITION, DIAGNOSIS, & TREATMENT

This test is performed during periods of hypoglycemia and BEFORE administration of dextrose supplementation. What that means to you?

Canine insulinomas can be difficult to catch and even trickier to treat! In this VETgirl article, Dr. Amy Kaplan-Zattler, cVMA, DACVECC, MRCVS reviews how to recognize, diagnose, and treat canine insulinoma. Read on to spot the clinical signs of acute and chronic hypoglycemia, which diagnostics you need STAT, and how to manage these patients for better short-term and long-term success with this rare, but serious condition!

Amy Kaplan-Zattler, DVM, cVMA, DACVECC, MRCVS CE Program Manager, VETgirl Insulinomas are small - generally < 2.5 cm in diameter - and more often found in the right or left limbs of the pancreas as opposed to the body of the pancreas. These are functional tumors, meaning they overproduce insulin, resulting in hypoglycemia. Due to an impaired negative feedback mechanism, neoplastic pancreatic beta cells fail to suppress insulin release in response to falling glucose levels, thus exacerbating the hypoglycemia. WHAT SIGNALMENT DEVELOPS CANINE INSULINOMA? Generally, it’s the older (> 9 years of age), larger breed dogs that we see with insulinoma including:

REMINDER Anemia falsely elevates BG on handheld glucometers (e.g., Alphatrak)!

REMEMBER Fill that extra red top tube BEFORE giving a dextrose bolus or starting a dextrose CRI!

On the other end of this spectrum, rapid, severe or persistent drops in BG can lead to more serious neurologic issues like tremors or seizures. HOW DO WE DIAGNOSE INSULINOMAS IN DOGS? First, we have to make sure we keep this differential on our radar for any dog presenting with subtle or episodic behavior changes. For emergency doctors, we might more commonly see these patients for seizures - so be sure to keep a glucometer handy when triaging those seizure patients!

Gold standard imaging for insulinomas is a contrast-enhanced CT scan to localize the tumor, check for metastasis, and help assign a TNM stage (TNM stands for tumor, node, and metastasis). Abdominal ultrasound may be more easily accessible and affordable, but is less reliable, identifying only about 1/3 of insulinomas. Ultrasound is still recommended for obtaining FNAs or biopsies of hepatic lesions or abdominal LN enlargements from local spread of insulinomas. Remember to also get a 3-view met check of the chest.

However, small breeds such as West Highland White Terriers, Chihuahuas and Yorkies are also at risk. This author has diagnosed insulinomas (confirmed on histopathology) in a variety of middle-aged (e.g. 6-8 year old) smaller breed dogs (e.g. Chihuahua mix, French Bulldog), so it’s important to keep this differential in your sights even for small dogs of middle to advanced age. CLUES OWNERS MIGHT NOTICE The early signs of insulinomas are vague and nonspecific. A common early complaint from owners is “My dog is acting ‘spacy’ and ‘lost’.” Symptoms can be episodic - usually triggered by exercise or fasting - and between episodes, dogs act totally fine! So, owners may disregard these infrequent, mild episodes and not bring their dogs in for a check-up until the frequency or severity of symptoms gets worse. As insulin production increases – possibly due to tumor growth, metastasis, or chronicity of neuroglycopenia (low glucose levels in the brain) - we start to see more severe symptoms.

ARE INSULINOMAS TREATABLE? Ideally, complete removal with surgery (e.g., enucleation, partial

Next, we investigate whether the patient fulfills Whipple’s triad:

LARGE DOG BREEDS COMMON FOR INSULINOMA

1. Hypoglycemia 2. Exhibits clinical signs related to hypoglycemia

pancreatectomy) is recommended and has been shown to prolong life expectancy by a few years. However, at the time of diagnosis, metastasis is present in about ½ of cases, resulting in a reduction in life expectancy even if the primary tumor is surgically removed. Medical management involves maintaining adequate glucose levels through medications, feeding adjustments, and exercise restriction. Diazoxide and glucocorticoids (i.e. prednisolone) are the primary medications used to reduce the frequency and severity of hypoglycemia. Diazoxide is a benzothiadiazine approved by the FDA for treatment of hyperinsulinism in people. It raises blood glucose levels by binding to the ATP-sensitive potassium (KATP) channels on pancreatic beta cells, causing excessive polarization, preventing their ability to release insulin. Additionally, diazoxide enhances hepatic glucose production while reducing hepatic glucose uptake. Side effects of diazoxide are not commonly seen in dogs, but may include anorexia, vomiting, and ptyalism. Glucocorticoids such as prednisone and

3. Demonstrates resolution of these clinical signs upon restoration of blood glucose levels (usually through IV dextrose or feeding)

CLINICAL SIGNS OF INSULINOMA

• Lethargy • Inappetence • 'ADR' (ain't doin' right) • Weakness • Ataxia/Paresis • Vomiting • Shaking/Tremoring/ Muscle Fasciculations

• Polyphagia • PU/PD • Collapse • Seizures (e.g., focal, generalized, or both)

• Coma • Death

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