Lulu, a sweet 9-year-old setter, came into my office recently. “I think there might be something wrong with her hind legs,” her owner said. A week previously they had been out for a walk when Lulu bolted off into the woods. When she returned a little while later, she seemed off in her hind end. Her owner couldn’t pin it down exactly. “Was she limping on any particular leg?” I asked. Nope. She just was kind of wonky in her back end. The incoordination resolved with rest. Then, five days later, a second episode. Same scenario. Everything seemed fine until she sprinted away on a high-powered run. Then she was wobbly. Then it resolved.
I examined Lulu carefully. Temperature, normal. No lameness. Lyme test, negative. I evaluated her hind legs, toe by toe, joint by joint. No pain, no swelling, no crepitus (crepitus is a fancy word for the crunchy sensation sometimes noted with conditions like osteoarthritis and broken bones). All Lulu’s joints had what we call “normal range of motion.” I moved my attention to her back. Back pain can cause weird behavior in dogs. Little dogs with back issues may hide, shake, and let out sudden screams if anyone touches them. It is unnerving for owners, but us old-timers can almost diagnose these cases based on the description written in the appointment book. (Okay, I am dating myself. I still use a paper appointment book.) Larger dogs are often more stoic. Some dogs will tense their abdominal muscles when veterinarians palpate their backs, to protect the painful areas. Others will show discomfort on their faces — a change in expression, a baleful glance back at the doctor, or even a snap.
Lulu did tense a little as I palpated her spine, but it was subtle. At forty-five pounds, Lulu was neither a timid toy poodle nor a big goofy Labrador. I didn’t know how seriously to take this nuanced reaction. “Maybe the vigorous running caused back muscle spasms?” I speculated. Many other things can cause incoordination and/or hind- end lameness in an active dog of Lulu’s size, but I couldn’t think of any that would resolve so quickly after each episode. I advised restricting exercise and dispensed anti-inflammatory pain medication to have on hand should the episodes recur. “And maybe we should run basic blood work,” I added, belatedly. “Just to rule out any underlying metabolic illness.”
Lulu’s owner hesitated. The setter seemed completely fine now. “What do you think I should do?” he asked.
When owners ask me that question, I often feel conflicted. The younger generation of veterinarians, raised in the litigious social media world, seem to prefer the approach of always getting a “complete database.” In other words, lots of tests. My generation was taught “Don’t run a test unless you know exactly what you are looking for.” I suspect the best medicine lies somewhere between these two philosophies. “If you ask me what I think you should do, I have to advise doing the tests,” I replied. So we drew blood, and sent Lulu and her ownerthem on their way. An hour later, I had results. There was one glaring abnormality. Lulu’s blood glucose was low. Scary low.
Hypoglycemia. Commonly known as low blood sugar. Signs depend on exactly how low, but can include weakness, staggering, vomiting, blindness, altered mental state, seizures, coma, and death. If this result was real, hypoglycemia could explain Lulu’s episodes. The first step is to rule out lab error. If whole blood is left sitting too long, the cells can continue to consume glucose, resulting in an artificially low blood sugar reading. Lulu’s lab work had been done very promptly, so this was unlikely, but we could draw a new sample and repeat the test to confirm results. If it was real, what could be the cause?
The next thing to rule out was exposure to medications or foods that affect blood sugar. Diabetes drugs like insulin, metformin, glipizide. No, Lulu had not beenwas not exposed to any of these. Then there’s xylitol — a common artificial sweetener used in everything from sugar-free gum to some peanut butters. It’s fine for people, but dogs respond differently. In dogs, xylitol ingestion can cause extreme, persistent, even fatal, hypoglycemia. But this didn’t fit Lulu’s history. Did we really think Lulu found and ate a pack of sugar-free candy in the woods? Twice? And xylitol toxicity wouldn’t have improved so quickly, especially without treatment.
Now, the big worry. Could Lulu have insulinoma — a pancreatic tumor that secretes excessive insulin, causing hypoglycemic episodes? Although insulinomas are uncommon, Lulu fit the classic picture for this cancer — a middle-aged, largish dog with sporadic clinical signs consistent with low blood sugar. Definitive diagnosis is difficult and expensive, including fancy blood tests and advanced imaging. These tumors are often quite small and do not show up on radiographs or ultrasound, requiring CT scans to identify them. Treatment is surgical removal of the tumor, but in more than half the cases, the cancer has already spread by the time of diagnosis. Prognosis is guarded to poor.
My hope is that Lulu’s episodes have a less troubling explanation. “Hunting dog hypoglycemia” is a syndrome diagnosed by ruling out everything else. Most cases occur in thin dogs who are relatively out of shape and then exercise vigorously. Lean dogs often have less energy reserves (called glycogen) stored in their livers. Intense activity quickly depletes these stores, and blood glucose plummets. Signs may include lethargy, muscle weakness, incoordination, trembling, and seizures. This fits with Lulu’s history of episodes occurring with unaccustomed exertion. Treatment is simple: Feed multiple small meals daily. Do moderate regular exercise to improve conditioning. Carb-load before athletic activities with small but nutrient-rich meals. Avoid overwork. Carry a small bottle of something sweet like corn syrup or honey to give Lulu should she exhibit signs. Time will tell if there is a bigger underlying illness, or if all that is needed is a fitness program and an occasional emergency sweet for a sweet dog.
