Visiting Vet: X-rays are helpful diagnostic tools, but they can be misleading

Like many Islanders, Sito, the Jack Russell Terrier, rents his house out during the summer and lives elsewhere, in this case on a boat in the harbor. An adaptable fellow, he adjusts readily to the Island Shuffle, so when his owners needed to make a brief trip, they left him with other family members here. Returning home a few days later, they found Sito under the weather. “He doesn’t want to eat his dry food,” his mom reported. “He even refused a milk bone…and he cries sometimes like he’s uncomfortable.”

On physical exam, Sito had a mild fever and was noticeably subdued, but besides the elevated temperature, I couldn’t find anything to explain his malaise. Having seen a gazillion cases of Lyme disease, Rocky Mountain Spotted Fever, Anaplasmosis, and the like in my 30 years here, my first thought was to blame Sito’s illness on the ticks. “He acted like this four years ago when he had Lyme,” I said, scanning his history. “Let’s run a quick Lyme test here while you wait.”

Ten minutes later I watched the “Lyme spot” turn a barely visible blue. “Technically this test is positive,” I said hesitantly. “It means his body has produced antibodies to the Lyme organism…, but I’m not completely convinced that’s his current problem.”

We agreed to start doxycycline, which he had responded to well before, but also to run additional tests, including sending a second, more definitive Lyme test out to the big laboratory. His owner asked us to give his first doxycycline dose right away so we popped him a pill and sent them on their way.

Not long after, his mom called. Sito had vomited in the car going home. I had to decide. Was the vomiting a doxycycline reaction? It can affect some animals this way. But Sito had taken it before without difficulty. Or was the vomiting another symptom of whatever was making him ill in the first place? Could he just be car sick? Hard to believe of a dog who lives on a boat.

I needed more information. The Lyme titer would take several days, but the other tests were running right here. Maybe they would clarify the diagnosis. But no. When the tests were completed, the picture was even more confusing.

There were two abnormalities. First, a mildly elevated eosinophil count. Eosinophils are a type of white blood cell that increase with parasitic infections and/or allergies. Second, a mildly elevated amylase — a pancreatic enzyme that may increase with gastrointestinal, pancreatic, or renal disease, all of which could produce vomiting, anorexia, and lethargy.

So did Sito have Lyme? A parasitic infection? An allergy? Pancreatitis? Something else entirely?

“Okay, here’s the plan,” I told his mom on the phone. “We want to determine if the vomiting is from the doxycycline or from something else. Stop the doxy and put him on a bland diet. Bring me a fecal sample to test for intestinal parasites.”

By the next day, Sito was eating baby food, not vomiting, and seemed improved. No evidence of parasites was found on the fecal study. Because he appeared to be getting better all on his own, I suggested we delay restarting the doxycycline until the second Lyme test came back.

Within two days, Sito was dramatically worse. His owners found a lump under his neck and, although he wasn’t vomiting, he was barely eating and acting increasingly uncomfortable. “It’s like he doesn’t want to stretch his neck, ” his dad observed. “Like it hurts to chew or swallow.”

His fever was now a whopping 104.9 and there was a tender lump palpable in the middle of his throat. “You know, he went fishing with the family last week,” his dad remarked. “They said he started acting funny right on the beach. Maybe he ate something there?” Having nearly choked on a fishbone in my salmon the night before, I immediately suggested we take radiographs of his neck.

When the films were done, both his dad and I instantly saw it. An inch-long slender white line on one of the films, right at the level of the swelling in his neck. Fish bone! That would explain everything! “You’re going to need a specialist with a fiberoptic endoscope to get that bone out,” I sighed.

As we started referral procedures, I looked again at the film. Something was bugging me. That thin white line sure looked like a fish bone. It was exactly where the swelling was. But I couldn’t see it on the second film (a different view taken from a different angle to help us visualize things three-dimensionally.) “Before you rush off to a specialist, let’s make absolutely sure this isn’t an artifact.” In other words, was the line a mark on the film not actually from something in the patient but from something on the film or the case that holds the film, called a cassette? I asked my assistant to retake the X-rays, this time orienting the cassette in the opposite direction.

Soon I was examining the new films. No white line in the neck. Instead there was a similar line down in the chest. Turning the new film upside down and placing it on top of the original one, the lines matched up exactly. It wasn’t a fish bone. It was a fishbone-shaped scratch from the X-ray cassette.

Despite this (pardon the pun) red herring, it was still likely that a fishbone, or similar item, swallowed at the beach that day was the source of Sito’s troubles. The swelling in his throat was a “retropharyngeal abscess,” i.e. an infection behind the throat. Something like a fish bone had probably poked a tiny hole in his esophagus on its way down. The bone itself then passed through his system uneventfully but the hole allowed bacteria to leak into the surrounding tissue. This led to an infection that ultimately came to a head creating the lump.

Two weeks of antibiotics had Sito shipshape again. The Lyme titer came back negative. No Lyme. No fish bone. No problem.