Incidental Findings: Veterinary X-Ray Surprises

Incidental findings can be alarming or amusing, deadly serious or completely innocent; they are always fascinating.

An incidental finding, according to AppliedRadiology: The Journal of Practical Medical Imaging and Management,

…also referred to as an incidentaloma, is a mass or lesion detected on diagnostic imaging studies performed for an unrelated reason.

Finding an unexpected health issue in a patient undergoing screening for an entirely unrelated concern can throw a wrench in treatment, but there may be tangible benefits to the patient as well. When a friend of mine had testing to work up some lesions on his liver, the doctors found he had a severe infection in his lungs. The doctors couldn’t believe he was working his construction job much less walking around… he thought he just had a cold! After starting treatments for his respiratory condition, he feels amazing. And happily, he learned that his liver lesions are nothing to worry about, too.

In veterinary medicine, most of our incidental findings are surprises on x-rays. Here are several of our favorite incidental finding cases!

Purple arrow points to mineralization in the kidneys. Green arrow points to gall bladder stones.

1. A geriatric dog, Lucy, comes in for screening chest x-rays after a new heart murmur is found on her annual physical exam. For an old dog, she’s actually pretty healthy and she’s not even symptomatic for heart disease. Lucy is a tiny dog, so the technician takes a “dog-o-gram” or set of a full body x-rays rather than limiting the field of view to her chest. “Cat-o-grams” and “dog-o-grams” are technically breaking some radiographic rules because we veterinarians are taught to focus an x-ray on the part of the body that has the problem. However, general practice veterinarians take full-body x-rays all the time because we like to give pet owners “the most bang for their buck” by fitting as much of the pet as possible on the film. Certainly, our tendency to take “pet-o-grams” is one reason why we discover incidental findings. In Lucy’s case, in addition to radiographic evidence of heart disease, we found out she also has mineralization in both of her kidneys and gall bladder stones. These findings were true surprises because she was not acting sick in any way and her bloodwork was unremarkable.

Two blue arrows identify two microchips.

2. After surgery to remove bladder stones, we take an x-ray on a little rescue dog named Berry. We are shocked to find that she has TWO microchips! Even weirder, only one of the microchip numbers is readable no matter how we scan her. In the end, this is a good thing because if she ever gets lost her microchip identification will work without any confusion of having two microchip numbers.

In cats, a common incidental finding is osteoarthritis. Cats are classic for hiding osteoarthritis from their owners and veterinarians. Osteoarthritis changes in cats can be very subtle, especially early on. A cat with arthritis in his lower back, for example, might show hesitancy to jump onto high surfaces or stops jumping onto the countertops which is seen as a victory by the pet owner! On physical exam, cats often lay in a “loaf” position with their hind legs tucked under their abdomen and front legs curled up under their chest. It is very difficult to perform range of motion exercises on a cat, most of whom think we’ve lost our minds for touching them without permission!

Red arrow points to right hip joint with severe irregularities in the head and neck of the femur.

3. Bucky is a perfect example of an older kitty hiding arthritis. He comes in for a screening “cat-o-gram” because he is losing weight even though his hyperthyroid condition is well controlled on medication. We take x-rays to see if maybe something bad like cancer is lurking in his chest or abdomen. What we find shocks us but doesn’t explain his weight loss. Bucky’s right hip joint has dramatic changes in the head of the femur. It looks like it should be painful, but Bucky does not have lameness or pain on handling or palpation of the area. We are left with more questions than answers right now…Did he have a previous injury resulting in abnormal bone remodeling? Does he have severe arthritis from a congenital orthopedic problem? Could this be bone cancer and he’s just amazingly stoic and unwilling to reveal pain? Bucky’s x-rays will be rechecked over time, and his owner is monitoring him at home.

A very common incidental finding on dog and cat x-rays is BB’s or pellets lodged under the skin. Sadly, stray animals may have had “pot shots” taken at them but even beloved hunting dogs sometimes get peppered with shot out working in the field. These firearm injuries are almost never serious, do not cause long term problems, and are a complete surprise to the owner and veterinary staff.

Yellow arrows point to pellet and the healed right femur.

4. Our last case involves a middle-aged kitty named Molly who presented for urination problems. Upon taking a screening x-ray for bladder stones, we are startled to see a bright white, round object “in” Molly’s bladder. Bladder stones don’t look this perfectly round or bright! The round object is whiter than bone; it’s metal opacity and probably a pellet (BBs are smaller). Therefore, a second x-ray — what is called an orthogonal view, one perpendicular to the side view– is taken to hone in on the exact location of the pellet. Not unexpectedly the pellet is not actually in her bladder but is lodged in the thigh muscles.

Yellow arrow points to pellet. Note different appearance of right femur compared to Left.

What really surprises us is that Molly’s right femur was fractured in the distant past (probably tragically by the pellet) and healed in an extraordinary way! The ends of the bone are really far apart, but her body bridged the gap with a large callus. Molly was adopted from the shelter and has never exhibited lameness or pain! When I showed the x-ray to a human orthopedic surgeon, he observed she must have been a kitten when it happened for her body to heal such a bad fracture all by itself. Incidentally (ba dum tss), Molly does not have bladder stones…

There are many sayings that wise veterinary school teachers pass on to their students. One is “when you hear hoofbeats, think horses not zebras” which is a really cool way of saying common diseases are going to be commonly diagnosed and rare diseases are going to be rarely diagnosed. Another pearl of wisdom is “if you don’t look you won’t see it” which reminds us to run that routine test even if we don’t anticipate finding any abnormalities — it might just save your patient’s life because not all problems are detectable from an examination and thorough history. Certainly incidental findings are a fascinating aspect of practicing medicine that proves the point of only seeing something when you take a close look. Incidental findings also satisfy the veterinarian’s innate curiosity.

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