I had an interesting case come through this past week. It was a sporting dog with no specific issues. He was just in for routine care.
The dog in question is white and liver in colouring, and the thing I noticed first was that he had a faintly pinkish area over his lumber spine. I checked the skin and saw nothing unusual. Next, I palpated along the epaxial muscles. There was increased tone adjacent to L4, more so on the right side than the left. Furthermore, L4 was painful to push on the spinous process from the right side as well. Dorsoventral pressure to the articular pillar of the L4/L5 facet joint on the right was painful as well. My synopsis was that the dog had a bit of a neuritis at that location
Upon questioning the owner about this spot, she said that she had noted the discolouration, and she thought the dog had rolled in something. She had never seen him lick or chew at that area either, but it was the only thing that made sense in the scenario.
I mobilized the joint to open up the right L4/L5 facet joint, did tail pull traction, and lasered the region. The home program consists of tail pull traction, and we’ll see how it goes!
The case made me think about porphyrin staining in general and how it should be a clue to help with your physical assessment and clinical reasoning. So, let’s talk a little bit about porphyrin staining. What is porphyrin staining in 30 seconds or less?
Saliva and tears contain substances called porphyrins, which stain light fur pink, red or brown. The staining of hair in a location other than adjacent to the eyes or mouth can be the result of a dog licking or chewing at a particular area.
It should also be noted that while staining of hair might not be perceivable in a dark haired animal, a practitioner should also take note of an area where the hair is slicked down or a different texture than elsewhere. These can be clues than an animal is licking or chewing.
Why might a dog lick or chew at an area?
Inflammation - Seasonal and non-seasonal environmental or food allergies can cause an animal to lick or chew on their feet, limbs, or other body parts. Inflammation can also be caused by foreign bodies embedded in the skin, flea bites, etc.
Infection - Bacterial, fungal, or even parasitic infection of the skin can motivate an animal to attempt to resolve the issue themselves by licking or chewing.
Altered sensation – Pain at a joint could cause a dog to lick the affected joint, a pinched nerve can cause numbness, tingling, or pain at the sight of the pinched nerve or distal to that site along the path of the neural dermatome.
Anxiety – Some people report that their dog will lick of chew an appendage when they are stressed about a situation.
All in all, porphyrin staining or evidence of licking and chewing should be a clue that there is an issue somewhere. I always start by evaluating the area directly nearest to the licked area. Check the skin. Check the joints. Then I evaluate the spine. If the licking and chewing is of all four feet, or the belly then I think of allergies or a contact dermatitis. (Not physio problems… but things that I can redirect the client to consult their veterinarian about.) If I can correlate the lick areas to a joint issue or spine issue, then I treat the area.
It sounds simple, but taking note and realizing that porphyrin staining (or evidence of licking) can be a rehab issue, is important for all animal owners and the veterinary to be aware of.
Just my musings for the week!
On that note… Cheers!