What this means
Some dogs have a small opening in the skin on the back or neck, along the midline. It may look like a little dimple with a tuft of hair sticking out, and when stroking the back a thin cord or firm lump can sometimes be felt under the skin. Often such a spot has been there since the dog was very young, and it can be a developmental feature that formed as the body grew.
A pit or cord like this may cause no trouble at all, but sometimes it becomes inflamed: it swells, weeps, or a painful lump appears on the back. If the channel under the skin reaches deep, deeper structures can be involved, so it should not be pressed, picked at or have the hairs pulled out of it. Only a vet can examine how the spot looks and whether it is connected to deeper tissue.
Show the spot to your vet even if your dog seems perfectly well. Write down when you noticed the pit, whether it has changed, whether there has ever been discharge and whether your dog reacts when the back is touched. Photograph it so that its size and position can be seen.
Possible causes
These are things that can cause this sign. It is not a diagnosis, and they are not equally likely for your dog.
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A channel in the skin present from birth
This is a channel that formed as the body developed and runs from the skin inwards. It often shows as a pit with a tuft of hair or a cord under the skin.
About the condition: Dermoid sinuses -
An inflamed or infected channel
Hair or dirt that gets into the pit can cause inflammation, swelling, pus or discharge.
About the condition: Dermoid sinuses -
A skin cyst
A lump in a capsule can form under the skin and feel like a firm round spot.
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An old wound or bite scar
After an earlier wound the skin can stay drawn in or hardened, so the spot looks like a dimple or a cord.
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A skin growth
Sometimes a lump or uneven spot is a skin growth. To know what it is, it has to be examined and, if needed, tested.
What else to watch for
These observations help your vet build the picture faster. Note down what you saw and when.
- Exactly where the spot is: towards the neck, the middle of the back or the tail
- Whether a tuft of hair sticks out of the pit
- Whether there has ever been discharge, pus or a bad smell
- Whether the area swells, reddens or turns warm
- Whether your dog reacts or whimpers when you touch its back
- Whether its walking or stair-climbing has changed
When to book a routine visit
A pit, cord or discharge on the back is worth showing to a vet at the first visit, even if your dog feels well. Say when you noticed it and whether it has changed.
Related conditions
Conditions whose entries mention this sign. The list is somewhere to read on, not a way to reach a diagnosis.
Body systems: Skin and coat