granulation tissue

Granulation tissue is seen on a dog's foreleg after surgery to close a large wound. Photo by Dr. Teri Ann Oursler.

I love wounds. Love, love, love them – big ones, small ones, gooey ones, pus-filled ones – just no maggots, please! 

Okay, I should probably specify that I love repairing wounds, not creating or having them. Though, come to think of it, my professional love for wound repair may have something to do with my personal affinity for acquiring them (I have a quirky relationship with gravity.) Wound repair is fun. It’s like working on a craft project or jigsaw puzzle with the added bonus of improving a life.

But as fun as it is to sew it all up, tie up the patient with a neat bow, etc., sometimes the best thing to do with a wound is to NOT repair it.

Telling a pet owner that neither the horses nor the king’s men can put Fluffy together again and that we have to wait for nature to do the job is NOT fun.

Waiting for an Amazon order to ship is bad enough. No one wants to sit and watch an open, oozing wound change shape at a pace that makes drying paint seem adrenaline-filled.

Lucky for us, healing is one of the things bodies do best. Our goal is to help the natural process along and to stay out of the way where we can't help.

Immediately after injury, the body leaps into paramedic mode, doing its best to staunch the flow of the red stuff by clotting the blood.

Next it goes into caring nurse mode: cleaning the wound and scooping out all the dead, icky, dirty stuff. Cells called macrophages move into the wound gobbling up and carrying off bacteria, dirt, hair, dead tissues and any other invaders. The macrophages and their cargo flow out of the wound – this, folks, is how we get pus!

Once all the dead tissue and contaminants are gone – through the work of macrophages or from your veterinarian cleaning and debriding (cutting away dead stuff) the wound – the construction crew can get to work.

The body starts to lay down its first layer a few days after the wound occurs. The granulation tissue is sort of pink, spongey looking stuff – like someone stuck a naked starfish to your pet. Granulation tissue doesn’t have a nerve supply of its own, but it has lots and lots and LOTS of small blood vessels. The granulation bed is the wall spackle of the wound. It fills in any empty space below the skin edges and gives the skin something to close over.

Next the wound contracts; the body pulls the skin edges closer together, narrowing the gap the skin cells will need to bridge.

The last step in the healing process is epithelialization – the migration of the skin cells across the granulation tissue that creates new skin we call a scar.

Contrary to what your great-great-great-great grandmother may have told you, scar tissue is not stronger than normal tissue. It’s actually much weaker. So the goal with wound repair is to reduce the amount of new skin the body is forced to create. We want to keep that gap as small as possible, making it as easy as possible for the contraction phase to occur.

When your veterinarian sutures (stitches up) a wound, we aren’t so much fixing things as we are putting things back into a decent location for them to fix themselves. We’re just rearranging. The body still has to do all the heavy lifting. As a general rule, sutures make it so there is less granulation and contraction that the body needs to do. Basically, by suturing, we are turning a big (or biggish) wound into a smaller, narrower one.

However, there are times when suturing a wound is as bad an idea as the plaid polyester pant suit.

Contamination

Remember our friends the macrophages? With heavily contaminated wounds or wounds with lots of dead or traumatized tissue (i.e. dog bites), macrophages have to go into overtime and recruit all their friends to get the icky stuff out of the way. That means, lots of pus. So, closing these wounds is often not the best plan since what do we call a closed pocket of pus? That’s right – ABSCESS!

Tension

That’s not referring to how your veterinarian feels about suturing the wound. Remember, suturing a wound involves pulling the two edges closer together. Since animals aren’t made from elastic, there’s only so much pulling that can happen before things go wonky. Tension depends on several things besides just the acreage of the wound. Like real estate, ease of wound closure is all about location, location, location. Areas with lots of motion – across or near joints, for instance, put high tension on the wound edges. (Think about how long it takes a paper cut across your knuckle to heal compared to one on the pad of your thumb.) Areas without much extra skin, such as the lower leg compared to the neck or shoulder, also make suturing a challenge – sort of like fighting your partner for bed covers.

Too much tension has the same effect on the suture line and tissue edges as overstuffing a soft-sided suitcase has on the zipper and surrounding seams. RRRRRRIIIIIIP

Old Wound

Contrary to some of the myths out there, there is no hard-and-fast rule about “You can’t suture a wound if it’s been more than X hours.” In fact, some wounds actually do better with what we call delayed closure – cleaning and wrapping a wound (letting the macrophages do their thing) then coming back a day or two later to debride and suture the wound. But, you have to pick and choose with delayed closure. Some wounds may have gotten a good enough head start that they don’t need suturing. Others may have been contaminated, found late, and developed infection that makes sutures a bad idea (see previous pus pocket problem). Sometimes, especially if the wound occurred under any sort of crushing conditions, there may be lots of damaged tissue that the body (and veterinarian) need to remove before any kind of healing can begin.

So, what if your veterinarian recommends leaving the wound open?

This doesn’t mean they just didn’t feel like sewing that day. It means that in their professional judgement, this wound isn’t a good suture candidate. 

Will it still heal? Barring weird physiologic anomalies (aliens or a compromised immune system) or lack of proper home care, absolutely.

Did you catch the bit about home care?

Whether your veterinarian sutures a wound or suggests leaving it open, there are things you can (and SHOULD) do at home to help your pet’s healing process.

• Restrict exercise. Remember that part about motion being the enemy of healing? Depending on the location of the wound, your veterinarian may tell you to restrict your animal’s exercise. This doesn’t mean only let them run for 15 minutes instead of an hour. It means no running at all.
  
  
• Use the e-collar (or other no-bite device). I don’t care how sad your pet looks. Don’t take off the e-collar. Not even for a minute. Not just to let him go outside. Just don’t. You know how your cuts itch as they start to heal? Your animals experience the same thing. And they don’t have your self-restraint.
  
  
• Don’t put anything on the wound unless your veterinarian prescribed it. New cells are fragile, finicky things. Many, many, MANY of the over-the-counter or internet-available powders, lotions, potions, and tinctures not only won’t help the wound heal faster, they’ll interfere with healing. I’ve even seen sutures dissolve under certain ointments (This aggravates your veterinarian.)
  
  
• Monitor bandages and casts closely. Wet bandages act like a wick, pulling dirt and bacteria from the outside world straight into the wound. Even well-placed bandages can move around and tighten up if an animal is overly active. Casts can rub and cause sores especially if an animal is moving too much. Check any bandages or casts several times a day and call your vet immediately if you notice any of the following: moisture, swelling (above or below the bandage), heat, a bad smell, pus, or limping.

The body is a great healing machine. Sometimes our job is just to stay out of its way.