Wound Closure in Cats: Sutures, Open Healing, or a Flap

A cat wound is closed in 1 of 3 ways, and the decision is mostly made in the first 6 to 8 hours. Primary closure sews the edges together the same day. Second intention leaves the wound open and lets granulation tissue fill it over 3 to 6 weeks. A flap moves a sheet of skin with its own blood supply to cover a defect that cannot be pulled shut. Each has its own suture size, dressing interval, and recheck date, and picking the wrong one costs 2 to 4 extra weeks.

The 3 routes at a glance

Route	Best fit	Closure time	Dressing change	Recheck
Primary closure	Clean wound under 6 hours, edges that meet without tension	Immediate, 15 to 30 min	Day 2, then every 48 hours	Day 10 to 14, sutures out
Delayed primary closure	Contaminated wound, 6 to 24 hours old	Day 3 to 5	Every 24 hours until closed	Day 10 to 14 after closure
Second intention	Infected, tissue loss, bite abscess cavity	3 to 6 weeks	Every 24 to 48 hours	Day 3, day 7, then weekly
Flap or graft	Defect over 2 cm on a limb or the face	45 to 120 min surgery	Day 1, day 3, then every 48 hours	Day 2, day 5, day 14

The 6-hour clock and the 100,000 bacteria line

A clean cut seen within 6 hours can usually be closed. Between 6 and 12 hours the count of bacteria in the tissue climbs, and above roughly 100,000 per gram of tissue a closed wound becomes an abscess. Past 12 hours, or with dirt, bite crush, or dead muscle, most surgeons clean, pack, and wait 3 to 5 days before closing. A cat bite abscess is the classic example: the puncture seals in 24 to 48 hours, the pocket fills, and it needs drainage rather than a stitch.

Primary closure: 3 numbers per stitch

Cat skin is thin, about 1 to 2 mm on the flank, so 3-0 or 4-0 monofilament is the usual size and 5-0 for the face. Bites sit 3 to 5 mm from the edge, 3 to 5 mm apart, and include 2 to 3 mm of depth so the edges roll slightly outward. A simple interrupted pattern of 6 to 10 stitches closes most 3 to 5 cm wounds. Sutures come out at day 10 to 14 on the body and day 7 to 10 on the face, where blood supply is richer.

Tension is the failure point, not the thread. If the edges pull apart when you release them, the wound needs a releasing incision, a walking suture, or a flap. Closing under tension cuts blood flow, and a 3 mm gap at day 3 becomes a 10 mm gap at day 5. A drain, when one is placed, stays 24 to 72 hours and comes out when fluid drops below 1 to 2 mL a day.

Second intention: 1 mm a day of progress

An open wound heals from the bottom up. Granulation tissue appears by day 3 to 5, contraction pulls the edges in at 0.5 to 1 mm a day, and epithelium migrates 1 to 2 mm a day from each edge. A 2 cm circular wound therefore takes 3 to 6 weeks and leaves a scar about 60% to 80% of the original size. Dressings are changed every 24 to 48 hours, and a moist wound heals 30% to 50% faster than one left to dry and scab. That is the whole argument for a covered, slightly damp wound over a scab.

Open healing is not neglect. It is the correct route for an infected pocket, a wound with missing skin, or a cat that cannot be anesthetized today. The cost is 3 to 6 weeks of 2-minute daily checks and a scar that stays visible.

Flaps: ratio, drain, and the 72-hour verdict

A random flap (no named artery) survives on a length-to-width ratio of about 1.5 to 1, and it is safer at 1 to 1 on a cat's limb. A flap is checked at 48 hours for color and at 72 hours for the real verdict: pink with capillary refill under 2 seconds is alive, purple or black is not. Sutures stay 14 days, and the drain comes out at 24 to 72 hours. Unlike a simple closure, a flap needs a plan for the donor site, which is closed directly or left to heal by second intention.

When a wound is more than a wound

Five signals mean the plan changes: a wound over 5 cm, a wound that crosses a joint, exposed bone or tendon, a bite over the chest or abdomen (a 1 cm hole can hide a 3 cm tear in the muscle below), and any wound in a cat with diabetes or on steroids. Diabetic cats heal 2 to 3 times slower, and sugar in the urine is a 5-minute test that changes the plan before surgery, which is why the urinalysis breakdown is part of the workup. A wound with a foreign body needs imaging first; the x-ray reading primer covers what soft tissue and gas look like on film.

Infection signals in the first 72 hours

Call for swelling that grows after day 2, heat over the wound, discharge that turns yellow-green or smells, a gap over 3 mm, a fever above 39.4 C, or no food for 24 hours. Redness spreading more than 1 cm past the wound edge in 24 hours is the earliest reliable sign. Most wound infections show up between day 2 and day 5, which is why the first recheck sits at day 2 rather than day 7.

Scar, fur, and itch

Fur regrows over 6 to 8 weeks and often comes back a different shade for 1 to 2 cycles. A scar matures over 3 to 6 months, flattening and fading. Itch at the wound edge is normal for 5 to 10 days; licking past day 10 is not, and a collar for 14 days prevents most of it. Shaving adds 2 to 3 weeks to the cosmetic timeline, so clip only what the closure needs.

Your 5-step plan

1. Photograph the wound at hour 0 and note the time; the 6-hour clock starts then.
2. Cover with a clean damp dressing and skip powders, creams, and hydrogen peroxide.
3. Ask the vet which of the 3 routes is planned and why.
4. Keep the collar on 14 days and check the line 2 times a day.
5. Attend the day 2, day 7, and day 10 to 14 visits, and photograph the wound each time for comparison.

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