ConditionInfections
Surgical Site Infections
A surgical site infection (SSI) is an infection in the part of the body where surgery took place, appearing within 30 days of the operation, or within 90 days when an implant such as a joint replacement was used. It can affect only the skin incision, the deeper muscle and tissue layers, or the organ or space operated on. Signs include increasing redness, warmth, swelling, pain, pus from the wound, and fever. Most superficial infections respond to opening and cleaning the wound and sometimes antibiotics; deeper infections may need drainage or further surgery.
Also called: SSI, post-surgical infection, postoperative wound infection, incision infection, infected surgical wound
At a glance
- What it is
- Infection of the incision, deeper tissues or organ space within 30 days of surgery (90 days with implants).
- How common
- Among the most common hospital-associated infections; risk varies with the type of surgery.
- Signs
- Increasing redness, warmth, swelling and pain; pus or cloudy drainage; wound opening; fever.
- Common bacteria
- Staphylococcus aureus (including MRSA), streptococci, gut bacteria after bowel surgery.
- Treatment
- Opening and draining the wound, wound care, antibiotics; surgery for deep or organ-space infections.
When to get help
Call 911 or go to the ER
- Rapidly spreading redness, severe pain out of proportion to the wound, dusky or blistering skin, or crackling under the skin (possible necrotizing infection)
- Fever with confusion, fast breathing, a racing heart or low blood pressure (possible sepsis)
- A wound that splits open with organs or deep tissue visible
- Severe belly pain, vomiting or a rigid abdomen after abdominal surgery
See a doctor within a day or two
- Increasing redness, warmth or swelling around the incision after the first 2 to 3 days
- Pus, cloudy or foul-smelling drainage from the wound
- Fever above 38 °C (100.4 °F) after surgery
- Increasing pain, swelling or redness around a joint replacement or other implant
Book a routine appointment
- A small amount of clear or slightly pink drainage that is decreasing
- Questions about wound care or when stitches come out
Usually safe to manage at home
- Mild pinkness at the edges of the incision and mild tenderness in the first few days, which improve day by day
Types of surgical site infection
| Type | What it involves | Typical signs |
|---|---|---|
| Superficial incisional | Skin and tissue just under the skin | Redness, warmth, pus at the incision |
| Deep incisional | Muscle and fascia layers | Deeper pain, swelling, wound opening, fever |
| Organ or space | The area operated on, such as an abscess in the abdomen or infected joint | Fever, pain, organ dysfunction; may have few skin signs |
Normal healing vs infection
Some redness, swelling and tenderness are normal in the first few days after surgery. Infection is more likely when:
- redness and swelling spread or worsen after day 2 or 3
- pain increases rather than decreases
- the wound becomes hot or hard
- pus or cloudy, smelly fluid drains
- the wound edges separate (wound dehiscence)
- fever develops, usually 3 to 7 days after surgery
Causes and risk factors
Infection occurs when bacteria, usually from the patient's own skin, nose or gut, enter the wound during or after surgery.
Patient factors
- diabetes and high blood sugar around the time of surgery
- smoking
- obesity
- older age and poor nutrition
- weakened immunity, including steroid use
- carrying Staphylococcus aureus or MRSA in the nose
- existing infection elsewhere
Surgical factors
- contaminated or dirty surgery, such as bowel surgery or trauma
- long operations
- implants such as joint replacements or mesh
- emergency surgery
- hypothermia during surgery
- drains and blood transfusion
Diagnosis
- examination of the wound
- wound swab or fluid culture to identify bacteria and guide antibiotics
- blood tests: white cell count, CRP and blood cultures if unwell
- ultrasound or CT for deeper collections or abscesses
- joint aspiration if a prosthetic joint infection is suspected
Treatment
- opening the wound: removing some stitches or staples to drain pus; often the most important step for superficial infections
- wound care: cleaning, packing or dressings; sometimes negative pressure wound therapy (a wound vacuum)
- antibiotics: when there is spreading cellulitis, fever, or deeper infection; chosen to cover likely bacteria including MRSA where common
- drainage of abscesses: by a radiologist with a needle or by surgery
- further surgery: for deep infections, infected implants, mesh or necrotizing infections
- control blood sugar in people with diabetes
Prevention
Before surgery
- stop smoking, ideally at least 4 weeks before
- control blood sugar
- shower or bathe with soap or antiseptic the night before or morning of surgery, as instructed
- do not shave the surgical area yourself; clippers are used if hair must be removed
- MRSA screening and decolonization for some operations
During surgery
- antibiotics given within 60 minutes before the incision when indicated
- skin preparation with antiseptic
- keeping the patient warm
After surgery
- keep the wound clean and dry, and follow dressing instructions
- wash hands before touching the wound or dressing
- do not apply creams or powders unless advised
- ask visitors not to touch the wound
- report warning signs promptly
Frequently asked questions
How do I know if my incision is infected?
Signs of infection include redness or swelling that spreads or worsens after the first few days, increasing pain, warmth, pus or cloudy smelly drainage, the wound opening, and fever. Contact your surgical team promptly if you notice these.
How soon after surgery can an infection start?
Most surgical site infections appear 3 to 7 days after surgery, but they can develop up to 30 days later, or up to 90 days after surgery involving an implant such as a joint replacement.
How are surgical site infections treated?
Superficial infections are often treated by opening the wound to drain pus, with wound care and sometimes antibiotics. Deeper infections may need antibiotics, drainage of abscesses or further surgery, especially if an implant is infected.
Can I prevent an infection after surgery?
You can lower your risk by stopping smoking, controlling blood sugar, showering as instructed before surgery, not shaving the area yourself, keeping the wound clean and dry, and washing hands before touching it.
Sources
This guide was written from current patient and clinical guidance, including:
- CDC: Surgical Site Infection (SSI) Event, National Healthcare Safety Network
- CDC and HICPAC: Guideline for the Prevention of Surgical Site Infection (2017)
- American College of Surgeons and Surgical Infection Society: Surgical Site Infection Guidelines (2016 Update)
- World Health Organization: Global Guidelines for the Prevention of Surgical Site Infection (2018)
- MedlinePlus: Surgical wound infection