Conditions · Surgery and trauma
Surgical site infection !
A surgical site infection is an infection where an operation was done, from the skin cut to deep organs. It is one of the most common hospital infections.
Updated 2026-11-01
Structures involved
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- Skin
- Rectus abdominis
- Linea alba
- Rectus sheath
- Superficial abdominal fascia
- Transversalis fascia
- Peritoneum
Why it happens
- Patterns of acute inflammation: serous, fibrinous, purulent, abscess, ulcer
- What delays healing: infection, diabetes, nutrition, glucocorticoids, poor blood flow
- Wound healing: phases and scar
What it is
Infection of the incision, the deeper tissues or the organ or space handled during an operation, appearing within 30 days (or up to 90 days when an implant is left in place). It is a healthcare-associated infection.
Who gets it
Surgical site infection is one of the most frequent healthcare-associated infections worldwide and is more common in low- and middle-income countries. In Colombia it is under national surveillance by the Instituto Nacional de Salud as an infection associated with medical and surgical procedures.
Causes
- Skin flora: Staphylococcus aureus (including MRSA) and coagulase-negative staphylococci
- Gram-negative bacilli and anaerobes after bowel surgery
- Streptococci (rapid, early infections)
- Contamination at operation from the patient's own flora, the environment or the team
Risk factors
- Contaminated or dirty wounds and emergency surgery
- Diabetes and poor glucose control
- Obesity, smoking, malnutrition and immunosuppression
- Long operations, hypothermia and blood transfusion
- Shaving with a razor, incorrect timing of antibiotic prophylaxis
- Remote infection at the time of surgery
Pathophysiology
Bacteria enter the wound during surgery, mostly from the patient's skin or opened viscera. Infection develops when the bacterial load and virulence overcome local defences, which are weakened by dead tissue, haematoma, foreign material, poor perfusion and systemic disease.
Classification
- Superficial incisional: skin and subcutaneous tissue
- Deep incisional: fascia and muscle
- Organ/space: any deeper area handled at operation (for example an intra-abdominal abscess)
- Wound class: I clean, II clean-contaminated, III contaminated, IV dirty-infected
Symptoms and signs
- Redness, warmth, swelling and pain around the incision
- Cloudy or purulent drainage from the wound
- Fever
- Wound opening (dehiscence)
- Abdominal pain, ileus or persistent fever in organ/space infection
Diagnosis
- Clinical
- Based on findings at the incision within the defined time window: purulent drainage, local signs of inflammation or a wound opened deliberately by the surgeon. Surveillance definitions such as those of the CDC classify depth.
- Tests
- Gram stain and culture of pus or deep tissue (not superficial swabs), blood count and C-reactive protein, and blood cultures when sepsis is suspected.
- Imaging
- Ultrasound for collections in the wound; CT for deep and organ/space infections, which can guide percutaneous drainage.
Differential diagnosis
- Seroma or haematoma
- Stitch reaction or suture granuloma
- Cellulitis unrelated to the incision
- Other postoperative fever sources: pneumonia, urinary infection, venous thrombosis, catheter infection
- Contact dermatitis from dressings
Goal of treatment
Drain infection, remove dead tissue and infected material, treat systemic infection with targeted antibiotics and allow the wound to heal, while preventing new cases through perioperative measures.
Treatment
- Procedure
- Opening of the incision, drainage and debridement; the wound is then left to heal by secondary intention or closed later, sometimes with negative-pressure wound therapy.
- Medical
- Antibiotics directed by culture when there is cellulitis, systemic signs or deep or organ/space infection; superficial infections drained well may not need them.
- Surgical
- Reoperation or percutaneous drainage for deep abscesses, anastomotic leaks and necrotising infection; removal of an infected implant in selected cases.
- Conservative
- Prevention bundle: treatment of remote infections, clipping instead of shaving, skin antisepsis with chlorhexidine-alcohol, antibiotic prophylaxis within the hour before incision when indicated, normothermia and glucose control.
- Follow-up
- Nursing priorities: aseptic wound care and hand hygiene, daily inspection of the incision, temperature, documentation of drainage, patient education on warning signs and active surveillance after discharge.
Drugs for this condition
Complications
- Sepsis
- Wound dehiscence and evisceration
- Incisional hernia
- Necrotising soft-tissue infection
- Prosthetic or implant infection
- Longer hospital stay, readmission and higher costs
Prognosis
Most superficial infections resolve with drainage and wound care. Deep and organ/space infections prolong hospital stay, may need further operations and increase mortality, especially in emergency abdominal surgery.
Prevention
- Antibiotic prophylaxis timed before incision for clean-contaminated and selected clean procedures
- Hair clipping (not shaving) only when needed
- Smoking cessation and glucose control before elective surgery
- Strict aseptic technique and hand hygiene
- Keeping the patient warm during surgery
Test yourself
Think of the answer, then tap the question to see it.
What are the three depth categories of surgical site infection?
Superficial incisional (skin and subcutaneous tissue), deep incisional (fascia and muscle) and organ/space.
Which surgical wound class does an elective cholecystectomy or bowel resection with controlled opening of the gut belong to?
Class II, clean-contaminated.
Which organism most often causes surgical site infections after clean surgery?
Staphylococcus aureus, from the patient's skin flora.
When should prophylactic antibiotics be given to prevent surgical site infection?
Within about one hour before the incision so that tissue levels are adequate during surgery, with repeat doses in long operations.
What is the main treatment of a superficial incisional infection with pus?
Opening and draining the wound with local care; antibiotics are added if there is surrounding cellulitis or systemic signs.
Related conditions
- Sepsis and septic shock
- Incisional (ventral) hernia
- Peritonitis
- Acute appendicitis
- Type 2 diabetes mellitus
- Obesity
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Surgical Site Infection Basics (Centers for Disease Control and Prevention (CDC), 2024); Intraoperative surgical site infection control and prevention: a position paper and future addendum to WSES intra-abdominal infections guidelines (World Journal of Emergency Surgery, 2020).
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