Surgical Site Infection
The parent definition — what counts as an SSI, and why time does not exclude it.
Consensus Definition
An infection that occurs following a surgical intervention, involving the skin / mucous membranes and subcutaneous tissue of the incision, and/or the deep soft tissue of the incision, and/or any part of the anatomy other than the incision that was opened or manipulated during the procedure — and which may involve implants placed during that intervention.
The development of an SSI is considered independent of its occurrence in time. Any infection that can be linked to a previous surgical intervention qualifies as an SSI, even if diagnosed beyond a predefined surveillance period.
VETSSI Clinical Interpretation
SSI is an umbrella term, not a single diagnosis. The consensus deliberately ties the definition to anatomy that was 'opened or manipulated' — which means the surgical exposure itself, not the calendar, determines eligibility. A draining incision diagnosed on day 45 is still an SSI if it can be linked to the procedure. This is a clinical diagnosis built from varied criteria; a degree of subjective surgical judgment is expected to remain.
Why This Matters Clinically
If your team treats the surveillance window as the definition of SSI, late-onset infections silently disappear from your data — and your rate looks better than your practice actually is. Anchoring the definition to manipulated anatomy rather than to time is what makes rates comparable between surgeons, between years, and between hospitals. It is also what makes an SSI rate honest.
Diagnostic Criteria
An infection is present following a surgical intervention.
The infection involves tissue that was incised, opened, or manipulated during that intervention — or an implant placed during it.
The link to the prior procedure can be reasonably established, regardless of how much time has passed.
Clinical Signs
- Pyrexia
- Pain or tenderness
- Localized swelling — edematous (acute) or fibrous (chronic)
- Erythema
- Heat
- Lack of function
Practical Clinical Examples
A dog returns 5 weeks after tibial plateau leveling osteotomy with a draining stifle. Beyond a 30-day window, but clearly linked to the procedure — still an SSI.
Incisional cellulitis 9 days after celiotomy involving skin and subcutis only — an SSI of the superficial layer.
Periprosthetic infection identified months after total hip replacement — an implant-associated SSI, time notwithstanding.
Diagnostic Gray Zones
Differential reasoning at the bedside. Expand for the clinical breakdown.
- Pyrexia and malaise are non-specific. A patient can be febrile from pneumonia or a urinary infection while the incision is healing normally.
- An SSI is anchored to the operated anatomy: localizing signs at the incision or manipulated structure. Pyrexia alone, without local findings, points away from SSI.
- Examine the wound directly before attributing systemic signs to it. Look elsewhere for a source.
- Misattributing a non-surgical infection to the wound inflates the SSI rate and obscures the real problem.
Common Misclassification Scenarios
The recurring ways this definition is mis-applied — and what to do instead.
- Teams conflate the 30-day active monitoring period with the definition itself.
- Late implant and organ/space infections are under-recognized and under-treated.
- Artificially low rates; benchmarking becomes meaningless.
- Record any infection linked to the procedure with its appearance interval, regardless of timing.
Connected Across the System
How this definition links into the contamination pathways, protocols, and roles that produce or prevent it.
Surveillance Implications
Every SSI should be recorded with its date of event and appearance interval (days from surgery). Direct wound inspection by the operating surgeon is the preferred method; a trained professional or structured telemedicine review are acceptable alternatives.
Source
Verwilghen DR, Pelosi A, Abbas M, et al. Surgical site infection definitions consensus: a first step toward improving prevention in veterinary medicine. American Journal of Veterinary Research, 2026.
DOI: 10.2460/ajvr.25.03.0099 · Open Access — CC BY-NC
Surgical site infection definitions consensus: a first step toward improving prevention in veterinary medicine.
Verwilghen DR, Pelosi A, Abbas M, et al. — American Journal of Veterinary Research, 2026
DOI: 10.2460/ajvr.25.03.0099 · Open Access — CC BY-NC
Every definition, criterion, surveillance term, and wound class on these pages derives from this expert consensus. Consensus text on each page paraphrases the paper; clinical interpretation, gray zones, and misclassification scenarios are VETSSI editorial.