Postoperative Leukocytosis: A Normal Physiologic Response
Yes, surgery routinely causes postoperative leukocytosis in 29-67% of patients, representing a normal physiologic stress response rather than infection, and typically does not warrant further workup in the absence of clinical signs of infection. 1, 2, 3
Natural History and Incidence
White blood cell counts typically increase by approximately 3,000 cells/μL over the first 2 postoperative days, then decline to slightly above preoperative levels by day 4. 1
The incidence of postoperative leukocytosis ranges from 29% after robotic hysterectomy to 38% after joint arthroplasty to 67% after endovascular aortic repair. 1, 2, 3
Marked leukocytosis (WBC >15,000/μL) occurs in approximately 4% of cases and still represents normal surgical stress in most patients. 2
Delayed postoperative leukocytosis (days 4-7) occurs in 58% of lung transplant recipients, with 36% having no identifiable infectious or pathologic cause. 4
Factors Associated with Postoperative Leukocytosis
Knee arthroplasty produces higher leukocytosis than hip arthroplasty, bilateral procedures cause more elevation than unilateral, and older age with higher comorbidity burden increases the magnitude of response. 1
Elevated preoperative WBC is the only factor significantly associated with elevated postoperative WBC (P < 0.001). 2
Operative time, BMI, and performance of lymphadenectomy do not correlate with postoperative leukocytosis. 2
Diagnostic Accuracy for Infection
Postoperative leukocytosis has poor diagnostic accuracy for early periprosthetic infection, with sensitivity of 79% but specificity of only 46%. 1 This means leukocytosis alone cannot reliably distinguish infection from normal surgical stress.
Superior Markers for Infection Detection
C-reactive protein (CRP) has remarkably higher sensitivity and specificity than WBC or neutrophil count for detecting postoperative complications. 5, 6, 7
CRP ≥5 mg/dL has high specificity for postoperative complications including infection, though normal CRP does not completely rule out complications. 5, 6, 8
Procalcitonin has higher diagnostic accuracy and specificity than CRP for bacterial sepsis, though it is more expensive. 6
In immunocompromised patients (transplant recipients), CRP is more reliable than WBC count for detecting serious infection, as only 25-43% of transplanted patients with acute appendicitis show leukocytosis. 5, 8
When to Investigate Further
Obtain CRP, procalcitonin, serum lactate, and blood cultures when clinical signs suggest infection: 5, 6
- Fever ≥38.0°C 6
- Productive cough or respiratory symptoms 6
- Wound erythema or drainage 6
- Hemodynamic instability or shock 5
- Abdominal pain or distension 5
Contrast-enhanced CT with oral and IV contrast is the study of choice when postoperative complications are suspected, providing 95% sensitivity and 94% specificity. 8, 7
Special Populations and Pitfalls
Immunocompromised Patients
Transplant recipients with acute appendicitis have median WBC of 7,500 cells/mm³ versus 12,500 in non-transplanted patients (p = 0.002), while CRP is 6.1 mg/dL versus 0.8 (p = 0.009). 5
Leukocytosis is rare in kidney transplant patients developing appendicitis, but CRP is generally elevated. 5
Endovascular Surgery
Transient leukopenia (not leukocytosis) occurs immediately after TAVI, EVAR, and TEVAR, with WBC declining by 25-43% in the immediate postoperative period. 9
This leukopenia resolves within 24 hours and is not associated with postimplantation syndrome or infectious complications. 9
Postimplantation syndrome (fever and leukocytosis) after endovascular aortic repair occurs in 67% of patients but does not represent infection. 3
Perigraft air on CT scan occurs in 67% of patients after stent-graft repair and does not indicate infection even when concurrent with fever and leukocytosis. 3
Bariatric Surgery
Elevated CRP levels predict 30-day complications in bariatric surgery patients. 5
Leukocytosis alone should not be used as a single marker to exclude internal herniation, as elevated serum lactate occurs late in the presence of intestinal ischemia. 5
Lung Transplantation
Delayed postoperative leukocytosis (days 4-7) without identifiable cause is not associated with increased mortality (HR = 0.94, P = 0.800). 4
However, leukocytosis attributed to acute graft rejection carries an 8-fold increased mortality risk (HR = 8.21, P < 0.001). 4
Critical Pitfalls to Avoid
Do not rely on leukocytosis alone to diagnose or exclude postoperative infection—it lacks specificity. 1, 2
Do not ignore fever ≥38.0°C in postoperative patients—obtain blood cultures and measure CRP/procalcitonin before starting antibiotics. 6
Do not use leukocytosis as a single marker to exclude specific surgical complications like internal herniation or anastomotic leak. 5
Do not assume leukocytosis indicates infection in the absence of clinical signs—it represents normal surgical stress in most cases. 1, 2, 3