What causes leukocytosis in a ruptured peptic ulcer?

Leukocytosis in Ruptured Peptic Ulcer: Pathophysiological Mechanisms

Leukocytosis in ruptured peptic ulcer is primarily caused by the body's immune response to bacterial contamination of the peritoneal cavity, resulting in systemic inflammatory response syndrome (SIRS) due to peritonitis. 1

Pathophysiological Mechanisms

The development of leukocytosis in ruptured peptic ulcer involves several key processes:

1. Bacterial Peritonitis

   • When a peptic ulcer perforates, gastroduodenal contents spill into the peritoneal cavity
   • This introduces a polymicrobial contamination with gram-positive, gram-negative, and anaerobic bacteria 1
   • Peritoneal fluid cultures often show mixed bacterial populations that trigger immune activation

2. Systemic Inflammatory Response

   • The peritoneal contamination triggers a robust inflammatory cascade
   • This leads to increased production and release of white blood cells from bone marrow
   • Laboratory tests typically show elevated white blood cell counts, particularly neutrophils 1

3. Endotoxemia and Cytokine Release

   • Bacterial endotoxins enter the bloodstream (endotoxemia)
   • This stimulates the release of pro-inflammatory cytokines including:
     • Interleukin-1 (IL-1)
     • Interleukin-6 (IL-6)
     • Neutrophil-elastase 2
   • These cytokines further stimulate leukocyte production and mobilization

4. Metabolic Response to Peritonitis

   • Peritonitis causes metabolic acidosis, which is commonly associated with perforation 1
   • This metabolic derangement contributes to the overall inflammatory state

Clinical Significance

The presence and degree of leukocytosis has important clinical implications:

• Diagnostic Value: Leukocytosis is a common laboratory finding in perforated peptic ulcer and supports the diagnosis when combined with imaging findings 1

• Prognostic Indicator: Higher leukocyte counts correlate with more severe peritonitis and may predict worse outcomes 1

• Treatment Monitoring: Normalization of leukocyte count is used as a marker to guide antibiotic therapy duration (typically 3-5 days or until inflammatory markers normalize) 1

• Complication Risk: Persistent leukocytosis may indicate inadequate source control or development of intra-abdominal abscesses 1

Management Implications

Understanding the cause of leukocytosis influences management decisions:

• Antibiotic Selection: Empiric broad-spectrum antibiotics should be started promptly to cover the polymicrobial nature of the infection 1

• Source Control: Surgical intervention is necessary to repair the perforation and perform peritoneal lavage to reduce bacterial load 1

• Monitoring Response: Serial white blood cell counts help assess treatment response and guide antibiotic duration 1

Potential Pitfalls

• Immunocompromised Patients: May not mount an appropriate leukocyte response despite severe infection

• Elderly Patients: May present with less pronounced leukocytosis despite significant peritonitis

• Prior Antibiotic Use: May mask the typical leukocytosis pattern

• Fungal Co-infection: Candida species are commonly isolated from peritoneal fluid in perforated peptic ulcer and may contribute to the inflammatory response, but routine antifungal therapy is not recommended unless the patient is critically ill or immunocompromised 1

The degree of leukocytosis, along with other clinical and laboratory parameters, helps guide the intensity of treatment and monitoring required for patients with perforated peptic ulcer.