What is Intraabdominal Sepsis
Intraabdominal sepsis represents the host's systemic inflammatory response to intra-abdominal infections, defined as life-threatening organ dysfunction caused by a dysregulated host response to infection originating from the abdominal cavity. 1, 2
Core Definition and Pathophysiology
Intraabdominal sepsis occurs when infection within the peritoneal cavity or abdominal organs triggers a dysregulated inflammatory response that leads to organ dysfunction, represented by an increase in the Sequential Organ Failure Assessment (SOFA) score of 2 points or more 1, 2
The condition is a dynamic process that evolves from localized intra-abdominal infection to systemic inflammation, potentially progressing to septic shock and multi-organ failure if left untreated 1
The inflammatory response depends on both the causative pathogen and host factors including genetic characteristics, age, and co-existing illnesses, with differential responses at local, regional, and systemic levels 1, 2
Types of Intra-Abdominal Infections Leading to Sepsis
Complicated intra-abdominal infections are the primary source of intraabdominal sepsis and include:
Infections that extend beyond the hollow viscus of origin into the peritoneal space, associated with either peritonitis or abscess formation 1
Common causes include appendicitis (especially perforated), acute cholecystitis, acute cholangitis, acute diverticulitis, secondary bowel perforation, abdominal abscess, and acute necrotizing pancreatitis 1
These infections are typically polymicrobial, involving aerobic gram-negative bacilli (particularly E. coli) and anaerobes (especially Bacteroides fragilis) that reflect the endogenous gastrointestinal microflora 3, 4, 5
Clinical Identification Using Sepsis-3 Criteria
Patients with intraabdominal sepsis present with rapid-onset abdominal pain combined with signs of systemic inflammation including fever, tachycardia, and tachypnea 1
Quick SOFA (qSOFA) criteria can rapidly identify patients at risk outside the ICU: respiratory rate ≥22 breaths/min, altered mental status (Glasgow Coma Scale ≤13), and systolic blood pressure ≤100 mmHg—presence of at least 2 criteria suggests higher risk of poor outcomes 1, 2
Hypotension and signs of hypoperfusion (oliguria, acute mental status changes, lactic acidosis) indicate progression to septic shock 1
Septic Shock as the Most Severe Form
Septic shock represents a subset of intraabdominal sepsis with particularly profound circulatory, cellular, and metabolic abnormalities 2, 6
Clinically identified by vasopressor requirement to maintain mean arterial pressure ≥65 mmHg AND serum lactate level >2 mmol/L (>18 mg/dL) in the absence of hypovolemia 1, 2, 6
Mortality rates escalate dramatically with severity: no sepsis 1.2%, sepsis only 4.4%, severe sepsis 27.8%, and septic shock 67.8% 1
Special Population Considerations
Elderly patients (octa- and nona-genarians) may present with fewer signs of peritonitis and attenuated inflammatory responses despite severe infection, making diagnosis more challenging 1, 2
HIV-infected patients have increased susceptibility to intraabdominal sepsis due to pre-existing immune system activation and exhaustion, even when on antiretroviral therapy 1, 2
Healthcare-associated intra-abdominal infections (occurring >48 hours after surgery or in patients with recent hospitalization) are associated with multidrug-resistant organisms and higher mortality 1
Key Clinical Pitfalls to Avoid
Failing to recognize that the previous SIRS criteria (temperature, heart rate, respiratory rate, white blood cell count) are no longer used in the current Sepsis-3 definition—focus instead on organ dysfunction as measured by SOFA score 1, 2
Delaying recognition in immunocompromised or elderly patients who may not mount typical inflammatory responses 1, 2
Underestimating severity in patients with post-operative peritonitis, which carries increased mortality due to underlying comorbidities, atypical presentation, and risk of multidrug-resistant organisms 1
Epidemiology and Clinical Impact
Intra-abdominal infections are the second most common cause of infectious morbidity and mortality in the intensive care unit, affecting approximately 5% of ICU patients 1, 7
Mortality with intraabdominal sepsis in ICU patients ranges from 5% to 50%, with variability related to the specific infection, patient comorbidities, severity of illness, and degree of organ dysfunction 7
Appendicitis alone affects approximately 670,000 patients per year worldwide, making complicated intra-abdominal infections a commonly encountered clinical situation 1