The Respiratory System (Pneumonia) is the Most Common Source of Sepsis
The respiratory tract, specifically pneumonia, represents the most common source of sepsis, accounting for approximately 38-40% of cases. 1, 2
Primary Sources of Sepsis in Order of Frequency
1. Respiratory System (Most Common)
- Pneumonia is identified as the septic focus in 38.6% of emergency department patients with suspected sepsis 1
- Among patients undergoing chest CT for suspected infection, a pathologic infectious source was found in the chest in 72% of cases 1
- Pulmonary infections are consistently reported as the most commonly associated site of infection in patients with sepsis-related acute lung injury 1, 2
- Pneumonia as the primary source of sepsis is independently associated with higher 28-day in-hospital mortality (41% vs. 30% for non-pulmonary sources) 3
2. Intra-Abdominal Infections (Second Most Common)
- Abdominal infections account for 22.0% of identified septic foci 1
- Intra-abdominal infections represent the second leading cause of sepsis globally 2
- Gastrointestinal system infections are among the most common sites alongside respiratory tract 4, 5
3. Genitourinary/Pelvic Infections (Third Most Common)
- Pelvic and genitourinary tract infections account for 20.5% of septic foci 1
- The genitourinary system is consistently identified as one of the major sources 4, 5
4. Bloodstream and Skin/Soft Tissue
- Primary bloodstream infections account for a significant proportion of sepsis cases 5
- Skin and soft tissue infections are also common sources 4
Clinical Implications for Source Identification
When evaluating a patient with suspected sepsis, prioritize investigation of the respiratory tract first, as it yields the highest diagnostic probability:
- Initial chest radiography has 58% sensitivity and 91% specificity for pneumonia in septic patients 1
- CT chest with IV contrast demonstrates 81.82% positive predictive value for identifying septic foci and leads to management changes in 45% of cases 1, 2
- If chest imaging is unrevealing and symptoms persist, proceed to abdominopelvic evaluation as the next highest-yield investigation 1
Important Caveats
- More than 90% of sepsis cases are caused by bacteria, with Gram-negative and Gram-positive organisms occurring with approximately equal frequency 1
- Since 1987, Gram-positive bacteria have become the most common organisms responsible for sepsis development 5
- The development of ARDS occurs in 25-42% of septic patients, with risk increasing with persistent hypotension 1, 2