How I search for a sepsis source
KeywordsSepsis Septic shock Infection Diagnosis Antibiotic therapy
Intensive care unit
Magnetic resonance imaging
Identifying the infection source in a sepsis patient is important  as it allows for better antibiotic choices, recognizes the need for ancillary treatment, and identifies the need for source control interventions [2, 3]. Searching for the source of infection cannot be disconnected from the other aspects of sepsis management . We will start antibiotics based on local guidelines in parallel to the search for the infection source in these patients, but we adopt a watchful waiting strategy in doubtful cases without life-threatening organ failure .
Know your epidemiology
Check the patient’s history
Clinical examination is the key
Local clinical manifestations are more helpful than fever and other systemic signs of inflammation to identify the source of infection. For instance, patients with respiratory infections develop respiratory symptoms such as coughing, increased and purulent sputum, and respiratory insufficiency. In sedated patients or patients with impaired consciousness, we will not rely on symptoms such as pain and clinical examination alone; here, imaging will be more important in the diagnostic process.
We use imaging selectively and not to confirm obvious infections, unless it is used to plan source control procedures or diagnose the presence of complications, including ultrasound, conventional X-rays, and computed tomography (CT) scan. Ultrasound is primarily helpful for diagnosing specific infections such as cholecystitis or endocarditis; we do not use it alone to diagnose pneumonia or its complications. A conventional chest X-ray is useful to screen for respiratory infections, but not in the diagnostic workup for other sites of infection.
CT scan is the go-to examination for many infections, and we keep a low threshold for (abdominal) CT scans in surgical patients and those with unclear infections. In most patients, IV contrast media will be necessary, possibly complemented with oral or rectal contrast when a GI leak is suspected. Complex cases should be preferably discussed with the attending radiologist to maximize the diagnostic yield of the examination. CT scan may be done if the clinical picture does not improve.
Specific infections require specific approaches
If clinical examination and imaging suggest the presence of more rare and unclear infections, specific diagnostic procedures may be required, e.g., lumbar puncture to diagnose CNS infections.
Laboratory investigations can be helpful
Directed laboratory investigations, with a special emphasis on microbiological sampling and cultures, help to confirm the site of infection. Direct examination of biologic samples may be helpful to detect the presence of microorganisms, inflammatory cells, or biochemical substances.
Timing of investigations and procedures
Recommended timing of source control procedures in patients with sepsis and septic shock
Emergent (within 1 h of diagnosis)
Urgent (within 6 h of diagnosis)
Necrotizing skin and soft tissue infection debridement
Peritonitis with gastrointestinal leak
Infected pancreatic necrosis
Wound abscess drainage
Peritonitis with abdominal compartment syndrome
We will base the definitive source identification on the clinical picture, complemented with imaging and/or microbiology confirmation where relevant. This will vary among patients; in some, you will need all three elements, and in a patient with cellulitis or necrotizing infection, the clinical picture may be enough. In conclusion, identifying the source of infection can be challenging, yet important for managing the patient. A stepwise, structured approach helps to do so in minimal amount of time.
JDW and YS drafted the text. All authors have seen and approved the final manuscript.
Jan J. De Waele is the senior clinical investigator funded by the Research Foundation Flanders (FWO, Ref. 1881015N).
Ethics approval and consent to participate
Consent for publication
Jan J. De Waele has been consultant for Accelerate Diagnostics, Bayer Healthcare, Grifols, MSD, and Pfizer. Yasser Sakr has no competing interests.
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