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Bacterial Sepsis Workup

  • Author: Burke A Cunha, MD; Chief Editor: Michael Stuart Bronze, MD  more...
Updated: Mar 18, 2016

Approach Considerations

Workup for sepsis may include the following:

  • Blood and urine studies, including appropriate cultures
  • Diagnostic imaging of the chest and abdomen/pelvis
  • Cardiac studies such as ECG and troponins, as indicated
  • Interventions such as paracentesis, thoracentesis, lumbar puncture, or aspiration of an abscess, as clinically indicated
  • Measurement of biomarkers of sepsis such as procalcitonin levels

Histologic examination is generally unhelpful, because sepsis does not cause diagnostic findings in various organs.


Laboratory Studies

Complete blood cell count

A complete blood cell (CBC) count is usually not specific, because of the numerous conditions that mimic sepsis and produce leukocytosis with variable degrees of a left shift. Leukocytosis with a left shift is a nonspecific diagnostic finding that is as common in noninfectious states as in infection. Leukopenia, anemia, and thrombocytopenia may be observed in sepsis.

Bacterial cultures

Obtain blood cultures in all patients upon admission to demonstrate the organism responsible for infection. Negative blood culture results are also necessary to include pseudosepsis in the differential diagnosis.[21] Blood culture isolates might suggest the underlying disease process. Bacteroides fragilis suggests a colonic or pelvic source, whereas Klebsiella species or enterococci suggest a gallbladder or urinary tract source.

If central intravenous (IV) line sepsis is suspected, remove the line and send the tip for semiquantitative bacterial culture. If culture of the catheter tip yields positive results and demonstrates 15 or more colonies and if the isolate from the tip matches the isolate from the blood culture, an infection associated with the central IV line is diagnosed.

The rationale for nasal cultures is that nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) is often viewed as a potential marker of subsequent risk for severe MRSA infection. However, a meta-analysis found nasal colonization with MRSA to be a poor predictor for the subsequent occurrence of MRSA lower respiratory tract infections and MRSA bloodstream infections that require antimicrobial treatment.[10] Thus, caution should be exercised in interpreting nasal cultures in patients in the intensive care unit (ICU).

Gram staining

Buffy coat analysis of CBC may be useful in identifying certain infectious agents.[22]

Although the yield is low, stained buffy coat smears, if positive, are the best available rapid tests for demonstrating organisms that cause bacteremia. If the stained buffy coat smear yields a positive result, it demonstrates the morphology of the bacteria that is causing the bacteremia, which provides rapid information on which to base empiric antimicrobial therapy.

Urine studies

If urosepsis is suspected, obtain a urine Gram stain, urinalysis, and urine culture. A systematic review found that in adult ICU patients, catheter-associated urinary tract infection was associated with significantly higher mortality and a longer stay.[23]


Chest Radiology

Chest radiography is important to rule out pneumonia and diagnose other causes of pulmonary infiltrates, such as the following:

  • Pulmonary drug reactions
  • Pulmonary embolism
  • Pulmonary hemorrhage
  • Primary or metastatic pulmonary neoplasms
  • Lymphangitic spread of malignancies
  • Large pleural effusions
  • Pneumothorax
  • Hydrothorax
  • Fluid overload
  • Congestive heart failure (CHF)
  • Acute myocardial infarction (MI)
  • Acute respiratory distress syndrome – This condition should suggest an intra-abdominal source (eg, acute pancreatitis)

Abdominal Ultrasonography, CT, and MRI

Perform abdominal ultrasonography if biliary tract obstruction is suspected on the basis of the clinical presentation. However, abdominal ultrasonography is suboptimal for the detection of abscesses or perforated hollow organs. Ultrasonograms in patients with cholecystitis may show a thickened gallbladder wall or biliary calculi but no dilatation of the common bile duct (CBD). Stones in the biliary tract are visible in patients with cholangitis, but the CBD is dilated.

Use computed tomography (CT) or magnetic resonance imaging (MRI) of the abdomen if a nonbiliary intra-abdominal source of infection is suspected on the basis of the history or physical examination findings. These 2 imaging modalities are superior to ultrasonography in demonstrating all lesions, except those related to the biliary tract. Abdominal CT or MRI is also helpful in delineating intrarenal and extrarenal pathology. Gallium or indium scanning has no place in the initial workup of sepsis; patients with sepsis are acutely ill by definition, and rapid diagnostic tests (eg, CT or MRI of the abdomen and ultrasonography of the right upper quadrant) are time-critical, life-saving tools.[24]


Cardiac Studies

If an acute MI is likely, perform electrocardiography (ECG) and obtain cardiac enzyme levels. Remember that certain patients may present with a silent, asymptomatic MI, which should be included in the differential diagnosis of otherwise unexplained fever, leukocytosis, and hypotension. Silent MIs are common in elderly patients and in those who have recent undergone abdominal or pelvic surgical procedures. They are also common in individuals with alcoholism, diabetes, and uremic conditions.


Invasive Interventions


Perform thoracentesis for diagnostic purposes in patients with substantial pleural effusion. Perform paracentesis in patients with gross ascites.

Swan-Ganz catheterization

In some cases, a Swan-Ganz catheter may be useful in managing the fluid status of the patient and in assessing left ventricular dysfunction. However, routine use is not recommended.


Procalcitonin Levels

A study from van Nieuwkoop et al examined the use of PCT levels in predicting bacteremia in a group of 581 patients, 136 of whom had bacteremia; PCT levels successfully identified 94-99% of the patients with bacteremia.[25] Use PCT for blood cultures.

Heyland et al, in a systematic review of the economic value of PCT-guided reduction in antibiotic use in intensive care, found that with hospital mortality and length of stay unchanged, PCT testing to reduce antibiotic treatment broke even when daily antibiotics cost about $150 in Canadian dollars.[26] The authors concluded that under some conditions, PCT testing could result in savings from reduced antibiotic use, but they were unable to exclude a possible 7% hospital mortality increase.

Contributor Information and Disclosures

Burke A Cunha, MD Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital

Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Specialty Editor Board

Thomas E Herchline, MD Professor of Medicine, Wright State University, Boonshoft School of Medicine; Medical Director, Public Health, Dayton and Montgomery County, Ohio

Thomas E Herchline, MD is a member of the following medical societies: Alpha Omega Alpha, Infectious Diseases Society of Ohio, Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Chief Editor

Michael Stuart Bronze, MD David Ross Boyd Professor and Chairman, Department of Medicine, Stewart G Wolf Endowed Chair in Internal Medicine, Department of Medicine, University of Oklahoma Health Science Center; Master of the American College of Physicians; Fellow, Infectious Diseases Society of America

Michael Stuart Bronze, MD is a member of the following medical societies: Alpha Omega Alpha, American Medical Association, Oklahoma State Medical Association, Southern Society for Clinical Investigation, Association of Professors of Medicine, American College of Physicians, Infectious Diseases Society of America

Disclosure: Nothing to disclose.


Pranatharthi Haran Chandrasekar, MBBS, MD Professor, Department of Internal Medicine, Director of Infectious Disease Fellowship, Harper Hospital, Wayne State University School of Medicine

Pranatharthi Haran Chandrasekar, MBBS, MD is a member of the following medical societies: American College of Physicians and Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Thomas M Kerkering, MD Chief of Infectious Diseases, Virginia Tech Carilion School of Medicine

Thomas M Kerkering, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians, American Public Health Association, American Society for Microbiology, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, Medical Society of Virginia, and Wilderness Medical Society

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

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A right lower quadrant abdominal wall abscess and enteric fistula are observed and confirmed by the presence of enteral contrast in the abdominal wall.
Table 1. Clinical Conditions Associated With Sepsis
Associated With Sepsis (Fever ≥102°F) Not Associated With Sepsis (Fever ≤102°F)
GI tract source





Intestinal obstruction


GI tract source




Small bowel disorders

GI bleeding

GU tract source


Intra- or perinephric abscess

Renal calculi

Urinary tract obstruction

Acute prostatitis/abscess

Renal insufficiency

Instrumentation in patients with bacteriuria

GU tract source





Catheter-associated bacteriuria (in otherwise healthy hosts without genitourinary tract disease)

Pelvic source



Upper respiratory tract source





Lower respiratory tract source

Community-acquired pneumonia (with asplenia)


Lung abscess

Lower respiratory tract source

Community-acquired pneumonia (in otherwise healthy host)

Intravascular source

IV line sepsis

Infected prosthetic device

Acute bacterial endocarditis

Skin/soft-tissue source


Uncomplicated wound infections

Cardiovascular source

Acute bacterial endocarditis

Myocardial/perivalvular ring abscess

Cardiovascular source

Subacute bacterial endocarditis

  CNS source

Bacterial meningitis

CNS = central nervous system; GI = gastrointestinal; GU = genitourinary; IV = intravenous.
Adapted from: Cunha BA, Shea KW. Fever in the intensive care unit. Infect Dis Clin North Am. Mar 1996;10(1):185-209.[18]
Table 2. Noninfectious Conditions Mimicking Clinical and Hemodynamic Parameters of Sepsis
Clinical Presentations Mimicking Sepsis Hemodynamic Parameters Mimicking Sepsis
Hemorrhage Acute pancreatitis
Pulmonary embolism Anaphylaxis
Myocardial infarction Spinal cord injury
Pancreatitis Adrenal insufficiency
Diabetic (abdominal crisis) ketoacidosis  
Systemic lupus erythematosus flare with abdominal crisis  
Ventricular pseudoaneurysm  
Massive aspiration/atelectasis  
Systemic vasculitis  
Diuretic-induced hypovolemia  
Table 3. Characteristics of Pseudosepsis and Sepsis
Parameters Pseudosepsis Sepsis
Microbiologic No definite source PLUS ≥1 abnormalities

Negative blood cultures excluding contaminants

Proper identification/process/source PLUS ≥1 microbiologic abnormalities

Positive buffy coat smear result OR 2/3 or 3/3 positive blood cultures

Hemodynamic ⇓ PVR

⇑ CO


⇑ CO

Left ventricular dilatation

Laboratory ⇑ WBC count (with left shift)

Normal platelet count


⇑ Lactate

⇑ D-dimers


⇓ Albumin

⇓ Fibrinogen

⇓ Globulins

⇑ WBC count (with left shift)

⇓ Platelets


⇑ Lactate

⇑ D-dimers


⇓ Albumin

Clinical ≤102°F ±

Tachycardia ±

Respiratory alkalosis ±


≥102°F OR

Hypothermia ±

Mental status changes ±


CO = cardiac output; FSP = fibrin split products; GI = gastrointestinal; GU = genitourinary; PT/PTT = prothrombin time/partial thromboplastin time; PVR = peripheral vascular resistance; WBC = white blood cell.
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