eMedicine Specialties > Infectious Diseases > Bacterial Infections
Sepsis, Bacterial: Differential Diagnoses & Workup
Updated: Oct 19, 2009
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
Differential Diagnoses
Other Problems to Be Considered
Table 1. Clinical Conditions Associated With Sepsis and Its Mimics
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Table
| Associated With Sepsis (Fevers ³ 102ºF) | Associated With Sepsis (Fevers £ 102ºF) |
|---|---|
Gastrointestinal tract source
| Gastrointestinal tract source
|
| Genitourinary tract source Pyelonephritis | Genitourinary tract source
|
Pelvic source
| Upper respiratory tract source
|
| Lower respiratory tract source Community-acquired pneumonia (with asplenia) | Lower respiratory tract source Community-acquired pneumonia (in an otherwise healthy host) |
| Intravascular source Intravenous-line sepsis | Skin/soft-tissue source Osteomyelitis |
Cardiovascular source
| Cardiovascular source
|
Central nervous system source
|
| Associated With Sepsis (Fevers ³ 102ºF) | Associated With Sepsis (Fevers £ 102ºF) |
|---|---|
Gastrointestinal tract source
| Gastrointestinal tract source
|
| Genitourinary tract source Pyelonephritis | Genitourinary tract source
|
Pelvic source
| Upper respiratory tract source
|
| Lower respiratory tract source Community-acquired pneumonia (with asplenia) | Lower respiratory tract source Community-acquired pneumonia (in an otherwise healthy host) |
| Intravascular source Intravenous-line sepsis | Skin/soft-tissue source Osteomyelitis |
Cardiovascular source
| Cardiovascular source
|
Central nervous system source
|
Adapted from: Cunha BA, Shea KW. Fever in the intensive care unit. Infect Dis Clin North Am. Mar 1996;10(1):185-209.1
Pseudosepsis
It is important to consider other causes or conditions that mimic the clinical and hemodynamic parameters of sepsis. The causes of pseudosepsis need identification because they require supportive, rather than antimicrobial, therapy. Pseudosepsis is a common cause of misdiagnosis in hospitalized patients, particularly in the emergency department and in medical and surgical intensive care units. The most common causes of pseudosepsis include the following:
- GI hemorrhage
- Pulmonary embolism
- Acute myocardial infarction (MI)
- Acute pancreatitis (edematous or hemorrhagic)
- Diuretic induced hypovolemia
- Relative adrenal insufficiency
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Table
| Clinical Presentations That Mimic Sepsis | Hemodynamic Parameters That Mimic Sepsis |
|---|---|
| Hemorrhage | Acute pancreatitis |
| Pulmonary embolism | Anaphylaxis |
| MI | Spinal cord injury |
| Pancreatitis | Adrenal insufficiency |
| Diabetic (abdominal crisis) ketoacidosis | |
| SLE flare with abdominal crisis | |
| Ventricular pseudoaneurysm | |
| Massive aspiration/atelectasis | |
| Systemic vasculitis | |
| Diuretic-induced hypovolemia |
| Clinical Presentations That Mimic Sepsis | Hemodynamic Parameters That Mimic Sepsis |
|---|---|
| Hemorrhage | Acute pancreatitis |
| Pulmonary embolism | Anaphylaxis |
| MI | Spinal cord injury |
| Pancreatitis | Adrenal insufficiency |
| Diabetic (abdominal crisis) ketoacidosis | |
| SLE flare with abdominal crisis | |
| Ventricular pseudoaneurysm | |
| Massive aspiration/atelectasis | |
| Systemic vasculitis | |
| Diuretic-induced hypovolemia |
Before embarking on a workup for sepsis or beginning empiric antibiotics, it is vital to first rule out the treatable causes of pseudosepsis early in the disease process. Patients with pseudosepsis may have fever, chills, leukocytosis, and a left shift, with or without hypotension. All causes of pseudosepsis produce Swan-Ganz catheter readings that are compatible with sepsis (eg, increased cardiac output, decreased peripheral resistance), which could misdirect the unwary clinician.
Table 3. Sepsis Syndrome Versus Sepsis
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Table
| Sepsis Syndrome: No Infection | Sepsis: Bacteremia From GI, GU, Pelvic, Intravenous Source | |
|---|---|---|
| Parameters |
| Proper ID/Process/Source Plus ³ 1 Microbiologic Abnormalities |
| Microbiologic | Positive buffy coat smear result or 2/3 or 3/3 positive blood cultures | |
| Hemodynamic |
| |
| LV|| dilatation | |
| Laboratory |
| ß WBC |
| ß PLTs¶ | |
| ||
| Negative blood cultures excluding contaminants |
| |
| Clinical |
|
|
| Sepsis Syndrome: No Infection | Sepsis: Bacteremia From GI, GU, Pelvic, Intravenous Source | |
|---|---|---|
| Parameters |
| Proper ID/Process/Source Plus ³ 1 Microbiologic Abnormalities |
| Microbiologic | Positive buffy coat smear result or 2/3 or 3/3 positive blood cultures | |
| Hemodynamic |
| |
| LV|| dilatation | |
| Laboratory |
| ß WBC |
| ß PLTs¶ | |
| ||
| Negative blood cultures excluding contaminants |
| |
| Clinical |
|
|
*Peripheral vascular disease
† Cardiac output
‡ Fibrin split products
§ Prothrombin time/partial thromboplastin time
|| Left ventricular
¶ Platelets
It is important to appreciate that otherwise healthy hosts with community-acquired pneumonia virtually never present with hypotension or sepsis. Patients with decreased or absent splenic function may present with overwhelming pneumococcal sepsis. If an otherwise healthy patient with community-acquired pneumonia presents with shock and all of the other causes of pseudosepsis are ruled out, then it must be assumed that the patient is a compromised host with impaired or absent splenic function.
Workup
Laboratory Studies
- Blood 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 diagnoses.
- 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 more frequently than an intra-abdominal source.
- A CBC count is usually not helpful because of the numerous conditions that mimic sepsis (eg, pseudosepsis) and that manifest as leukocytosis with variable degrees of a left shift. Leukocytosis with a left shift is a nonspecific diagnostic finding. It is as common in noninfection as in infection.
- Other
- Obtain a urine Gram stain, urinalysis, and urine culture if urosepsis is suspected.
- If central intravenous-line sepsis is suspected, remove the line and send the tip for semiquantitative bacterial culture. If the catheter-tip culture results are positive and demonstrate 15 or more colonies and if the catheter-tip isolate matches the blood-culture isolate, an infection associated with the central intravenous line is diagnosed.
- Obtain a buffy coat of the white cells from peripheral blood stained by acridine orange, or use the Gram method to demonstrate bacteria responsible for the bacteremia or septic process. While the yield is low, stained buffy coat smears, if positive, are the best rapid test available to demonstrate 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.
Imaging Studies
- Chest radiography is important to rule out pneumonia and diagnose other causes of pulmonary infiltrates, as follows:
- Pulmonary drug reactions
- Pulmonary emboli
- Pulmonary hemorrhage
- Primary or metastatic pulmonary neoplasms
- Lymphangitic spread of malignancies
- Large pleural effusions
- Pneumothorax
- Hydrothorax
- Fluid overload
- Congestive heart failure
- Acute MI
- Acute respiratory distress syndrome should suggest an intra-abdominal source (eg, acute pancreatitis).
- Ultrasonography
- Perform abdominal ultrasonography if biliary tract obstruction is suspected based on the clinical presentation.
- Sonograms in patients with cholecystitis may show a thickened gallbladder wall or biliary calculi but no dilatation of the common bile duct.
- Stones in the biliary tract are visible in patients with cholangitis, but the common bile duct is dilated.
- Abdominal ultrasonography is suboptimal for the detection of abscesses or perforated hollow organs.
- CT scan or MRI
- Use CT scan or MRI of the abdomen if a nonbiliary intra-abdominal source of infection is suspected based on the history or physical examination findings.
- CT scan and MRI are superior to ultrasonography in demonstrating all lesions except those related to the biliary tract.
- An abdominal CT or MRI scan is also helpful in delineating intrarenal and extrarenal pathology.
- Gallium or indium scan: These modalities have no place in the initial workup of sepsis, as patients with sepsis are acutely ill by definition, and rapid diagnostic tests (eg, CT scan or MRI of the abdomen, ultrasonography of the right upper quadrant) are time-critical, life-saving tools.
Other Tests
- ECG: Obtain an ECG and cardiac enzymes in patients in whom acute MI is likely. Remember that certain patients may present with a silent asymptomatic MI, which should be included in the differential diagnoses of otherwise unexplained fever, leukocytosis, and hypotension. Silent MIs are common in elderly patients and in those who have undergone recent abdominal or pelvic surgery. They are also common in individuals with alcoholism, diabetes, and uremic conditions.
Procedures
- Thoracentesis: Perform thoracentesis for diagnostic purposes in patients with substantial pleural effusion.
- Paracentesis: Perform paracentesis in patients with gross ascites.
- Swan-Ganz catheter
- Use data obtained via Swan-Ganz catheter to manage the fluid status of the patient and to assess left ventricular dysfunction in patients with acute MI.
- Do not use Swan-Ganz hemodynamic parameters to diagnose sepsis. While most patients with sepsis demonstrate an increased cardiac output with a low peripheral vascular resistance, the converse is not true. Most patients with Swan-Ganz readings compatible with sepsis without a definite intravenous abdominal or GU source do not have sepsis, but rather pseudosepsis, as described above (see Other Problems to Be Considered).
Histologic Findings
Sepsis does not cause diagnostic findings in various organs.
More on Sepsis, Bacterial |
| Overview: Sepsis, Bacterial |
 Differential Diagnoses & Workup: Sepsis, Bacterial |
| Treatment & Medication: Sepsis, Bacterial |
| Follow-up: Sepsis, Bacterial |
| References |
| Further Reading |
| « Previous Page | Next Page » |
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Keywords
sepsis, bacterial sepsis, urosepsis, septic shock, bacteremia, symptomatic bacteremia, septicemia, leukocytosis, pseudosepsis, bacteruria
