Lung abscess laboratory findings
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]
Overview
Diagnosis of lung abscess is made based on clinical symptoms, physical examination, radiographic studies and bacterial culture. Laboratory findings include increased acute phase reactants (ESR and CRP) levels and leukocytosis with consolidation on lung x-ray. Blood cultures should be performed in all suspected cases.
Laboratory Findings
CBC and CXR should be part of the initial evaluation of all patients with a suspected lung abscess.
CBC
- Pronounced leukocytosis (usually >15,000 WBC/microliter) is often present.
- Anemia of chronic disease is present with chronic abscesses.
- Raised inflammatory markers ( high ESR, CRP) are usual but not specific.
Chest X-ray
- Consolidation is evident in a segmental or lobar distribution with central cavitation and an air-fluid level.
- The cavity wall is typically thick and irregular.
Microbial testing
- To identify the etiologic agent and to initiate appropriate antibiotic therapy.
- When patients present with typical symptoms of fever with chills, cough with purulent sputum for more than 2 weeks and with risk factors of aspiration it is appropriate to suspect anaerobes as a possible pathogen.[1]
- Sputum, blood, empyema and lower respiratory secretions are generally collected for microbial testing.
- Cultures of the sputum for anaerobic bacteria is not recommended because of its contamination by the normal flora in the oral cavity and long wait time for culture to grow. The only cultures that can give a positive result for anaerobes is empyema.
- It is often difficult to get uncontaminated sputum specimens as both upper respiratory tract and the lower respiratory tract along oral cavity is contaminated with various flora.
- The only methods available for obtaining uncontaminated specimens are trans-tracheal aspirates (TTA), transthoracic needle aspirates (TTNA), culture of pleural fluid, or blood cultures are recommended before administration of empiric antibiotics.
- Sputum analysis and culture is recommended for finding out aerobic and other causative agents of lung abscess.The contamination of the sputum sample can be minimized by
- Obtaining the sputum sample prior to antibiotic treatment.[2]
- Rinsing the mouth prior to expectoration
- NPO for one to two hours prior to expectoration
- Inoculation of the culture media immediately after the specimen is obtained
- All patients should undergo routine blood cultures.
- Interpretation of sputum cultures in these cases must take into account the clinical features of the patient, concentrations of the different organisms found in the culture and Gram stain, and the antibiotics the patient has received.
| Sputum Analysis | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Acid Fast Stain | Culture on Sabourad's medium | Direct Microscopic Examination for sulphur granules | Gentain Voilet Stain | Aerobic Culture | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Tuberculosis | Yeast and Fungi | Actinomyces and other mycelia of Fungi | Fusiform Bacteria and Spirochetes | Pyogenic organsims | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
- Fibre optic bronchoscopy is often performed to exclude obstructive lesion; it also helps in the bronchial drainage of pus.
Reference
- ↑ Bartlett JG (1977). "Diagnostic accuracy of transtracheal aspiration bacteriologic studies". Am. Rev. Respir. Dis. 115 (5): 777–82. doi:10.1164/arrd.1977.115.5.777. PMID 857717.
- ↑ Bartlett JG, Mundy LM (1995). "Community-acquired pneumonia". N. Engl. J. Med. 333 (24): 1618–24. doi:10.1056/NEJM199512143332408. PMID 7477199.