eMedicine Specialties > Pulmonology > Aspiration and Atelectasis

Pneumonia, Aspiration: Differential Diagnoses & Workup

Author: Anita B Varkey, MD, Assistant Professor, Department of Medicine, Loyola University Medical Center; Associate Program Director, Internal Medicine Residency; Medical Director, General Internal Medicine Clinic, Loyola Outpatient Center
Coauthor(s): Basil Varkey, MD, FCCP, Professor, Department of Internal Medicine, Division of Pulmonary and Critical Care, Medical College of Wisconsin; Consulting Pulmonologist, Froedtert Memorial Lutheran Hospital
Contributor Information and Disclosures

Updated: Aug 7, 2009

Differential Diagnoses

Acute Respiratory Distress Syndrome
Lung Abscess
Tuberculosis

Other Problems to Be Considered

Necrotizing pneumonia
Bronchopleural fistula
Lung carcinoma
Mycoses

Workup

Laboratory Studies

  • Arterial blood gas demonstrates acute hypoxemia in patients with chemical pneumonia (CP) and normal-to-low partial pressure of carbon dioxide with respiratory alkalosis.
  • CBC count may reveal an elevated WBC count, increased neutrophils, anemia, and thrombocytosis in patients with bacterial pneumonia (BP) caused by anaerobic bacteria.
  • Elevated WBC count and increased neutrophils may be present in patients with CP.
  • Sputum Gram stain and microscopy reveal a multitude of bacteria (eg, cocci, bacilli, coccobacillary forms, spirochetes, fusiforms) in patients with BP caused by anaerobic bacteria. Findings on sputum culture may not isolate organisms because the major pathogens are anaerobes.
  • In nosocomial BP, sputum culture may be helpful in detecting gram-negative bacteria.

Imaging Studies

  • Chest radiographic findings in patients with CP are characterized by the presence of infiltrates, predominantly the alveolar type, in one or both lower lobes or diffuse simulation of the appearance of pulmonary edema. Volume loss in any lobar area suggests obstruction (eg, by aspirated food particles or other foreign bodies) in the bronchus.
  • Chest radiographic findings in patients with anaerobic BP typically demonstrate an infiltrate with or without cavitation in one of the dependent segments of the lungs (ie, posterior segments of the upper lobes, superior segments of the lower lobes). Lucency within the infiltrate suggests a necrotizing pneumonia. Air-fluid level within a circumscribed infiltrate (density) indicates a lung abscess or a bronchopleural fistula. Costophrenic angle blunting and the presence of a meniscus are signs of a para-pneumonic pleural effusion.
  • Ultrasonography is helpful when confirming and locating pleural effusion.
  • CT scan of the chest is not needed in all cases. CT scan is helpful in detecting necrosis within infiltrates, cavities, and loculated pleural effusions. CT scan provides a better definition of the affected areas and is used to differentiate pulmonary abnormalities from pleural abnormalities.

Procedures

  • Bronchoscopy is indicated in patients with CP only when aspiration of a foreign body or food material is suspected.
  • Transtracheal aspiration (TTA) is useful in obtaining a sputum specimen for anaerobic culture because it bypasses the mouth flora. However, this procedure has now been supplanted by bronchoscopy and use of a protected catheter to retrieve pathogens in BP.
  • Bronchoscopy is useful when ruling out the presence of an obstructing neoplasm in anaerobic BP with lung abscess.
  • Pulmonary artery catheter placement may be needed to differentiate cardiac from noncardiac pulmonary edema caused by CP and for appropriate fluid management.
  • Mechanical ventilation is needed in severe cases of CP that cause ARDS.

More on Pneumonia, Aspiration

Overview: Pneumonia, Aspiration
Differential Diagnoses & Workup: Pneumonia, Aspiration
Treatment & Medication: Pneumonia, Aspiration
Follow-up: Pneumonia, Aspiration
Multimedia: Pneumonia, Aspiration
References
Further Reading
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References

  1. Mendelson CL. The aspiration of stomach contents into the lungs during obstetric anesthesia. Am J Obstet Gynecol. 1946;52:191.

  2. [Guideline] Coffin SE, Klompas M, Classen D, Arias KM, Podgorny K, Anderson DJ, et al. Strategies to prevent ventilator-associated pneumonia in acute care hospitals. Infect Control Hosp Epidemiol. Oct 2008;29 Suppl 1:S31-40. [Medline].

  3. [Guideline] Tablan OC, Anderson LJ, Besser R, Bridges C, Hajjeh R. Guidelines for preventing health-care--associated pneumonia, 2003: recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee. MMWR Recomm Rep. Mar 26 2004;53:1-36. [Medline].

  4. American Thoracic Society. Hospital-acquired pneumonia in adults: diagnosis, assessment of severity, initial antimicrobial therapy, and preventive strategies. A consensus statement, American Thoracic Society, November 1995. Am J Respir Crit Care Med. May 1996;153(5):1711-25. [Medline].

  5. Bartlett JG. Anaerobic bacterial infections of the lung and pleural space. Clin Infect Dis. Jun 1993;16 Suppl 4:S248-55. [Medline].

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  11. LaForce FM. Hospital-acquired gram-negative rod pneumonias: an overview. Am J Med. Mar 1981;70(3):664-9. [Medline].

  12. Levison ME, Mangura CT, Lorber B. Clindamycin compared with penicillin for the treatment of anaerobic lung abscess. Ann Intern Med. Apr 1983;98(4):466-71. [Medline].

  13. Marik PE. Aspiration pneumonitis and aspiration pneumonia. N Engl J Med. Mar 1 2001;344(9):665-71. [Medline].

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  15. Matthay MA, Rosen GD. Acid aspiration induced lung injury. New insights and therapeutic options. Am J Respir Crit Care Med. Aug 1996;154(2 Pt 1):277-8. [Medline].

  16. Sullivan RJ Jr, Dowdle WR, Marine WM. Adult pneumonia in a general hospital. Etiology and host risk factors. Arch Intern Med. Jun 1972;129(6):935-42. [Medline].

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  18. van Westerloo DJ, Knapp S, van't Veer C, Buurman WA, de Vos AF, Florquin S. Aspiration pneumonitis primes the host for an exaggerated inflammatory response during pneumonia. Crit Care Med. Aug 2005;33(8):1770-8. [Medline].

  19. Varkey B, Kutty K. Pulmonary aspiration syndromes. In: Kochar's Concise Textbook of Medicine. Baltimore, Md:. Lippincott Williams & Wilkins;1998:902-906.

  20. Wynne JW, Ramphal R, Hood CI. Tracheal mucosal damage after aspiration. A scanning electron Microscope study. Am Rev Respir Dis. Dec 1981;124(6):728-32. [Medline].

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Further Reading

Clinical guidelines

Coffin SE, Klompas M, Classen D, Arias KM, Podgorny K, Anderson DJ, Burstin H, Calfee DP, Dubberke ER, Fraser V, Gerding DN, Griffin FA, Gross P, Kaye KS, Lo E, Marschall J, Mermel LA, Nicolle L, Pegues DA, Perl TM, Saint S, Salgado CD, Weinstein RA, Wise R, Yokoe DS. Strategies to prevent ventilator-associated pneumonia in acute care hospitals. Infect Control Hosp Epidemiol 2008 Oct;29 Suppl 1:S31-40. 2

Tablan OC, Anderson LJ, Besser R, Bridges C, Hajjeh R. Guidelines for preventing health-care--associated pneumonia, 2003: recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee. MMWR Recomm Rep 2004 Mar 26;53(RR-3):1-36. 3

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Keywords

aspiration pneumonia, Mendelson syndrome, chemical pneumonitis, anaerobic bacterial pneumonia, chemical pneumonia, CP, aspiration of gastric acid, bacterial pneumonia, BP, aspiration of bacteria from oral and pharyngeal areas, exogenous lipoid pneumonia, aspiration of oil, aspiration of a foreign body, acute respiratory emergency, parenchymal inflammatory reaction, community-acquired pneumonia, CAP, nosocomial pneumonia, acute respiratory distress syndrome, ARDS

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Contributor Information and Disclosures

Author

Anita B Varkey, MD, Assistant Professor, Department of Medicine, Loyola University Medical Center; Associate Program Director, Internal Medicine Residency; Medical Director, General Internal Medicine Clinic, Loyola Outpatient Center
Anita B Varkey, MD is a member of the following medical societies: American College of Physicians and Society of General Internal Medicine
Disclosure: Nothing to disclose.

Coauthor(s)

Basil Varkey, MD, FCCP, Professor, Department of Internal Medicine, Division of Pulmonary and Critical Care, Medical College of Wisconsin; Consulting Pulmonologist, Froedtert Memorial Lutheran Hospital
Basil Varkey, MD, FCCP is a member of the following medical societies: American Association of Physicians of Indian Origin, American College of Chest Physicians, American Federation for Clinical Research, American Thoracic Society, and Royal College of Physicians
Disclosure: Nothing to disclose.

Medical Editor

Laurie Robin Grier, MD, Medical Director of MICU, Associate Professor of Medicine, Section of Pulmonary and Critical Care Medicine, Louisiana State University Health Science Center at Shreveport
Laurie Robin Grier, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, American Society for Parenteral and Enteral Nutrition, and Society of Critical Care Medicine
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

,, Kathy Roarty Placeholder
Disclosure: Nothing to disclose.

CME Editor

Timothy D Rice, MD, Associate Professor, Departments of Internal Medicine and Pediatrics and Adolescent Medicine, Saint Louis University School of Medicine
Timothy D Rice, MD is a member of the following medical societies: American Academy of Pediatrics and American College of Physicians
Disclosure: Nothing to disclose.

Chief Editor

Zab Mosenifar, MD, Director, Division of Pulmonary and Critical Care Medicine, Director, Women's Guild Pulmonary Disease Institute, Executive Vice Chair, Department of Medicine, Cedars Sinai Medical Center; Professor of Medicine, David Geffen School of Medicine at UCLA
Zab Mosenifar, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, American Federation for Medical Research, and American Thoracic Society
Disclosure: Nothing to disclose.

 
 
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