eMedicine Specialties > Emergency Medicine > Infectious Diseases

Legionnaires Disease: Differential Diagnoses & Workup

Author: Frank C Smeeks lll, MD, Chief Medical Officer, Frye Regional Medical Center
Contributor Information and Disclosures

Updated: Jun 1, 2009

Differential Diagnoses

Bronchitis
Pneumonia, Bacterial
CBRNE - Q Fever
Pneumonia, Empyema and Abscess
Congestive Heart Failure and Pulmonary Edema
Pneumonia, Immunocompromised
Costochondritis
Pneumonia, Mycoplasma
Gastroenteritis
Pneumonia, Viral
HIV Infection and AIDS
Prostatitis
Meningitis
Respiratory Distress Syndrome, Adult
Pleural Effusion
Shock, Septic
Pneumonia, Aspiration

Workup

Laboratory Studies

  • CBC: Look for leukocytosis, left shift, hematologic malignancy, and disseminated intravascular coagulation (DIC).
  • Electrolytes: Look for hyponatremia, since syndrome of inappropriate secretion of antidiuretic hormone (SIADH) has been associated with this disease.
  • BUN and creatinine: Look for renal failure and dehydration.
  • Liver function tests (LFTs): Look for nonspecific LFT abnormalities, which are very common in this disease and may help distinguish Legionnaires disease from other pneumonias.
  • Alkaline phosphatase: Look for nonspecific depression, which along with LFT abnormalities is very common.
  • Creatine phosphokinase: Look for elevation indicating rhabdomyolysis, which occasionally is seen in Legionnaires disease. The rhabdomyolysis may be so severe as to cause renal failure.
  • Urinalysis: Look for proteinuria, hematuria, and renal failure.
  • Sputum Gram stain: Look for increased polymorphonuclear leukocytes and monocytes without bacteria.
  • Sputum and blood cultures: Although no findings will return to the ED, this will assist consultants caring for the patient. Respiratory culture specifically for Legionella (buffered charcoal yeast extract agar [BCYE]) may be indicated.
  • ABG: Look for hypoxemia.
  • Polymerase chain reaction (PCR) testing has been used in the past, although its role in current diagnosis and practice has yet to be established
  • Serology for Legionella species: Several tests are available.
    • Acute and convalescent sera (at 8-12 wk) demonstrating a 4-fold increase in titer to >1/128 must be present for serological diagnosis.
    • Urine antigen testing is highly specific and sensitive and, if available within the treatment facility, very rapid.
    • Indirect fluorescent antibody testing and nucleic acid hybridization testing also may be available.
    • Direct fluorescent antibody examination has fallen out of favor.

Imaging Studies

  • Chest radiography
    • Legionella infection almost always produces an abnormal chest radiographic finding, but abnormality is variable and may be focal or diffuse.
    • Up to 50% of patients have a pleural effusion.
    • Chest radiography is not a specific test for Legionnaires disease.
    • Chest radiograph often shows patchy alveolar infiltrates with consolidation in the lower lobe (although all lobes may be affected).
    • It may take 1-4 months for the chest radiographic finding to return to normal.
    • Progression of the infiltrate may be seen despite antibiotic therapy.  
  • Noncontrast head CT scan
    • This is indicated for patients with altered mental status.
    • Findings should be normal in Legionnaires disease.

Other Tests

  • Silver and Gimenez stains for lung tissue/specimens

Procedures

  • Lumbar puncture: This procedure is indicated for patients with altered mental status. In uncomplicated Legionnaires disease, the cerebrospinal fluid (CSF) findings are generally normal.
  • Bronchoscopy with or without bronchoalveolar lavage (BAL) may be helpful in establishing or excluding the diagnosis if respiratory culture specimens are difficult to obtain.

More on Legionnaires Disease

Overview: Legionnaires Disease
Differential Diagnoses & Workup: Legionnaires Disease
Treatment & Medication: Legionnaires Disease
Follow-up: Legionnaires Disease
Multimedia: Legionnaires Disease
References
Further Reading
[ CLOSE WINDOW ]

References

  1. CDC. Summary of notifiable diseases, United States 1995. MMWR Morb Mortal Wkly Rep. Oct 25 1996;44(53):1-87. [Medline].

  2. [Guideline] Mandell LA, Wunderink RG, Anzueto A, Bartlett JG, Campbell GD, Dean NC, et al. Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults. Clin Infect Dis. Mar 1 2007;44 Suppl 2:S27-72. [Medline].

  3. Amsden GW. Treatment of Legionnaires' disease. Drugs. 2005;65(5):605-14. [Medline].

  4. Blanquer J, Blanquer R, Borras R, et al. Aetiology of community acquired pneumonia in Valencia, Spain: a multicentre prospective study. Thorax. Jul 1991;46(7):508-11. [Medline].

  5. CDC. Legionnaires disease associated with a whirlpool spa display--Virginia, September-October, 1996. MMWR Morb Mortal Wkly Rep. Jan 31 1997;46(4):83-6. [Medline].

  6. Cunna B. Legionnaire's disease - Case studies in infectious disease. Emerg Med. 1992;24:227-234.

  7. Falco V, Fernandez de Sevilla T, Alegre J, Ferrer A, Martinez Vazquez JM. Legionella pneumophila. A cause of severe community-acquired pneumonia. Chest. Oct 1991;100(4):1007-11. [Medline].

  8. Lane G, Ferrari A, Dreher HM. Legionnaire's disease: a current update. Medsurg Nurs. Dec 2004;13(6):409-14. [Medline].

  9. Marrie TJ, Haldane EV, Noble MA, Faulkner RS, Martin RS, Lee SH. Causes of atypical pneumonia: results of a 1-year prospective study. Can Med Assoc J. Nov 15 1981;125(10):1118-23. [Medline].

  10. Marston BJ, Lipman HB, Breiman RF. Surveillance for Legionnaires' disease. Risk factors for morbidity and mortality. Arch Intern Med. Nov 14 1994;154(21):2417-22. [Medline].

  11. Palmer L. Legionella pneumonia - Cardiopulmonary problems in the office. Emerg Med. 1992;24:84-94.

  12. Reingold AL. Role of legionellae in acute infections of the lower respiratory tract. Rev Infect Dis. Sep-Oct 1988;10(5):1018-28. [Medline].

  13. Shah A, Check F, Baskin S, Reyman T, Menard R. Legionnaires' disease and acute renal failure: case report and review. Clin Infect Dis. Jan 1992;14(1):204-7. [Medline].

[ CLOSE WINDOW ]

Further Reading

Other resources

Legionellosis Resource Center

Clinical guidelines

Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults. Mandell LA, Wunderink RG, Anzueto A, Bartlett JG, Campbell GD, Dean NC, Dowell SF, File TM Jr, Musher DM, Niederman MS, Torres A, Whitney CG. Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults. Clin Infect Dis 2007 Mar 1;44 Suppl 2:S27-72. [335 references] PubMed

[ CLOSE WINDOW ]

Keywords

Legionnaires disease, Legionnaires' disease, Legionella pneumophila, L pneumophila, atypical pneumonia, pulmonary infection, Pontiac fever, community-acquired bacterial pneumonia, CAP

[ CLOSE WINDOW ]

Contributor Information and Disclosures

Author

Frank C Smeeks lll, MD, Chief Medical Officer, Frye Regional Medical Center
Frank C Smeeks lll, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Emergency Physicians, American College of Physician Executives, American Medical Association, and North Carolina Medical Society
Disclosure: Nothing to disclose.

Medical Editor

Eric M Kardon, MD, FACEP, Attending Emergency Physician, Georgia Emergency Medicine Specialists; Physician, Division of Emergency Medicine, Athens Regional Medical Center
Eric M Kardon, MD, FACEP is a member of the following medical societies: American College of Emergency Physicians
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Jeter (Jay) Pritchard Taylor III, MD, Compliance Officer, Attending Physician, Emergency Medicine Residency, Department of Emergency Medicine, Palmetto Health Richland, University of South Carolina; Medical Director, Department of Emergency Medicine, Palmetto Health Baptist
Jeter (Jay) Pritchard Taylor III, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

CME Editor

John D Halamka, MD, MS, Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center
John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Chief Editor

Rick Kulkarni, MD, Medical Director, Assistant Professor of Surgery, Section of Emergency Medicine, Yale-New Haven Hospital
Rick Kulkarni, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine
Disclosure: WebMD Salary Employment

 
 
HONcode

We subscribe to the
HONcode principles of the
Health On the Net Foundation

All material on this website is protected by copyright, Copyright© 1994- by Medscape.
This website also contains material copyrighted by 3rd parties.

DISCLAIMER: The content of this Website is not influenced by sponsors. The site is designed primarily for use by qualified physicians and other medical professionals. The information contained herein should NOT be used as a substitute for the advice of an appropriately qualified and licensed physician or other health care provider. The information provided here is for educational and informational purposes only. In no way should it be considered as offering medical advice. Please check with a physician if you suspect you are ill.