- On 7/25 Dr. Yu presented an terrific case. Patient presented with of 5-7 days of fever, cough, and loose stools. As the case developed, it became clear the diagnosis was legionella pneumiona.
Teaching Points
- During our diagnostic evaluation, we discussed the importance of physical exam. A fantastic resource at your disposal is NEJM's Review Article, Fundamentals of Lung Auscultation.
->Check it out: https://www.nejm.org/doi/full/10.1056/NEJMra1302901
- We reviewed common radiographic chest X-ray signs consistent with consolidation including the silhouette sign and spine sign.
-> Silhouette Sign: If two objects of the same radiographic density touch each other then the edges between them disappear. This can help to localize an area of consolidation (i.e loss of left diaphragm is suggestive of left lower lobe consolidation).
-> Spine Sign: Normally, the thoracic spine gets darker as you move down the lateral chest x-ray. If there is an area of increased radio-density as you move down the spine, consider consolidation in that area.
-> Read more at: https://radiopaedia.org/articles/silhouette-sign-x-rays?lang=us AND https://radiopaedia.org/articles/more-black-sign?lang=us
- We discussed the CURB-65 tool as a quick, easy, and validated score to triage outpatient vs inpatient management of pneumonia.
- We reviewed community acquired pneumonia vs hospital acquired pneumonia diagnostic criteria. Making this differentiation is important as it affects antibiotic selection.
- We reviewed the common features of legionella pneumonia...
-> Facultative gram negative bacilla. 15 serogroups, serogroup 1 is most common (85%).
-> Transmitted via aerosols from water or soil.
-> Commonly associated with nausea, vomiting, diarrhea, hyponatremia, mild transaminitis, and failure to respond to B-lactam therapy.
-> Gold standard for diagnosis is sputum culture, although Dr. Figueroa Castro pointed out that a regular sputum culture will not grow legionella. You need to request the lab to use a buffered charcoal yeast extract (BCYE) agar.
-> In clinical practice, we more commonly use PCR from the respiratory tract or urine legionella Ag to diagnose legionella. Remember the urine antigen test only identifies serogroup 1
- Finally, I wanted to go over diagnostic testing for pneumonia but we didn't have time to cover. Check out this helpful table from the IDSA pneumonia guidelines on how to workup our presumed pneumonia cases.
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