Aspiration pneumonia is bronchopneumonia that develops due to the entrance of foreign materials into the bronchial tree, usually oral or gastric contents (including food, saliva, or nasal secretions). Depending on the acidity of the aspirate, a chemical pneumonitis can develop, and bacterial pathogens (particularly anaerobic bacteria) may add to the inflammation.
The location is often gravity dependent, and depends on the patient position. Generally, the right middle and lower lung lobes are the most common sites of infiltrate formation due to the larger caliber and more vertical orientation of the right mainstem bronchus. Patients who aspirate while standing can have bilateral lower lung lobe infiltrates. The right upper lobe is a common area of consolidation in alcoholics who aspirate in the prone position.
Aspiration pneumonia is typically diagnosed by a combination of clinical circumstances (debilitated or neurologically impaired patient), radiologic findings (right lower lobe pneumonia) and microbiologic cultures. Some cases of aspiration pneumonia are caused by aspiration of food particles or other particulate substances like pill fragments; these can be diagnosed by pathologists on lung biopsy specimens.
^Oliver, N.M., Stukenborg, G.J., Wagner, D.P., Harrell, F.E., Kilbirdge, K.L., Lyman, J.A., Einbinder, J., & Connors, A.F. (2004). Ethnicity on In-Hospital Mortality from Aspiration Pneumonia. Journal of the National Medical Association, 96(11), 1462-1469.
^Scannapieco, F.A., Mylotte, J.M. (1996). Relationship between periodontal disease and bacterial pneumonia. Journal of Periodontal, 67, supple 10, 1114-1122.
^van der Maarek-Wierink, C.D., Vanobbergen, J.N., Bronkhorst, E.M., Schols, J.M., & de Baat, C., (2011). Risk factors for aspiration pneumonia in frail older people: a systematic literature review. Journal of American Medical Directors Association, 12(5), 344-354.
^Taylor, G.W., Loesche, W.J., & Terpenning, M.S. (2000). Impact of Oral Diseases on Systemic Health in the Elderly: Diabetes Mellitus and Aspiration Pneumonia. Journal of Public Health Dentistry, 60(4), 313-320
^ abcdTable 13-7 in: Mitchell, Richard Sheppard; Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson. Robbins Basic Pathology: With STUDENT CONSULT Online Access. Philadelphia: Saunders. ISBN1-4160-2973-7. 8th edition.
^Mukhopadhyay S, Katzenstein AL (2007). "Pulmonary disease due to aspiration of food and other particulate matter: a clinicopathologic study of 59 cases diagnosed on biopsy or resection specimens.". American Journal of Surgical Pathology31 (5): 752–759. doi:10.1097/01.pas.0000213418.08009.f9. PMID17460460.