title: Postobstructive Pneumonia: An Underdescribed Syndrome.
abstract: BACKGROUND
  Postobstructive community-acquired pneumonia (PO-CAP) is relatively common in clinical practice. The clinical syndrome is poorly defined, and the role of infection as a cause of the infiltrate is uncertain. We prospectively studied patients with PO-CAP and compared them to a cohort of patients with bacterial community-acquired pneumonia (B-CAP).
  
  
  METHODS
  We prospectively studied patients hospitalized for CAP; 5.4% had PO-CAP, defined as a pulmonary infiltrate occurring distal to an obstructed bronchus. Sputum and blood cultures, viral polymerase chain reaction, urinary antigen tests, and serum procalcitonin (PCT) were done in nearly all cases. Clinical and laboratory characteristics of patients with PO-CAP were compared to those of patients with B-CAP.
  
  
  RESULTS
  In a 2-year period, we identified 30 patients with PO-CAP. Compared to patients with B-CAP, patients with PO-CAP had longer duration of symptoms (median, 14 vs 5 days;P< .001). Weight loss and cavitary lesions were more common (P< .01 for both comparisons) and leukocytosis was less common (P< .01) in patients with PO-CAP. A bacterial pathogen was implicated in only 3 (10%) PO-CAP cases. PCT was <0.25 ng/mL in 19 (63.3%) patients. Although no differences were observed in disease severity or rates of intensive care unit admissions, 30-day mortality was significantly higher in PO-CAP vs B-CAP (40.0% vs 11.7%;P< .01).
  
  
  CONCLUSIONS
  Although there is substantial overlap, PO-CAP is a clinical entity distinct from B-CAP; a bacterial cause was identified in only 10% of patients. Our study has important implications for the clinical recognition of patients with PO-CAP, the role of microorganisms as etiologic agents, and the use of antibiotic therapy.
authors.affiliation: Department of Medicine, Massachusetts General Hospital Harvard Medical School, Boston, Massachusetts.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Abers
authors.affiliation: Department of Head and Neck Surgery, Kaiser Permanente Medical Center, Oakland, California.
authors.forename: Barcleigh P
authors.initials: BP
authors.lastname: Sandvall
authors.affiliation: Division of Infectious Diseases, Mayo Clinic, Rochester, Minnesota.
authors.forename: Rahul
authors.initials: R
authors.lastname: Sampath
authors.affiliation: Medical Care Line (Infectious Disease Section), Michael E. DeBakey Veterans Affairs Medical Center Department of Medicine and Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas.
authors.forename: Carlo
authors.initials: C
authors.lastname: Zuno
authors.affiliation: Medical Care Line (Infectious Disease Section), Michael E. DeBakey Veterans Affairs Medical Center Department of Medicine and Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas.
authors.forename: Natalie
authors.initials: N
authors.lastname: Uy
authors.affiliation: Department of Medicine, University of Pittsburgh, Pennsylvania.
authors.forename: Victor L
authors.initials: VL
authors.lastname: Yu
authors.affiliation: Medical Care Line (Infectious Disease Section), Michael E. DeBakey Veterans Affairs Medical Center Department of Medicine and Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas.
authors.forename: Charles E
authors.initials: CE
authors.lastname: Stager
authors.affiliation: Medical Care Line (Infectious Disease Section), Michael E. DeBakey Veterans Affairs Medical Center Department of Medicine and Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Musher
mesh_terms: D000368:Aged; D000818:Animals; D002116:Calcitonin / Q000097:blood; D017714:Community-Acquired Infections / Q000175:diagnosis / Q000382:microbiology / Q000401:mortality / Q000821:virology; D005260:Female; D006760:Hospitalization; D006801:Humans; D007362:Intensive Care Units; D008173:Lung Diseases, Obstructive / Q000150:complications* / Q000382:microbiology; D008297:Male; D008875:Middle Aged; D011014:Pneumonia / Q000175:diagnosis* / Q000209:etiology / Q000401:mortality; D018410:Pneumonia, Bacterial / Q000175:diagnosis*; D011379:Prognosis; D011446:Prospective Studies; D011498:Protein Precursors; D013577:Syndrome
chemical_list: D011498:Protein Precursors; D002116:Calcitonin
keywords: community-acquired pneumonia; pneumonia; postobstructive pneumonia