Lung - nontumor
Other nonneoplastic disease
ARDS / diffuse alveolar damage (DAD)

Author: Elliot Weisenberg, M.D. (see Authors page)

Revised: 9 March 2017, last major update October 2011

Copyright: (c) 2003-2017,, Inc.

PubMed search: Diffuse alveolar damage [title] (DAD)

Related topics: Acute fibrinous and organizing pneumonia

Cite this page: ARDS / diffuse alveolar damage (DAD). website. Accessed August 20th, 2017.
Definition / general
  • Also called adult respiratory distress syndrome, acute lung injury and noncardiogenic pulmonary edema
  • Note: disease in absence of known cause is acute interstitial pneumonia (AIP)
  • Rapid onset of severe, life threatening respiratory insufficiency, cyanosis, severe arterial hypoxemia refractory to oxygen therapy; usually with severe pulmonary edema and diffuse alveolar infiltration on xray
  • Causes: sepsis, aspiration, diffuse pulmonary infections (viral, mycoplasma, Pneumocystis, tuberculosis), mechanical trauma, surfactant deficiency in newborns or near drowning; also other injury, inhaled irritants, chemical injury, radiation, amiodarone, chemotherapy, acute pancreatitis, burns or uremia
Pathophysiology / etiology
  • Pathophysiology: due to final common pathway of diffuse damage to alveolar capillary walls in both lungs
  • Capillary defect in adults attracts white blood cells and cytokines, which further damage endothelium; may be due to endotoxin
  • Nitric oxide (vasodilator) decreases pulmonary vascular resistance and reduces ventilation-perfusion mismatch
  • Supportive care
  • Aggressively treat underlying pathology if possible (infection, pancreatitis, etc.)
  • Mortality now 40%, down from 60%; 190,000 cases and 75,000 - 80,000 deaths per year in US
Gross description
  • Heavy, firm, red and boggy lung
Gross images

Images hosted on other servers:

Congestive phase

Microscopic (histologic) description
  • Congestion and hemorrhage, interstitial and intra-alveolar edema, fibrin deposition, hyaline membranes (composed of edema fluid and cellular debris), type II pneumocyte proliferation with atypia, mitotic activity, cytoplasmic hyaline bodies and intracytoplasmic lipid, intra-arterial thrombosis and bronchiolitis obliterans
  • Minimal chronic inflammatory infiltrate
  • May have extensive squamous metaplasia with atypia simulating squamous cell carcinoma (Hum Pathol 2002;33:1052)
  • Early phase is exudative, later phase is organizing with fibrin, intra-alveolar fibrosis
  • May have superimposed pneumonia
Microscopic (histologic) images

Images hosted on other servers:

In immature lung

Hyaline membranes

Differential diagnosis
  • Pneumocystic carinii