- Decreased or absent air in the entire or part of a lung, with resulting loss of lung volume. Loss of lung volume itself. SEE ALSO: pulmonary collapse. [G. ateles, incomplete, + ektasis, extension]- adhesive a. alveolar collapse in the presence of patent airways, especially when surfactant is inactivated or absent, especially in respiratory distress syndrome of the newborn, acute radiation pneumonitis, or viral pneumonia. SYN: microatelectasis, nonobstructive a..- cicatrization a. 1. the decrease in air per unit lung volume due to fibrosis, causing decreased lung compliance, and increased tissue. 2. a. due to scarring or pulmonary fibrosis.- a. of the middle ear reduction in the volume of the middle ear because of eustachian tube obstruction followed by absorption of the oxygen in the middle ear and subsequent retraction of the tympanic membrane medially.- nonobstructive a. SYN: adhesive a..- passive a. the pulmonary collapse that occurs due to a space-occupying intrathoracic process such as pneumothorax or hydrothorax. SYN: relaxation a..- platelike a. SYN: subsegmental a..- primary a. nonexpansion of the lungs after birth, found in all stillborn infants and in liveborn infants who die before respiration is established.- resorption a. the slow partial collapse of a lobe that occurs when communication between alveoli and trachea is obstructed.- rounded a. an area of atelectatic lung caused by parenchymal infolding due to pleural fibrosis, most often from asbestos exposure; appears as a masslike opacity and can be mistaken for lung cancer; may be associated with a comet tail sign; high level of contrast enhancement on dynamic computed tomography aids diagnosis. SYN: folded-lung syndrome.- secondary a. pulmonary collapse at any age, but particularly of infants, due to hyaline membrane disease or elastic recoil of the lungs while dying from other causes.- subsegmental a. collapse of the portion of the lung distal to an obstructed subsegmental bronchus, manifested as a linear opacity on a chest radiograph. See Fleischner lines, under line. SYN: platelike a..
* * *at·el·ec·ta·sis .at-əl-'ek-tə-səs n, pl -ta·ses -.sēz collapse of the expanded lung also defective expansion of the pulmonary alveoli at birthat·el·ec·tat·ic -ek-'tat-ik adj
* * *n.failure of part of the lung to expand. This occurs when the cells lining the air sacs (alveoli) are too immature, as in premature babies, and unable to produce the wetting agent (surfactant) with which the surface tension between the alveolar walls is overcome. It also occurs when the larger bronchial tubes are blocked from within by retained secretions, inhaled foreign bodies, or bronchial cancers, or from without by enlarged lymph nodes, such as are found in patients with tuberculosis and lung cancers. The lung can usually be helped to expand by physiotherapy and removal of the internal block (if present) via a bronchoscope, but prolonged atelectasis becomes irreversible.
* * *at·e·lec·ta·sis (at″ə-lekґtə-sis) [atel- + -ectasis] 1. incomplete expansion of a lung or a portion of a lung; it may be a primary (congenital), secondary, or otherwise acquired condition. 2. airlessness or collapse of a lung that had once been expanded. 3. absence of air in a normally air-filled space such as the middle ear. atelectatic adj
Right lower lobe atelectasis. Complete collapse of the right lower lobe with volume loss evidenced by shift of the trachea and cardiac border to the right side (black arrows). Air in the right lower lobe has been resorbed, resulting in a diffuse infiltrate (white arrows).
Medical dictionary. 2011.