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INTRODUCTION TO ABNORMAL DEVELOPMENT OF THE RESPIRATORY TRACT

Learning Objectives

  • The student will be able to describe the anatomical and/or physiological abnormalities underlying major congenital malformations of the lungs.

  • The student will be able to identify useful indices of pulmonary function to assess severity of impairment based upon a history and description of the patient.

  • The student will be able to tabulate the relative values of the history, physical exam, bronchoscopy, and imaging modalities to establish the likelihood of specific anomalies at different locations within the respiratory system.

Accurate and timely identification of congenital anomalies often makes the difference between an infant's survival and death. Such respiratory system defects also illustrate how physicians must carefully choose among many diagnostic modalities available to most effectively and appropriately arrive at a diagnosis and treatment plan. History obtained from caregivers, and a physical exam tailored to the very young patient (Chap. 14), often only point to the need for more advanced diagnostic procedures. While direct visualization is possible with some lesions, diagnostic imaging is often essential. Each diagnostic modality carries with it a unique risk/benefit assessment. Radiography can be helpful, particularly when contrast studies are feasible (Chap. 15), but the latter creates risks of aspiration injuries. Endoscopy or bronchoscopy are often the definitive modalities in specific anatomical regions, notably in the trachea and upper airways (Chap. 18), but these may not be necessary before an operative assessment and intervention. Marked advances in computerized imaging such as CT have led to improved diagnostic accuracy of lesions found at all levels of the respiratory tract. They are most useful in delineating the scope of suspected parenchymal anomalies (Chap. 15), including those in which the traditional boundaries between the conducting and respiratory zones are blurred by the presence of unanticipated structures. Throughout this chapter, the relative values of these diagnostic tests will be emphasized for each type of anatomical deviation from the normal pattern of lung development.

CONGENITAL DEFECTS OF THE LARYNX

Suspicions regarding defective laryngeal anatomy often arise during the physical exam with stridor, chest retractions, and respiratory distress readily visible. Direct visualization may reveal the lesion during attempted intubation to secure the child's airway, whereas imaging modalities often add little unless contrast is used to confirm aspiration events or a para-laryngeal mass is suspected. Use of a rigid endoscope is the preferred means of confirming laryngeal clefts (see below).

Bifid epiglottis is a rare lesion characterized by a midline cleft in the epiglottis. Patients may be asymptomatic or have feeding difficulties with aspiration. Direct visualization of this lesion is the only means of diagnosis. Specific therapy is rarely needed.

Laryngeal atresia is the most catastrophic anomaly of the airways in the newborn. This extremely rare lesion results from failed recanalization of the laryngeal orifice in utero. There is usually no specific cause identified. ...

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