Atresia

Atresia (plural: atresias) refers to a situation where there is absence, underdevelopment or abnormal closure, of a normal anatomical tubular structure or opening. 

Contrast this with agenesis which refers to the complete absence of any anatomical structure including its primordial precursors.

For example:

• respiratory tract

  • bronchial atresia

  • choanal atresia

  • tracheal atresia

  • laryngeal atresia

• alimentary tract

  • esophageal atresia

  • pyloric atresia

  • duodenal atresia

  • ileal atresia

  • jejunal atresia

  • jejunoileal atresia

  • colonic atresia

  • anal atresia

• bile ducts

  • biliary atresia

• genitourinary tract

  • vaginal atresia

    • lower vaginal atresia

  • urethral atresia

• skeleton

  • oval window atresia

Some authors occasionally overlap the two terms (i.e. atresia and agenesis), which in general is an erroneous practice.