• Orientation
  • Orifice - see condition
  • Origin, both great vessels from right ventricle 745.11
  • Ormond's disease or syndrome 593.4
  • Ornithosis 073.9
  • Orodigitofacial dysostosis 759.89
  • Oropouche fever 066.3
  • Orotaciduria, oroticaciduria (congenital) (hereditary) (pyrimidine deficiency) 281.4
  • Oroya fever 088.0
  • Orthodontics V58.5
  • Orthopnea 786.02
  • Os, uterus - see condition
  • Osgood-Schlatter
  • Osler's
  • Osler-Rendu disease (familial hemorrhagic telangiectasia) 448.0
  • Osler-Vaquez disease (M9950/1) (polycythemia vera) 238.4
  • Osler-Weber-Rendu syndrome (familial hemorrhagic telangiectasia) 448.0
  • Osmidrosis 705.89
  • Osseous - see condition
  • Ossification
  • Osteitis (see also Osteomyelitis) 730.2
  • Osteo-onycho-arthro dysplasia 756.89