OAC Optical Aspirating Curette

OB Obstetrics - See Obstetrics dictionary

OB/GYN Obstetrics and Gynecology

OBS Organic Brain Syndrome

OD Over Dose

ODTS Organic Dust Toxic Syndrome

OHL Oral Hairy Leukoplakia

OI Opportunistic Infection (same as IO)

OMI Oedème des Membres Inférieurs

OMS Organic Mental Syndrome

ONB Olfactory NeuroBlastoma

Op. Operation / Opération

OPLL Ossification of The Posterior Longitudinal Ligament

OR Operation Room / Salle d'opération

ORS Oral Rehydration Salts

ORT Oral Rehydration Therapy

OTC Ornithinine Transcarbamylase Deficiency

OTS Optical Tracking System