"OCB: oligoclonal band(s) (CSF)"
"A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z - misc"
"O"
"O&G: obstetrics and gynaecology"
"Obl: oblique"
"Obs: observations"
"O/E: on examination"
"Og: oganesson"
"O/N: overnight"
"Ordercomms: order communications"
"Os: osmium"
"Osm"
"OxyHb: oxygenated haemoglobin"
"blood type (ABO system)"
"OA: osteoarthritis"
"OAB: overactive bladder"
"OAC: oral anticoagulant"
"OAML: orbital adnexal MALT lymphoma"
"OAR: organ at risk"
"OAS: orbital apex syndrome"
"OAT"
"OATS: oligoasthenoteratozoospermia"
"OBI: on-board imaging (in radiotherapy)"
"OB/GYN: obstetrics and gynaecology"
"OB/GYN: obstetrics and gynaecology"
"OBL: office-based labarotory"
"OBO: on background of"
"OC"
"OCA: osteochondral allograft transplantation"
"OCB: oligoclonal band(s) (CSF)"
"OCD"
"OCF"
"OCG: oral cholecystogram"
"OCI: osteitis condensans ilii"
"OCL: osteochondral lesion"
"OCP"
"OCS: otic capsule sparing (temporal bone fractures)"
"OCV: otic capsule violating (temporal bone fractures)"
"OD"
"ODD: optic disc drusen"
"ODG: oligodendroglioma"
"ODT: oroduodenal tube"
"OE: otitis externa"
"OEIS: omphalocele, exstrophy, imperforate anus, and spinal defects"
"OFC: osteitis fibrosa cystica"
"OFD"
"OFDI: optical frequency domain imaging"
"OGD: oesophagogastroduodenoscopy"
"OGS: orthognathic surgery"
"OGT: orogastric tube"
"OHCA: out-of-hospital cardiac arrest"
"OHS"
"OHSS: ovarian hyperstimulation syndrome"
"OHT: orthotopic heart transplant"
"OHVIRA: obstructed hemivagina with ipsilateral renal anomalies"
"OI"
"OLB: open lung biopsy"
"OLIF: oblique lumbar interbody fusion"
"OLLIF: oblique lateral lumbar interbody fusion"
"OM"
"OMC: ostiomeatal complex"
"OMFS: oral and maxillofacial surgery"
"OMU: ostiomeatal unit"
"OMX: osteochondromyxoma"
"ON"
"ONG: optic nerve glioma"
"ONH"
"ONHS: optic nerve head swelling"
"ONSD: optic nerve sheath diameter"
"ONTD: open neural tube defect"
"OOA: oesophageal obturator airway"
"OOB: out of bed"
"OOC: orthokeratinized odontogenic cyst"
"OOH"
"OOHCA: out-of-hospital cardiac arrest"
"OOHVFA: out-of-hospital ventricular fibrillation arrest"
"OOKP: osteo-odontokeratoprosthesis"
"OOP: out-of-plaster"
"OP"
"OPARACHEE: on resonance paramagnetic chemical exchange effect"
"OPC: oropharyngeal carcinoma"
"OPG"
"OPK: osteopoikilosis"
"OPL: oblique posterior ligament"
"OPLL: ossification of the posterior longitudinal ligament"
"OPPT: orientated to person, place, and time"
"OPT: orthopantomogram"
"OPV: oral polio vaccine"
"OR"
"ORF: open reading frame (in protein synthesis)"
"ORIF: open reduction internal fixation"
"ORN: osteoradionecrosis"
"ORS: oral rehydration solutions"
"ORSA: oxacillin-resistant staphylococcus aureus"
"ORT: oral rehydration therapy"
"ORTI: ossifying renal tumour of infancy"
"OS"
"OSA: obstructive sleep apnoea"
"OSAIRIS: Open-Source AI Radiotherapy Image Segmentation"
"OSAIRIS: Open-Source AI Radiotherapy Image Segmentation"
"OSD"
"OSNA: one step nucleic acid amplification"
"OSP: oncocytic sinonasal papilloma"
"OT"
"OTC"
"OTD"
"OTTR: organ transplant tracking record"
"OU: both eyes (Latin: oculus uterque)"
"OV"
"OWR: Osler-Weber-Rendu syndrome"
"OYL: ossification of the yellow ligament"
"OSAIRIS: Open-Source AI Radiotherapy Image Segmentation"
"ova, cysts and parasites"