obtundation: The obtunded patient may be aroused (by gentle shaking or mildly noxious stimuli such as a pinch). He will look at you and try to respond however will do so slowly and often without making sense. Generally there is little interest in, or engagement of, the surrounding environment. Go to page

obturator sign: The obturator sign is right lower quadrant pain elicited with internal rotation of the hip. Again, this is suggestive of inflammation of the appendix. Go to page

occult blood: Rectal bleeding can be a symptom of hemorrhoids, rectal or colon polyps, or cancers. Sometimes, bleeding is not obvious. Screening fecal material for occult blood can identify asymptomatic colon lesions.

olecranon bursa: The olecranon bursa may be inflamed due to systemic diseases such as gout or rheumatoid arthritis, due to local trauma from recurrent pressure, or due to infection. Infection may be due to hematogenous spread in the setting of sepsis. It is more commonly due to local infection from a break in the skin or a nearby cellulitis. Go to page

oral mucosa, color changes of: The normal oral mucosa is pinkish. White plaques or patches that do not scrape off may represent oral leukoplakia, a precancerous lesion of the oral mucosa. Leukoplakia itself is hyperplasia of the squamous epithelium. The natural history of this lesion depends on the degree of dysplasia seen on biopsy. The plaques tend to occur in areas prone to trauma, mechanical irritation, or carcinogen exposure. This lesion is particularly common in users of smokeless tobacco. Go to page

orientation: Orientation refers to knowledge about self (the person's name), place (state, city, specific location), and time (time of day, day of week, month, year, season). Questions to assess this may be comfortably embedded into the general interview. Do not assume that a patient is oriented to person, place, and time just because his answers seem coherent and relevant. Patients may have impairment of memory or attention, or may be disoriented during an acute illness. They may also demonstrate disorientation as a part of an underlying but previously undiagnosed dementia. Go to page

osteoarthritis: In osteoarthritis, nodules may be found on the dorsolateral aspect of the distal interphalangeal joints, called Heberden's nodes. Less common are the nodules on the proximal interphalangeal joints called Bouchard's nodes. The first carpometacarpal joint is commonly affected. There may be tenderness of the joints although rarely any evidence of associated inflammation. Joint effusions may be present.