| edema | <clinical sign> The presence of abnormally large amounts of fluid in the intercellular tissue spaces of the body, usually applied to demonstrable accumulation of excessive fluid in the subcutaneous tissues. Oedema may be localised, due to venous or lymphatic obstruction or to increased vascular permeability or it may be systemic due to heart failure or renal disease. Collections of oedema fluid are designated according to the site, for example ascites (peritoneal cavity), hydrothorax (pleural cavity) and hydropericardium (pericardial sac). Massive generalised oedema is called anasarca. Origin: Gr. Oide ma = swelling (18 Nov 1997) |
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| edema, cardiac | A manifestation of congestive heart failure caused by increased venous and capillary pressures and often associated with the retention of sodium by the kidneys. (12 Dec 1998) |
| absolute refractory period | The period following excitation when no response is possible regardless of the intensity of the stimulus. (05 Mar 2000) |
| anaemia, refractory | Anaemia (a shortage of red blood cells) unresponsive to treatment. (12 Dec 1998) |
| anaemia, refractory, with excess of blasts | Chronic refractory anaemia with granulocytopenia, and/or thrombocytopenia. Myeloblasts and progranulocytes constitute 5 to 40 percent of the nucleated marrow cells. (12 Dec 1998) |
| refractory | Not readily yielding to treatment. Origin: L. Refractorius (18 Nov 1997) |
| refractory anaemia | <haematology> A form of myelodysplasia which primarily affects the red cell production by the bone marrow. In some cases the developing red cells show an internal ring of iron granules. These cells are called sideroblasts. Refractory anaemia and refractory anaemia with sideroblasts are the most common forms of myelodysplasia. Origin: Gr. Haima = blood (13 Nov 1997) |
| refractory anaemia with excess blasts | <haematology> A form of myelodysplasia characterised by the build up of immature white blood cells (blasts) in the bone marrow. If the immature cells are particularly numerous it may indicate a chance of transformation to acute leukaemia and the condition is called refractory anaemia with excess blasts in transformation (RAEBt). Acronym: RAEB (13 Nov 1997) |
| refractory cast | A cast made of material that will withstand the high temperatures of metal casting or soldering without disintegrating. Synonym: investment cast. (05 Mar 2000) |
| refractory flask | A metal tube in which a refractory mold is made for casting metal dental restorations or appliances. Synonym: casting flask, casting ring. (05 Mar 2000) |
| refractory lining | A lining, usually of ceramic, capable of resisting and maintaining high temperatures. (05 Dec 1998) |
| refractory period | <neurology, physiology> most commonly used in reference to the interval (typically 1ms) after the passage of an action potential during which an axon is incapable of responding to another. This is caused by inactivation of the sodium channels after opening. The maximum frequency at which neurons can fire is thus limited to a few hundred Hertz. An analogous refractory period occurs in individuals of Dictyostelium discoideum, which are insensitive to extracellular cyclic AMP immediately after a pulse of cAMP has been secreted. The term can be applied to any system where a similar insensitive period follows stimulation. (18 Nov 1997) |
| refractory period of electronic pacemaker | The time required to restore full sensitivity after detecting cardiac activity or delivering a pacing impulse. (05 Mar 2000) |
| refractory period, psychological | A delayed response interval occurring when two stimuli are presented in close succession. (12 Dec 1998) |
| refractory rickets | Rickets that does not respond to treatment with usual doses of vitamin D and adequate dietary calcium and phosphorus. Most often due to inherited renal tubular disorder e.g., Fanconi syndrome. Renal rickets, a form of rickets occurring in children in association with and apparently caused by renal disease with hyperphosphatemia. Synonym: pseudorickets, renal fibrocystic osteosis, renal infantilism, renal osteitis fibrosa. (05 Mar 2000) |