| lateral alveolar abscess | An alveolar abscess located along the lateral root surface of a tooth. Synonym: pericemental abscess. (05 Mar 2000) |
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| lateral periodontal abscess | An abscess that forms at the depth of a periodontal pocket due to multiplication of pyogenic microorganisms or the presence of foreign material. (05 Mar 2000) |
| liver abscess | A condition where there is a pus-filled cavity in the liver secondary to a bacterial infection. Liver abscess may result from sepsis, intestinal perforation, post-operative infection, appendicitis, diverticulitis, trauma (to the liver) or cholangitis. Other nonbacterial causes of liver abscess include amoebiasis, due to infection with Entamoeba histolytica (protozoan). (27 Sep 1997) |
| liver abscess, amebic | Liver abscess caused by entamoeba histolytica. (12 Dec 1998) |
| lung abscess | A collection of pus within a cavity in the lung due to a bacterial infection (bacterial endocarditis). Certain bacteria (Staphylococcus, Pseudomonas, Tuberculosis, Klebsiella) are more likely to cavitate the lung and cause abscess formation. (27 Sep 1997) |
| adrenal cyst | <radiology> Same characteristics as renal cysts, but less common, thick wall, septations, calcifications suggests pseudocyst (12 Dec 1998) |
| adventitious cyst | 1. An accumulation of fluid in a cystlike loculus, but without an epithelial or other membranous lining. Synonym: adventitious cyst, false cyst. 2. A cyst whose wall is formed by a host cell and not by a parasite. 3. A mass of 50 or more Toxoplasma bradyzoites, found within a host cell, frequently in the brain; formerly called a pseudocyst, but now considered a true cyst enclosed in its own membrane within the host cell that may rupture to release particles that form new cysts, and apparently is infective to another vertebrate host. See: bradyzoite. Origin: pseudo-+ G. Kystis, bladder (05 Mar 2000) |
| allantoic cyst | Cyst occurring in a persistent portion of the urachus, presenting as an extraperitoneal mass in the umbilical region. It is characterised by abdominal pain, and fever if infected. It may rupture, leading to peritonitis, or it may drain through the umbilicus. (12 Dec 1998) |
| alveolar hydatid cyst | A hydatid cyst of a multiloculate type, usually in the liver, caused by Echinococcus multilocularis, adults of which are in foxes; larvae (alveolar hydatid) are found chiefly in microtine rodents, but also among humans such as trappers and others handling pelts of infected foxes and other carnivores; growth is by exogenous budding and is not limited by an outer laminated membrane as in the hydatid cyst from E. Granulosus; necrosis, cavitation, contiguous spread, and death usually ensue. Synonym: multilocular hydatid cyst, multiloculate hydatid cyst. (05 Mar 2000) |
| aneurysmal bone cyst | <radiology> ABC, 10 - 30 yrs, 75% before skeletal maturity, sites: long bones; also, flat bones Findings: metaphyseal if unfused, metaepiphyseal after fusion, lytic, expansile, thin, continuous rim, thin internal bony strands (12 Dec 1998) |
| angioblastic cyst | Mesenchymal tissue capable of forming blood in the embryo. (05 Mar 2000) |
| apical periodontal cyst | An inflammatory odontogenic cyst derived histogenetically from Malassez' epithelial rests surrounding the root apex of a nonvital tooth. Synonym: periapical cyst, radicular cyst, root end cyst. (05 Mar 2000) |
| apoplectic cyst | A pseudocyst formed of extravasated blood as in a stroke. (05 Mar 2000) |
| arachnoid cyst | A fluid-filled cyst lined with arachnoid membrane, frequently situated near the lateral aspect of the fissure of Sylvius; usually congenital in origin. Synonym: leptomeningeal cyst. (05 Mar 2000) |
| baker cyst | <radiology> Bursal fluid collection between: medial head of gastrocnemius muscle and, semimembranosus tendon, associated with knee injury, may contain osteocartilaginous fragments (12 Dec 1998) |