Type:
Educational Exhibit
Keywords:
Parasites, Diagnostic procedure, Ultrasound, MR, CT, Liver, Extremities, Abdomen
Authors:
A. Al-Taie, Z. AHMED, Z. Jaleel; Doha/QA
DOI:
10.26044/ecr2019/C-1176
Background
*Hydatid disease (HD) is a worldwide parasitic infection endemic in many parts of the world.
*It is caused by genus Echinococcus.
*It affects human in two forms: 1.
Cystic echinococcosis caused by the tapeworms Echinococcus granulosus. 2.
Alveolar echinococcosis,
caused by Echinococcus multilocularis.
*Definitive hosts are carnivores (e.g.
dogs,
foxes,
cats),
and the intermediate hosts are mainly sheep,
pigs and cattle. Humans are accidental hosts,
and the infection occurs by ingesting food contaminated with Echinococcus eggs.
*Hydatid cyst layers:
- The outer pericyst: Composed of inflammatory tissue of host origin.
- The middle exocyst: An acellular laminated membrane,
which allows the passage of nutrients.
- The inner endocyst: Germinal layer where the scolices (the larval stage of the parasite) and the laminated membrane are produced.
*Although Hydatidosis can involve any part of the body,
the liver is most common site of involvement,
followed by the lungs.
*In primary echinococcosis,
larval cysts may develop in every organ.
Most patients (as many as 80%) have single-organ involvement and harbor a solitary cyst.
*Imaging appearances of HD vary according to growth stage,
associated complications and tissue/organ of involvement.
*Ultrasound is the screening modality of choice for involvement of soft tissues,
and abdominal viscera.
*CT is an important preoperative tool to determine vascular,
biliary and extrahepatic extension.
*CT is also the modality of choice in peritoneal seeding.
*MRI is superior for demonstrating cyst wall defect,
internal architecture and biliary communication.