Gas Luft in Echinococcuszyste der Leber
Gas Luft in Echinococcuszyste der Leber
rupturierte Echinokokkuszyste der Leber
Echinokokkose Radiopaedia • CC-by-nc-sa 3.0 • de
Hydatid cysts result from infection by the Echinococcus tapeworm species and can result in cyst formation anywhere in the body.
Epidemiology
Cystic echinococcosis has a worldwide geographical distribution. The Mediterranean basin is an important endemic area .
Pathology
There are two main species of the Echinococcus tapeworm :
- Echinococcus granulosus
- more common
- pastoral: the dog is the main host; most common form
- sylvatic: the wolf is the main host
- Echinococcus alveolaris/multilocularis
- less common but more invasive
- fox is the main host
Definitive hosts are carnivores (e.g. dogs, foxes, cats), and the intermediate hosts are most commonly sheep. Humans are accidental hosts, and the infection occurs by ingesting food contaminated with Echinococcus eggs .
Cyst structure
The cysts usually have three components :
- pericyst: composed of inflammatory tissue of host origin
- exocyst
- endocyst: scolices (the larval stage of the parasite) and the laminated membrane are produced here
Cyst classification
Based on morphology the cyst can be classified into four different types :
- type I: simple cyst with no internal architecture
- type II: cyst with daughter cyst(s) and matrix
- type IIa: round daughter cysts at the periphery
- type IIb: larger, irregularly shaped daughter cysts occupying almost the entire volume of the mother cyst
- type IIc: oval masses with scattered calcifications and occasional daughter cysts
- type III: calcified cyst (dead cyst)
- type IV: complicated cyst, e.g. ruptured cyst
For hepatic hydatid infection on ultrasound also refer to World Health Organization 2001 classification of hepatic hydatid cysts.
Location
- hepatic hydatid infection: most common organ (76% of cases)
- pulmonary hydatid infection: second most common organ (15% of cases)
- splenic hydatid infection: third most common organ (5% of cases)
- cerebral hydatid infection
- spinal hydatid infection
- retroperitoneal hydatid infection
- renal hydatid infection
- musculoskeletal hydatid infection
- mediastinal hydatid infection (very rare)
Markers
Radiographic features
A chest film or other plain films can be the first diagnostic modality when echinococcosis is suspected, depending on clinical indications.
CT and MRI imaging are indicated when considering surgical treatment, particularly in regions like the brain, spine, and locations inaccessible for conventional radiography or ultrasound, or in case of diagnostic uncertainty.
Ultrasound
The Gharbi ultrasound classification consists of five stages:
- stage 1: homogeneously hypoechogenic cystic thin-walled lesion
- stage 2: septated cystic lesion
- stage 3: cystic lesion with daughter lesions
- stage 4: pseudo-tumor lesion
- stage 5: calcified or partially calcified lesion (inactive cyst)
Treatment and prognosis
Four treatment options are currently available :
- surgical excision
- PAIR (Puncture, Aspiration, Injection of protoscolicidal agent and Reaspiration)
- chemotherapy with an anti-helminthic agent (albendazole, mebendazole)
- watch and wait for inactive and silent cysts
Treatment outcomes were improved when surgery or PAIR was combined with benzimidazole given before and after surgery . Regarding medical management, higher scolicidal and anti-cystic activity was seen in combination therapy with albendazole plus praziquantel and was more likely to result in cure or improvement .
Echinococcus Leber Radiopaedia • CC-by-nc-sa 3.0 • de
Hepatic hydatid disease is a parasitic zoonosis caused by the Echinococcus tapeworm. In the liver, two agents are recognized as causing disease in humans:
- Echinococcus granulosus
- Echinococcus multilocularis
For a general discussion, and links to other system-specific manifestations, please refer to the article on hydatid disease. For a more specific discussion related to the invasive pattern attributed to the E. multilocularis infection, please refer to the article on alveolar echinococcosis.
Pathology
The parasite E. granulosus is endemic in North America and Australia and is commonly seen in the liver. It typically forms a spherical, fibrous-rimmed cyst with little, if any, surrounding host reaction. Classically it has a large parent cyst within which numerous peripheral daughter cysts are present. Satellite daughter cysts (outside the parent cyst) are seen frequently (~16% cases).
There are two forms of E. granulosus:
- pastoral: the most common form; the domestic dog is the main host
- sylvatic: wolf or dog is the main host
The E. multilocularis definitive host (adult parasite) is the red fox (Vulpes vulpes) (sometimes cats and dogs as well), with humans serving as the accidental intermediate host. It is widely distributed throughout the Northern hemisphere.
Radiographic features
This article will discuss the most common presentation of the hepatic hydatid disease, characterized by well-defined encapsulated cystic or multicystic masses related to E. granulosus. For a specific discussion on the less common invasive form, caused by E. multilocularis, please refer to the article on alveolar echinococcosis.
Plain radiograph
May show a curvilinear or ring calcific shadow overlying the liver due to calcification of the pericyst.
Ultrasound
Septated cyst with "daughter" cysts and echogenic material between the cysts. Appearances can vary. May show a double echogenic shadow due to the pericyst. The stage of the cyst may be classified on ultrasound, see: World Health Organization 2001 classification of hepatic hydatid cysts.
CT
Fluid density cyst, with frequent peripheral focal areas of calcification, usually indicates no active infection if completely circumferential. Septa and daughter cysts may be visualized. The water-lily sign indicates a cyst with a floating, undulating membrane, caused by a detached endocyst. May also show hyperdense internal septa within a cyst showing a spoke wheel pattern. The fluid is of variable attenuation, depending on the amount of proteinaceous debris. May show dilated intrahepatic bile ducts due to compression or rupture of the cyst into bile ducts.
MRI
- T1: mixed low signal (depending on the amount of proteinaceous cellular debris)
- T2: mixed high signal (depending on the amount of proteinaceous cellular debris), septa and daughter cysts are well visualized (especially on single-shot T2 sequences)
- T1 C+ (Gd): the walls and septa enhance
Treatment and prognosis
Complications
Rupture into the:
- biliary tree
- peritoneal space (if exophytic)
- bloodstream
- lung
Siehe auch:
Assoziationen und Differentialdiagnosen zu Gas Luft in Echinococcuszyste der Leber:
