CT Abdoment With Contras Indications hydatid cysts

CT Abdoment With Contras Indications
An imaging classification of hydatid cysts consists of the following:
Type 1: Simple unilocular cyst. Believed to be an early stage in hydatid cyst formation, these cysts are water dense on CT and anechoic on US. Cyst wall and septal enhancement is seen with CT and MR contrast, thus
differentiating this entity from simple cysts.
Type 2: Cyst containing daughter cysts.
Round or irregular daughter cysts are surrounded by a higher density fluid in the mother cyst.
Type 3: Dead cysts containing extensive calcifications.
Type 4: Complex cysts. These consist of superinfected cysts or ones that have ruptured. In a contained rupture imaging identifies endocyst separation from the surrounding pericyst. Bacterial superinfection implies the presence of cyst rupture.
Curvilinear cyst rim calcifications are common with Echinococcus granulosus infections, and a cystic pattern is detected in about half.
The CT appearance varies, although a hydatid cyst tends to have an oval and sharply defined outline. Precontrast, cysts are mostly inhomogeneous and of low density; postcontrast enhancement is inhomogeneous (Figs. 7.7 and 7.8). 

CT Abdoment With Contrast for Hydatid cyst. CT also identifies a soft-tissue component within the cyst (arrow). (Courtesy of Algidas Basevicius, M.D., Kaunas Medical University, Kaunas, Lithuania.)
The sonographic appearance ranges from an anechoic cyst, mural nodules, and visualization of the endocyst, to a complex multicystic structure.
Debris either tends to be displaced toward the center of the primary cyst or is located in the dependent portion; or, in some cysts, a fluid–fluid interface is evident. A gas–fluid level within the cyst implies communication with bile duct or viscus, although occasionally an infected, noncommunicating cyst has a gas–
fluid level. Detachment of the inner layer into the cyst lumen results in a soft tissue tumor either floating or in the most dependent portion of the cyst, an appearance termed the water lily sign.
Daughter cysts lead to a cyst-within-a-cyst appearance. At times numerous daughter cysts result in an imaging finding of multiple small cysts in an otherwise solid-appearing tumor, an appearance mimicking a honeycomb.
Computed tomography and US often visualize intrabiliary hydatid material once biliary communication is established. Computed tomography reveals intrabiliary hydatid membrane particles as “sand”; at times the actual communication is identified. In some patients adjacent bile ducts dilate.A fat–fluid level within
the cyst is a sign of biliary communication.
Occasionally, hydatid material is observed in the gallbladder lumen. A hydatid cyst sonographic classification is outlined in Table under.
Table under. US classification of hydatid cysts
Type I: Simple cyst
Type II: Multiple cysts
Type III: Cysts with detached membrane
Type IV: Mixed cysts
Type V: Cysts with heterogeneous echogenicity
Type VI: Hyperechoic cysts
Type VII: Calcified cysts
 This classification differs from the general imaging classification of hydatid cysts outlined above; it divides cystic hydatid disease into a proliferative stage and an involution stage. The US findings of types I through V represent the proliferative stage, and patients should be treated, but types VI and VII are part of disease involution and these patients do not require therapy. The cyst becomes hyper echoic as its content changes from a watery consistency to a viscid gel and the germinal layer folds within the viscid gel assume a curvilinear appearance, which no longer moves with a change in patient position.
At times endoscopic retrograde cholangiopancreatography (ERCP) is helpful, although MR cholangiography also defines bile duct involvement. Cyst communication with bile ducts, bile duct obstruction, and debris in the bile ducts can be detected and, at times, treated by endoscopic sphincterotomy. Extensive publications confirm that ERCP is safe in a setting of hepatic echinococcosis.
CT Abdoment With Contrast Hydatid liver cyst in a 12-year-old. A: CT identifies a large cystic structure replacing most of the left lobe (arrows). A detached inner layer is seen floating in the cyst lumen. B: Ultrasonography (US) reveals an irregular cyst containing solid content (endocyst). (Courtesy of Luann Teschmacher, M.D., University of Rochester.)
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