Hydatid cyst signs

There are numerous named imaging signs of hydatid cysts in echinococcal infection. There is considerable variability in the naming and definition of many of the signs in the literature. In general, the signs demonstrate the presence of laminated cyst membranes in various morphologies within a larger pericyst, with variable intervening material such as fluid, debris, or air, depending on the organ and stage of disease:

• signs of nonruptured cysts in various organs
  • honeycomb (wheel spoke, spoke wheel, rosette, racemose) pattern: multivesicular mother cyst with daughter cysts separated by radiating septae representing cyst walls and hydatid sand/matrix
  • double line sign: unilocular cyst with double layered wall representing pericyst and laminated cyst membrane ^7,8
• signs of partially ruptured cyst in pulmonary hydatid disease ⁶
  • crescent sign: when the hydatid cyst erodes the adjacent bronchus or bronchiole, the trapped air between the pericyst and the laminated membrane of the endocyst give a crescent-shaped rim of air around the cyst ^4,5
  • inverted crescent sign: crescent-shaped rim of air at the lower edge of the cyst ^4,5
• signs of complete rupture / cyst degeneration in pulmonary hydatid disease ⁶
  • cumbo (onion peel, double arch) sign: curvilinear membrane outlined by air both inside the endocyst and a crescent of air between the endocyst and pericyst
  • water lily (camalote) sign: folded membranes floating at the air-fluid interface
  • empty (dry) cyst sign: air filled cyst after expectoration of membranes and fluid
• signs of ruptured endocyst in hydatid cysts in various organs (e.g. hepatic hydatid infection)
  • serpent (snake) sign: wavy membranes within the cyst
  • spin (whirl) sign: twisting membranes within the cyst
  • ball of wool (yarn, congealed water lily, mass within a cavity) sign: solid conglomeration of membranes settled in the dependent portion of the cyst