Hydatid disease throughout the abdomen and pelvis due to remote hepatic cyst rupture. 

The "worm" floating in the cyst was almost certainly the "water lily" sign from the floating membrane in the inferolateral hepatic cyst, which is best seen on the coronal images. 

Varying degrees of calcification indicate inactive/chronic cysts.

Humans are incidental/accidental intermediate hosts, which means that worms do not reside in our small bowel.

• the worms live in the definitive hosts (commonly dogs)
• eggs are ingested by the intermediate hosts (commonly sheep) which release oncospheres, which migrate into the portal circulation and infect the liver and other organs
• the embryos die or form hydatid cysts
• when the viscera of infected intermediate hosts are consumed by the definitive host, the life cycle is complete

The hydatid cysts are composed of three layers¹:

• pericyst: host response to the parasite
• ectocyst: middle laminated membrane
• endocyst: produces daughter vesicles containing protoscolioces; when these are ingested by the definitive host, they attach to the intestinal mucosa and develop into adult worms