Abdominal hydatid disease
Abdominal discomfort. Right upper quadrant ultrasound concerning for a worm floating in a liver cyst.
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Numerous cystic masses throughout the abdomen and pelvis containing variable amounts of debris or calcifications:
- anterior right hepatic lobe, likely responsible for atrophy of the left hepatic lobe (with compensatory caudate hypertrophy)
- along lateral/inferior liver margin, with floating membrane (best on coronal)
- very large in the spleen
- left lower abdomen insinuating among bowel loops posteriorly
- pelvis/pouch of douglas
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