Hydatid Cysts & Echinococcosis
It's a tapeworm that forms cysts.
Cold open with a very short case report
30F in Mexico presents with RUQ pain and nausea
on examination of her abdo, authors felt a RUQ mass
She received an MRI of her abdo, revealing a cystic mass
on histopatho following a cystectomy, they found Echinococcosis cysts, she also had positive IgG serology to echinococcosis granulosus
a tapeworm that forms cysts that are usually found in the liver or lungs (if not filtered out by the liver), rarely found elsewhere but possible (numerous case reports out there reported in the brain, bones, spleen, kidneys, muscles etc.)
in humans, these cysts can remain in a person's body for years, causing no harm and no symptoms
they can grow by 1 cm per year in the liver
The tapeworm itself is incredibly eerie to look out, as per CDC website:
4 species of concern in people:
E. granulosus = cystic echinococcosis, or hydatid cysts
E mlutilocularis = alveolar
E. vogeli & oligarthrus = polycystic
intermediates: sheep, goats, pigs
humans are 'incidental or accidental hosts" via contact with a reservoir animal - that is to say, the parasite relies on the above 2 hosts for it's life cycle (not necessarily humans)
transmission: faecal oral, ingestion of eggs in from host faeces
larvae from the eggs penetrate the intestine and is transported in blood/lymphatics to liver (and if through liver to lungs), sometimes other organs
cysts = layers with a fibrous capsule, daughter cysts can bud off, can grow up to multiple litres and can septate and have daughter cysts over time, so may not remain unilocular. hosts may develop a granulomatous reaction
can be asymptoamtic for decades, as per 1 case report in a South Korean journal, cysts in one patient caused no issues for 30-40 years (after exposure during the Vietnam war)
become symptomatic when large enough to cause them (if in liver = nausea, vomiting, RUQ pain as per the case report, on exam: abdo distension, palpable mass and hepatomegaly, obstructive jaundice)
in cystic liver disease, it's considered a hydatid cyst and usually assiocaited with cystic echinococcosis
cysts can also eventually rupture and the fluid can cause extreme reactions such as anaphylaxis (IgE mediated Type 1 hypersensitivity reaction), leaking into the peritoneum = hydatidosis
65%: liver, 25% lungs, but 20-40% of patients can have multiorgan involvement
often acquired in childhood but present later in life (excpetion: eye and brain)
in lung: SOB, chest pain, chronic cough, haemoptysis
brain = raised ICP, seizures
spinal cord = compression
kidneys = haematuria, flank pain
bones = pathologic fractures
a/w endemic areas - South America (as per case report above), former soviet union (kinda random), middle east, eastern med, Western China (I suppose these areas are all geographically connected), but also East Africa and Australia
however, alveolar echinococcosis is endemic only to Russia, China, North America and Europe
rural/grazing areas (not surprisingly given the hosts are dogs and sheep), communities needing dogs for herding
30-40 yos more likely to have hydatid cysts while > 50 are a/w alveolar
elderly and immunocompromised are more vulnerable
look for these RFs above (esp contact with dogs + cattle)
imaging is definitive, look for the cysts, pretty big if symptomatic
nonspecific, but clues on bloods: mild eosinophilia, leukopaenia and thrombocytopaenia, deranged LFTs in hydatid cysts (abnormal in only 40% of patients, ALP usually high the rest can be normal)
imaging: USS, CT are sufficient, MRI great but no real advantage over CT, useful in the seronegative
serology is useful both in diagnosis and in follow-up after treatment, but many do not have an immune response depending on cyst wall intactness
avoids: aspiration, unless USS/CT guided given the risk of the fluid causing anaphylaxis
in the event the biliary tree is affected, await an ERCP
Stages determine management
WHO informal working group stages (IWGE) based on USS:
CE 1: simple cyst, double line sign
CE2: mlutiseptated, honeycomb/rosette
CE3A: watery lily sign - fluid collection with a detached membrane
CE3B: daughter cysts ina. solid matrix
CE4: heterogenous, hyperechoic, matrix, no duaghter cysts
1&2: active, 3 = transitional (cyst compromised), 4 and 5= inactive
ring like calcifications can be present in all stages
CT over USS = complications, like rupture, infection and biliary/vascular involvement
albendazole - antiparasite medication is the foundation
generally depends on the size and number of cysts and there's whole WHO staging and guidelines for this
medical therapy can be anywhere from 1-3 months up to 6, but are futile if the sole treatment cysts > 5 cm or daughter cysts involved
Stage 4&5: watch and wait, USS regularly, these are uncomplicated
CE1 and CE3a: cysts < 5 cm in liver and lung, but inoperable and >2 organs involved = albendazole (CI: pregnancy and cysts vulnerable to rupture), also used following surgery and perc drainage (CT/USS guided) to prevent recurrence
surgery in: complicated cysts for removal of large stage 2 and 3b cysts or cysts that can rupture (superficial), infected, biliary tree communication and pressure on organ. Inovlves excision of cyst and possibly liver resection, contamination with daughter cysts is possible so adj albendazole and praziquantel often done (i.e. 1-4 weeks prior then 4 weeks post. has lower recurrence rates
PAIR = puncture, aspiration, inj with 20% hypertonic saline and re aspiration = USS guided in the inoperable or relapsing cases or failing to respond. usually in cysts > 5 cm with albendazole for 4 weeks, stage 1 only/single compartment cysts (PAIR ineffective in higher stages = multiple compartments)
post treatment: USS 3-6 monthly then yearly
lungs: 2 years of treatment and surgery, simple cysts may just require medical therapy
straight from stat pearls - abscess, simple benign cysts, budd chiari, biliary colic, cirrhosis, TB, carcinoma, haemagiomas
Australian guidelines (behind a paywall)
