Role of interventional radiology in the management of hepatic hydatid disease

Table 1 World Health Organization classification of hydatid cyst, highlighting its imaging features[12,13]

WHO classification	Stage	Features
CL	Active	Unilocular cystic lesion without a well-defined wall (double wall sign is not seen); no internal debris or septations (without evident signs of non-parasitic aetiology); seen during the initial phase of hydatid development; requires diagnostic tests to differentiate from other cystic lesions
CE1	Active	Unilocular cystic lesion with a well-defined wall; fine internal echoes/debris may be seen representing hydatid sand (pathognomonic): “Snowflake sign”; “double wall sign” (pathognomonic): Two echogenic lines seen representing the parasite larval cyst and the host-derived fibrous cyst capsule, separated by minimal hypoechoic fluid. However, may not always be seen, and care should be taken not to dismiss a CE1 cyst on the basis of not seeing this sign; internal septae/membranes not seen
CE2	Active	Multivesicular cystic structure with daughter vesicles; rosette/Honey-comb pattern: Daughter cysts fill the entire mother cyst; spoke-wheel pattern: Daughter vesicles arranged peripherally with minimal central high-density matrix
CE3a	Transitional	Detachment of endocyst from pericyst: Can be due to decreasing intracystic pressure, degeneration, host response, trauma, or response to therapy: Produces serpentine linear floating membranes: “Water-lily sign” (highly specific sign); detachment may be partial or complete
CE3b	Transitional	Few daughter cysts in a predominantly avascular solid matrix: “Swiss cheese” because of significant solid component it can mimic malignancy
CE4	Inactive	Heteroechoic solid avascular mass with no daughter cysts: Pseudotumour/ball-of-wool/canalicular/cerebroid appearance; due to solid nature: Mimics malignancy (requires contrast-enhanced CT/MRI: Showing lack of enhancement to differentiate from malignancy)
CE5	Inactive	Thick, densely calcified walls (complete or near complete); partial wall calcification does not always indicate parasite death; however, densely calcified cysts may be assumed to be inactive; wall calcification is most extensively found in, but not limited to CE4 and CE5; heterogeneous avascular solid content (when acoustic shadow allows visualization)

WHO: World health organization; CL: Cystic lesions; CE: Cystic echinococcosis; CT: Computed tomography; MRI: Magnetic resonance imaging.

Table 2 Comparison between radical and non-radical surgical procedures

	Radical surgery (closed method): Hepatic resection and total cystectomy	Non-radical conservative surgery (open method): Partial cystectomy
Ref.	Baimakhanov et al[17], 2021; Deo et al[18], 2020; Farhat et al[19], 2022; Akbulut et al[20], 2010; Stojkovic et al[21], 2016
What is resected	The entire parasitic larval cyst and the host-derived fibrous capsule are removed	The entire parasitic larval cyst and only a part of the host-derived fibrous capsule are removed
Difficulty of surgery	More challenging	Easier
Intraoperative opening of the cyst	Not opened, so lower risk of spillage and secondary hydatidosis	Opened, so risk of spillage and secondary hydatidosis
Perioperative albendazole prophylaxis	Can be theoretically stopped immediately after surgery	Essential to be continued after surgery
Long-term follow-up for secondary echinococcosis	Theoretically not required	Essential
Postoperative biliary leakage/bilioma	Less common	More common
Bleeding	More common	Less (as the host-derived posterior segment of the fibrous capsule that is intimately aligned with the liver is left in place)
Anatomically critical sites	Surgery may not be possible	May be performed (as the host-derived fibrous capsule is left untouched): e.g., HHC intimately attached to the main portal vein
HHC is in proximity to the liver capsule	Can be performed even if HHC is completely surrounded by liver parenchyma, and does not extend till the liver capsule	Only suitable for cysts where the host-derived fibrous capsule is extending to the surface of the liver (otherwise high risk of bleeding/hematogenous dissemination)

HHC: Hepatic hydatid cyst.

Table 3 Summary of the various percutaneous interventions for hepatic hydatid cyst

Technique	Indications	Specific features
PAIR	CE1 and CE3a (usually > 5 cm size)	Usually not done for HHC < 5 cm due to limited space; if cysto-biliary communication is present, then PAIR should be terminated or converted into S-CAT
S-CAT	CE1 and CE3a (usually > 5 cm size)	Very useful in the presence of cysto-biliary fistulas, and if technical difficulty is encountered during PAIR; recurrence, complications, and duration of hospitalization are higher with S-CAT as compared to PAIR
MoCAT	CE2 and CE3b (significant solid component present)	Potential to replace surgery for the cyst types with a significant solid component not amenable to PAIR; lower recurrence rate as compared to PAIR and S-CAT; higher rate of complications (e.g., cysto-biliary fistula development and abscess formation)
PEVAC	CE2 and CE3b (with or without cysto-biliary communication)	Suction is applied via the inserted catheter, without the use of scolicidal agents; useful in patients with vascular or biliary obstruction, and centrally located lesions (as there is no risk of scolicidal agent entering the adjoining vital structures); higher incidence of cysto-biliary fistula formation and secondary infection of the HHC
Örmeci technique	CE1, CE2, CE3a and CE3b	A thinner puncture needle is used compared to PAIR, so the risk of cyst fluid leakage and secondary peritoneal hydatidosis is less; scolicidal agents are not re-aspirated: Increases scolicidal effect; more studies are required to validate its efficacy

CE: Cystic echinococcus; PAIR: Puncture-aspiration-injection-reaspiration; S-CAT: Standard catheterization technique; MoCAT: Modified catheterization technique; HHC: Hepatic hydatid cysts; PEVAC: Percutaneous evacuation.