Treatment of Cystic Echinococcosis (CE)
The CE therapy depends on the radiological cyst stage and the associated vitality assessment [1]. Surgical resection is generally possible at all stages but may lead to overtreatment. Lesions in stage CE4 and CE5 should be observed due to their inherent inactivity. In all other stages, a conservative therapy with albendazole for 3 to 6 months can be attempted for lesions up to 5 cm, with a cure probability of 60 to 70% [2].
A promising and simpler alternative to resection is puncture, aspiration, instillation, and reaspiration (PAIR) for cysts in stage CE1 or CE3a that are less than 10 cm in size. Cysts in stage CE2 or CE3b, as well as all cysts over 10 cm, should be treated surgically.
| Stage | ABZ Mono | PAIR (+ ABZ) | Surgery (+ ABZ) | Observation |
|---|---|---|---|---|
| CE1 | up to 5 cm | < 10 cm, ABZ unsuccessful | primary or after unsuccessful PAIR | - |
| CE2 | up to 5 cm | not useful | always | - |
| CE3a | up to 5 cm | < 10 cm, ABZ unsuccessful | primary or after unsuccessful PAIR | - |
| CE3b | up to 5 cm | not useful | always | - |
| CE4 | - | - | - | always |
| CE5 | - | - | - | always |
ABZ Albendazole, CE cystic echinococcosis, PAIR puncture, aspiration, instillation, reaspiration, Surgery Operation; [2]
Pharmacological Therapy
Albendazole acts parasiticidal on Echinococcus granulosus and can lead to sterilization, reduction, and healing of the cysts. Treatment with albendazole should begin 24 hours, preferably 5 days before an intervention [3].
After PAIR and radical resection, current recommendations suggest a pharmacological follow-up treatment for approximately 4 weeks, rarely 3 – 6 months [1, 3].
If there is a cyst rupture or dissemination of infectious protoscolices (tapeworm larvae) spontaneously, iatrogenically, or interventionally, the combined administration of albendazole and praziquantel can be considered [3].
PAIR - Puncture, Aspiration, Instillation, and Reaspiration
Due to their almost liquid internal composition, CE1 and CE3a cysts can generally be well treated by PAIR. A puncture of the cyst is performed either percutaneously or surgically (open or laparoscopically), and the cyst content is aspirated with a large-bore catheter. Then, an antiparasitic substance is injected, and the fluid is aspirated again after sufficient time [4].
It should be noted that the risk of a connection between the cyst and bile ducts increases with size [5]. The risk of a cystobiliary communication is 80% at a cyst size of 7.5 cm [6]. If bile can be aspirated during the puncture and instillation maneuver, the instillation of hypertonic NaCl solution or ethanol must be stopped, as this can lead to toxic cholangitis [7]. Before a laparoscopic puncture is performed, it must be considered in the planning that the management of a cystobiliary fistula using MIC technique should also be possible [8, 9].
In German-speaking countries, ethanol 95% and NaCl 20% are most commonly used as protoscolicidal substances. With increasing dilution, the protoscolicidal effect decreases. Only ethanol 95%, NaCl 20%, and chlorhexidine 10% can achieve a protoscolicidal effect after 5 minutes of exposure [4]. To prevent the spread of parasites during an open surgical procedure, cysts and liver should be covered with abdominal towels soaked in 20% NaCl solution.
Surgical Treatment
In hepatic CE, there is principally the possibility to resect the cyst along with the affected liver segment, as is indicated in alveolar echinococcosis due to the required safety margin. However, in CE, a safety margin is not necessary; rather, the affected liver portion should be sparingly resected without accidental perforation of cysts.
For all cysts > 10 cm and for smaller cysts in stage CE2 and CE3b, where PAIR is not promising due to the cyst's internal structure [1, 10], surgical resection techniques represent the most promising therapy option, usually either as total (pericystectomy) or partial cystectomy (endocystectomy).
Another surgical procedure is the subadventitial pericystectomy, where the exocyst and inflammation-induced adventitia are bluntly separated, leaving the adventitia on the liver [11, 12]. Leaving the adventitia on the resection surface reduces the risk of bile leaks, which occur more frequently after total pericystectomy [11].
Watch and Wait
Calcified, healed cysts (CE4 and CE5) can be monitored using imaging and serology. If there is an increase in size or titer, resection may be indicated [13].
Follow-up Treatment
After curative treatment of a CE, regular clinical and sonographic follow-up is recommended [1]. Since serology normalizes after years, a titer control alone is not sufficient [14].