Hydatid Infection of the Liver PDF

Hydatid infection of the liver By Dr. Heba Ahmed Osman Associate professor of tropical medicine and gastroenterology  Introduction Echinococcosis also known as (hydatid disease) has a worldwide distribution. Hydatid disease is a zoonotic parasitic disease cau...

Hydatid infection of the liver By Dr. Heba Ahmed Osman Associate professor of tropical medicine and gastroenterology  Introduction Echinococcosis also known as (hydatid disease) has a worldwide distribution. Hydatid disease is a zoonotic parasitic disease caused by a small tapeworm of the genus Echinococcus. CG A Mu Echinococcus granulosus causing cystic echinococcosis (CE) and Echinococcus multilocularis causing alveolar echinococcosis. 2 Mode of transmission The adult worm inhabits the intestine of a canine species commonly the dog which is the definitive host. The gravid worm releases embryonated eggs in dog feces. (infective stage) These are ingested by the intermediate host, commonly sheep, swine, horses, camels, and men. Man is an accidental intermediate host. The eggs hatch in the intestines of the intermediate host and release oncospheres which penetrate the host intestines to enter the portal circulation and travel to the liver. Once through the liver, oncospheres enter the general circulation and travel to other organs. 3  Pathogenesis and Cyst Wall Components The liver and lung were the common sites for developing hydatid cysts in 75% and 15%, respectively. The compression of the liver due to the growing cyst and the inflammatory response elicited from the presence of the cyst result in the formation of the pericyst which is entirely host tissue. The tough fibrotic pericyst prevents complete collapse of the residual cystic cavity after therapeutic evacuation. 4  The inner layer is the lamellar layer of the hydatid cyst. On the inside, it is covered with the germinal layer, producing the daughter cysts which can get detached or burrow through the wall to fistulate into surrounding body structures. The intracystic contents degenerate in older longstanding cysts to a gelatinous amber colored structure called the “matrix.” The appearance is often referred to as a pseudotumor and needs differentiation from a pyogenic abscess. Endocyst calcification when seen is indicative of a dead cyst. Pericyst calcification alone is commonly detected by imaging techniques in a third of cases and does not necessarily indicate a dead cyst. 5 Diagnosis In our approach to the cyst, we need to confirm the diagnosis and exclude other cystic lesions of the liver. Liver hydatid cysts may present in three ways: 1. Asymptomatic: these get picked up incidentally on imaging done for surveillance in endemic areas or during imaging for an unrelated indication. 2. Uncomplicated cysts: presenting due to size and location. 6 3. Complicated cysts: due to infection and/or rupture into bile ducts, surrounding organs, or cavity. (A rupture into the peritoneal cavity and biliary tree can present with pain, shock, and features of anaphylaxis). In addition, cysts can become infected and then behave like a liver abscess and need treatment accordingly. Pressure on the portal vein can cause features of extrahepatic portal vein obstruction with splenomegaly and enlarged collaterals and varices. Caval compression directly by a large cyst can cause features of IVC obstruction with dependent edema and dilated flank veins. 7 Serum Tests for Hydatid Disease Serological tests for antibody detection and assay using ELISA are widely available, even though sensitivity for liver hydatid is reported between 85 and 98%, the specificity is limited due to cross-reaction with presence of other parasites. Presently, there are no serological tests which can differentiate sub-species of Echinococcus. ELISA positivity increases with duration of the infestation and with age. 8 Imaging Ultrasound provides a very effective means of diagnosing hydatid cysts. Imaging with CT and MRI is needed to further define the location of the cyst for therapeutic planning as also to look for complications, the most important being the presence of cyst-biliary communication. 9 Treatment of Hydatid Liver Current treatment options include one or more of the following modalities: 1. Drug treatment 2. Puncture aspiration injection reaspiration (PAIR) 3. Surgery 4. Wait and watch 10 Drug Treatment Albendazole is the current drug of choice for management of hydatid cyst. It is not recommended for primary treatment alone unless the patient is unwilling or unfit for surgery. Drug treatment in a dose of 10–15 mg/kg in divided doses daily for 8–12 weeks. The addition of praziquantel does not increase intracystic albendazole levels. Drug bioavailability is increased by taking the drug with a fatty meal and avoiding a high intragastric pH, e.g., due to use of proton pumps inhibitors while on albendazole therapy. 11  Safety profile of the drug is good, and even prolonged use is free from serious side effects. The common side effects are transient increase in liver enzymes and leukopenia. Complete hair loss is a very rare occurrence and fortunately reversible. 12 Puncture Aspiration Injection Reaspiration What is PAIR? PAIR refers to image-guided, usually ultrasound-guided percutaneous drainage of the intraabdominal hydatid cysts of the liver by a fine needle which is also used for injection of a scolicidal solution (e.g. 20% hypertonic saline) to kill live elements of the cyst. Large cysts more than 5 cm may require a drainage tube to be left in the cyst cavity, in which case the procedure is known as PAIR-D. 13 Indications for PAIR Multiple cysts if accessible to puncture Infected cysts Pregnant women and patients who are not fit for or refuse surgery Patients who recur after surgery or who do not respond to chemotherapy alone Contraindications for PAIR - Non-co-operative patients - Non-accessible cyst location - Mature calcified cysts - Cysts with biliary communication - Cysts opening into body cavities are considered unsuitable for PAIR. 14  Pre-PAIR treatment with albendazole for at least 4 h to 1 week and continuation of drug treatment for at least 1 month or more after the procedure. The duration of treatment depends on the size of the cyst and continues till the cyst appears almost solid in follow-up ultrasound examinations. The optimum duration of treatment with albendazole has not yet been fully studied and may vary from a few weeks to several months. 15 Surgical Treatment Surgery remains the treatment of choice for complicated cysts and was considered the only curative option for hepatic hydatid disease. Aims of Surgery These include total removal of live infected components, prevention of spillage, management of residual cavity and cystobiliary communication. Indication for Surgery Active Cyst (cyst with Multivesicular fluid collection with multiple daughter cysts or septae [honeycomb], cyst with Fluid collection with membrane detached [water lily sign]) with size > 5–6 cm and any cyst with size >10 cm. Complicated and recurrent cysts after previous surgery or PAIR. 16 Wait and Watch Cyst with (heterogenous matrix or Solid cystic wall) can remain inactive and dormant for prolonged periods, sometimes indefinitely. These can be safely followed up by ultrasound examination. In these cases, intervention is only indicated when complications occur (e.g., pain). 17 Thank you