OVERVIEW
Hepatic encapsulated cysts are most commonly found in pastoral areas, with the onset of disease in populations in South America, Southern Europe and Australia associated with sheep herding, in Iran and Iraq with camels, and in Canada and Alaska possibly with reindeer. China’s Inner Mongolia, northwest, western Sichuan, Tibet and other regions are more common. The disease is also known as hepatic echinococcosis, caused by the larvae of the fine-grained echinococcus tapeworm invading the liver.
Etiology
Human liver cysts are the asexual stage of Echinococcus granulosus tapeworm with a human intermediate host. The primary hosts of this tapeworm are dogs, foxes, or wolves, and the intermediate hosts are sheep, cattle, horses, pigs, and humans. The tapeworm parasitizes the villi of the small intestine of dogs, and the adult tapeworm continuously excretes shell-protected hexacoccid larvae, which are excreted in the feces and adhered to the dog’s coat or wool. People or other intermediate hosts can be infected by contacting and swallowing water or food contaminated with this larva. After digestion in the stomach or upper small intestine, the larvae are released from their shells and pass through the gastrointestinal wall to enter the portal vein, with most of them staying in the liver, and a few of them escaping to the lungs and other organs. Echinococcus granulosus in the relevant organs first formed the initial encapsulated cysts, the wall of this cyst that is followed by the internal capsule, and the intermediate host tissue in the formation of a fibrous envelope around it for the external capsule. The internal capsule is further divided into the outer and inner layers, the outer layer is called the cuticle, the inner layer is the germinal layer, and the germinal layer produces the germinal capsule, the head node, the daughter capsule, and the grandson capsule. The parasite completes its life cycle when the internal organs of sheep, cattle or other intermediate hosts infected with the parasite are eaten by dogs, foxes or wolves.
Symptoms
Clinical manifestations are not obvious, and are common in young and middle-aged people. Initially, there may be no symptoms, and as the cysts increase, epigastric masses, abdominal distension, abdominal pain may be detected, and respiratory symptoms may be observed due to elevation of the diaphragm, if located in the right upper liver. Many patients have had allergic reactions. In a few cases, jaundice may occur due to compression of the biliary tract by the cyst. There are also cases of co-infection or penetration into the bile ducts, resulting in cholangitis or even sepsis. Respiratory symptoms or bronchobiliary fistula may occur if the cyst penetrates into the thoracic cavity. Physical signs are mainly cystic masses in the epigastric region, and only hepatomegaly is seen if the cyst is located above the liver.
Examination
1. Intradermal test for encapsulated cystic fluid (Cassoni test)
It is a specific immune reaction.
2. Complement binding test
Positive rate can reach 70%～80%.
3. Blood tests
Eosinophils are increased.
4. B-mode ultrasonography
Liquid dark area can be seen in the liver area, and the location and size of the cyst can be determined. Hepatic vesicular echinococcosis needs to be diagnosed in conjunction with the history and the carsoni test.
5. Hepatic nuclear scan
If the diameter of the cyst is >2~3cm, it can show space-occupying lesions in the liver.
6. X-ray examination
The liver shadow is enlarged and the right side of the diaphragm is elevated or bulging. Hepatic area may show shadows or calcified shadows, and cysts in the anterior and inferior part of the liver may show signs of gastrointestinal tract compression.
7. CT, selective abdominal arteriography
Helpful in differential diagnosis.
Diagnosis
Diagnosis can be made on the basis of epidemiologic history, clinical manifestations and the above tests. Anyone who is suspected of having a liver cyst should not be punctured.
Differential diagnosis
1. Congenital liver cyst
There is no history of pastoral residence, ultrasound shows that the cyst wall is extremely thin and clear, and the intradermal test of peritoneal cyst fluid is negative.
2. Liver abscess
No history of pastoral residence, but often have history of dysentery or septicemia, ultrasound shows fluid occupying unclear boundary, clinical history or manifestation of inflammation, negative peritoneal test for cystic fluid. However, co-infected hepatic cysts are easily confused with it, and the intradermal test for cystic fluid is the main basis for differentiation.
Complications
Rupture of the cyst and spillage of cystic fluid leading to allergy, anaphylaxis, or the entry of the cephalic ganglia into the abdominal cavity to form a secondary worm cyst.
Treatment
1. Follow-up
For small and deep-lying liver cysts, close follow-up and regular ultrasonography can be performed. If the cysts increase in size to close to the surface of the liver, they can be treated surgically.
2.Removal of internal capsule
It is the most common surgical procedure for this disease.
3. Combined infection
Drainage is needed. Hepatic resection is seldom used and is only suitable for individual cases, such as those who estimate that the cyst wall is thick and calcified and the internal capsule is not easy to remove, or those who estimate that it is difficult to heal the residual cavity or sinusoidal tracts after drainage of multiple encapsulated cysts confined to one lobe.
Prognosis
The operative mortality rate for surgical treatment of hepatic inclusion cysts varies from 1.8% to 9%, usually 2% to 4%, and the postoperative recurrence rate varies from 5% to 12%, most often due to the omission of small, deep-lying cysts at the time of the first operation or implantation of the head nodes at the time of surgery.