Echinococcosis of the liver, also known as hydatid disease of the liv-er, is caused by infection with the larvae or encysts of cestodes. Echinococcus granulosus is parasitic in dogs and is the final host, with humans, sheep and cattle as intermediate hosts. It is not infectious from human to human. Etiology and pathologyThere are four recognized species of tapeworms: fine-grained echinococcus, alveolar echi-nococcosis or echinococcus multilocularis, echinococcusVogeli Rausch, and oligococcus echinococcus (echinococcus oligaris). echinococcus oligarthrus). Its morphology, hosts and distribution areas vary slightly, and it is mainly prevalent in livestock areas. In China, it is common in Xinjiang, Qinghai, Gansu, Ningxia, Tibet, Inner Mongolia, Shaanxi and western Sichuan, and there are also disseminated cases in Hebei and northeastern provinces. Fine-grained Echinococcus tapeworm is the most common, and vesicular Echinococcus tapeworm has also been reported. The PLA 302 Hospital General Surgery Treatment Center Chu Yankui direct infection is mainly in close contact with the dog, the eggs on the fur contaminated hands after oral infection. If the eggs in dog feces contaminate vegetables or water sources, especially if humans and animals drink from the same water source, they can also be indirectly infected. In arid and windy areas, respiratory infection may also occur when eggs are carried in the wind. Most of the larvae are blocked and remain in the liver (75%), while a few may pass through the liver to the lungs (15%) and even spread to the brain, orbit, spleen, kidney and muscle. The larvae then develop into encysted larvae in the body. Echinococcosis entering the liver is initially a cystic structure, which stimulates the surrounding cells to react and form internal and external cysts. The inner capsule is divided into two layers: the inner layer is the germ layer, which grows into a tipped, germ cell-bearing head and germinal capsule. The hair growth capsule eventually ruptures, releasing the head nodes into the capsule fluid, which settles to the bottom and is called capsule sand. The nutrients in the cyst fluid are consumed by the cysts and cephalopods, resulting in the death of the worm and calcification of the cyst wall. The outer layer is a multilayered cuticle, elastic and white and translucent. The outer capsule is derived from a fibrous envelope formed by the host tissue and is thick and calcifiable (Figure 41-4). Calcification does not always mean that the encysted cyst is dead