A Case of Hydatid Cyst in County Antrim

HYDATID disease is due to the development in man, acting as an intermediate host, of the cystic larval form of a small tapeworm, Echinococcus granulosus, the normal habitat of which is the ileum of the dog. Ova from an infected dog are deposited with its faeces on the ground. By this means grass and vegetables are polluted with ova, and when eaten by sheep, cattle, goats or occasionally by man the ova gain access to the alimentary tract. The alkaline juices of the duodenum dissolve the outer coat and release the embryo. By means of its sharp hooklets, the embryo bores its way through the mucosa of the duodenum and enters the venous channels of the portal system. It is then carried to the liver, and if it passes through the liver, it is carried to the lungs via the right side of the heart. If it is not caught in either the liver or the lungs, it reaches the general circulation by means of the left side of the heart, and can then be carried to lodge anywhere in the body. When the embryo lodges in an organ it forms an hydatid cyst. The cyst consists of an outer layer, the ectocyst, which is formed from the tissues of the host, and an inner layer, the endocyst which produces both the hydatid fluid and the scolices. If a dog eats infected tissues of a sheep or cow each scolex which reaches the intestine of the dog can form an adult tapeworm. The disease has a definite geographical distribution, and is common in Australia, the Middle East, Algeria, and Iceland. It is rare in the British Isles, and I have found only one reference in the literature to a case in Northern Ireland (Fraser, 1930). It is for that reason that the following case is reported.