The sacs may be seated at any part of the liver, but are more common in the right lobe than in the left. The liver is generally enlarged by them, and may appear uniformly swollen if the sac is deep-seated. If superficially placed, the cyst raises a bump or tumour at the correspond ing part of the surface. When it lies close under the peritoneal coat of the liver, this membrane becomes thickened and may form adhesions with parts around. The pressure of the sac upon the parenchyma of the organ causes destruction and atrophy of the hepatic tissue. The larger blood vessels and bile-ducts are seldom affected ; but occasionally the ducts may be obliterated, or a communication may be formed between the sac and a large duct or blood-vessel. In such cases the death of the cyst usually fol lows.
After a time changes generally take place in the mother sac. It may rupture from over-distention, and only a few shreds of the original vesicle may be left amongst the daughter cysts. Sometimes the .sac suppurates, or is converted into semi-solid atheromatous matter composed of phosphate and carbonate of lime, cholesterine, and a substance resembling albumen. In other cases adhesions may be formed with neighbouring parts, and the cyst may burst into the stomach or bowels, or through the diaphragm into the pleura or lung. Accidental injiuies have caused rupture of the cyst and extravasation of its contents into the peritoneal cavity. In rare cases the hydatid sac has been known to open externally through the ab dominal prides or a lower intercostal space. After escape of the fluid by any of these means, suppuration of the cyst may still take place, and pymmia is one of the consequences which may result. Sometimes, al though rarely, the increase in thickness of the capsule, which may acquire a cartilaginous consistence, so interferes with the development of the echinococcus that death ensues and a spontaneous cure is effected. This, however, is not likely to occur except in hydatids of small size which have not been detected during life.
Symptoms.—When the cyst is small and is planted deeply in the sub stance of the liver, it may give rise to no symptoms at all. In most cases, however, the liver becomes enlarged, but not uniformly. A tumour is felt at one part of the organ which may project upwards into the chest or down wards into the belly. The swelling is painless as a rule, and may give rise to no uneasiness, but a feeling of weight. It is smooth, round, often elas tic, and may convey a distinct sense of fluctuation. Sometimes, however, as in a case to be afterwards narrated, it feels firm and solid like a fibrous growth. In exceptional cases a sense of vibration, first described by Piorry
as the " hydatid fremitus," is felt by sharply percussing the finger allowed to rest upon the tumour. This vibration, according to Dr. Sadde, denotes the presence of daughter vesicles. Therefore, if vibration is absent, we should expect to find few or no hooklets. Occasionally, pain has been no ticed from mere distention, as in a case mentioned by Frerichs, where the pain ceased after puncture and removal of a quantity of watery fluid from the cyst. As a rule, pain, if present, indicates inflammation and suppura tion of the sac.
As the tumour seldom interferes with the channels of the bile-ducts or portal vessels, jaundice and ascites are rare, and dyspeptic symptoms are seldom observed. In ordinary cases, therefore, the nutrition of the child is not interfered with, and there is no fever. The patient is brought for advice merely on account of the unusual size and unilateral hardness of his belly. In young subjects the projection, as a rule, is readily detected by the eye, and if seated near the convex surface of the right lobe, as it usu ally is, forms a swelling which protrudes downward from beneath the lower ribs.
A little boy, aged five years and a half, was brought to me at the hos pital on account of the size of his belly and occasional pains which he com plained of in the right hypochondrium. He had, besides, some cough in the morning. On examination of the abdomen, a prominent swelling was discovered in the hepatic region, bounded above by the ribs, and below by a line drawn just below the level of the navel. Its transverse measurement was three and a half inches. The liver dulness began above one finger's breadth below the nipple, and its lower edge could be felt just below the lower border of the tumour. The swelling was smooth, elastic, and gave a semi-fluctuating sensation to the finger. There was no hydatid fremitus. When pressure was made upon it, the child flinched and said it was sore. There was no jaundice, ascites, or prominence of the superficial abdominal veins. The swelling was punctured with the pneumatic aspirator through the abdominal parietes, and about an ounce of purulent matter was evac uated. No hooklets could be detected. Ten days afterwards the cyst had refilled. It was again punctured, and a quantity of perfectly clear fluid escaped. The cyst did not again refill, and the size of the liver was greatly reduced when the child left the hospital.