In primary echinococcosis, approximately two thirds of patients experience liver hydatid cysts. In 85% of cases, the cysts are located in the right lobe of the liver. The second most commonly involved organ is the lungs. Because of the slow rate of growth of the cysts, patients with simple uncomplicated cysts are usually asymptomatic. The cysts are often discovered incidentally on routine imaging studies. In patients with liver echinococcosis, the most common symptoms are mild abdominal pain and an upper abdominal mass. Upon physical examination, hepatomegaly may be present in addition to a palpable abdominal mass. In about 10% of the patients, an elevated eosinophil count is noted.
More dramatic findings are present when complications of hydatid cyst disease occur. The most frequent complication in hepatic echinococcosis is intrabiliary rupture, which occurs in approximately 10-15% of patients. This results in biliary obstruction manifested by jaundice and biliary colic. In some cases, cholangitis or, even more rarely, pancreatitis may ensue. Infection of the cyst may also occur, and it is usually caused by bacteria residing in the biliary system. This may result in fever, leukocytosis, and possible formation of a liver abscess. Patients may be septic and should be treated aggressively with broad-spectrum antibiotics if signs of systemic infection are present.
Rupture of a hydatid cyst into the peritoneal cavity may happen spontaneously or may be caused by trauma, as in this case. Symptoms following the rupture are often dramatic and may include severe abdominal pain, syncope, or fever. Some patients exhibit signs of an allergic reaction, such as pruritus, urticaria, eosinophilia, or even anaphylaxis. Intraperitoneal rupture usually results in secondary implantation of cysts into the peritoneal cavity. Some rare but possible complications of liver echinococcosis include ascites, portal hypertension, Budd-Chiari syndrome, or compression of the vena cava.
Rupture of the cyst into the vena cava is a very rare but universally fatal complication. Pulmonary hydatid cysts, when symptomatic, can cause chest pain, chronic cough, or hemoptysis. They may rupture into the bronchial tree and cause expectoration of a cyst fluid. Rupture of the hydatid cyst into the pleural cavity leads to pleuritic chest pain and dyspnea. Although rare, localization of hydatid cysts in the CNS can cause neurologic symptoms related to mass effect, including headache and seizures. Infection of skeletal tissue can cause pathologic fractures as a result of invasion of the medullar cavity and slow bone erosion. Cardiac involvement may result in pericarditis or conduction abnormalities.
Various radiographic and related imaging techniques can be used in detecting and evaluating echinococcal cysts in different parts of the body. Plain x-rays may show pulmonary cysts as round masses with uniform density. Hydatid cysts are not typically seen on plain abdominal x-rays unless calcification is present. Ultrasonography is the method of choice in detecting and evaluating hepatic hydatid cysts. It can reveal well-defined cysts with thick or thin walls in otherwise solid organs. It can also elucidate the density of the fluid inside the cyst.
The most pathognomonic finding on ultrasonography is the presence of daughter cysts; however, small cysts under 2 cm in size and peripherally located cysts can be missed by ultrasonography. Hydatid cysts may be unable to be distinguished from simple benign cysts if no signs of daughter cysts are present. CT scanning is no more sensitive or specific than ultrasonography, but it is useful in localization of the cyst and defining its relation to other structures, such as large blood vessels or biliary structures. This is very valuable when the clinician is considering surgery.
Immunologic diagnosis is highly sophisticated and is used to distinguish simple benign cysts from hydatid cysts. It is also used for postsurgical monitoring of persistent disease. The most valuable serologic test in the diagnosis of human hydatid disease is immunoelectrophoresis. It is highly specific but requires high levels of antibodies for sensitivity. It is also the most valuable test for postsurgical monitoring because of its relative rapid reversion to negative when the organism is cleared. Enzyme-linked immunosorbent assay (ELISA) is a valuable test for primary diagnosis, but it is not useful in postsurgical follow-up because it takes years to revert to negative. Latex agglutination or indirect hemagglutination tests may be also be used for diagnosis. The sensitivity of these tests is best for hepatic disease, but it is much less sensitive for detecting lung or other organ disease.
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