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The Liver and the Biliary System
Published in E. George Elias, CRC Handbook of Surgical Oncology, 2020
Hydatid disease is rare in this country. However, it is common in South America, the Middle East, Australia, South Africa, Greece, and Eastern Europe. It is usually caused by Echinococcus granulosa, but occasionally by Echinococcus multilocularis which is a more serious disease as it has infiltrative power. The cyst usually appears as a calcified lesion on the X-ray which helps in making the diagnosis. The wall of the cyst consists of three layers: an outside layer of compressed liver tissue, a laminated layer, and an inner epithelial layer. This inner layer contains the daughter cysts. The fluid in the hydatid cysts is usually under high pressure that may reach up to 300 mm of water. The diagnosis of hydatid cysts is made by the Casoni test which is a purified hydatid fluid injected intradermally and read in 15 min. Erythema indicates a positive test. However, this test has a 25% margin of error.
Laboratory Investigations in Infectious Uveitis
Published in Ocular Immunology and Inflammation, 2023
Parthopratim Dutta Majumder, Manabu Mochizuki, Julio J González-López, John Gonzales, Megha Sharma, Kusum Sharma, Jyotirmay Biswas
The use of skin tests in diagnosing infectious uveitis has reduced dramatically in the last few decades. Tuberculin skin test remains the most common test used as supportive evidence towards establishing a diagnosis of ocular tuberculosis.107 The test measures the degree of type IV delayed hypersensitivity reaction after 48–72 hours of an intradermal injection of 5 tuberculin units (0.1 ml) of purified protein derivative. The test is considered positive if the induration exceeds 5 mm and at various thresholds of 5,10, and 15 mm, depending on the health condition and risk profile of the patients.108 The test cannot discriminate between latent tuberculosis and active tuberculosis and has low specificity and sensitivity. The false-positive reaction can be seen in previous Bacille Calmette-Guérin (BCG) vaccination and infections with non-tuberculous bacteria. A false-negative reaction can be seen in patients with compromised immune function. Care must be taken while interpreting tuberculin skin test result in patients with psoriasis and Behçet’s disease with uveitis, as these conditions can show false-positive results secondary to their primary disease process.109 The lepromin test is a similar skin test where inactivated M. leprae extracted from lepromas is injected intradermally. The test result is interpreted in two-phase. The early one is read at 24 to 48 hours, known as the Fernández reaction. The late interpretation of the test is done at 21 days and is called the Mitsuda reaction.110 Healthy individuals and patients with lepromatous leprosy will not show any reaction, whereas a positive skin reaction will be seen in tuberculoid and borderline tuberculoid leprosy patients.102 Thus, the lepromin test has very little diagnostic value and is rarely used. The literature on the use of skin tests in various other infectious entities remains sparse. The diagnosis of subretinal hydatid cyst in a 2-year-old boy who presented without inflammation and secondary convergent strabismus was made by a positive Casoni test.111 The Casoni test has a sensitivity and specificity of 63.8% and 47%, respectively, for the diagnosis of hydatid cyst and has now largely been replaced by the use of immunoassays. The histoplasmin test has been reported to cause exacerbation of the intraocular inflammation secondary to ocular histoplasmosis and is currently not used routinely.112 The leishmanin skin test (also known as Montenegro skin test), though rarely used for the routine diagnosis of leishmaniasis, is recently being advocated to determine exposure and immunity to Leishmania, which could be helpful in vaccine campaigns against this pathogen.113