Thursday, November 19, 2009

Cardiac hydatid cyst

CT scan of 58 year old male patient showing large well defined well capsulated hypodense lesion seen in the myocardium of the left ventricle with multiple daughter cysts within suggestive of hydatid cyst.
  • Hydatid disease is a parasitic infection caused by larvae of Echinococcus granulosus, which is still endemic in many sheepraising countries.
  • Hydatid cysts can be located in various tissues, although they are most common in the liver (50–70% of cases) and the lung (20–30% of cases) in humans.
  • Cardiac involvement in hydatid disease is uncommon, constituting only 0.5–2% of all cases of hydatidosis.
  • Heart involvement - LV – 60%, RV – 10%, pericardium – 7%, pulm Artery – 6%, left atrial appendage – 6%, and interventricular septum is rare – 4%.
  • Cardiac involvement occurs by invasion of the myocardium - Through coronary circulation or pulmonary vein from rupture of pulm cysts in to vein.
  • Signs and Symptoms •No symptoms due to its latency and slow growing nature unless it is situated in critical site. •Signs and symptoms are extremely variable and directly related to location and size of the cysts. •Precordial pain is the most common symptom and is most often vague and does not resemble angina pectoris. •Sudden rupture of intracardiac cysts is a frightful complication and can cause acute pericarditis or tamponade, acute pulmonary hypertension by embolization of several scolices, systemic arterial embolization, and severe anaphylactic shock can be life thretening.

  • Imaging - Echocardiography, CT, and MRI can show the cystic nature of the mass and its relation to the cardiac chambers •CT best shows wall calcification. •MRI depicts the exact anatomic location and nature of the internal and external structures and is the technique used for posttreatment follow-up.
  • The appearance of a hydatid cyst on MRI is usually a characteristic oval lesion that is hypointense on T1-weighted images and hyperintense on T2-weighted images. •A typical finding on T2-weighted images is a hypointense peripheral ring, which represents the pericyst (a dense fibrous capsule from the reactive host tissue). •A variety of tumors in the heart and a congenital pericardial cyst must be considered in the differential diagnosis; however, the multivesicular nature of the cystic mass and membrane detachment indicate the true diagnosis.
  • The cysts may be single or multiple, uni or multiloculated, and thin or thick walled. •More specific signs are •Cyst wall calcification. •Presence of daughter cysts and Membrane detachment.
  • •Surgery remains the treatment of choice in the management of hydatid disease. •Although antihelminthic drugs have been used in the preoperative and postoperative periods since 1977, extirpation of the lesion under cardiopulmonary bypass is recommended.
  • To conclude CT and MRI are helpful for localizing and defining the morphologic features of hydatid cysts. •Specific signs include calcification of the cyst wall, presence of daughter cysts, and membrane detachment. •CT best shows wall calcification, whereas MRI depicts the exact anatomic location and nature of the internal and external structures.

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