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Type I lesions have a non-specific cystic appearance but if the patient is rotated immediately before US scanning the settling hydatid sand produces signals which have been likened to falling snow (Fig. 3.33). The pericyst is rarely identified by US (Fig. 3.35), and is seen by CT only if it is calcified (Fig. 3.34). However, it is demonstrable by MRI, particularly on T2-weighted images which produce a low intensity rim. Neither the cyst nor the pericyst enhance by CT or MRI as they are avascular. Lung hydatids are sometimes umbilicated on plain radiographs due to pressure on the cyst wall from adjacent blood vessels or major bronchi.

Fig. 3.33 Type I and II hydatid liver cysts in 3 different Saudi Arabian patients. (A) Non-contrast CT scan shows a solitary type I liver hydatid. (B) Ultrasound scan reveals echos at bottom of a liver hydatid caused by hydatid sand (arrows). (C) Type I and II hydatid cysts demonstrated on non-contrast CT. The type II cysts appear septated because the walls of multiple daughter cysts abutt one another (white arrows). Some hydatids show edema (black arrows) surrounding the cysts after albendazole treatment. (Courtesy of Dr. von Sinner and Eur J Rad, 1991).

	Imaging of Unruptured Cysts Type I lesions have a non-specific cystic appearance but if the patient is rotated immediately before US scanning the settling hydatid sand produces signals which have been likened to falling snow (Fig. 3.33). The pericyst is rarely identified by US (Fig. 3.35), and is seen by CT only if it is calcified (Fig. 3.34). However, it is demonstrable by MRI, particularly on T2-weighted images which produce a low intensity rim. Neither the cyst nor the pericyst enhance by CT or MRI as they are avascular. Lung hydatids are sometimes umbilicated on plain radiographs due to pressure on the cyst wall from adjacent blood vessels or major bronchi. .. Fig. 3.33 Type I and II hydatid liver cysts in 3 different Saudi Arabian patients. (A) Non-contrast CT scan shows a solitary type I liver hydatid. (B) Ultrasound scan reveals echos at bottom of a liver hydatid caused by hydatid sand (arrows). (C) Type I and II hydatid cysts demonstrated on non-contrast CT. The type II cysts appear septated because the walls of multiple daughter cysts abutt one another (white arrows). Some hydatids show edema (black arrows) surrounding the cysts after albendazole treatment. (Courtesy of Dr. von Sinner and Eur J Rad, 1991). .. .. Fig. 3.34 Type I, II and III unruptured hydatid cysts in 4 different patients from Tunisia. (A) Univesicular uncomplicated type I cyst in a 54-year-old man. (B) Multivesicular type II hydatid with multiple daughter cysts giving a septated appearance to the cyst in a 21-year-old woman. Dilated pericystic bile ducts are seen about the cyst periphery posteriorly. (C) Old hypermature liver hydatid in a 64-year-old man. Non-contrast CT shows calcification in the cyst wall and matrix and fluid within the cyst, suggesting it is still evolving and not innocuous and should be treated. (D) Two hydatid liver cysts in a 75-year-old man. The larger pseudotumoral cyst has some calcification in its wall while the smaller type III cyst is totally calcified on non-contrast CT. (Courtesy of Dr. Ben Cheikh and Dr. Gharbi, Tunis, Tunisia). .... .... Fig. 3.35 Ultrasound identification of type I and II liver hydatid cysts in 3 different Kenyan patients. (A) Large simple type I liver hydatid with clear fluid. (B) Type II hydatid with multiple daughter cysts. (C and D) Large hypermature hydatid cyst filled with debris. Some detachment of the cyst wall from the host pericyst is noted. (Courtesy of Dr. Wachira, Nairobi, Kenya). Next Page Previous Page