If there is calcification within the wall of a splenic cyst, it is usually recognizable on plain radiographs of the abdomen and sometimes of the chest (Fig. 3.69). Where one or more large noncalcified hydatids are present, splenomegaly may be noted and may lead to accidental discovery of the cyst on ultrasonography (Fig. 3.70), angiography, or nuclear scanning. Hydatid cysts may also be accidentally discovered on CT and/or MRI done for other purposes (Fig. 3.71). All the imaging findings are similar to those described earlier for the liver and other organs.

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Fig. 3.69 Large calcified unilocular hydatid cysts of the spleen in 4 different patients. (A) In addition to the large calcified splenic cyst, there is a smaller calcified hydatid in the liver just to the right of the midline. (B) Dense calcification within a large splenic hydatid. (C) Calcified splenic hydatid with downward displacement of splenic flexure of colon on barium enema. (D) Large calcified splenic hydatid seen as a chance finding on barium swallow exam of a woman from Nairobi, Kenya.

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Fig. 3.70 Ultrasound scans of splenic hydatids. (A) Large hydatid cyst with a number of smaller cysts in a Saudi Arabian patient. Echos from the bottom of daughter cysts indicate "hydatid sand". (Courtesy of Dr. von Sinner). (B) 60-year-old woman from Tunisia with multiple hydatid cysts in the spleen. (Courtesy of Dr. Gharbi, Tunis). (C) Old calcified collapsed splenic hydatid (arrow) in a patient from Kenya. (Courtesy of' WHO, Geneva).

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Fig. 3.71 CT scans of splenic hydatids in 4 different Saudi Arabian patients. (A) Multiple type I and II hydatids in both lobes of the liver and a solitary huge unilocular type I hydatid which has replaced most of the splenic parenchyma on a noncontrast CT scan. (B) Eccentrically located splenic hydatid causing a prominent bulge in the posterior splenic capsule on contrast-enhanced CT. Such a cyst can rupture into the retroperitoneum. (C) Contrast-enhanced CT scan showing a huge type II hydatid with numerous daughter cysts, which has replaced virtually the entire splenic parenchyma. (D) Multiple hypermature type II hydatids in the left lobe of the liver and in the spleen with multiple daughter cysts and considerable matrix on contrast-enhanced CT scan. The wall of the anterior splenic cyst is partially calcified. (E) Unilocular type III splenic hydatid. There is thick rim calcification of the pericyst and calcification of collapsed whirl-like parasitic membranes within the cyst. (Courtesy of Dr. von Sinner and Acta Radiologica, 1992).