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Hydatid Disease: Radiologic and Pathologic Features and Complications¹

(CME Available in print version and on RSNA Link)

¹ From the Department of Diagnostic Imaging, Hospital Clínico San Carlos, Universidad Complutense, C/ Martín Lagos s/n, 28040 Madrid, Spain. Presented as a scientific exhibit at the 1998 RSNA scientific assembly. Received April 5, 1999; revision requested May 10 and received July 7; accepted July 7. Address reprint requests to I.P. (e-mail: ipedrosa@hotmail.com).

View larger version (93K): [in a new window]   Figure 1.   Geographic distribution of hydatid disease. Map shows areas in which hydatid disease is endemic due to the transmission of E granulosus by means of the dog-sheep cycle (solid red areas). Red stripes indicate areas where transmission occurs by means of alternative life cycles in which carnivores such as wolves and foxes serve as definitive hosts and goats, camels, and horses serve as intermediate hosts. Transmission by means of alternative life cycles is common in North Africa, the Middle and Far East, the United States, Canada, and Iceland.

View larger version (56K): [in a new window]   Figure 2.   Life cycle (dog-sheep cycle) of E granulosus. Diagram shows the most prevalent life cycle of E granulosus, in which a dog and sheep serve as the definitive and intermediate hosts, respectively.

View larger version (115K): [in a new window]   Figure 3a.   Calcified cysts in an intermediate host. (a) Photograph of a resected specimen from a sheep liver shows two calcified cysts (arrows). (b) Computed tomographic (CT) scan of the specimen shows the larger cyst (arrow). Dense calcification of the pericyst and cyst contents is common in end-stage hydatid disease and implies the death of the parasite.

View larger version (64K): [in a new window]   Figure 3b.   Calcified cysts in an intermediate host. (a) Photograph of a resected specimen from a sheep liver shows two calcified cysts (arrows). (b) Computed tomographic (CT) scan of the specimen shows the larger cyst (arrow). Dense calcification of the pericyst and cyst contents is common in end-stage hydatid disease and implies the death of the parasite.

View larger version (137K): [in a new window]   Figure 4.   Multivesicular cyst. Photograph of a human kidney that has been sectioned along the midcoronal plane demonstrates a large cyst with the typical "bunch of grapes" appearance (black arrows) due to the presence of daughter cysts (arrowheads). White arrows indicate the ureter. (Courtesy of Mónica García-Cosío, MD, Department of Pathology, Hospital Ramón y Cajal, Madrid, Spain.)

View larger version (79K): [in a new window]   Figure 5.   Scolex in a middle-aged man who presented with jaundice, fever, and right upper quadrant pain. Photomicrograph (original magnification,  x 40; Papanicolaou stain) clearly depicts a scolex obtained from pleural fluid. E granulosus uses hooklets (arrows) to attach itself to the duodenal mucosa of the host.

View larger version (197K): [in a new window]   Figure 6.   Completely calcified hydatid cysts in a 62-year-old patient. Digital scout image from an abdominal CT examination shows three round, densely calcified lesions (arrows). The lesions were discovered incidentally. The patient confirmed that they had been present for many years.

View larger version (177K): [in a new window]   Figure 7a.   Hydatid cyst mimicking a solid mass. (a) US image shows a round lesion with a mixed echogenic pattern in segment IV of the liver (L). Note the serpentine structures within the matrix representing collapsed membranes (arrowheads). PV  = left portal vein. (b) Unenhanced CT scan obtained in a different patient shows a hydatid cyst with the characteristic solid appearance growing exophytically from the right hepatic lobe. There are several minimally calcified foci within the cyst (arrows).

View larger version (149K): [in a new window]   Figure 7b.   Hydatid cyst mimicking a solid mass. (a) US image shows a round lesion with a mixed echogenic pattern in segment IV of the liver (L). Note the serpentine structures within the matrix representing collapsed membranes (arrowheads). PV  = left portal vein. (b) Unenhanced CT scan obtained in a different patient shows a hydatid cyst with the characteristic solid appearance growing exophytically from the right hepatic lobe. There are several minimally calcified foci within the cyst (arrows).

View larger version (147K): [in a new window]   Figure 8.   Calcified unilocular hydatid cyst. Contrast material-enhanced CT scan shows a round lesion with water attenuation and a ringlike pattern of calcification (arrows). This pattern represents calcification of the pericyst and strongly suggests a diagnosis of hydatid cyst.

View larger version (149K): [in a new window]   Figure 9.   Typical unilocular hydatid cyst. Unenhanced CT scan shows a large hydatid cyst with a noncalcified, high-attenuation wall in the right hepatic lobe (arrows). This finding can be missed if only contrast-enhanced CT is performed. Because of its elasticity, the cyst accommodates itself to neighboring structures.

View larger version (122K): [in a new window]   Figure 10.   Hydatid cyst with collapsed parasitic membranes. Unenhanced CT scan shows a dense circular area of increased attenuation within the cyst representing detached membranes (arrows).

View larger version (136K): [in a new window]   Figure 11a.   Hydatid cyst with multiple daughter vesicles. (a) US image shows three distinct daughter vesicles (arrows) with the typical peripheral location within the mother cyst. A hydatid matrix with a solid appearance is seen filling the rest of the cavity. (b) Unenhanced CT scan shows the typical peripheral location of the daughter vesicles within the mother cyst (arrows). There is partial calcification of the pericyst.

View larger version (149K): [in a new window]   Figure 11b.   Hydatid cyst with multiple daughter vesicles. (a) US image shows three distinct daughter vesicles (arrows) with the typical peripheral location within the mother cyst. A hydatid matrix with a solid appearance is seen filling the rest of the cavity. (b) Unenhanced CT scan shows the typical peripheral location of the daughter vesicles within the mother cyst (arrows). There is partial calcification of the pericyst.

View larger version (111K): [in a new window]   Figure 12.   Noncalcified hydatid cysts. Axial spin-echo T1-weighted MR image demonstrates two large cystic lesions in the right hepatic lobe. The more anterior cyst has high signal intensity, probably due to a reduction in the water content of the fluid. The cyst also contains several round, nodular, low-signal-intensity lesions representing daughter cysts (arrowheads). The mother cyst has a characteristic low-signal-intensity rim (straight solid arrows). The more posterior cyst has homogeneous low signal intensity with a double ring: The hypointense outer ring represents the pericyst (open arrows), and the partially "wrinkled," intermediate-signal-intensity inner ring represents incompletely detached membranes (curved arrow).

View larger version (119K): [in a new window]   Figure 13.   Intrahepatic rupture of a hydatid cyst in a patient with acute abdominal pain in the right upper quadrant that was not related to trauma. Unenhanced CT scan shows a partially collapsed cyst that has lost its normal spherical shape. The lesion is partially calcified, and a daughter cyst is identified within the lesion (arrowhead). An incomplete wall is seen along the lateral aspect of the cyst in connection with a hypoattenuating area caused by intrahepatic extravasation of the cyst contents (arrows).

View larger version (112K): [in a new window]   Figure 14a.   Infected hydatid cyst in a patient with a history of hepatic hydatid disease. The patient presented with sudden onset of pain in the right upper quadrant, fever, and leukocytosis. (a) Unenhanced CT scan reveals an irregular, bilobulated cystic lesion in the right lobe of the liver. The thin, high-attenuation wall of the lesion (solid arrows) is surrounded by an area of low-attenuation liver parenchyma (open arrows). (b) On a dynamic CT scan obtained with bolus injection of contrast material, the cyst wall demonstrates enhancement as well as multiple layers ("split wall") (straight arrows), findings that indicate early separation of the laminated membrane from the pericyst. There is also marked enhancement of the surrounding liver parenchyma (curved arrows), probably due to perilesional inflammatory changes.

View larger version (117K): [in a new window]   Figure 14b.   Infected hydatid cyst in a patient with a history of hepatic hydatid disease. The patient presented with sudden onset of pain in the right upper quadrant, fever, and leukocytosis. (a) Unenhanced CT scan reveals an irregular, bilobulated cystic lesion in the right lobe of the liver. The thin, high-attenuation wall of the lesion (solid arrows) is surrounded by an area of low-attenuation liver parenchyma (open arrows). (b) On a dynamic CT scan obtained with bolus injection of contrast material, the cyst wall demonstrates enhancement as well as multiple layers ("split wall") (straight arrows), findings that indicate early separation of the laminated membrane from the pericyst. There is also marked enhancement of the surrounding liver parenchyma (curved arrows), probably due to perilesional inflammatory changes.

View larger version (129K): [in a new window]   Figure 15a.   Exophytic growth. (a) Drawing illustrates the two most common routes of exophytic growth: the bare area of the liver (A) and the gastrohepatic ligament (B). Growth through the bare area leads to involvement of the diaphragm (arrows) and extension into the thorax. From our experience, the gastrohepatic ligament appears to be the path by which the cyst reaches the stomach (S). (b) CT scan demonstrates a partially calcified multivesicular cyst in the right lobe of the liver. The cyst has grown posteriorly through the bare area of the liver and has a typical hourglass shape. Note the proximity of the cyst to the diaphragm (arrows), which facilitates transdiaphragmatic thoracic involvement. Arrowheads indicate daughter vesicles.

View larger version (138K): [in a new window]   Figure 15b.   Exophytic growth. (a) Drawing illustrates the two most common routes of exophytic growth: the bare area of the liver (A) and the gastrohepatic ligament (B). Growth through the bare area leads to involvement of the diaphragm (arrows) and extension into the thorax. From our experience, the gastrohepatic ligament appears to be the path by which the cyst reaches the stomach (S). (b) CT scan demonstrates a partially calcified multivesicular cyst in the right lobe of the liver. The cyst has grown posteriorly through the bare area of the liver and has a typical hourglass shape. Note the proximity of the cyst to the diaphragm (arrows), which facilitates transdiaphragmatic thoracic involvement. Arrowheads indicate daughter vesicles.

View larger version (121K): [in a new window]   Figure 16.   Diaphragmatic involvement. Unenhanced CT scan demonstrates a cystic lesion with a partially calcified septum (straight arrow). There is no evidence of perforation of the diaphragm (curved arrows), although at surgery, the cyst was seen to adhere to the diaphragmatic surface.

View larger version (165K): [in a new window]   Figure 17.   Transdiaphragmatic migration in a patient with hydatid disease at a lower hepatic level. Unenhanced CT scan reveals multiple cysts. The most external cyst is seen splitting the leaves of the diaphragm (straight arrow), the middle cyst has an incomplete posterior wall and appears to be growing into the chest cavity (arrowheads), and the medial cyst is clearly located in the thoracic cavity (curved arrow). These findings were confirmed at surgery.

View larger version (148K): [in a new window]   Figure 18.   Transdiaphragmatic migration in a 56-year-old man with a history of surgery for hepatic hydatid disease. Lateral chest radiography demonstrated a lesion that appeared to be a lung nodule. Contrast-enhanced CT scan obtained at the level of the dome of the diaphragm shows a partially calcified cyst originating in the posterior segment of the right hepatic lobe and growing through the diaphragm into the lung (arrows). The cyst has the characteristic hourglass shape. There is a triangular, low-attenuation area in the lateral aspect of the right lobe (arrowhead) that is related to the prior surgery.

View larger version (165K): [in a new window]   Figure 19a.   Pleural empyema secondary to a perforated hepatic hydatid cyst in a patient with a history of hepatic hydatid disease. The patient presented with acute chest pain, fever, and leukocytosis. Chest radiography demonstrated findings typical of empyema. (a) Sagittal T1-weighted MR image obtained after intravenous administration of contrast material shows a posteriorly located hepatic cyst (C) in communication with a loculated pleural collection (P). There is marked enhancement of the thickened pleura (arrows). (b) Sagittal T2-weighted MR image obtained at the same level shows multiple vesicles within the mother cyst (C), the fistula (arrows), and the pleural cavity (P). Note the exophytic growth of the cyst through the bare area of the liver (L). K  = right kidney.

View larger version (152K): [in a new window]   Figure 19b.   Pleural empyema secondary to a perforated hepatic hydatid cyst in a patient with a history of hepatic hydatid disease. The patient presented with acute chest pain, fever, and leukocytosis. Chest radiography demonstrated findings typical of empyema. (a) Sagittal T1-weighted MR image obtained after intravenous administration of contrast material shows a posteriorly located hepatic cyst (C) in communication with a loculated pleural collection (P). There is marked enhancement of the thickened pleura (arrows). (b) Sagittal T2-weighted MR image obtained at the same level shows multiple vesicles within the mother cyst (C), the fistula (arrows), and the pleural cavity (P). Note the exophytic growth of the cyst through the bare area of the liver (L). K  = right kidney.

View larger version (170K): [in a new window]   Figure 20a.   Pulmonary involvement with a bronchial fistula in a patient with cough, fever, malaise, and a high white blood cell count. (a) Coronal fat-suppressed fast spin-echo T2-weighted MR image obtained at the hepatic level shows a large pulmonary cyst with partial rupture of the wall (black arrows). Another cyst is seen superiorly in the lung parenchyma (C) with a high-signal-intensity band along its lateral aspect due to pleural effusion (arrowheads). White arrow indicates linear structures within the cyst representing detached membranes. (b) On a sagittal fat-suppressed fast spin-echo T2-weighted MR image, the central portion of the diaphragm is clearly absent (solid arrows). The cyst contains an air-fluid level (arrowheads) due to the presence of a bronchial fistula, a finding that was confirmed at surgery. Note the high signal intensity of the accompanying pleural empyema (E). Open arrow indicates linear structures within the cyst (cf a).

View larger version (130K): [in a new window]   Figure 20b.   Pulmonary involvement with a bronchial fistula in a patient with cough, fever, malaise, and a high white blood cell count. (a) Coronal fat-suppressed fast spin-echo T2-weighted MR image obtained at the hepatic level shows a large pulmonary cyst with partial rupture of the wall (black arrows). Another cyst is seen superiorly in the lung parenchyma (C) with a high-signal-intensity band along its lateral aspect due to pleural effusion (arrowheads). White arrow indicates linear structures within the cyst representing detached membranes. (b) On a sagittal fat-suppressed fast spin-echo T2-weighted MR image, the central portion of the diaphragm is clearly absent (solid arrows). The cyst contains an air-fluid level (arrowheads) due to the presence of a bronchial fistula, a finding that was confirmed at surgery. Note the high signal intensity of the accompanying pleural empyema (E). Open arrow indicates linear structures within the cyst (cf a).

View larger version (114K): [in a new window]   Figure 21a.   Hydatid cyst perforation into the gastric antrum. (a) Contrast-enhanced CT scan obtained at the level of the kidneys shows two congruous air-fluid levels. One air-fluid level is inside a calcified cyst (solid arrow), and the other is in the gastric antrum (open arrow). (b) Contrast-enhanced CT scan obtained with the patient in the left lateral decubitus position shows emptying of the cyst contents (C) into the antrum. The interruption of the cyst wall and the fistula are well depicted (arrow). Surgery revealed that the cyst was growing from the left lobe of the liver through the gastrohepatic ligament with a direct rupture into the gastric antrum.

View larger version (116K): [in a new window]   Figure 21b.   Hydatid cyst perforation into the gastric antrum. (a) Contrast-enhanced CT scan obtained at the level of the kidneys shows two congruous air-fluid levels. One air-fluid level is inside a calcified cyst (solid arrow), and the other is in the gastric antrum (open arrow). (b) Contrast-enhanced CT scan obtained with the patient in the left lateral decubitus position shows emptying of the cyst contents (C) into the antrum. The interruption of the cyst wall and the fistula are well depicted (arrow). Surgery revealed that the cyst was growing from the left lobe of the liver through the gastrohepatic ligament with a direct rupture into the gastric antrum.

View larger version (139K): [in a new window]   Figure 22.   Peritoneal seeding in the region of the transverse mesocolon in a patient with a history of surgery for hepatic hydatid disease. Unenhanced CT scan shows two cystic masses in the right lobe of the liver (arrows). There are multiple cysts (C) lying between the transverse colon (arrowheads) and the collapsed, contrast material-filled stomach (S), which is seen anterior to the pancreas (P).

View larger version (133K): [in a new window]   Figure 23a.   Daughter cyst in the distal common bile duct in the same patient as in (a) Contrast-enhanced upper abdominal CT scan demonstrates a "wrinkled" cyst in the right hepatic lobe with peripheral enhancement due to associated infection (C). Note the biliary tree dilatation (arrows) and the marked dilatation of the common bile duct at the porta hepatis (arrowhead). There is also a right adrenal mass with low attenuation, a finding that is consistent with adenoma. (b) On a CT scan obtained at the lowest level of the head of the pancreas, a round, cystic structure is barely seen within the dilated common bile duct (arrow). Surgery revealed multiple daughter vesicles filling the distal common bile duct.

View larger version (135K): [in a new window]   Figure 23b.   Daughter cyst in the distal common bile duct in the same patient as in (a) Contrast-enhanced upper abdominal CT scan demonstrates a "wrinkled" cyst in the right hepatic lobe with peripheral enhancement due to associated infection (C). Note the biliary tree dilatation (arrows) and the marked dilatation of the common bile duct at the porta hepatis (arrowhead). There is also a right adrenal mass with low attenuation, a finding that is consistent with adenoma. (b) On a CT scan obtained at the lowest level of the head of the pancreas, a round, cystic structure is barely seen within the dilated common bile duct (arrow). Surgery revealed multiple daughter vesicles filling the distal common bile duct.

View larger version (101K): [in a new window]   Figure 24.   Intracystic fat-fluid level. Axial spin-echo T1-weighted (left) and fat-suppressed fast spin-echo T2-weighted (right) MR images demonstrate a fat-fluid level within a cyst. In our experience, this finding suggests that intracystic fat derives from the lipid elements in bile, implying that there is a communicating rupture. Communication with the biliary tree was proved at surgery. (Reprinted, with permission, from reference 16.)

View larger version (122K): [in a new window]   Figure 25a.   Portal vein involvement in a patient with a history of surgery for hydatid disease of the right hepatic lobe. A Doppler US image obtained at the level of the porta hepatis (not shown) revealed the absence of flow in the main portal vein and helped confirm the presence of flow in collateral vessels (cavernous transformation of the portal vein). (a) Contrast-enhanced CT scan obtained at the level of the liver shows multiple cysts occupying the region of the main portal vein and its bifurcation (arrows). Multiple contrast material-filled vessels are seen surrounding the cysts (arrowheads), findings that are suggestive of portal cavernomatosis. A residual cyst is seen in the surgically reduced right lobe (C). (b, c) Axial (b) and coronal (c) maximum-intensity-projection images from a fat-suppressed T2-weighted MR imaging study show that the residual cyst in the right lobe (C) is connected by a cyst-filled track (arrowheads in b) to the right branch of the portal vein (RV in b). Multiple daughter vesicles are seen replacing the lumen of the main portal vein (straight arrows). In c, the gallbladder (G) and the common bile duct (curved arrow) are identified.

View larger version (114K): [in a new window]   Figure 25b.   Portal vein involvement in a patient with a history of surgery for hydatid disease of the right hepatic lobe. A Doppler US image obtained at the level of the porta hepatis (not shown) revealed the absence of flow in the main portal vein and helped confirm the presence of flow in collateral vessels (cavernous transformation of the portal vein). (a) Contrast-enhanced CT scan obtained at the level of the liver shows multiple cysts occupying the region of the main portal vein and its bifurcation (arrows). Multiple contrast material-filled vessels are seen surrounding the cysts (arrowheads), findings that are suggestive of portal cavernomatosis. A residual cyst is seen in the surgically reduced right lobe (C). (b, c) Axial (b) and coronal (c) maximum-intensity-projection images from a fat-suppressed T2-weighted MR imaging study show that the residual cyst in the right lobe (C) is connected by a cyst-filled track (arrowheads in b) to the right branch of the portal vein (RV in b). Multiple daughter vesicles are seen replacing the lumen of the main portal vein (straight arrows). In c, the gallbladder (G) and the common bile duct (curved arrow) are identified.

View larger version (158K): [in a new window]   Figure 25c.   Portal vein involvement in a patient with a history of surgery for hydatid disease of the right hepatic lobe. A Doppler US image obtained at the level of the porta hepatis (not shown) revealed the absence of flow in the main portal vein and helped confirm the presence of flow in collateral vessels (cavernous transformation of the portal vein). (a) Contrast-enhanced CT scan obtained at the level of the liver shows multiple cysts occupying the region of the main portal vein and its bifurcation (arrows). Multiple contrast material-filled vessels are seen surrounding the cysts (arrowheads), findings that are suggestive of portal cavernomatosis. A residual cyst is seen in the surgically reduced right lobe (C). (b, c) Axial (b) and coronal (c) maximum-intensity-projection images from a fat-suppressed T2-weighted MR imaging study show that the residual cyst in the right lobe (C) is connected by a cyst-filled track (arrowheads in b) to the right branch of the portal vein (RV in b). Multiple daughter vesicles are seen replacing the lumen of the main portal vein (straight arrows). In c, the gallbladder (G) and the common bile duct (curved arrow) are identified.

View larger version (171K): [in a new window]   Figure 26.   Abdominal wall invasion. Unenhanced CT scan reveals a hepatic cyst with a partially calcified wall in the left lobe (C). The lesion is seen herniating through the anterior abdominal wall into the subcutaneous fat and has the classic hourglass shape.

View larger version (107K): [in a new window]   Figure 27.   Pulmonary hydatid cyst in a 3-year-old boy. Posteroanterior chest radiograph shows a well-circumscribed, masslike lesion with a polycyclic configuration in the left lower lobe (arrows). There is obliteration of the left costophrenic angle (arrowheads).

View larger version (124K): [in a new window]   Figure 28.   Open lung cysts in a child with symptoms of pulmonary infection including fever, cough, and expectoration. Chest radiograph obtained with the patient in the left lateral decubitus position demonstrates a large cavitary lesion with an air-fluid level in the inferior left lung (black arrow). Air is seen between the pericyst (white arrow) and the laminated membrane of the cyst (arrowhead). Taken together, these findings are known as the Cumbo sign. There is also a pulmonary infiltrate adjacent to the cyst as well as pleural effusion due to superimposed bacterial infection.

View larger version (140K): [in a new window]   Figure 29.   Lung involvement in a child with previous episodes of cough and expectoration. Collimated lateral chest radiograph shows an intracystic serpentine structure representing collapsed membranes (serpent sign) (arrows).

View larger version (112K): [in a new window]   Figure 30.   Open lung cyst in a 20-year-old man who had experienced a sudden coughing attack followed by expectoration of clear fluid. Chest radiograph obtained with the patient in the left lateral decubitus position reveals a cavitary lesion in the right upper lobe with solid contents that have settled in the most dependent part of the cavity ("mass within a cavity") (arrows). The solid component represents the detached, crumpled endocyst.

View larger version (100K): [in a new window]   Figure 31.   Renal hydatid cyst in a 45-year-old man with right flank pain. Unenhanced CT scan shows a round, cystic lesion in the right kidney with irregular, ringlike calcification of the pericyst (arrowheads). Small daughter cysts are faintly visualized within the cavity (straight arrows). The cyst is seen displacing the fat-filled renal sinus medially (curved arrow).

View larger version (112K): [in a new window]   Figure 32.   Hydatid disease involvement of the sacrum in a 50-year-old woman who presented with severe lower back pain and radicular pain. Contrast-enhanced CT scan obtained at the level of the iliac crest demonstrates sacral destruction and replacement by a multiloculated cystic mass, which also occupies the spinal canal and extends anteriorly into both psoas muscles and posteriorly into the soft tissues. Note the presence of multiple "septa" within the lesion, which actually represent the opposing walls of the daughter vesicles.

View larger version (106K): [in a new window]   Figure 33a.   Costal hydatid disease with spinal involvement in a middle-aged woman with clinical findings of spinal cord compression. (a) Axial contrast-enhanced T1-weighted MR image shows rib destruction by anterior and posterior low-signal-intensity masses (solid arrows). Another mass is seen within the spinal canal displacing the spinal cord anteriorly (open arrow). Note also the meningeal enhancement in the spinal canal (arrowheads). (b) Axial T2-weighted MR image shows the three lesions with high signal intensity (arrows), a finding that is consistent with their cystic nature. Note the different signal intensities of the cysts due to variations in distance from the surface coil.

View larger version (104K): [in a new window]   Figure 33b.   Costal hydatid disease with spinal involvement in a middle-aged woman with clinical findings of spinal cord compression. (a) Axial contrast-enhanced T1-weighted MR image shows rib destruction by anterior and posterior low-signal-intensity masses (solid arrows). Another mass is seen within the spinal canal displacing the spinal cord anteriorly (open arrow). Note also the meningeal enhancement in the spinal canal (arrowheads). (b) Axial T2-weighted MR image shows the three lesions with high signal intensity (arrows), a finding that is consistent with their cystic nature. Note the different signal intensities of the cysts due to variations in distance from the surface coil.

View larger version (117K): [in a new window]   Figure 34a.   Iliac crest hydatid disease with extension into the soft tissues in a 68-year-old man with excruciating pain in the left gluteal region. (a) Contrast-enhanced CT scan shows an expanding lesion with water attenuation in the left iliac crest (solid arrow). Multivesicular cysts are seen within the soft tissues posterior to the iliac crest (open arrows). (b) Axial fat-suppressed fast spin-echo T2-weighted MR image demonstrates complete replacement of the iliac wing by a high-signal-intensity lesion (arrows). The masses within the posterior soft tissues also have high signal intensity due to their cystic nature. (c) Photograph of a resected specimen from the surgically removed iliac crest demonstrates multiple collapsed membranes within the medullary cavity (arrows). Note the perfect correlation between the surgical specimen and the MR image (cf b).

View larger version (99K): [in a new window]   Figure 34b.   Iliac crest hydatid disease with extension into the soft tissues in a 68-year-old man with excruciating pain in the left gluteal region. (a) Contrast-enhanced CT scan shows an expanding lesion with water attenuation in the left iliac crest (solid arrow). Multivesicular cysts are seen within the soft tissues posterior to the iliac crest (open arrows). (b) Axial fat-suppressed fast spin-echo T2-weighted MR image demonstrates complete replacement of the iliac wing by a high-signal-intensity lesion (arrows). The masses within the posterior soft tissues also have high signal intensity due to their cystic nature. (c) Photograph of a resected specimen from the surgically removed iliac crest demonstrates multiple collapsed membranes within the medullary cavity (arrows). Note the perfect correlation between the surgical specimen and the MR image (cf b).

View larger version (93K): [in a new window]   Figure 34c.   Iliac crest hydatid disease with extension into the soft tissues in a 68-year-old man with excruciating pain in the left gluteal region. (a) Contrast-enhanced CT scan shows an expanding lesion with water attenuation in the left iliac crest (solid arrow). Multivesicular cysts are seen within the soft tissues posterior to the iliac crest (open arrows). (b) Axial fat-suppressed fast spin-echo T2-weighted MR image demonstrates complete replacement of the iliac wing by a high-signal-intensity lesion (arrows). The masses within the posterior soft tissues also have high signal intensity due to their cystic nature. (c) Photograph of a resected specimen from the surgically removed iliac crest demonstrates multiple collapsed membranes within the medullary cavity (arrows). Note the perfect correlation between the surgical specimen and the MR image (cf b).

View larger version (153K): [in a new window]   Figure 35a.   Cerebral hydatid cyst in a patient with intracranial hypertension and papilledema. (a) Sagittal T1-weighted MR image of the brain reveals a bilobed, hypointense mass (arrows). Other MR images (not shown) demonstrated mass effect on the right lateral ventricle. (b) On an axial T2-weighted MR image, the lesion has high signal intensity due to its cystic nature. Note the lack of edema in the surrounding parenchyma. The lesion was confirmed to be a hydatid cyst at surgery. (Fig 35a and 35b courtesy of Ricardo Gomez Pereda, MD, Department of Diagnostic Radiology, Hospital Miguel Servet, Zaragoza, Spain.)

View larger version (151K): [in a new window]   Figure 35b.   Cerebral hydatid cyst in a patient with intracranial hypertension and papilledema. (a) Sagittal T1-weighted MR image of the brain reveals a bilobed, hypointense mass (arrows). Other MR images (not shown) demonstrated mass effect on the right lateral ventricle. (b) On an axial T2-weighted MR image, the lesion has high signal intensity due to its cystic nature. Note the lack of edema in the surrounding parenchyma. The lesion was confirmed to be a hydatid cyst at surgery. (Fig 35a and 35b courtesy of Ricardo Gomez Pereda, MD, Department of Diagnostic Radiology, Hospital Miguel Servet, Zaragoza, Spain.)