Mri Image Of A Human Polycystic Liver

Fig. 53a-g. Congenital hepatic fibrosis in polycystic kidney disease. In contrast to the situation in adult polycystic kidney disease, the liver is not affected by cysts in congenital fibrosis associated with infantile polycystic kidney disease. Images a-c show fibrosis of the liver with cirrhotic changes and dilatation of the peripheral bile ducts (arrows). Additionally, hypertrophy of Segment 1 and the left liver lobe can be noted. In (c), polycystic kidneys are displayed. These are better appreciated on the coronal image (d). On Tl-weighted images (e), the liver has a homogenous signal, however, the bile ducts are irregularly shaped and show dilatation due to fibrosis. In the equilibrium phase after contrast agent injection, the dilated bile ducts appear hyperintense while the liver parenchyma shows homogenous enhancement (f). Due to liver fibrosis and resulting portal hypertension in this 14-year old girl, a splenorenal shunt was initiated. This is demonstrated on contrast-enhanced MR angiography (g) in which early filling of the shunt (arrow) and the renal vein as well as of the inferior caval vein (arrowhead) can be observed. Note additionally, the small caliber of the renal arteries due to polycystic kidney disease

Fig. 54a-f. Polycystic liver and kidneys in adult polycystic kidney disease. Both the kidneys and the liver show multiple high signal intensity cysts on T2-weighted images (a-c). On T1-weighted images (d) the liver cysts appear hy-pointense whereas some of the kidney cysts appear hyperintense due to hemorrhage (arrows). After contrast medium injection, homogenous enhancement of liver parenchyma can be noted in both the arterial phase (e) and portal-venous phase (f). The remaining kidney parenchyma also shows homogenous enhancement. Since the risk of developing renal cell carcinoma is increased in patients with polycystic kidney disease, a very precise evaluation of the renal cysts is necessary

Fig. 54a-f. Polycystic liver and kidneys in adult polycystic kidney disease. Both the kidneys and the liver show multiple high signal intensity cysts on T2-weighted images (a-c). On T1-weighted images (d) the liver cysts appear hy-pointense whereas some of the kidney cysts appear hyperintense due to hemorrhage (arrows). After contrast medium injection, homogenous enhancement of liver parenchyma can be noted in both the arterial phase (e) and portal-venous phase (f). The remaining kidney parenchyma also shows homogenous enhancement. Since the risk of developing renal cell carcinoma is increased in patients with polycystic kidney disease, a very precise evaluation of the renal cysts is necessary

jaundice, systemic infections and in patients with polycystic liver disease and portal hypertension. Microscopically, acquired cysts are serous or muci-nous in content and are caused by periductal gland obstruction.

Peribiliary cysts are generally located near the intra- and extrahepatic main ducts.

Although patients are usually asymptomatic, large lesions can cause biliary obstruction and jaundice (Figs. 55, 56).

Fig. 55a-e. Peribiliary cysts on US and CT. On the US scan (a) numerous small, well-defined, hypo- to anechoic lesions (arrows) are demonstrated. On the pre-contrast CT scan (b), the cysts appear as hypodense, round lesions. They do not show significant enhancement after contrast medium administration (c-e). Note the "rosary beads" - like arrangement (arrowheads in c) of the cysts

Fig. 55a-e. Peribiliary cysts on US and CT. On the US scan (a) numerous small, well-defined, hypo- to anechoic lesions (arrows) are demonstrated. On the pre-contrast CT scan (b), the cysts appear as hypodense, round lesions. They do not show significant enhancement after contrast medium administration (c-e). Note the "rosary beads" - like arrangement (arrowheads in c) of the cysts

Fig. 56a-f. Peribiliary cysts on MR after Gd-BOPTA. On MR imaging, peribiliary cysts are characteristically markedly hyperintense lesions on T2-weighted images (a), and hypointense on T1-weighted GE "in-phase" (b) and "out-of-phase" (c) images. The cysts remain hy-pointense during the dynamic study after bolus administration of Gd-BOPTA (d, e) and do not show enhancement in the hepatobiliary phase (f) due to the absence of communication between the cysts and the biliary tree

Fig. 56a-f. Peribiliary cysts on MR after Gd-BOPTA. On MR imaging, peribiliary cysts are characteristically markedly hyperintense lesions on T2-weighted images (a), and hypointense on T1-weighted GE "in-phase" (b) and "out-of-phase" (c) images. The cysts remain hy-pointense during the dynamic study after bolus administration of Gd-BOPTA (d, e) and do not show enhancement in the hepatobiliary phase (f) due to the absence of communication between the cysts and the biliary tree

Miscellaneous Tumors 4.1.6.1

Lipomatous Tumors

Benign hepatic tumors composed of fat cells include lipoma, and combined tumors such as an-giomyolipoma (fat and blood vessels), myelolipoma (fat and hematopoietic tissue) and an-giomyelolipoma [32].

Grossly, lipomatous tumors are usually solitary, round and well-circumscribed masses occuring in non-cirrhotic livers [31]. They contain variable proportions of adipose and smooth muscle tissue with thick-walled blood vessels. Flow cytometry shows a DNA-diploid pattern consistent with a benign lesion [ 104]. Hematopoietic foci may be present, and when prominent, the term myelolipoma [74] or angiomyelolipoma is used.

Angiomyolipomas are rare, usually asymptomatic solitary tumors. However, these tumors occasionally bleed, causing abdominal pain. Liver an-giomyolipomas usually range in diameter from 0.3 to 36 cm and occur predominantly in women [47].

Liver angiomyolipomas may occur in association with Bourneville-Pringle syndrome. In this clinical setting, the lesions are generally multiple, progressive, and symptomatic.

Angiomyolipomas are often highly echogenic on US and are essentially indistinguishable from hemangiomas, although they may also present a mixed hyper-hypoechoic pattern (Fig. 57) [81].

Density measurements on unenhanced CT are characteristic of fat (-20 to -115 HU). Pure lipomas do not enhance, but variable enhancement occurs in lesions containing angiomatous elements (Fig. 58) [51,81].

On MR imaging, the fatty and angiomatous components of angiomyolipomas lead to a high signal intensity on both T1- and T2-weighted images [69]. Hepatocellular carcinomas containing fat deposits may have a similar appearance. The early phase of contrast-enhanced dynamic CT or MR imaging may be useful in discriminating between angiomyolipomas and HCC with fat, because the fatty areas of angiomyolipoma are well-vascularized and enhance early. Conversely, the areas of fatty changes in HCC are relatively avascu-lar, and enhancement is less obvious.

MR imaging with fat suppression techniques is useful to characterize hepatic angiomyolipomas, since lipid components show a typical signal drop with these sequences [48]. In contrast to the high signal intensity on T1- and T2-weighted images, the lesions appear hypointense compared to the

Fig. 57. Lipomatous tumors in Bourneville-Pringle syndrome on US. On US, multiple well-defined, hyperechoic (arrows) as well as small hypoechoic lesions (arrowheads) can be seen

Fig. 58a, b. Lipomatous tumor in Bourneville-Pringle syndrome on CT. Pre-contrast CT (a) reveals multiple hypodense lesions (asterisk) and mixed lesions (arrows). The hypodensity of the largest lesion reflects the abundant fatty content. After administration of contrast medium (b), some nodules enhance homogeneously (arrowheads) whereas others enhance heterogeneously (asterisk). Note the presence of angiomyolipomas in both kidneys as well

Fig. 58a, b. Lipomatous tumor in Bourneville-Pringle syndrome on CT. Pre-contrast CT (a) reveals multiple hypodense lesions (asterisk) and mixed lesions (arrows). The hypodensity of the largest lesion reflects the abundant fatty content. After administration of contrast medium (b), some nodules enhance homogeneously (arrowheads) whereas others enhance heterogeneously (asterisk). Note the presence of angiomyolipomas in both kidneys as well

Fig. 59a-i. Lipomatous tumor in Bourneville-Pringle syndrome. Same case as shown in Fig. 58. On the unenhanced HASTE T2-weighted image (a) numerous hyperintense lesions (asterisks) can be seen in the liver. On the unenhanced GE T1-weighted image (b) some of the lesions are hypointense. Several of these lesions (arrows) demonstrate a decrease of signal intensity on the Tl-weighted "out-of-phase" images due to the fat component (c). On the unenhanced coronal VIBE image (d) the nodules are seen as predominantly hypointense. Some lesions are seen as hypointense while others are hyperintense during the arterial phase after the administration of Gd-BOPTA (e). Numerous lesions remain hyperintense on the portal-venous phase image (f). On GE Tl-weighted axial (g) and coronal (h) fat-suppressed images acquired during the delayed hepatobiliary phase, all of the lesions appear hypointense. MR angiography obtained with the VIBE sequence

(i) reveals dilated and tortuous tripod celiac and hepatic arteries (arrow) -<-

Fig. 59a-i. Lipomatous tumor in Bourneville-Pringle syndrome. Same case as shown in Fig. 58. On the unenhanced HASTE T2-weighted image (a) numerous hyperintense lesions (asterisks) can be seen in the liver. On the unenhanced GE T1-weighted image (b) some of the lesions are hypointense. Several of these lesions (arrows) demonstrate a decrease of signal intensity on the Tl-weighted "out-of-phase" images due to the fat component (c). On the unenhanced coronal VIBE image (d) the nodules are seen as predominantly hypointense. Some lesions are seen as hypointense while others are hyperintense during the arterial phase after the administration of Gd-BOPTA (e). Numerous lesions remain hyperintense on the portal-venous phase image (f). On GE Tl-weighted axial (g) and coronal (h) fat-suppressed images acquired during the delayed hepatobiliary phase, all of the lesions appear hypointense. MR angiography obtained with the VIBE sequence

(i) reveals dilated and tortuous tripod celiac and hepatic arteries (arrow) -<-

h normal liver parenchyma on images obtained with fat suppression.

The appearance on contrast-enhanced MR imaging with gadolinium agents may mimic the pattern observed in hemangioma with peripheral nodular enhancement or irregular non-nodular vascular enhancement. However, arterial hyperin-tensity is also a common pattern of enhancement (Fig. 59).

4.1.6.2 Leiomyoma

This extremely rare lesion is a well-circumscribed smooth muscle tumor arising in the liver [45]. Several cases of leiomyoma have been reported in adults and children infected with the human immunodeficiency virus, suggesting that there may be a clinical association between these two entities [68,109].

Leiomyoma has non-specific radiological characteristics. On US, leiomyomas may appear solid or hypoechoic with internal echoes [85, 109]. Leiomyomas are of low attenuation relative to normal liver on unenhanced CT scans, but following contrast agent administration, may display two distinct enhancement patterns: either peripheral rim enhancement, similar to that seen in abscesses, or homogeneous enhancement, which may some times be delayed [68, 109]. On MR imaging, leiomyomas are hypointense relative to the liver on Tl-weighted images and hyperintense on T2-weighted images [85,109]. Enhancement patterns after contrast agent administration are similar to those described for CT imaging.

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