*4.2.3 Magnetic resonance imaging*

*Liver Disease and Surgery*

**Figure 3.**

**Figure 4.**

*Heterogeneous matrix. Ball of wool sign (CE4).*

areas with high risk of affectation [30, 32, 33]. Due to the difficult differentiation of certain forms of alveolar echinococcosis from other kinds of hepatic tumors, CEUS is being increasingly used in certain regions with endemic affectation of

Sometimes, the ultrasound does not help much in the diagnosis of liver hydatidosis for different reasons, such as obesity, presence of abundant intestinal gas, hydatid recurrence, or residual cavities secondary to previous surgery. When that is the case, CT is used, taking advantage of its higher sensitivity and specificity. Unenhanced CT allows to have a better radiological diagnosis of the different forms of cyst calcification [33]. The contrast-enhanced CT aids in choosing the best surgical techniques according to the different forms of presentation or complications related to the disease, e.g., by allowing a more accurate appreciation of the involvement of the vasculature and biliary tree. CT also aids in diagnosing the cystic migration to the thorax and the biliary tree [35, 36]. Another advantage of the use of contrast-enhanced CT is to achieve a better differential diagnosis from other

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this pathology [34].

*4.2.2 Computed tomography*

focal liver lesions [37] (**Figures 5–11A**, **B**).

*Calcified anterior wall of cyst. Arciform image (white arrow).*

MRI is useful for diagnosis of cases of cholangiohydatidosis. Compared to US and CT, the MRI T2-weighted sequence is better at defining the internal structure of the cyst. In general, it is indicated for patients that present difficulties when performing ultrasound, such as bowel gas excess, previous surgeries, disseminated hydatidosis, and obesity. In addition, MRI is recommended when CT is contraindicated due to comorbidities. MRC is used to determine the existence of cysto-biliary fistula and the presence of hydatid material in the biliary tree. It also visualizes the cysto-biliary fistula both toward the bronchi and to the biliary tree [38, 39] (**Figures 11a**, **b**–**17**).
