Predicting the outcome of asymptomatic univesicular liver hydatids: diagnostic accuracy of unenhanced CT.

OBJECTIVES

To establish the role of unenhanced CT in predicting the outcome of liver hydatid cysts. We sought to determine whether the presence of laminated membrane detachment (LMD) or pericyst degenerative changes (PDCs) detected on CT were reliable signs for predicting a favorable outcome of liver hydatids.

METHODS

In a 20-year-long study, we prospectively followed changes occurred in CT of 106 cysts of 98 patients with incidentally discovered asymptomatic univesicular liver hydatids who accepted to enter a watch-and-wait program. An "unfavorable" outcome was defined as the occurrence of a complication (most commonly, cyst fistula or infection) or increase in the cyst size during the follow-up; otherwise, the outcome was considered "favorable." The parameters derived from a binary logistic regression analysis (with the outcome taken as the dependent variable), after appropriate transformation of the independent variables (presence of LMD or PDCs on CT), were used to calculate the sensitivity, specificity, positive and negative likelihood ratios, and positive and negative predictive values of the presence of either the abovementioned CT findings for the prediction of a favorable outcome.

RESULTS

The presence of LMD or PDCs had a high specificity (88%) and positive predictive value (96%) for a favorable outcome; they had high false-negative rates.

CONCLUSIONS

The presence of either LMD or PDCs on unenhanced CT, in incidentally discovered asymptomatic univesicular liver hydatids, was associated with a high probability of a favorable outcome. Their absence does not rule out a favorable outcome.

KEY POINTS: • Computed tomography can be used for predicting the outcome of those with incidentally discovered univesicular liver hydatids. • The presence of laminated membrane detachment and/or pericyst degenerative changes is associated with a favorable outcome. • Their absence does not necessarily indicate an unfavorable outcome.