Cystic echinococcosis (CE) is a chronic, complex, and overlooked zoonotic disease caused by Echinococcus granulosus. In humans, it may result in a wide spectrum of clinical manifestations depending on the type of complications, ranging from asymptomatic infection to fatal disease. The primary complications and risk factors associated with CE are not well defined. We performed a retrospective, observational study of inpatients diagnosed with CE from January 1998 to December 2017 in the public health-care system of western Spain. Five hundred and six cases were analyzed. More than half of the patients (302 [59.7%]) were asymptomatic, and the diagnoses were made incidentally. A total of 204 (40.3%) patients had complications associated with CE; 97 (47.5%) were mechanical, 62 (30.4%) were infectious, 15 (7.3%) were immunoallergic, and 30 (14.7%) involved a combination of complications. Mortality was higher in patients with mechanical complications (9.4%) than in patients with infectious complications (5.6%) and in patients with allergic complications (0%) (odds ratio = 19.7, 95% CI, 4.3-89.1, P < 0.001). In summary, CE frequently results in complications, especially in the liver in younger patients and, regardless of other variables, such as size or stage of cyst. Mechanical problems and superinfection are the most frequent complications. CE is an obligatory diagnosis in patients with urticarial or anaphylactoid reactions of unknown cause in endemic areas.