Intraabdominal tumors require precise diagnosis for patient preparation for optimal surgical procedure. For diagnosis of these lesions, the principal studies used are ultrasonography, computed axial tomography (CAT) and occasionally the use of magnetic resonance imaging, a study not always possible to accomplish in all hospitals. We present the case of a patient with a giant retroperitoneal cyst whose diagnosis was missed by means of conventional ultrasound and CAT. For this reason, we chose to use ultrasound with echography using contrast agent (Levovist) to determine if the tumor was dependent on the liver or pancreas. By means of this technique, we were able to make the diagnosis that the tumor did not depend on any organ, but rather was an independent retroperitoneal tumor. Final surgical and histopathological diagnosis was a retroperitoneal multilocular lymphangioma. We conclude that ultrasonography with contrast agent (Levovist) is an alternative method for studying intraabdominal tumors.