Postsurgical evaluation of hydatid disease with CT: diagnostic pitfalls.

Forty-five patients having previously undergone surgical removal of hydatid cysts were examined for recurrence using CT. Recurrence of hydatid disease was demonstrated in 11 patients. At the site of surgical cyst evacuation, cyst-like structures (pseudocysts) were demonstrated in 15 patients. Although pseudocysts were smaller than the original cysts and demonstrated a flattened appearance and a thicker wall, differentiation from recurrent viable hydatid cysts was difficult. Five of the pseudocysts had attenuation values between 10 and 35 HU, and eight had attenuation values close to that of fat (- 20 to - 100 HU). The findings of this study may be important in the follow-up of patients with hydatid disease.