Two cases of hemolytic-uremic syndrome (HUS) with colonic gangrene are analyzed. Colonic gangrene is an uncommonly reported complication, and it determines a greater severity of the disease, and consequently additional therapeutic measures should be taken. One of the patients died and the survivor needed colonic resection, external ileostomy, and arteriovenous hemofiltration to overcome his renal failure. In the long term follow up this patient recovered uneventfully. The initial features were similar for most of the patients with this disease. The sudden decompensation with hypotension, toxic aspect, bulged and painful abdomen, with blood stools, could indicate this complication. The patient that was undertaken to an aggressive surgical approach had a favorable outcome. In the other patient, complications such as sepsis and septic shock were present with fatal outcome. We believe that this was in part due to the delayed surgical treatment. Reports in the literature suggest a poor prognosis in the presence of this complication, because of protracted renal damage and chronic renal failure.