The hemolytic-uremic syndrome consists of hemolytic anemia, acute renal failure and thrombocytopenia. In childhood, some hemolytic-uremic syndrome can take the mask of a pseudo-surgical crisis mimicking intussusception or ulcerative colitis. Two cases are reported in children with abdominal pain, rectal bleeding, anomalies on the barium enema and in one case histologic features of ulcerative colitis. In the two cases, the biological disturbance of the hemolytic-uremic syndrome appeared with delay after the onset of the abdominal syndrome making the diagnosis difficult. Typical findings on the barium enema must evoke the hemolytic-uremic syndrome before renal failure: narrowing of the lumen of the colon, "thumbprinting", spasms and ulceration. But sometimes the diagnosis is more complicated because of the possibility of true surgical complications of hemolytic-uremic syndrome.