Acute diarrhea is a leading cause of morbidity and mortality indeveloping countries including Egypt. Renal involvement is one of the most serious complications of it and a high blood urea is not uncommon finding in most of the cases on admission. Acute renal failure may occur and the clinical features of which may be vague and masked by those due to diarrhea and vomiting. In this work, we looked for the different patterns of renal involvementsecondary to acute diarrhea and we tried to high lighten the risk factors for the development of these serious complications.This study included 40 patients with acute diarrhea, dehydrationtogether with oliguria admitted to the gastroenteritis unit at cairo-university children hospital. According to the outcome, cases were divided into two groups:Group 1: showing no improvement in renal condition and included 10 patients, nine patients died from renal failure, five of which suffered from haemolytic uremic syndrome and the remaining one patient survived with chronic renal impairement and needed dialysis. Group 2: showing improvement in renal condition and included 30 patients. These patients survived without any renal impairment and the renal codition improved as soon as the dehydration, shock and acidosis were properly managed.