background: Diarrhea is the second leading cause of death in children under-fives worldwide. It accounted for 21% of all deaths in the developing countries with several factors described to affect the outcome. Objective: To evaluate the anthropometric clinical and laboratory parameters in acute gastroenteritis as predictors of length of stay. Methods: An observational cross-sectional study was carried out at Cairo University Children's Hospital, including 200 patients admitted with acute gastroenteritis, aged 3-50 months. Anthropometry, serum sodium, potassium and albumin were done for all patients. Statistical analysis included grouping of patients according to age and mid-upper arm circumference categories.

Results: The length of hospital stay was significantly longer among infancy group (89% of the enrolled patients) and low MUAC group (<12.5 cm). Low MUAC group had significantly lower anthropometric measurements and higher frequency of hypokalemia, hypernatremia and hypoalbuminemia. Prolonged LOS was significantly predicted by low MUAC (Odd's ratio: 5.221, 95% CI: 1.703 to 16.008, p= 0.004) and hypernatremia (Odd's ratio: 5.779, 95% CI: 2.208 to 15.123, p< 0.001). On the other hand, LOS was significantly shorter in males (Odds ratio: 0.393, 95% CI: 0.156 to 0.991, p= 0.048), older children (Odds ratio: 0.278, 95% CI: 0.093 to 0.832, p= 0.022) and those with higher MUAC z-scores: 0.531, 95% CI: 0.369 to 0.764, p= 0.001).

Conclusion: MUAC, serum Na, gender and age were significant predictors of length of stay for children hospitalized with acute gastroenteritis.