hello sir,first of all few things iam not clear here,whether your child is well hydrated,any fever,feeding intake,amount of urine she/he is passing aequately...if your doctor has seen the baby and suggested for admission then he needs it,coz seeing a baby virtually matters a lot than any other mode of medical advice...even a mild gastroeneteritis cannot be ignored in babies less than 2 yrs,coz they get dehydrated very soon ,so simple admission with supportive care (iv fluids, paracetamol and Oral rehydration solition(if tolerating), probiotics , zinc supplemetation) is all needed initially and mostly for the child to get betterif its just simple viral gastroenteritis...so please go ahead and admit your child as advised at the earliest...