High PUS Cells. Right medication?

My child was having heavy feverand vomiting since yesterday. Therefore, I got her admitted and got basic tests done. In the Urine examination, she is having high PUS Cells (range should be 1-2 but she is having 8-10). Doctor has just given her "Amicacin injection" to treat the infection. Doctor also suggested to stay admitted for few more days for observation. I had few queries: 1. Do we need to stay admitted in the hospital? The child is being restless and wants to go home. Can this be treated at home? 2. How serious is this problem? How long will it take to get cured? 3. Is doctor suggesting right medication? I read that one should start with antibiotics first and go for injection in very severe case. Age of child: 5 years