Symptoms to watch for in a 3 1/2 year old girl for a urinary infection include pain in the lower abdomen, frequent and urgent need to urinate, cloudy or blood-tinged urine, irritability, loss of appetite, vomiting and nausea, and fever. It is important to monitor these symptoms closely and seek medical evaluation if they persist or new symptoms arise. Urinary infections can be treated with antibiotics. To prevent these infections, it is recommended to change the child's diaper frequently, address any issues with constipation, avoid bubble baths and scented soaps, and teach the child to wipe from front to back.