Welcome to Healthcare Magic forum.
Hernia is protrusion of any normal part of our body through a abnormal opening. In your mother there might be protrusion of intestines through an abnormal opening from the Umbilicus. A doctor need not ask for an investigation to confirm that it is umbilical hernia
as it can be diagnosed through a clinical examination.
But investigations like Abdominal Sonography might be required before Surgery
. Surgery is considered to be the only definitive treatment
Please trust your doctor on this and follow his advise.
Hope this answers your query.
Wish your mother a speedy recovery.