Hi, My Husband Has Acute Gastroenteritis And Was Hospitalised For

Hi, my husband has acute gastroenteritis and was hospitalised for 3 days last week due to severe dehydration. He now has run pain and his left side that gets worse throughout the day. I have read it can be from excessive vomiting but he wasn’t sick much he had diahorreah. Any idea what this could be, does he need to go back to GP? Thanks