Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Call emergency services for trouble breathing, collapse, severe uncontrolled bleeding, or another rapidly worsening emergency.
Contact the surgical team promptly for fever, worsening pain, repeated vomiting, increasing redness or drainage from an incision, foul-smelling urine, or pain when urinating.
Also call if a catheter stops draining, falls out, or leaks heavily around its insertion site.
Seek urgent medical advice if your child cannot urinate, cannot keep fluids down, has worsening abdominal swelling, passes large blood clots, or becomes unusually sleepy or difficult to wake.
And for anyone, someone who:
Questions about activity, school, medicines, stent removal, or a scheduled test can usually wait for routine office hours.
Every sign above is quoted from the sofidex article on Ureteral reimplantation surgery - children. If you are not sure, err upward — it is always reasonable to be checked.