Thanks for your question.
i understand your concern.
The pain he is experiencing is likely from small pieces of stone passing through the ureter.
sometimes the small stone piece may get stuck at PUJ junction ( this is a junction between pelvis & ureter). This can result in severe back pain & lower abdominal pain.
He should drink plenty of fluids.
Medication tamsulosin ( Flomax) is also helpful in passing the stones by dilating the ureter.
narcotic pain meds may also be used to control the acute pain episodes.
This pain usually subsides within 3-4 weeks.
But, if persistent pain in spite of above measures, he requires another urological evaluation.