Picking primary diagnosis for hospital patient- reason for Surgery or reason for admit?

Patient with BPH has TURP as outpatient. Spends night in routine outpatient recovery. Next day, still has severe hematuria so doctor admits patient as inpatient and keeps another day.

When coding, is primary diagnosis hematuria since that is the reason for the actual admission as inpatient or is it BPH since that was the reason for the surgery and overall hospital care, even though the surgery was done as outpatient?

What DRG would be assigned? Does the fact the admission was for hematuria affect that DRG choice?