4 weeks post surgery. Stuff in urine

My hubby is 4 week post Davinci surgery.  Doing really well all cancer confined to prostate.  Avcouplebofbday ago he had some blood in urinebwhichbi understand is normal but last night it looks like someone ground pepper in his urine . The pieces appear to be heavy as they sink.  Does anyone know if this is okay.  We will call doctor later today. thank you.