Horseshoe kidney

My sone is 6 with a horseshoe kidney,  His MRI showed secondary (had an MRI due to back pain and excess spacing in lower discs)  distended bladder, horseshoe kidney, fluid around kidney and bladder and a cyst.  We followed up with a urologist who did an ultrasound without contrast, and said very abruptly " he has a horseshoe kidney what are you even here for?"  follow up in 1 year with an ultrasound.  I tried to ask about the fluid, along with the fact that my son has intermittant fevers (no other symptoms) chronic stomach and back pain.  The answer I got was this would not be the cause of any of that.  He then explained that after seeing the ultrasound his ureters were fine.  After getting a copy of ther report I see "left ureter not visualized" right ureter not visualized"  not sure if he was making it up but my real concern is the fluid around his organs and his pain.  Any advice?