Looks very dysplastic to me
Looks very dysplastic to me but yes Bx necessary as juvenile pyelonephritis can mimic renal dysplasia but doubt it here. If its a breeding money back thing then I would prepare the terrain and can do an eventual post mortem US-guided Bx as well because px is not good.

Here is a confirmed renal
Here is a confirmed renal dysplasia case…tubules not attached to nephrons and such on bx…from the sonopath pathology CD to make a comparison.

Thanks for the picture. I am
Thanks for the picture. I am not familiar with juvenile pyelonephritis. Would you expect the dog to be sick (depressed, febrile)? Would you be able to see bacteruria or get a positive urine culture? If this was juvenile pyelonephritis, would the kidneys still be salvageable? In other words, would the prognosis be good despite the markedly abnormal renal architecture seen on US in this patient?

The dog had a positive urine culture for E. coli in Aug. and was tx with TMS. Subsequent U/A and culture were both neg for infection. Clinical signs persisted througout (dysuria, PU/PD). This dog was also tx with Doxycycline for 2 weeks.

Based on the breed, history,
Based on the breed, history, lab findings, and US changes I would make a provisional diagnosis of congenital renal disease. However, the only way a diagnosis can be made is on histopathology.
With juvenile pyelonephritis/other infections, I would expect evidence of UTI and systemic signs such as pyrexia, leukocytosis.

Fever is not always present
Fever is not always present in UTI/pyelonephritis cases in my experience…especially in chronic cases. You can of course get uti along with congenital too which is likely what you have here.

Thank you Remo and Eric for
Thank you Remo and Eric for your input.