Can a septated kidney cyst somehow become non-septated and no longer complex? could the u/s be showing something that looks like separation but isn't?

These are common: The kidney is a bunch of tubes. They can get blocked, injured, plugged and can deform. The kidney can scar, can grow back some parts somewhat (and have injuries, scars, stones, infections, etc.). So..deformities are common and they change over time. BUT kidney cancer grows and is solid and irregular. U/S are grainy and can't get the same angle. Picture changes/thing changes/kidney changes.