Good Day!
CT scan are more accurate and sensitive in detecting stones than an
ultrasound. Although there are stone compositions that doesn't show up in a CT SCan (e.g
indinavir stones).
I would suggest doing a
urinalysis to check for infection and determine the mucous in the urine. They might be phosphate in the urine and have no clinical significance. If you are diabetic then it might be tissue sloughing off from the ureter and kidneys. Again these are speculation and a urine sample in the laboratory is still the best.
I Hope I have answered your question.