Final answer:
Abdominal ultrasound is the most sensitive and accurate study for scarring and renal size. CKD is differentiated from ARF based on the gradual rise in serum creatinine. Additional tests like MAG3 and DMSA scans are used for evaluating kidney function and blood flow. Urine sample culture can exclude urine infection as a cause of pain or secondary to the presence of a stone.
Step-by-step explanation:
The most sensitive and accurate study of scarring and renal size, but not first line for UTI workup, is an abdominal ultrasound. This imaging test measures the size of the kidneys. In chronic kidney disease (CKD), the kidneys are usually smaller than normal kidneys, except in cases of diabetic nephropathy and polycystic kidney disease. Gradual rise in serum creatinine over months or years is a diagnostic clue for CKD, while a sudden increase in serum creatinine over days to weeks suggests acute renal failure (ARF).
Additional tests for evaluating kidney function and blood flow include nuclear medicine MAG3 scan and DMSA scan. The MAG3 scan helps confirm blood flows and establish the differential function between the two kidneys, while the DMSA scan is used for renal imaging. Both of these tests use the radioactive element Technetium-99.
To exclude urine infection as a cause of pain or as a secondary condition to the presence of a stone, a urine sample can be cultured.