Final answer:
Urine sodium levels can determine the location of a sodium issue by indicating the excretion of sodium by the kidneys.
Step-by-step explanation:
Urine sodium levels can help determine the location of a sodium issue by indicating the excretion of sodium by the kidneys. When sodium levels in urine are higher than normal, it suggests that the kidneys are unable to reabsorb sodium effectively, indicating a renal cause for the sodium issue. On the other hand, if urine sodium levels are lower than normal, it suggests that the kidneys are retaining sodium, indicating an extrarenal cause for the sodium issue.