Final answer:
Urea and creatinine are two substances that will show elevated levels in the blood when there is kidney pathology, reflecting the kidneys' diminished ability to filter waste from the blood.
Step-by-step explanation:
When assessing kidney function, blood tests measure levels of substances including urea and creatinine. Urea, a waste product formed in the liver from the metabolism of proteins, is normally excreted by the kidneys. Elevated blood urea levels, a condition known as uremia, indicate that the kidneys may not be filtering the blood effectively. Moreover, creatinine, a breakdown product of muscle metabolism, is also filtered by the kidneys. Elevated levels of serum creatinine in the blood suggest renal impairment. These values are critical in diagnosing kidney disorders as they reflect the organ's ability to perform its filtration function.
Other substances like albumin, which usually does not pass into the urine, can be found in higher levels there when the glomerular capillaries are damaged, indicating conditions such as diabetic nephropathy. However, albumin's increase in urine, as opposed to in blood, would signal kidney pathology.
Lastly, the presence of abnormal proteins such as Bence Jones proteins may be observed in certain kidney pathologies associated with diseases like multiple myeloma. Still, these proteins would not typically be evaluated as routine markers of kidney function like urea and creatinine.