Urinalysis

Biology: Cambridge International A Level, topic 14.4.3

Urine samples are useful diagnostic tools in medicine. They are convenient as collecting urine samples can be easier than collecting blood.

Protein in urine is called proteinuria.
Proteinuria indicates damage to the kidneys.
Protein molecules are normally too large to pass through the glomerulus. Protein in the urine can suggest:
High blood pressure. High blood pressure can force protein through the glomerulus into the proximal convoluted tubule.
Leaky glomerular kidneys. This can be due to infection, diabetes, or inflammation in the kidneys.

Glucose is small enough to pass through the glomerular capillaries and enter the nephron.
However, most glucose is selectively reabsorbed in the proximal convoluted tubule (PCT).
If the amount of glucose entering the renal filtrate reaches a certain threshold, not all the glucose can be reabsorbed.
This leads to glucose in the urine.
As the glucose in urine originates from blood, high urine in glucose can suggest high blood glucose.
Glucose in urine suggests diabetes.

Ketones in the urine can also suggest diabetes.
Individuals with diabetes have high blood glucose. Because the glucose is in the blood rather than in cells, the glucose cannot be used for respiration.
This means cells respire using other respiratory substrates, namely lipids.
Respiring lipids produces ketones.
This metabolic state is sometimes referred to as "ketosis".
Ketones are excreted in urine.

Test yourself on Urinalysis