Macroscopic Analysis of Urine

Macroscopic analysis is one step of urinalysis. It is a gross examination of a urine sample's physical characteristics, such as volume, color, clarity, and odor.

Volume of urine

A patient should typically excrete 600 to 2000 mL of urine daily. If a patient consistently expels more than 2000 mL in 24 hours, the cause could be a health condition, such as diabetes mellitus or diabetes insipidus. However, if a patient occasionally passes more than 2000 mL of urine in 24 hours, the cause may be the consumption of coffee, alcohol, tea, caffeine, or other diuretics. If a patient excretes less than 400 mL in 24 hours, possible causes include dehydration, urinary tract obstruction, and various kidney problems.

Color of Urine

Urine can have a variety of colors, as shown in Figure 1. The patient's diet, hydration level, health conditions, and the time of urine excretion can affect the urine's color.

For example, alcohol consumption, large fluid intake, diabetes mellitus, and diabetes insipidus can cause pale yellow urine. In contrast, dark yellow urine could be due to urinary tract medication, low fluid intake, dehydration, or an early morning urine sample.

Blood in the urine can turn urine a red color. However, food and drugs can result in abnormal urine colors too. For example, beetroots may turn urine red, and vitamin B12 can turn urine bright yellow. Therefore it is good to note what a patient has consumed in the last 24 to 36 hours.

Clarity of Urine

Typically, a fresh urine sample is clear and initially has a small amount of foam. If the urine has a cloudy appearance, that could indicate a health condition such as a urinary tract infection or diabetes mellitus. Large amounts of foam suggest that the urine contains protein or bilirubin, which could indicate a problem with the kidneys or liver, but this needs to be confirmed by chemical analysis.

Odor of Urine

Usually, a fresh urine sample from healthy individuals has a faint odor. Over time the urine sample's smell will become more intense as urea in the urine breaks down. Unusual-smelling urine can indicate possible health conditions. For example, the cause of a strong, pungent odor could be a urinary tract infection, while the cause of a sweet smell might be diabetes mellitus. However, the patient's diet can also have an effect; for example, the consumption of asparagus can cause smelly urine. Interestingly, only individuals with a specific gene can smell this asparagus odor.

Figure 1: A reference value chart for urine color. From 1 to 8, the color changes from pale yellow to dark yellow.