Developing and Analyzing Urine Samples as a Model of Kidney Function

In this activity, students will:

• Gain an understanding of normal and abnormal urine composition
• Apply knowledge to develop a model of a urine sample that may or may not indicate disease
• Test models of urine samples
• Apply knowledge of normal versus abnormal urine to determine diagnoses on unknown samples

Essential question

How is urinalysis used in a health care setting?

Kidneys filter waste products from our blood. Normal urine contains approximately 95% water, nitrogen compounds (including urea, ammonia, and uric acid), salts, small amounts of protein, and glucose.

Abnormal urine composition often indicates disease or infection. Diabetes is often diagnosed after a patient has a positive test for glucose in the urine. Diabetes is the result of an inability to absorb glucose from the blood. The body compensates for these elevated blood glucose levels by filtering the glucose out through the kidneys; the excess glucose exits the body through the urine.

When urine tests positive for protein, kidney damage could be to blame. If the kidneys are damaged by high blood pressure, diabetes, or some types of medication, they begin to break down. The breakdown of the tissue within the kidney results in protein being excreted through the urine.

Urine that is outside the normal pH range can be an indicator of disease or infection. If urine is more acidic than normal, it could be the result of respiratory problems, dehydration, or starvation. Urine that is more alkaline than normal can indicate kidney disease or urinary tract infection.

Ketones can be found in the urine as well. Ketones in a urine sample are the result of the breakdown of fat in the body when glucose is not present. Often, the presence of ketones in the urine are a symptom associated with diabetes and can be an indication of a life-threatening condition called diabetic ketoacidosis.

Urinalysis is a test that analyzes the composition of urine. A urine sample can be collected in a sterile container or a nonsterile container, depending upon the tests being completed. Often, test strips are used to test whether common components are present within a normal range. Glucose, proteins, red or white blood cells, ketones, and pH are a few of the components tested for through urinalysis and the presence of each in varying quantities can help professionals diagnose patients with health concerns.

Examination of the urine is an essential procedure for diagnosing human disease. With this kit, students test normal and abnormal simulated urine specimens and determine probable disorders. Included are tests for color, pH, specific gravity, glucose, and protein.

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Materials (per group)

Water
25 Specimen Cups (with caps)
25 Stirring Rods
Table Salt
Glucose Solution
Albumin Powder
Ketone Powder
Ammonia
Acetic Acid
Yellow Food Coloring
Four-Factor Urinary Test Strips

Procedure

Students will work in 5 groups. Students should familiarize themselves with the information about the common urinalysis results and the diseases that are indicated. Each group will develop a different urine sample.
Write the names of the samples being tested on note cards:

• Normal urine
• Diabetic ketoacidosis
• Diabetes
• Urinary tract infection
• Kidney damage

Have students select one notecard per group and keep their sample a secret. Each group will test all 5 samples and make diagnoses of the unknown samples.

Each group will randomly select a sample and decide what materials are needed to prepare a sample that tests positive for the designated indicator. Allow students an opportunity to plan their procedure for developing an appropriate urine sample. They should design 3 to 5 different formulations for their sample and have those formulations approved by the instructor. (Be sure to verify that they are using appropriate ingredients and quantities.)

After approval of their formulations, students should work in their groups to prepare the samples. They should test each of their formulations to ensure that the proper results are obtained from the simulated urine sample. When an appropriate formulation is found, students will label the specimen cups:

• Sample A for diabetes
• Sample B for diabetic ketoacidosis
• Sample C for normal urine
• Sample D for urinary tract infection
• Sample E for kidney damage

Students should then test each of the 5 class samples (A to E) and determine whether the urine sample is normal or abnormal. Using the background information and the results of their urinalysis, students will determine which disease or disorder may be indicated.