PHYSO LAB: Clinical Examination of Urine and Fluid Regulation Lab
Objectives
1.
2.
3.
4.
5.
Determine the composition of urine.
Examine urine sediments.
Predict changes in urine after ingesting fluids that differ chemically.
Monitor changes in urine volume and composition after ingesting various fluids.
Interpret the relationship between urinary physiology and circulatory physiology.
*** Be sure to use Universal Precautions while handling urine. ***
Part I: Clinical Examination of Urine
In this part of the lab, you will examine several aspects of the composition of urine. We will look at the
biological, chemical, and physical properties of urine.
Multistix Testing
Muultistix are plastic strips that have attached paper pads soaked with specific reagents. These strips provide a
colorimetric assay for a variety of urine components. A color reaction occurs that can be compared with known
standards.
Property
color
Expected range / Significance of positive test (or abnormal range)
clear to amber / redness due to blood from excessive glomerular permeability,
infections
turbidity
transparent, not cloudy (not turbid) / possible infection
odor
slightly aromatic, but not fruity or like acetone, no ammonia / ketosis, possible
infection
glucose
negative / possible diabetes mellitus
bilirubin
0.1-1.0 / hemolytic or pernicious anemia, liver dysfunction
ketones
negative-trace / diabetes mellitus, starvation, pregnancy, frequent/recent strenuous
exercise
specific
gravity
1.001-1.035 / high: dehydration or diabetes mellitus, low: diabetes insipidus
blood
negative/ inflammation/injury of urogenital tract or kidneys, menstrual
contamination
pH
4.6-8.0, normal or abnormal / continuously very acidic urine may indicate acidosis;
continuously very alkaline urine may indicate alkalosis or microbial infection.
protein
negative-trace / excessive glomerular permeability
urobilinogen negative / liver dysfunction, hemolytic disease
nitrite
negative/ associated with bacterial infection (bacteriuria)
leukocytes
negative-trace / urinary tract infection
Procedure
1.
2.
3.
4.
5.
Read the instructions for Multistix testing.
Remove a test strip from the vial and replace the cap.
Dip the test strip in your urine for no more than 1 second. Make sure that all of the pads are immersed.
Remove any excess urine from the strip by dragging the strip along the edge of the urinalysis cup.
After the appropriate time as indicated on the Multistix vial, hold the strip in the proper orientation
along the color keys on the Multistix vial. Make sure the strips are properly lined up.
6. Record your results in the table below.
Test
Multistix Result
pH
Protein
Glucose
Ketones
Bilirubin
Blood
Leucocytes
Specific gravity
Urine Sediment Analysis
Microscopic examination of the urine sediment may reveal the presence of various cells, crystals, bacteria, and
casts.
Cells are derived from the lining of the urinary tract and their presence at normal levels is simply from wear and
tear. Blood cells if present are likely an indication of inflammation and or disease.
Crystals form from the end products of metabolism, certain foods, and some drugs. We usually base
identification based upon shape. See the samples up front. Some common examples are calcium oxaloacetate
(oval, dumbbell, 8 and 12-sided “envelopes), uric acid (yellow or brown rhombic prisms, plates, or spheres, and
triple phosphate (6 or 8-sided “coffins” or “feathers”).
Casts are hardened masses of material that take the shape of various regions of the nephron. The form as the
result of precipitation of various filtrate solutes, usually under high concentration. Casts may also have cells in
them. Although a small number of casts are normal, their presence in high amounts could indicate glomerular
nephritis or nephrosis.
Procedure
1. Fill a conical centrifuge tube about three-quarters full with urine (about 10 mls in a 15 ml conical
centrifuge tube).
2. When centrifuge is full, centrifuge at moderate speed (about 3500 rpm) for about 5 minutes.
3. Discard supernatant in designated flask.
4. Place one drop of methylene blue dye on pellet.
5. Add 5 drops of normal saline to the pellet.
6. Mix well by aspirating with a transfer pipette.
7. Place one drop of stained sediment on a clean slide and cover with a coverslip.
8. Scan the slide with low illumination and identify the components of the sediment.
9. Draw and label representative components.
Part II: Fluid Balance
In this lab you will be testing the effects of a variety of ingested solutions on the cardiovascular and urinary
system. Most ingested materials are absorbed from the digestive system (small intestine) into the blood and then
soluble components are filtered in the urinary system (kidney). By assessing changes in the blood pressure, heart
rate and hematocrit, you can measure the effect of ingesting a given solution on the cardiovascular system.
Likewise, by measuring the chemistry and volume of the urine production after ingesting a particular solution
you can evaluate the effect on renal physiology. Interpreting the physiological mechanisms behind the changes
you observe is the primary objective of this lab.
Pre-lab assignment: To achieve good results for this lab it is vital that all students abstain from drinking or
eating anything for 4 hours before the lab. This will eliminate the extraneous effects of additional ingested
materials that will interfere with your body’s response to the experimental solutions.
After the introduction to the lab, all test subjects must take and record their blood pressure and pulse as well as
voiding their bladder and measuring urine volume, color, specific gravity, and pH. Once the initial
measurements are taken, each of the experimental subjects will drink one of the following solutions. It is best if
the entire class is in synchrony at this point so we will all proceed together and no single group will get behind.
There should be 2 students for every one of the following solutions:
Experimental Solutions:
1 liter Distilled water
1 liter 0.9% NaCl
1 liter 1.5% NaCl
1 liter 1.0% NaHCO3
1000mg Vitamin C + 1 liter distilled water
1 liter Coffee (caffeine) - optional
After taking the base-line readings (pre-ingestion), the experimental subjects should drink as much of the 1 liter
solution as they can and as quickly as you can handle (best within 5 min). If you are taking the vitamin C, drink
1 liter of water with the tablets. After drinking the solution you should take another series of measurements
every 20 minutes. Use the time of voiding as the time recorded. Even if you do not feel the need to void your
bladder you must still go to the restroom and try to produce a sample every 20 minutes no matter how small.
When you are finished you should have the pre-ingestion data and 5 post ingestion data.
Cardiovascular System
To monitor cardiovascular changes, you will take and record your pulse and blood pressure as you have done
previously in the Cardiovascular Labs. Have the same lab partner take these measurements throughout the
experiment. We will not measure hematocrit due to safety reasons.
Urinalysis
Urine volume: This is the total volume of urine produced at one time. The urine sample is collected in a
urinalysis cup in the bathroom. If you produce more urine than fits in the cup you may have to dump and refill
the cup keeping track of the total urinary output. You will need to save half a cup to perform the urinalysis. You
can perform the urinalysis in the bathroom.
Color: This is a qualitative assessment of the concentration of the urine. Evaluate the color based upon the
previous sample (pre-ingestion). Darker is more concentrated while getting lighter indicates the urine is getting
more dilute. The specific gravity (see below) is a better indicator of urine concentration.
Specific Gravity: This is the relative weight of a specific volume of fluid compared with an equal volume of
distilled water. Pure water has a specific gravity of 1.000 and any additional solutes will increase the specific
gravity. The normal range of a urine sample is 1.001-1.030. Thus, specific gravity is also a measure of the
concentration of solutes in the urine. This test is read from the urine test strips provided in lab. These strips have
many colormetric tests on them in addition to the specific gravity and each test must be read at a specific time
after dipping the test strip into the urine. You should only dip one strip to get all of the necessary data for all the
tests for one sample. Hold the test strips sideways/horizontally while you are reading the results. Note the
waiting time for each test provided on the original test strip container. If you wait too long the test will be
invalid. Dip the strip in the urine and read the specific gravity value at 45 sec based upon the color change in the
filter paper tab next to the specific gravity scale. The spectrum of colors and their values are also found on the
test strip container.
pH: Also found on the test strip is a panel for urine pH. You will read this at 60 sec. Urine is typically slightly
acidic with a pH range of 4.5-8.0 and an average around 6.
Urinary Lab Assignment
1. Renal Physiology
For distilled water, 0.9%, and 1.5 % salt, graph changes in Cumulative Volume, Specific Gravity, and MAP as a function
of time (one graph for volume, one for s.g., one for MAP). For NaHCO3 and Ascorbic acid, graph changes in pH as a
function of time (one graph).
Discuss the effect of ingesting one liter of each solution on:
1.
2.
3.
4.
5.
Blood volume
Blood osmolarity
Urinary output
Specific gravity or concentration of urine
Urine pH
Also, briefly discuss the expected homeostatic compensation for each type of ingestion, these may include:
1.
2.
3.
4.
5.
Behavior responses such as thirst
Hormonal responses such as changes in the levels of ADH, aldosterone, and ANP
Cardiovascular responses such as changes in cardiac output and vasoconstriction
Respiratory responses such as changes in ventilation rate
Renal responses such as the secretion of renin and secretion and reabsorption of certain ions
You may want to write one paragraph for each of the five types of solutions.
2. Microscopic analysis
Include drawings of some of the substances you observed in your urinary sediment. What did you find and why do you
think you found it.
3. Chemical Analysis
Describe the results from your Multistix testing. What were your values? Any abnormal?