Urinalysis

In today’s lab we will be separating into four groups: salty, caffeine, water and bicarbonate. Depending on your group assignment you will eat or drink and then go to the bathroom to void (pee) in a cup. Return with the cup and we will use a test strip and other equipment to determine the following components in your urine: leukocyte, nitrite, urobilinogen, protein, pH, blood, specific gravity, ketone, bilirubin, glucose, volume, color and clarity. See information on Chemical Properties of Urine listed below. After one hour you will need to void again. We will not use the urinalysis test strip, but we will measure changes in volume, pH (using pH paper), specific gravity (using a refractometer), color and clarity.

A data table is provided on my website. Please print it in color and bring it with you. All students will complete today’s lab unless they have a medical reason they cannot.

Chemical Properties of Urine

Mammalian urine can contain a veritable slew of organic and inorganic solutes. Knowing the concentrations of these solutes can tell us a great deal about the metabolic state of the person and help us to evaluate the function of the circulatory, digestive, urinary and endocrines systems. The relative concentrations of these chemicals are typically measured using multi-panel test strips. Each panel contains a unique chemical reagent which will change color when exposed to its respective solute. The degree of color change often of caution about the use of test strips; the results of the test can be affected by the specific gravity and age (freshness) of the sample as well as the age and storage condition of the reagent strips (check expiration dates and always re-cap the bottle!). In addition, small amounts of reagents can sometimes be transferred from one panel to another if the stick is dipped into the urine, thus causing incorrect results. For this reason, you should always pipette individual droplets of urine to each square and never let you pipette touch the reagent panel!

For this lab, you will be using DiaScreen® 10 strips, so named because they measure 10 different urine components. A brief description of each component is listed below.

Specific Gravity: It is the measure of the density of the solution, with water having an s.g. of 1. The value ofvery dilute urine is 0.001 and concentrated urine is 0.030. The more highly concentrated indicated perhaps too much salty food or you don’t drink enough water. It may also be indicative of kidney stones.

pH: The pH scale measures the relative concentration of hydrogen ions (H+) andhydroxide ions (OH-) in a solution. The pH scale ranges from 0 to 14. Solutions with an equal concentration of H+ and OH- ions (e.g., distilled water) have a pH of 7 and are termed neutral. Solutions which contain more OH than H+ have pH values greater than seven and are termed basic or alkaline. The greater the amount of OH-, the higher the number. Solutions with more H+ than OH- have pH values less than seven and are termed acidic. It is important to point out that the pH scale is a log scale, meaning that the H+ and OH concentrations change ten-fold for each step in the scale. One of the primary functions of the kidneys is to maintain a relatively constant blood pH by excreting excess H+ or OH- in the urine. This can cause urine pH to fluctuate depending on diet and metabolic state. That said, pH ranges from 4-8, with the average 6. pH close to 4 may be due to eating meat or wheat; pH close to 8 may be due to eating vegetables.

Blood: The DiaScreen® strips test for both whole (non-hemolyzed) as well as ruptured(hemolyzed) erythrocytes. Whole erythrocytes are much too large to pass through the glomerulus, and thus are not normally part of the glomerular filtrate. Presence of nonhemolyzedblood in the urine (hematuria) is more often a sign of bleeding down-stream of the glomerulus (e.g., in the ureters, urethra or urinary bladder). In contrast, presence of hemolyzed blood in the urine (hemoglobinuria) may indicate lysis (rupture) of blood cells within the systemic blood vessels.

Leukocytes: Leukocytes (white blood cells)are occasionally present in the urine in those with infections of the lowerurinary-tract.

Nitrite: Nitrites (NO2-) are abnormalcomponents of urine which are formed bybacterial decomposition of urinary nitrates.When present, they suggest a bacterial infection of the urinary tract contamination and improper storage ofthe sample.

Protein: Whole blood contains several types ofplasma proteins including albumin, fibrinogen,immunoglobulins (antibodies). With a fewexceptions, most plasma proteins are too largeto pass through the glomerulus. Presence ofplasma proteins in urine (proteinuria) mayindicate damage to the glomerular membraneand the onset of kidney disease. Somemammals (e.g., humans) may exhibittemporary, non-pathological (not due to illness)proteinuria as a result of pregnancy, vigorousexercise, or even prolonged periods of standing(less-common in the dog and cat). Finally,despite what it says on the bottle, most “protein”test panels will only detect albumin, and only infairly large amounts.

Bilirubin: Bilirubin is a bile pigment derivedfrom the normal recycling of erythrocytes (red blood cells) in thespleen. Like other hemoglobin by-products(e.g. urochromes and urobilogen), traceamounts of bilirubin may occasionally be foundin the urine. Large amountsof bilrubin in the urine may be an indicator ofliver disease.

Ketones: Presence of large amounts ofketones (ketonuria) is abnormal in humans and indicates that thebody is relying almost exclusively onmetabolism of fats to meet its metabolic needs.This can occur when an animal is starved or ison a high-fat/low-carbohydrate diet (thinkAtkin’s Diet). Ketonuria in a well-fed animalmay be a sign of diabetes mellitus.

Glucose: Glucose is a monosaccharide (simplesugar) which is always present in blood plasma.Although glucose is small enough to be filteredthrough the glomerulus, it is normallycompletely reabsorbed into the renal tubule and thus is not a normal component of urine.However, if blood glucose levels are severelyelevated (as with a diabetic person), there maybe insufficient membrane receptors to reabsorball of the glucose, and some will be excreted in the urine (glucosuria). A side-effectof glucosuria is that renal absorption of water is impaired, causing more water to be excreted inthe urine (which will have a lower than normal

SpG). Diabetes mellitus literally means“increased quantities of sweet urine” and was once confirmed by tasting the urine of a suspectperson (aren’t you glad they make glucose test strips?).

Urobilogen: Urobilogen (yet another byproductof hemoglobin recycling) is producedfrom bilirubin in the small intestine and isnormally present in urine in small amounts.Excessive levels of urobilogen may indicateliver disease.

Metabolic Disorders: Glucose + Ketones & low