Back To CoursePathophysiology Textbook
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A long time ago, disgusting as it may be, people used to actually taste and drink urine in order to try and diagnose a patient's disease! I'm not even kidding you. Thankfully, modern-day doctors do not have to resort to such disgusting and even dangerous methods.
One of the reasons the doctor barbers of yesteryear used to drink their patient's urine was to see if it had a sweet taste, often indicative of diabetes mellitus. Finding the sweet-tasting glucose in the urine was covered in detail in another lesson, so we'll focus on other important measurements here instead.
One value that can be measured in the urine is known as urine pH. pH is a measure of the acidity or alkalinity of a substance. If the pH is low, then it is acidic. If the pH is high, then it is basic, or alkaline.
To remember which is which, I'll give you a little trick that has worked for me. If you grew up watching cartoons, you probably saw some comical ones where cartoonish robbers poured acid on the roof of a bank vault and waited while the acid ate its way downward into the vault, so the robbers could get down there to steal all the cash. If you can recall that acid likes to eat its way downward into things, then you'll remember that acidic substances go down the pH scale. That is to say, their pH numbers are lower than basic substances.
Normal urine pH is roughly 4.6-8, with an average of 6. Urine pH can increase, meaning it will become more basic, or alkaline, due to:
On the flip side, causes for a decreased, or acidic, urine pH, include:
Other than urine pH, another important value in a urinalysis, a test measuring the levels of different substances in urine, is ketones. Ketones, or ketone bodies, are molecules produced by the body when fat is broken down in order to be used as a source of energy.
If you are happy and healthy and get enough nutrients, then your body breaks down carbohydrates as a source of fuel. But in conditions when you aren't getting enough carbohydrates, when you've used them up, or when they cannot be used as a source of energy (as in the case of diabetes mellitus), then the body begins to break down fat stores in order to provide you with energy, resulting in ketone bodies that are used as a source of energy instead.
As a familiar example of the same deal, if you own a hybrid car, then you know that the car can run on battery power for only so long. If you don't charge the car, the battery is used up, or it malfunctions, then the hybrid car switches to another energy source, gasoline. The ketones are essentially a backup source of fuel in times of great need or disease.
Normally, there should be no ketones in the urine. If ketones are found in the urine, called ketonuria, they may be indicative of:
Another thing that can be tested for in the urine is proteins. Normally, a test called a urine dipstick test is used as a routine scan for protein in the urine. This is the test that has all those pretty colored squares on a strip of paper. I'm sure you've seen it before. A typical urine dipstick test will not detect any normal amounts of protein in the urine, normally less than 150 mg/day. Foamy-looking urine is often indicative of abnormal amounts of protein in the urine, called proteinuria, which will be detected by the urine dipstick.
But the problem with a urine dipstick test is that it has several faults. Normally it only measures only one kind of protein, called albumin, and is much less sensitive to globulins and Bence-Jones proteins. Furthermore, the test strip indicators may sometimes be fooled by varying levels of urine concentration and may therefore give false results. Therefore, a more accurate test for proteinuria is known as the 'sulfosalicylic acid test.' Both of these tests give results with a series of plus signs indicating ever-increasing concentrations of proteins in the urine. Because the sulfosalicylic acid test is more accurate, we'll focus on interpreting its results in this lesson:
Protienuria itself may be a result of many different problems, including;
As a general rule, the larger the amount of proteinuria, the more likely the disease is one that affects the glomerulus.
A urine sample may also be examined under the microscope to look for cells and casts. Normally, there should be no more than 2 red blood cells in a high-power field under the microscope. Elevations beyond this may signify abnormal amounts of red blood cells in the urine, which we term hematuria. This may be a result of a lot of reasons, which can be remembered by the mnemonic TICS:
When hematuria occurs and significant amounts of red blood cells are present, the urine will be light pink, red, or cola colored.
Similarly to red blood cells, no more than 5 white blood cells per high-power field should be found in a normal healthy person. Any more than that and an infectious or inflammatory process should be suspected. Infections typically cause pus in the urine, called pyuria. Pus is a collection of dead white blood cells and bacteria, the latter of which should never be found in a normal urine sample.
As a parting note, casts may also be noted in a urine sample. Casts are collections of proteins and cells. There are many different types of casts. Red cell casts indicated glomerular disease, whereas white blood cell casts may indicate a kidney infection, aka pyelonephritis.
As a review, remember that a urinalysis can look at the pH of urine, which is a measure of the acidity or alkalinity of a substance, as well as for ketones. Ketones, or ketone bodies, are molecules produces by the body when fat is broken down in order to be used as a source of energy.
Furthermore, a urinalysis may indicate abnormal amounts of protein in the urine, called proteinuria, resulting in foamy-looking urine.
In certain instances, abnormal amounts of red blood cells in the urine, which we term hematuria, may be present in the urine, leading to a reddish discoloration of urine.
Finally, infectious processes might result in pus in the urine, something technically called pyuria.
At the end of this lesson you should be able to:
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Back To CoursePathophysiology Textbook
20 chapters | 274 lessons