Today, we’re talking about urinalysis. I recently went on a medical mission trip to Madagascar and we had limited labs, but we could always do a urine dipstick. The U/A is a really great lab test and I think it’s mandatory for all your belly pains.
When you use a U/A, you have to get an uncontaminated specimen. If your specimen is contaminated, it’s useless if you’re looking for cells. If someone doesn’t clean themselves off well, they’re going to get a lot of epithelial cells in the urine. When epithelial cells fall in, it makes the red blood cell and white blood cell count erroneously high.
When someone does a U/A they pee in a cup and you do two parts, a gross evaluation and then a microscopic evaluation. I’m going to take a urine dipstick, dip it in and then just look at some colors, plus two, plus three. If anything is funky, the lab tech should look at it under a microscope and tell you a red and white blood cell count. Do they see bacteria or epithelial cells?
If you get a urine back that says 40 to 50 epithelial cells, the cells in the urine are not valid because they didn’t clean themselves off well. If that becomes a trend, it’s a nursing problem. The nurses need to advise patients on how to clean themselves off. You also need to let nurses know they should be completing urinalysis at the same time as other labs.
When you order your U/A, you get the caloric testing where you hold the urine dipstick up to the
bottle. What are some of the things you get?
When you get a urinalysis back, first, they describe the color. Color isn’t a huge deal, but it gives you a hint of what you could expect. If you put a catheter in a geriatric patient and you see pus come out, this gives you a good idea of why they’re sick. If you see really dark urine, that’s a flag for proteins or blood. What I really need to see are cell counts.
After color, they’ll give you specific gravity, which is important. The most sensitive way to tell if someone’s dehydrated is urine specific gravity. If it’s concentrated urine, the patient is dehydrated. If it’s really dilute urine, they’re hydrating well.
Concentrated urine is 1.035, 1.040, 1.045. I’m going to expect a high specific gravity from someone with vomiting or diarrhea, someone dehydrated. If someone comes in and says they’re vomiting and having diarrhea and their urine is 1.005, a dilute urine, that’s not consistent.
Urine pH is not attached to serum pH. Do not be fooled by this; you can have someone in DKA but have a high pH in the urine.
The pH monitor on urine is for when you’re going to alkalize urine with a bicarb drip for things like rhabdomyolysis or a tricyclic converter dose. On this note, don’t run a bicarb drip without talking to someone else. It’s controversial and a little risky.
Protein will be positive if there a whites or reds in the urine. I don’t get too excited about protein unless the patient is over 20 weeks pregnant. Someone over 20 weeks spilling protein is an immediate OB/GYN referral because it’s possibly preeclampsia. If they are spilling protein, you’re going to look at blood pressure and talk about headache.
Leukocyte Esterase and Hemoglobin
Leukocyte esterase is an enzyme on the outside of a white blood cell. If it’s positive, expect white blood cells to be in the urine; this is a flag for a UTI. If I see hemoglobin in the urine, I expect red blood cells to be in the urine. It’s a flag.
I think nitrates are overly stressed at times. I think nitrates are a piece of the puzzle and I like to look at the whole picture before treating. I might lean more on the culture sensitivity there and not treat, but it really is situationally dependent.
Glucose is also included in U/A. The threshold to spill glucose into the urine is about 180. If someone’s blood sugar is 140, they typically don’t spill. That threshold goes down as the patient gets older. If you have someone who is plus four or five glucose, they’re probably a diabetic.
To make a diagnosis of diabetes, there’s four things to remember. You can use the mnemonic of R2F3.
- R: Random blood sugar of greater than 200 with symptoms of polyuria and polydipsia
- 2: Two-hour glucose tolerance test
- F: Fasting blood sugar greater than 26
- 3: Three-month blood sugar or a hemoglobin A1C of greater than 6.5
If someone’s ketones are positive, it means they don’t have any glycogen stores. Plus two or plus three ketones could mean DKA, a starvation state or a dehydration state. Elevated ketones may indicate the need for IV fluids or some calories in their IV.
On past podcasts you’ve heard me say a golden rule about respiratory rates: it’s never valid unless you took it yourself, because it’s commonly written down as 16. If you have a U/A and a respiratory rate that you took, you can tell if someone’s in a metabolic acidosis, especially DKA. If I’m concerned that someone’s an insulin-dependent diabetic and they’re DKA, I check their respiratory rate and realize it’s 28, then I check their urine. That is three huge flags.
They’re going to be really dehydrated with a high specific gravity, along with high glucose, plus four glucose and plus four ketones. I can confidently make the preliminary diagnosis of DKA with the respiratory rate and a U/A.
Diagnosing a UTI
Now, you come to the differential, with a number of whites and a number of reds. They’re going to look for epithelial cells or motile critters like trichomoniasis. They’ll give me a number for whites and reds, or TNTC (too numerous to count).
Overall, there are a number of different things I want to see with a UTI: hemoglobin positive, nitrite positive, leukocyte esterase positive and 40 to 60 whites. Reds are less significant to me. I’d like to see many bacteria. All of those are good things. This will also flag Trichomoniasis.
If you have hematuria, it needs to be addressed because it could be an acute problem like a hemorrhagic cystitis and some germs can give you red blood cells in the urine. Renal and bladder cancer present as hematuria. You have to look at all of your labs and even painless, asymptomatic hematuria demands follow-up.
Other U/A Tests
You can use your U/A as a pregnancy test by evaluating hCG, human chorionic gonadotropin. I feel just as confident about a urine hCG as a blood count. You can get a tox screen from your U/A as well.