On the Medgeeks Facebook page, we had a post recently with questions on how to appropriately interpret in office urinalysis results. I always thought that if one person has a question about a topic, then there are likely multiple others that could benefit from the information as well.
Regardless if you’re a practicing clinician or a current student, this review on the commonly ordered urinalysis will hopefully allow you to brush up on things, or perhaps glean some new information.
The urinalysis is an important test that can provide a litany of information and can aid in the diagnosis of many conditions including a UTI, or could point you towards others, such as a kidney stone or malignancy.
Collecting the Sample
The initial thing to do is collect the urine for testing. The external genitalia should be cleansed, and then a midstream, clean-catch sample is collected. There is some debate on whether cleansing of the genitalia is needed, and recent studies have found that contamination rates have been similar between both approaches.1
Urine Color and Odor
Once the specimen is collected, the first thing that should be assessed is the odor and color of the urine sample. Multiple things can alter the color of the urine, such as medications, infection, foods, or metabolic by-products.1
A common medication that will alter the color of a urine sample is Azo, which is an over the counter medication often used to offset the dysuria symptoms that can be caused by a UTI. Another common appearance seen in a urine sample is cloudy urine. This is often present if there is pyuria or if there are phosphate crystals present in alkaline urine.1
The odor of a urine sample can be altered with several medical conditions. If the sample smells fruity or sweet, this can be indicative of diabetic ketoacidosis. An ammonia smelling sample can be present if the urine sample has been held in the bladder for an extensive period of time.
Urinary tract infections will often have a pungent odor, an intestinal-urologic fistula would have a fecal odor, and cysteine decomposition would present with a sulfur smell.
False Positives and False Negatives
A point of care urinalysis often can have several things that may lead to a false positive or false negative result. These vary from medications, exercise, dehydration, and even if the UA test strip is excessively exposed to air. A full list of things to keep in mind is listed below.
Specific gravity on dipstick tells us about the patient’s hydration.
This can range from 1.003 to 1.030. If the value is less than 1.010 the patient is well hydrated, if the value is over 1.020 the patient is relatively dehydrated. Other than increased or decreased fluid intake, what else could affect specific gravity?
If the specific gravity is increased, this could also be related to excess sugar or glucose in the urine related to uncontrolled diabetes, or diabetic ketoacidosis, or SIADH where there is too much anti-diuretic hormone being released causing concentrated urine.
Causes of decreased urinary specific gravity could be related to diabetes insipidus, where there is a reduction or lack of antidiuretic hormone being produced, causing dilute urine, along with adrenal insufficiency, or hyperaldosteronism.1
The pH on a urinalysis can span from 4.5 to 8, but often will be slightly acidic around 5.5 to 6.5. Dietary habits such as eating cranberries can even affect the pH of the urine, causing an acidic pH, whereas diets that have high levels of citrate will lead to a higher urine pH.
More times than not, the urine pH will mirror the serum pH. However, this is not the case in renal tubular acidosis. In distal renal tubular acidosis, the serum pH will be acidic, however the urinary pH will be alkaline. This is due to the kidneys being unable to secrete protons into the urine.1
In proximal renal tubular acidosis, the kidney is unable to reabsorb bicarbonate ions, leading to alkaline urine in the beginning, but then subsequently leads to an acidic pH of the urine.
Urine that has an alkaline pH along with findings consistent with a UTI can be indicative of a urea-splitting organism that can lead to the formation of magnesium ammonium phosphate crystal, subsequently cause staghorn calculi. An acidic pH can be more likely associated with uric acid calculi.1
Hematuria on Dipstick
The next result, on a urinalysis I look at, is hematuria or lack thereof. Blood can be from things such as menses in females, but can also be due to more serious causes, such as renal calculi or malignancy. Hematuria etiologies are broken down into glomerular, renal, or urologic causes.
For a full workup and evaluation of hematuria, see the article Asymptomatic Hematuria on the Medgeeks blog.
Always remember, if there is blood present on an in-office UA, this needs to be confirmed by microscopy and entirely worked up!
Proteinuria on Dipstick
Proteinuria is diagnosed when there is more than 150 mg of protein present in the urine per day.
The presence of this much protein in the urine is a classic finding in renal disease. However, the presence of small amounts of protein in the urine, 30 to 150 mg per day, is an earlier sign of renal disease, microalbuminuria, which can be seen in diabetic patients.1
Normal urinary protein that can be present in smaller amounts include albumin and serum globulins. However, your routine in-office UA looks for albumin in the urine and may not find other types of proteinuria.
One question I had when I first started practicing was, what does 1+, 2+, 3+ protein on a UA even mean? And how much should be there before I get worried?
If the UA in office shows trace protein, this is equal to 5-10 mg/dL, which is below the significant threshold for proteinuria. If 1+ protein is seen, it is equal to 30 mg/dL, and is considered positive or significant.
A result of 2+ is equal to 100 mg/dL of protein, 3+ is equal to 300 mg/dL, and 4+ is equal to 1000 mg/dL of protein in the urine.
Proteinuria can be transient or persistent. Transient causes of proteinuria are typically related to intermittent changes in glomerular filtration or perfusion which leads to the seen protein excess.
The most commonly observed transient cause of proteinuria is orthostatic proteinuria, which is a benign etiology. This can be diagnosed with negative UA results for protein, after having the patient lay down for eight hours, and then having the patient provide a urine sample.
Persistent proteinuria can be split into glomerular, tubular, or overflow etiologies. Glomerular proteinuria is the most common type, in which excess urinary albumin is often the cause.
Tubular proteinuria often occurs when the renal system is not breaking down or absorbing the regularly filtered protein from the glomerulus. In tubular proteinuria, the amount of proteinuria is not routinely over 2 grams daily.1
Lastly, overflow proteinuria is seen when the renal system cannot overcome and absorb the amount of protein that is present in the filtrate. In any of these cases of persistent proteinuria, further evaluation is indicated with a 24-hour urinary protein evaluation or a urinary protein to creatinine ratio, microscopic urinalysis, urine protein electrophoresis, and BMP.1
Glucose and Ketones on Dipstick
Glucose is regularly filtered by the kidneys and is all customarily reabsorbed. However, when the amount of glucose is too much for the kidney to reabsorb, glycosuria occurs. This typically happens when the serum glucose is over 180 mg/dL, and is often seen in uncontrolled diabetes, liver disease, pancreatic disease, Fanconi syndrome, and Cushing syndrome.1
Ketones are present when the body is breaking down fat for energy; they are generally not seen in the urine. It is commonly seen in uncontrolled diabetics, but can also be seen in patients that may be doing a ketogenic diet (carbohydrate reduced or free), in pregnancy, or starvation.1
Nitrites and Leukocyte Esterase on Dipstick
Nitrites are seen in the urine when bacteria are present that convert nitrates to nitrites. Gram-negative and gram-positive bacteria, both are capable of this conversion, and if positive, is an indication that there are bacteria present in the urinary tract of the patient.
Nitrites in the urine is specific, but not very sensitive, meaning that if positive, there is a good chance a UTI is present, but if negative, it does not mean that a UTI is not present.
The UA dipstick is very sensitive to air, so the container should be closed ASAP. If not, this could lead to false positive nitrite results.
Leukocyte esterase is present if neutrophils are present in the urinary tract, and can be present if pyuria is present with a UTI.
Bilirubin on Dipstick
Lastly, bilirubin is not generally seen on a urinalysis. Indirect bilirubin is not water soluble and cannot be filtered by the kidneys. However, direct bilirubin is water soluble, and if present in the urine, a further workup for liver abnormalities or biliary obstruction is needed.1
Urine can have a small amount of urobilinogen present, which occurs due to the process of direct bilirubin being broken down in the intestine, reabsorbed into the portal circulation, and then filtered through the kidneys.1
If there is an increased amount of urobilinogen noted on UA, this can be due to liver disease or hemolysis, and decreased amounts can be due to biliary obstruction or antibiotic use.1
I hope this overview has answered some questions for those practicing as well as current students in their didactic studies, or in their rotations. If anyone has any questions, feel free to contact us, and I am more than happy to help!
1. Am Fam Physician. Urinalysis: A Comprehensive Review. 2005;71:1153-62.
2. Am Fam Physician. Urinalysis: Case Presentations for The Primary Care Physician. 2014;90(8):542-547.
3. UpToDate. Sampling and evaluation of voided urine in the diagnosis of urinary tract infection in adults. Accessed: February 7, 2018.
4. LabCorp. Urinalysis. https://www.labcorp.com/results. Accessed: February 7, 2018.
This article, blog, or podcast should not be used in any legal capacity whatsoever, including but not limited to establishing standard of care in a legal sense or as a basis of expert witness testimony. No guarantee is given regarding the accuracy of any statements or opinions made on the podcast or blog.