Everything you need to analyze the UA
Last Updated: August 29, 2022
Urinalysis or UA is a lab test frequently ordered in all types of medical settings: hospitals (ER, ICU, Inpatient floors), urgent cares, and outpatient offices. In many cases, the correct evaluation of the urinalysis is imperative to making an accurate diagnosis. To provide additional data, many labs perform urine microscopy, giving you exact details on the contents within the urine and quantifying the results. Read all about how to interpret the Urinalysis dipstick, as well as the urine microscopy in this article!
Initial Urine Assessment
Before you even run the urinalysis, you can tell quite a bit about the patient just by using your God-given senses.
The color of the urine is the easiest way to determine someone’s hydration status. Surprisingly, it can indicate other aspects of health as well.
Normal urine varies from very clear yellow to a darker amber color. Generally speaking, the less hydrated you are – the more concentrated your urine. The more hydrated you are, the more diluted the urine, leading to clear yellow urine.
The first void of the morning is typically darker and more concentrated – this is normal.
Red or Pink
When we see red urine – we typically think of blood. Medical conditions such as kidney stones (nephrolithiasis), UTIs, glomerular damage, or even malignancy. As little as 1mL of blood can cause a color-change, and the presence of red urine does not automatically mean large amounts of blood. There are a few different causes of red urine:
- Bloody causes: Cystitis, kidney stones, malignancy, trauma, menstrual contamination
- Non-bloody Conditions: Rhabdo (from myoglobin)
- Foods: Beets, Blackberries, and Rhubarb
- Meds: Propfolol, Chlorpromazine, Ex-Lax
Causes or orange urine include:
- Rifampin (Antibiotic for TB)
- Pyridium or over-the-counter AZO
Blue or Green
Also very rare, blue or green urine may be caused by:
- Conditions: Familial benign hypercalcemia, Pseudomonas infection
- Medications: Propofol, Amitriptyline, Indomethacin,
- Foods: Strong Food dyes
Termed “Purple Urine Syndrome” Or “Purple Urine Bag Syndrome”, this is very rare but can occur due to:
- Conditions: UTIs with certain gram-negative bacteria with alkaline urine
- Meds: Amitriptyline, Methylene Blue dye
- Foods: Diet high in Tryptophan
Urine turbidity is how cloudy urine is. When we see cloudy urine, our first thought should be an infection which may be accurate. However, other causes of cloudy urine are cell casts or cellular debris from kidney damage.
Stronger-smelling urine tends to mean dehydration, but foul-smelling urine usually indicates infection. This odor is caused by the bacteria that split urea to form ammonia.
Sweet-smelling urine may mean the patient is spilling glucose into the urine from hyperglycemia.
Lastly, If the urine smells like feces, a fistula might have formed somewhere between the GI tract and the Urinary tract.
Nah I’m just kidding – but did you know they used to taste urine to detect glucose in the urine?…. GROSS!
Once you’ve assessed the urine with your own senses, it’s time to assess the actual urinalysis. This can be done in the following ways:
- Dipping a dipstick in urine and assessing the colors next to a test strip color chart (usually printed on the dipstick bottle).
- Sticking the dipstick in an Automated Urine Analyzer. This will give you. a printout of the results.
- Send the urine off to the lab, where they will perform a urinalysis and upload the results to your electronic medical record. They will often perform microscopy if indicated, which can be used to help interpret the urine.
When serum glucose spills into the urine – this is termed glucosuria. Typically, glucose in urine does not occur until the kidney glucose threshold is reached – which is around 180mg/dL. As you can tell, this can be useful for evaluating hyperglycemia in the setting of diabetes. However, periods of stress or fever have been known to cause small amounts of glucose within the urine as well, so glucose in urine does not automatically mean diabetes
- Glucosuria can indicate hyperglycemia in undiagnosed diabetics when blood work is not obtained.
- Fever or stress could cause mild glucosuria in non-diabetics
- SGLT2 inhibitors like Farxiga can increase glucose in urine even without elevated glucose levels
- Ascorbic Acid (vitamin C) has been known to cause false-negatives
Urinary bilirubin may be present in low amounts in the urine normally, but increased levels are due to abnormalities of bilirubin metabolism or liver function.
- The presence of bilirubin may indicate elevated LFTs, but overall does not seem to add significant information toward diagnosis.
- Must be sent immediately as bilirubin is unstable when exposed to light
Normal Levels: None ( 0.3 mg/dL or 0.05 mmol/L)
The presence of ketones in the urine (ketonuria) indicates ketosis. This is usually caused by uncontrolled diabetes or DKA. However, acute illness, stress on the body, strenuous exercise, nausea/vomiting, and keto or other low-carb diets can cause ketonuria to occur.
- Parkinson’s medications (Levodopa) can cause a false positive
Normally ascorbic acid is not seen in the urine dipstick.
Ascorbid acid is Vitamin C. The presence of this in the urine can lead to false negatives for both Heme, glucose, leukocyte esterase, and protein.
Some dipsticks do add a chemical to neutralize the effect of ascorbic acid on the other tests.
The specific gravity indicates how dilute or concentrated the urine is. This can give the interpreter a pretty good idea of hydration status when looking at the urinalysis.
Normal Levels: 1.005 – 1.030
Low (<1.005): May indicate diabetes insipidus, renal failure, pyelonephritis, glomerulonephritis, psychogenic polydipsia, or malignant hypertension
High (>1.030): May indicate severe dehydration, hepatorenal syndrome, heart failure, renal artery stenosis, shock, or SIADH.
- Protein, ketones, and glucose, as well as recent IV contrast dye, can falsely elevate the specific gravity.
- Medications like diuretics can also impact this (like lasix).
Heme detects blood in the urine.
There are many potential causes of hematuria including UTIs, kidney/glomerular damage, trauma, kidney stones, malignancy, vaginal contamination, or coagulopathies.
In a patient over 50 years old who has persistent hematuria, malignancy should be ruled out.
Normal Levels: Negative
The test for heme is very sensitive and can detect down to 1-2 RBCs per High-powered field (HPF). So a negative dipstick excludes blood.
False Negative: Unlikely, but Ascorbic acid can lead to this
False-Positives: Myoglobin (as during rhabdomyolysis), semen (recent ejaculation), alkaline urine >9.0, contamination from hemorrhoids, vaginal blood, or oxidizing compounds used to clean the perineum can all cause false-positive heme to occur in the urinalysis.
A positive Heme requires urine microscopy for confirmation.
The pH of urine stands for the potential of hydrogen. The more hydrogen ions there are, the more acidic something is.
The pH scale runs of 0-14, with lower numbers being more acidic, and higher numbers being more basic.
Because the kidneys regulate your acid/base balance, any change within the body should show up in your urine. However, various different disease processes can interfere with your kidney’s ability to do this effectively.
Normal Levels: 6, but can range from 4.6 – 8
Acidic urine <7.0 is associated with metabolic or respiratory acidosis or an E Coli UTI.
Basic urine >7.0 is associated with most types of kidney stones, urea-splitting bacteria (proteus or klebsiella), renal tubular acidosis, or potassium depletion.
Diet: Cranberries and high-protein diets can cause acidic urine, whereas citrus fruits and low-carb diets can cause alkaline urine
Medications: Sodium bicarbonate and thiazide diuretics can cause more basic urine
The urine protein dipstick is specific for albumin, which is a type of protein. Any damage to the glomerular basement membrane will let albumin and other larger particles pass through the membrane and into the urine.
Protein in urine is typically used to evaluate kidney damage in diabetics, people with Congestive Heart Failure (CHF), or other causes of kidney damage.
Benign causes of high protein in urine include dehydration, emotional stress, fever, heat injury, inflammation, intense activity, acute illness, or an orthostatic disorder.
All other causes of proteinuria involve the kidney – specifically the glomerulus or the renal tubules. Some common causes of glomerular proteinuria include Diabetic nephropathy, lupus nephritis, preeclampsia, various infections (HIV, hepatitis B, post-streptococcal glomerulonephritis), certain cancers, and certain drugs like Heroin, NSAIDs, and Lithium. Some causes of tubular proteinuria include interstitial cystitis, Sickle-cell, and nephrotoxicity from NSAIDs or antibiotics like aminoglycosides.
Normal Levels: Undetectable
The urine normally has <150mg/day of protein and should be undetectable on a dipstick, but when this level exceeds 300mg/day, high protein in urine will show up on a dipstick.
Urinary concentration will impact the results, so correlate with the Specific Gravity. Very dilute urine can lead to underestimation of protein, and very concentrated urine can lead to overestimation.
In general, the dipstick is a crude estimate, and evaluation by 24-hr urine specimen is the standard of care for ongoing proteinuria. If renal cause is found, a Nephrology consult is warranted.
In the acute setting, the dipstick for protein isn’t too informative as acute illness, inflammation, stress, and dehydration are common presentations and can cause a temporary elevation in urinary protein.
Urobilinogen is a byproduct of bilirubin production, but unlike bilirubin is colorless.
Elevated levels can indicate malaria, hemolytic anemia, liver disease, or internal bleeding.
An increased urobilinogen level is one of the earliest signs of liver disease and hemolytic disorders.
Normal Levels: 0.1–1 Ehrlich U/dL or 1 mg/dL
Nitrates are present in the urine at baseline. Some species of bacteria, specifically the Enterobacteriaceae species (E. coli, Klebsiella, Proteus, Enterobacter, Citrobacter, and Pseudomonas), release an enzyme called nitrate reductase which converts urinary nitrate to nitrite, causing nitrites in urine.
If negative, it really doesn’t mean much. If positive, then it is highly likely an infection is present.
Normal Levels: Negative
This reaction requires dwelling time within the bladder to occur. Urinary frequency or the presence of a Foley catheter can make this impossible. It can take up to 4 hours of dwelling before nitrites are detected.
A person might not intake a sufficient amount of nitrates in their diet.
False-Positives: Azo dye metabolites and bilirubin, as well as letting the urine sit for too long can produce false positives. Higher specific gravity reduces the sensitivity.
False-Negatives: Ascorbic acid can produce false-negative.
Leukocyte esterase is a component of WBCs that is released when these white blood cells are lysed (split open).
The presence of leukocyte esterase supports the diagnosis of a Urinary Tract Infection (UTI). However, the presence can also indicate various autoimmune disorders, STDs, kidney stones, or intra-abdominal infections.
If there is no leukocyte esterase, infection is pretty much ruled out.
Normal Levels: Negative
False-Negatives: Proteinuria, glycosuria, excessively concentrated urine, or tetracycline.
False-Positives: Contamination with vaginal discharge, certain medications (ampicillin), salicylate toxicity, and strenuous exercise.
Urine microscopy is when they look at the patient’s urine under a microscope and further characterize the presence of certain cells.
Crystals, as the name implies, are crystallizations within the urine. Crystals in urine can be normal as long as they are composed of substances normally found within the urine.
Crystallization can occur for a variety of reasons, and the type and quantity of these will depend on the urine’s pH and underlying cause.
Amorphous crystals form naturally when urine cools, and are more often found in acidic urine. This is usually just some precipitation of electrolyte salts, and there is no clinical significance.
Uric Acid Crystal
Uric acid crystals are generally associated with gout. They can also be caused by kidney stones, tumor lysis syndrome, or chemotherapy
Calcium Oxalate crystals are usually found in acidic urine and associated with kidney stones. Dehydration and/or increased oxalate intake can cause this. Ingestion of antifreeze can also cause these.
Calcium carbonate crystals may be caused by too calcium supplementation, and is also associated with kidney stones.
Calcium phosphate crystals are more likely to precipitate in alkaline urine. This could rarely be caused by hypoparathyroidism.
Triple phosphate crystals, also called Struvite crystals, are made up of magnesium ammonium phosphate. These are typically found in alkaline urine and associated with kidney stones as well as UTIs with bacteria that split urea, like Proteus mirabilis and Pseudomonas aeruginosa.
Hippuric acid crystals are rare but can be found in normal or acidic urine.
Cystine crystals are found in acidic urine in patients with a genetic condition called cystinuria.
Bacteria are NOT normally found in the urine as it should be a sterile environment. If found, it usually indicates infection or contamination.
Bacteria multiply rapidly if the urine specimen is left standing for too long at room temperature.
If there are leukocyte esterase +/- nitrites present with <15-20 epithelial cells/HPF, then infection is highly likely.
Consider starting empiric antibiotics if symptomatic and obtain a culture and sensitivity for confirmation.
Red Blood Cells
Normally there are less than 2 RBCs/HPF.
Microscopic hematuria is defined as the presence of at least 3 RBCs/HPF.
Microscopic hematuria confirms a heme+ dipstick.
White Blood Cells
Normally there are less than 2-5 WBCs/HPF within the urine.
If >5 WBCS, this indicates possible infection, inflammation, or contamination.
Most of the WBCs found in the case of infection are neutrophils.
Squamous epithelial cells are the skin cell of the external urethra.
>15-20 epithelial cells/HPF indicates contamination and another urine sample should be obtained to rule out infection.
Casts are tube-like protein structures made of various cells. Low urine pH, low urine flow rate, and high urinary salt concentration promote cast formation by favoring protein denaturation and precipitation. The presence of casts, other than hyaline casts, represents pathology within the kidney itself.
Hyaline casts can be present in normal healthy adults and are nonspecific.
They can be found after strenuous exercise or dehydration, as well as with diuretic use.
RBC casts usually indicate glomerulonephritis or vasculitis.
Uncommon, but when present is usually seen with tubulointerstitial nephritis and acute pyelonephritis but also seen with renal tuberculosis and vaginal infections.
Muddy-Brown Granular casts are diagnostic of acute tubular necrosis, the leading cause of Acute Kidney Injury.
Waxy casts are consistent with acute or chronic renal failure.
Broad casts are consistenet with advanced renal failure.
Fatty casts indicate nephrotic syndrome.
Renal Tubular Epithelial Casts
Renal tubular epithelial cells are seen in acute tubular necrosis, interstitial nephritis, and proliferative glomerulonephritis.
Hopefully, this gives you a pretty good idea of how to interpret a urinalysis. Whether you are a nurse, an advanced practice provider, or a physician, this skill is important to have. If there are any other lab interpretation you would like to see, please leave a comment below!
Sampling and evaluation of voided urine in the diagnosis of urinary tract infection in adults (UpToDate)
Urinalysis in the diagnosis of kidney disease (UpToDate)
Manual of Laboratory and Diagnostic Tests (Chapter 3)
Tintinalli’s Emergency Medicine: A Comprehensive Study Guide
Crystals in the Urine: What You Need to Know (Healthline)
Proteinuria in Adults: A Diagnostic Approach (AAFP)