A urinalysis is exactly what the name entails. An analysis of a patients urine. A urinalysis is a fairly common test that may be ordered as part of an annual physical or part of diagnostic testing. It can be used as an evaluation of UTIs, Diabetes Mellitus, kidney disease, kidney stones, proteinuria, rhabdomyolysis, liver disease, or if a patient presents with particular symptoms such as abdominal pain, flank pain, painful urination, blood upon urination, and fever. Pregnancy testing is also part of a routine urinalysis if ordered.
The first step in an urinalysis is collection of the specimen from the patient. An optimal sample is an early morning sample, as it is the most concentrated produced during the day. There are no fasting requirements or medication schedule dosage changes unless otherwise directed by the patients ordering physician. 30-60 mL of urine is collected in a clean urine specimen cup through a clean catch method that should be explained to the patient upon request of sample.
There are different variants of urinalysis. One is the macroscopic observation of the urine. This is the direct visual observation which includes noting its quantity, clarity, and color. Urine is normally yellow and clear without any cloudiness. Abnormalities can mean different things and further analysis is needed.
Dark Yellow: Dehydration
Brown: Liver disease (caused by an accumulation of bilirubin)
Red: Blood (Indicates UTI, stones, tumors, renal trauma)
Orange/Tea Colored: Rhabdomyelitis (Breakdown of muscle)
Foamy: May suggest excess protein
It is important to note that certain medications taken for UTIs can change the color of the urine, Phenazopyridine in particular.
Dipstick chemical analysis is performed on a narrow plastic strip which has individual tests denoted with different colored squares. The entire strip is dipped into the urine sample and color changes of the squares are noted either by the technologist or by inserting it into an instrument to read it. Each square takes a specific amount of time to react so its important to allow the reaction to come to fruition before resulting. The color change of particular squares are compared to a reference guide and can point out abnormalities.
In no particular order the squares on the dipstick indicate;
Specific gravity (concentration of the urine)
Presence of Ketones
Leukocyte esterase (Suggestive of WBC in urine)
Nitrite (Suggestive of bacteria in urine)
Dipsticks are convenient and are easy to interpret and cost-effective. Its important to keep in mind that dipsticks are qualitative and not quantitative in that they only suggest that there is an abnormality, they don’t quantify that abnormality. Further analysis is required for such results.
Microscopic analysis can detect cells, cellular debris, bacteria, crystals, and certain casts to confirm the dipstick results and further quantify analysis. Once the samples are received they must be centrifuged and discarding the supernatant. Epithelial cells may suggest inflammation or damage to the gallbladder and casts and cellular debris suggest inflammation of the kidneys and upper urinary tract. On very rare occasions tumor cells can be seen which are diagnostic for certain renal carcinomas and other urinary tract cancers.
If red cells are noted it could indicate either an infection, trauma, or stones. They can also indicate glomerulonephritis which is inflammation of the kidneys. Sometimes small amounts of red cells will be seen in healthy individuals.
Urine is considered a sterile body fluid therefore there should be no white blood cells or bacteria. Any amount of WBC or bacteria within the urine is considered abnormal and is suggestive of an UTI, cystitis, or pyelonephritis.
Identifying crystals if any is important and lend diagnostic information as to what is pathologically going on within the body.
Uric acid crystals can vary in size and shape, but usually resemble a rhomboid shape. These crystals are common in individuals with urate nephrolithiasis or acute urate nephropathy.
Cystine crystals are usually colorless hexagonally shaped and look similar to benzene rings (bringing it back to organic chemistry days). These occur in patients with cystinuria which is a genetic defect in renal cystine transport and in acidic urine (pH <6.0).
Struvite crystals are often described as having a coffin-lid appearance. These crystals are typically magnesium ammonium phosphate and are seen in alkaline urine (pH >7.0). Seen in patients with UTIs caused by urea-splitting bacteria (Proteus mirabilis) or in patients with infected calculi (struvite stones).
Calcium oxalate crystals are typically found in acidic urine and can take on multiple shapes. Some may look like colorless ovoids, biconcave discs, or even rods. Usually seen in patients with high dietary oxalate ingestion, patients with nephrolithiasis or those in ethylene glycol toxicity with renal failure.
These are some of the more common crystals that will be seen. Urinalysis isn’t flashy and isn’t always fun as it is someones urine, but it is an important part of routine testing to better deliver care to the patient.