Urinalysis

rine is a sterile liquid by-product of the body secreted by the kidneys through a process called urination, and excreted through the urethra. Urine has an important role in filtering the blood, excreting waste products and any excess water that is not needed by the body. Because of this, urine testing or urinalysis, which is a routine part of patient assessment, can provide crucial information about the person’s general health (Collie and Hunter 2022: Mulryan 2011). It can give indications as to the functioning of the urinary system (kidneys, ureters and bladder) as well as signalling the presence of liver disease, diabetes mellitus and urinary tract infections. However, it is important to note that while routine urinalysis using a reagent strip is useful for excluding the existence of a urinary tract infection (UTI), it is not a good predictor of the presence of one, as not all UTIs are detectable. Urinalysis can also detect dehydration, or the presence of substances that would not normally be seen in urine such as blood (haematuria), nitrites, leucocytes, glucose or drugs (Collie and Hunter 2022; Bardsley 2015). In addition, the National Institute for Health and Care Excellence (NICE) (2016) recommend routine urinalysis for the detection of bacteraemia in pregnant women. 

Urinalysis means the visual, chemical (dipstick), and microbiological examination of urine and according to Daniel (2023) is a simple and cost-effective tool for the screening, diagnosis and management of various medical conditions. It includes an array of tests performed on urine, the most common of which is routine urinalysis, also referred to as a dipstick. Routine urinalysis is usually performed using urine test strips (reagent strips), which show the results as colour changes. A urine sample for a routine urinalysis can be collected randomly, in the early morning (first urination of the day), as a midstream or as a catheter specimen. Midstream or catheter samples are usually sent to the laboratory to be tested for microbiological and/or biochemical investigations and toxicology screening.

Urine reagent strips commonly test for the following:

  • Specific gravity (SG – normal range 1001–1035). Specific gravity gives a measure of the concentration of solutes in the urine. The density or concentration of the urine is compared to water, which has a specific gravity of 1. Urine that is concentrated will have a higher specific gravity while that which is dilute will have a lower one. Largely, the specific gravity of urine reflects the hydration status of the patient (Mulryan 2011). Concentrated urine with a higher specific gravity may indicate that the patient is dehydrated. A lower than normal specific gravity may indicate renal disease or a condition called diabetes insipidus, which is related to an insufficient production of anti-diuretic hormone (ADH).

  • pH (normal range 4.5–8.0, some sources may cite a different ‘normal range’ (Lister, Grafton and Hofland 2022). Despite this you simply need to know that pH measures the acidity or alkalinity of the urine. Normal urine is slightly acidic at about 6.0; but variations occur due to diet or metabolic processes (Mundt and Shanahan 2020). pH on its own should not be taken as an indication of the presence of disease and it is important that it is investigated and viewed in conjunction with other clinical information.     

  • Protein, glucose, ketones, blood, and bilirubin. All of these are negative in normal urine. The presence of these abnormalities might indicate the following:

    • Protein (proteinuria): protein in the urine can be an indicator of renal disease and can be present long before any clinical symptoms. It can also be a sign of a urinary tract infection, pre-eclampsia (a complication of pregnancy), diabetes mellitus or high blood pressure. On occasion small amounts of protein may be present but this is temporary and the urine will revert to normal.

    • Glucose (glycosuria): glucose in the urine is primarily associated with diabetes mellitus. However, it can present in acute pancreatitis, Cushing's syndrome, or sometimes pregnancy.

    • Ketones (ketonuria): the presence of ketones can indicate excessive fat metabolism due to diabetic ketoacidosis, vomiting, or severe dieting/starvation.

    • Blood (haematuria): blood in the urine is classified as macroscopic or microscopic or more recently as visible and non-visible haematuria (King and Steggall 2014). Visible (gross) haematuria colours the urine pink or red. Non-visible haematuria that can be detected on dipstick or reagent testing is further divided into symptomatic (other symptoms are present) or asymptomatic (no symptoms) (King and Steggall 2014). Haematuria can be an indication of malignancy and requires further investigation. It can also be a sign of kidney disorders (e.g., glomerulonephritis), disorders of the urinary tract (e.g., kidney stones, infection), trauma, or menstruation can result in positive blood presence in the urine but is typically attributed to sample contamination.

    • Bilirubin: bilirubin is a substance that is produced when red cells are broken down. Therefore, the presence of bilirubin in the blood indicates that a problem may exist with the excessive breakdown of red blood cells or that it is not being processed effectively by the liver. It could also indicate that there is an obstruction with bile drainage into the intestine. Therefore, bilirubin is associated with conditions such as liver disease (e.g. hepatitis) and biliary tract obstruction (e.g. gall stones, carcinoma of the head of pancreas).

  • Some reagent strips also test for nitrite and leucocytes.

    • Nitrite: nitrite in the urine indicates the presence of bacteria that have the ability to convert nitrate (which is present in the urine) to nitrite. However, it is important to note that the absence of nitrite does not mean that the patient does not have a urinary tract infection (Mulryan 2011). 

    • Leucocytes (white blood cells): leucocytes in the urine are a strong indicator of urinary tract infection (UTI). Leucocytes in the urine is referred to as pyuria (Mulryan 2011).  

PREPARATION AND SAFETY

  • Ask the patient to provide a urine specimen,if they are able, or obtain a specimen from a catheter port or use an intermittent catheter.

  • As the evidence regarding urethral meatal cleansing is debatable, local procedures should be followed and where necessary the patient should wash or be assisted with washing their genitals with soap and water. 

  • When passing urine, if possible, men should retract the foreskin and women should hold the labia apart (Mulryan 2011). 

  • For routine urinalysis where the specimen is not being sent to the laboratory for further testing a clean, dry container/jug can be used. However, using a sterile container reduces the risk of contamination (Mulryan 2011; Bardsley 2015). 

  • Ideally, a mid-stream specimen should be obtained to reduce the risk of urethral debris contaminating the sample (Mulryan 2011, Mundt and Shanahan 2020; Bardsley 2015). However, this may not be a local requirement and you should consult local policies and procedures in this regard. 

  • An apron and gloves should be worn.

  • Additional protective clothing may be necessary if indicated by the patient’s condition.

  • Make sure that you are familiar with the manufacturer’s instructions for the urine-testing strips you are using, and that they are in date.

  • The urine should be examined while fresh. Specimens left at room temperature begin to decompose primarily due to the presence of bacteria (Mundt and Shanahan 2020). 

  • Observe the urine for colour, concentration, odour, and the presence of particles. Normal urine is straw-coloured and clear. Dark-yellow urine indicates that it is more concentrated than normal. The smell of ammonia will develop if the urine specimen is left standing. A malodorous or ‘fishy’ smell and/or particles in the urine may indicate a urine infection. Any blood in the urine should always be reported, although be aware that menstruation may be the cause in female patients.

PROCEDURE

  1. Check the patient's ID and put on an apron and gloves. 
    Rationale – Urine is a body fluid and so use of PPE is important as it protects you and maintains infection control prevention.

  2. Check that there is a reporting pad/paper available to document the results. 
    Rationale - Results should be documented at the time of recording but patient’s records should not be taken into the sluice/dirty utility room.

  3. Check the expiry date of the reagent testing strips. 
    Rationale – Out of date testing sticks may provide incorrect results.

  4. Remove one reagent strip from the container of test strips, making sure that you do not touch the coloured reagent pads with your hands. Replace the lid to keep them dry. 
    Rationale – Your hands may contaminate the reagent strip and cause an inaccurate result. The reagent strips need to be kept dry as this may also affect the result.

  5. Dip the reagent strip into the urine specimen so that the coloured pads are completely covered. Remove immediately. Remove excess urine by slowly drawing the edge of the reagent strip across the top of the specimen container. 
    Rationale – This will stop it dripping and prevent the coloured pads running into each other, which could give an inaccurate reading.

  6. Note the time on your watch. Accurate timing according to the manufacturer’s instructions is crucial. 
    Rationale – To ensure accurate testing, recording, and prompt reporting of results.

  7. When the correct period of time has elapsed, read the results by holding the strip alongside (but not touching) the container of test strips and comparing the colour of each reagent pad with those on the colour reference grid.  
    Rationale – To ensure accurate testing. To prevent contamination of the container of test strips with urine.

  8. Record the result that corresponds to the colour change for each of the tests. 
    Rationale – Use the reporting pad to ensure accuracy. Do not take the patient’s charts into the sluice/dirty utility room. Local policy may require your signature, the date and time of the test, and the lot number and expiry date of the testing strips, at the time specified by the manufacturer.

  9. Discard the used strip in the clinical waste and dispose of the urine in the usual way. 
    Rationale – To maintain infection control prevention. This is essential, especially where the specimen may be infected.

  10. Clean the specimen container according to local policy. 
    Rationale – To maintain infection control prevention. This is essential, especially where the specimen may be infected. If the container is not disposable, it is usually cleaned in the bed pan washer.

  11. Remove your gloves and apron and wash your hands. 
    Rationale – To maintain infection control prevention.

  12. Document urinalysis and report any abnormalities. Place a copy of the results in the patient’s records, checking the patient details. 
    Rationale – To ensure that both normal and abnormal results are documented; both are clinically important.

ONGOING CARE, MONITORING, AND SUPPORT

  • Discuss the result with the patient as appropriate.

  • Remove gloves and apron and wash your hands.

DOCUMENTATION AND REPORTING

Place a copy of the results in the patient’s records. It is important to ensure that both normal and abnormal results are documented, as both are clinically important.

EQUIPMENT

  • Fresh urine specimen in clean container or jug. The urine sample should be fresh as it will begin to decompose at room temperature (Mundt and Shanahan 2020).

  • Urine testing strips.

  • Results pad or paper to document results.

  • Watch with a second hand.

  • Apron and gloves.