Urinalysis

Urinalysis

What is a Urinalysis?

A urinalysis or urine test is a common test to screen, detect, or monitor certain health conditions such as urinary tract infections, kidney disease, liver disease, and diabetes. A complete urinalysis involves the examination of the appearance, concentration, and content of the urine. Abnormal findings from the urinalysis usually require further investigations to determine the source of the problem.

What is a Urinalysis for?

A urinalysis is done for several reasons:

  • Prior to surgery
  • Pre-emptive screening during a pregnancy checkup
  • Routine medical or physical exams for certain health conditions
  • To test for diabetes, kidney disease, liver disease, and urinary tract infections
  • For further examination due to symptoms such as abdominal pain, back pain, hematuria, and painful urination

How do you prepare for a Urinalysis?

There is no need to fast for urinalysis. However, you should inform the urologist of any medications, vitamins, or supplements you have taken as they may interfere with the analysis results. You should also notify the doctor if you are on your period, as menstrual blood can affect the test results. The patient can use a tampon to prevent the menstrual blood from mixing with the voided urine.

In order to collect a clean urine sample that is free from contamination, the doctor may instruct you to collect the urine sample using the “midstream clean-catch” technique or a catheter. The clinic will then send the urine sample to the lab for further analysis.

Instructions for females:

Illustration on how to collect a clean catch or midstream clean-catch urine sample.

  1. Begin by washing your hands with soap and water and dry them with paper towels
  2. Open the lid of the specimen cup without touching the inside of the cup
  3. Sit on the toilet with legs spread apart
  4. Using two fingers from non-dominant hand, spread your labia (skin folds around around the urinary opening and vagina)
  5. Use the sterile wipes to clean the inner folds of the labia, wiping from front to back
  6. Use another sterile wipe to clean the urethra (urinary opening)
  7. Start urinating a small amount into the toilet and do not collect the initial part of the urine stream
  8. Keeping the labia spread, fill the specimen cup with midstream urine until the cup is about half full
  9. Finish urinating into the toilet
  10. Screw the lid onto the specimen cup without touching the inside of the cup

Instruction for males:

  1. Begin by washing your hands with soap and water and dry them with paper towels
  2. Open the lid of the specimen cup without touching the inside of the cup
  3. Using the non-dominant hand, pull the foreskin (the skin around the tip of the penis) away from the urinary opening
  4. Use the sterile wipes to clean the head of the penis, including the urinary opening at the tip of the penis
  5. Start urinating a small amount into the toilet and do not collect this first part of the urine stream
  6. Continue to urinate and fill the specimen cup with midstream urine until the cup is about half full
  7. Finish urinating into the toilet bowl/ urinal
  8. Screw the lid onto the specimen cup without touching the inside of the cup

 

For some patients, it may be necessary for us to obtain the urine specimen using a catheter (a thin tube that is inserted into the bladder via the urethra) to ensure accurate results.

What happens during a Urinalysis?

The accuracy of urinalysis is affected by the time lag between voiding and examination. The analysis is usually performed within a few hours to avoid unreliable results. In the laboratory, the urine sample is examined and evaluated using different methods:

Physical Exam

Visual inspection of the urine involves looking for any abnormalities regarding the colour, odour, and clarity of the urine.

  • Colour: Medications, supplements, and food can affect the colour of urine. Normal urine colour is usually some shade of yellow ranging from pale yellow to deep amber depending on how concentrated the urine is. Reddish or brownish appearance may be caused by the presence of blood in urine and could indicate urinary tract or kidney infections.
  • Odour: Normal urine odour is described as urinoid. Urine with a sweet or fruity odour could indicate diabetic ketoacidosis. Other pathological causes of abnormal urine odour include urinary tract infections, gastrointestinal-bladder fistulas, and cystine decomposition.
  • Clarity: Cloudy appearance could be due to certain substances in the urine which include sperm, skin cells, red blood cells, white blood cells, and bacteria. Cloudy appearance does not necessarily be a cause for concern but it may indicate dehydration, sexually transmitted diseases and infections (STDs/STIs), kidney stones, and diabetes.

Microscopic Exam

The microscopic exam looks for any abnormalities such as elevated amounts of cells, cell fragments, urinary casts, bacteria, and crystals.

  • Red blood cells: An elevated number of red blood cells shows that there is blood in the urine and may indicate bladder, kidney, or urinary tract issues.
  • White blood cells: An increased number of white blood cells or a positive test for leukocyte esterase may suggest an infection or inflammation in the urinary tract.
  • Epithelial cells: The urinary tract is lined with epithelial cells. However, an elevated number of epithelial cells in urine may indicate infection, inflammation, or cancer. Most of the time, it is contamination with skin cells.
  • Bacteria: The presence of an elevated bacterial count in the urine is suggestive of urinary tract infection.
  • Urinary casts: Casts are cylindrical structures produced by kidney cells and may be used to determine the location of the disease in the genitourinary tract. While the most common forms of casts are benign, others may indicate disease.
  • Urinary crystals: Urinary crystals are formed from chemicals concentrated in the urine and may be a sign of kidney stones.

 

Dipstick Test

The dipstick test is used to examine the chemical aspect of the urine. The urine test strips contain chemical pads that can change colour when they react with certain substances in the urine sample. The degree of colour change can also give an estimation of the amount of substance present in the urine. 

  • Protein: The test detects presence of proteins in urine such as albumin. Abnormal amount of proteins in the urine may be an indication of heart failure, kidney issues, and dehydration.
  • Urine pH: The test measures the acidity of the urine. A high urine pH could indicate kidney issue and urinary tract infections while a low urine pH could indicate diabetic ketoacidosis and diarrhoea.
  • Ketones: Ketones are derived from the breakdown of fats and fatty acids. The presence of ketones in urine may indicate diabetic ketoacidosis.
  • Glucose: The test measures the amount of glucose in urine. Normal sample of urine should not contain any glucose. As such, presence of glucose in urine may be a sign of diabetes or gestational diabetes.
  • Bilirubin: Bilirubin is a pigment found in bile which is a digestive fluid produced by the liver. The presence of bilirubin in urine may indicate liver or bile duct issues.
  • Urine: The test is able to detect hemolyzed and non-hemolyzed blood in urine. Hematuria (blood in urine) could be a sign of kidney damage, infection, cancer, or blood disorders.
  • Nitrite: A positive nitrite urine test is suggestive of urinary tract infections.
  • Leukocyte esterase: Leukocyte esterase is an enzyme that is present in most white blood cells and it could be a sign of inflammation in the urinary tract or kidneys. The most common cause of white blood cells in urine is a bacterial urinary tract infection.
  • Urine specific gravity: The test correlates with the osmolality of urine and reveals the patient’s hydration status. It also reflects the ability of the kidneys to concentrate urine.

After a Urinalysis

Although urinalysis is hardly a standalone test, it is invaluable in providing useful insight in aiding your doctor toward the right diagnosis. It can also alert the urologist to the possibility of disorders that may affect the patient’s urinary system. 

Abnormal urinalysis test results will usually require further testing, such as blood tests, imaging tests, and urine culture. Your urinalysis results – along with your medical history, medications, supplements – help your doctor discern whether a repeat urinalysis needs to be run or if other diagnostic tests are required.  

There are several interpretations for abnormal test results:

  • Signs of medical conditions such as kidney disease and diabetes
  • False positives due to medications, supplements, and food substances
  • Contamination of bacteria and other substances such as menstrual blood and vaginal discharge
  • Errors in the processing of the test

Summary

Urinalysis is a common test performed as part of routine medical exams and in the diagnosis of various health conditions such as diabetes, kidney disease, liver disease, and urinary tract infections. Abnormal urinalysis results can indicate several health conditions but it does not confirm the diagnosis and will require further diagnostic tests. 

It also does not necessarily indicate a medical condition as there are several factors that can interfere with the test results.  Factors such as medications, supplements, contamination of bacteria, and an error in processing the test can affect the accuracy of the test. Most importantly, if you notice any changes in your urine, seek medical help for proper diagnosis and treatment.

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Dr. Fiona Wu 2

Dr Fiona Wu
Consultant Urologist

MBBS (S'pore), MRCS (Edin), MMED (Surg),
MMED (Clinical Investigation),
FRCS (Urol) (RCPSG), FAMS (Urology)

Dr Fiona Wu is an experienced Consultant Urologist and is the Medical Director of Aare Urocare.

Prior to her private practice, Dr Fiona Wu spent 15 years in public service. She was a Consultant in the Department of Urology at National University Hospital (NUH), Alexandra Hospital and Ng Teng Fong General Hospital. She was also the Programme Director of Surgery-in-Training at NUH and a core faculty member of postgraduate junior doctors. 

Dr Wu’s clinical interests lie in Female Urology, Neuro-urology, Urinary Incontinence, Reconstructive Urology and Voiding Dysfunction. She believes in treating incontinence in a holistic way using minimally invasive methods. She worked closely with the gynaecology and colorectal departments to treat complex pelvic floor conditions and continues to do so in her own practice. 

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