URINALYSIS

A urinalysis is a test of the urine, non-invasive diagnostic tool that examines the visual, chemical, and microscopic properties of one’s urine.

Urinalysis is derived from the two words, Urine and Analysis, which literary means the Analysis of Urine.

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It is often done to check for a Urinary Tract Infections, Kidney Problems or Diabetes. it can be carried out during a checkup, when admitted to the hospital, before surgery, or in pregnancy. It can also monitor some medical conditions and treatments.

Physical urinalysis involves checking the urine for Colour, Appearance (whether it is clear or cloudy), Odor 

Chemical urinalysis involves dipping a urinalysis strip into the urine to check the pH level (acidity), Presence of substances that are not normally in urine, such as blood, protein, glucose, ketones, and bilirubin.

Microscopically for cells, crystals, and casts (tube-shaped proteins), bacteria or other micro-organisms.

pH

Urine pH is usually slightly acidic, though it can vary from as low as 4.5 to as high as 8.0 depending on the body's acid-base balance. The formation of kidney stones is highly influenced by urinary pH. Acidic urine favors the crystallization of uric acid or crystine stone, whereas alkaline urine promotes calcium and phosphate-containing stones. Alkaline urine can result from infection with urea-splitting bacteria—such as Proteus mirabilis, Klebsiella, or Pseudomonas—which break urea molecules into ammonium and carbon dioxide, thereby increasing urine pH to neutral or alkaline values. Urinary pH level is also influenced by dietary factors. A high protein diet can give rise to acidic urine, whereas eating a vegetarian diet can give rise to alkaline urine. 

Specific gravity (SG)

Specific gravity measures the kidney’s ability to concentrate or dilute urine by comparing its density to that of distilled water (1.000). Because urine contains various solutes, it has a higher specific gravity than water—usually ranging from 1.005 to 1.025. A high specific gravity represents concentrated urine and may indicate dehydration or increased levels of solutes in the urine. Low specific gravity, on the other hand, represents diluted urine and may occur with a high fluid intake, diabetes inspidus, or due to kidney disease when the kidney’s ability to concentrate urine is impaired.

Blood

The presence of blood in the urine is known as hematuria. It can be classified as gross hematuria when it is visible by the naked eye or microhematuria when it can only be detected using a microscope. Hematuria can occur due to a variety of causes, including damage to the kidney’s glomerular filtration barrier, which typically prevents blood from passing into the urine; lesions to the urinary tract, such as urinary tract infections, kidney stones, or tumors; as well as systemic disorders, like vasculitis, lupus, and tuberculosis among others. In menstruating individuals, blood in the urine can occur due to contamination of the urine specimen. 

Protein

In healthy individuals, urine only contains a small amount of proteins because most protein molecules, such as albumin, are too large to pass through the glomerular filtration barrier. When a significant amount of protein appears in the urine, it is known as proteinuria, and it is generally a sign of glomerular damage. Benign causes of proteinuria include fever, strenuous exercise, dehydration, emotional stress, and acute illness. More serious causes include glomerulonephritis and multiple myeloma.  

Glucose

Glycosuria, or glucose in urine, is a common finding in individuals with uncontrolled diabetes mellitus though it may also occur when glucose levels are normal, such as during pregnancy, in cases of physiological stress, and when taking corticosteroids. There is a group of hypoglycemic medications called sodium-glucose co-transporter-2 (SGLT-2) inhibitors (e.g. canagliflozin, empagliflozin, dapagliflozin) that act on the kidneys to promote the excretion of glucose in the urine, which also leads to glycosuria. 

Ketones

Ketones are metabolic products of fatty acid metabolism. Breakdown of fat may occur in states of prolonged starvation, persistent vomiting or diarrhea, chronic alcohol use, and with a low-carbohydrate diet (e.g. “keto” or ketogenic diets). More importantly, ketones may build up in the blood of individuals with poorly controlled diabetes mellitus (especially Type I diabetes mellitus) and cause acidosis. This is known as diabetic ketoacidosis (DKA) and constitutes a potentially life-threatening emergency. DKA can be suspected when high levels of ketones are detected in the blood or urine in individuals with diabetes.

White Blood Cells, Leukocyte Esterase, and Nitrites

The presence of white blood cells in the urine, or pyuria, is a common sign of Urinary Tract Infection (UTI). Because white blood cells can only be assessed by microscopic examination, dipstick tests use leukocyte esterase (i.e. an enzyme inside white blood cells) to estimate the concentration of white blood cells in urine. In cases where a UTI is suspected, a urine culture is obtained to confirm the diagnosis and identify the underlying organism. If no bacterial cells are detected, the individual is said to have sterile pyuria—a typical finding in urinary tuberculosis. 

Most species of Gram-negative bacteria that colonize the urinary tract produce nitrate reductase, an enzyme that converts dietary nitrates into nitrites. Both urinary nitrites and leukocyte esterase provide a good screening test for urinary tract infections; however, since not all bacteria produce nitrites, a negative nitrite test alone does not rule out a urinary tract infection. 

Bilirubin and Urobilinogen

Bilirubin is a breakdown product of red blood cell metabolism that is usually not found in the urine. If bilirubin is found in the urine, liver disease or biliary obstruction (where there is a problem with drainage of bile into the gut) may be suspected. On the other hand, there may be small amounts of urobilinogen in the urine of healthy individuals. Urobilinogen is the end-product of conjugated bilirubin after it passes through the bile duct and has been metabolized by bacteria in the intestines. Part of this urobilinogen is reabsorbed into the portal circulation and eventually filtered by the kidneys. Individuals with increased red blood cell destruction (i.e. hemolytic anemia) or liver disease may have elevated urobilinogen levels in the urine. On the other hand, if the bile duct is obstructed, less bilirubin enters the intestine, and ultimately, less urobilinogen is found in the urine.

When to do a urinalysis

A Urinalysis is a diagnostic tool that plays an essential role in the health assessment process and is typically done in individuals with urinary symptoms (e.g. painful urination, urinary frequency and urgency, lower abdominal pain) as well as in pregnant individuals to determine the presence of asymptomatic bacteriuria. It also offers clinicians valuable information for the monitoring of several medical conditions, including diabete mellitus, liver disease, or renal disease. 

Other urine tests that can be done but are not usually part of the urinalysis include screening for the usage of recreational drugs (e.g. cannabis, amphetamines, cocaine, opiates, etc.), urine cytology (i.e. examination of cells in the urine, used to screen for urological cancers), measuring electrolyte levels or hormones, as well as a urine pregnancy test.