Urinalysis

• common laboratory test on urine sample

• non-invasive procedure to check for the composition of urine

• to screen, diagnose & monitor a wide range of health conditions/clinical disorders

  • urinary tract infection, urologic disorders (e.g., calculi & malignancy), diabetes, kidney & liver diseases

Diagnostic Testing

Physical

• volume

  • closely regulated by kidneys

  • reflects overall fluid homeostasis

  • Polyuria

    • urine volume > 2000ml/day

    • due to osmotic diuresis in diabetes mellitus, hyperthyroidism & infections

    • insufficient secretion of / inability to respond to antidiuretic hormone (ADH)

    • lack of hormone aldosterone

    • after urination, it burns

    • excessive intake / infusion of fluid

    • renal diseases where the kidneys fail to concentrate urine

    • the use of diuretics, alcohol & caffeine

  • Oliguria

    • urine volume <500ml/day

    • as a consequence of conditions that decrease plasma volume, lead to dehydration, have impaired renal functions

  • Anuria

    • urine volume <100ml/day for 2-3 days despite high fluid intake

    • follows oliguria in shock; acute tubular necrosis caused by exposure to toxic agents

• Colour

  • normal: straw to dark-yellow colour

  • presence of the pigment urochrome which is produced at a fairly constant rate

  • colour intensity indirectly indicates urine concentration & state of hydration

  • examine the urine sample under good light against a white background

  • if the urine sample stands at room temperature, urochrome will increase & the colour may deepen

• Odour (not routinely reported)

  • normal: faintly aromatic odour

  • as the urine specimen stands, the odour of ammonia predominates

  • unusual odour is indicative of diseases states

  • fruity odour: ketonuria resulting from uncontrolled diabetes mellitus

  • “mousy” smell: associated with phenylketonuria

  • sweet-smelling like maple syrup: maple syrup urine disease

  • “fishy” odour: bacterial infection (e.g. urinary tract infection)

• Clarity

  • normal: clear or slightly cloudy

  • via visual examination

  • alkaline urine: precipitation of phosphates, carbonates

  • acidic urine: precipitation of urates, uric acid, calcium oxalate

  • foamy urine: presence of proteins

  • substances that can cause cloudy urine: white blood cells, red blood cells, bacteria, fats

  • may indicate inflammation or infection of kidneys, urinary & genital tracts, sexually transmitted diseases, kidney stones, diabetes

• specific gravity

  • density of liquid compared with that of a similar volume of distilled water, when both solutions are at the same or similar temperature

  • indicate the kidney’s ability to reabsorb water & chemical substances from the glomerular filtrate

  • normal: >1.000 (1.002-1.035)

  • influenced by the number and size of particles present

    • e.g. ↑USG with the presence of large amount of glucose and proteins

  • low USG: overhydration, diabetes insipidus, acute tubular necrosis, pyelonephritis

  • high USG: dehydration, uncontrolled diabetes mellitus, acute glomerulonepritis, heart & liver failure

  • constant fixed USG of 1.010 regardless of fluid intake

    • chronic glomerulonephritis with severe renal damage

    • loss of urine concentrating ability

  • as a preliminary rapid screening of urine concentration

  • urine osmolality → more reliable & accurate to evaluate kidney function, particularly the concentrating ability

Chemical

pH

• normal range: 4.5 - 8.0

• reflects the kidneys’ ability to regulate acid-base balance

• through regulation of hydrogen ions excretion

• only reliable when testing on freshly voided specimen

• influenced by diet & medications

Alkaline urine (pH >7.0)

• due to respiratory/metabolic alkalosis, presence of urease-producing bacteria, renal tubular acidosis, urinary tract infection

• promotes calcium-phosphate precipitation

• vegetarian diet, diets high in citrate, drugs i.e., sodium bicarbonate, potassium citrate & acetazolamide

Acidic urine (pH <7.0)

• diabetes mellitus, diabetes ketoacidosis, diarrhea, emphysema

• promotes the formation of uric acid & cystine kidney stones

• high-protein diet, intake of acidic fruits (e.g., cranberries), drugs (e.g., ammonium chloride)

Red blood cells (RBCs)

• normal: negative/<5 RBCs per ml

• Indications:

  • tumours/trauma/infections/inflammation in genitourinary tract

  • pyelonephritis, lupus nephritis, kidney stones, renal hypertension

  • non-renal: hemorrhagic disorder, exposure to toxic chemicals, strenuous exercise

Hematuria

• presence of 3 or more RBCs per high-powered field in 2 of three urine samples

White blood cells (WBCs)

• normal: only a few

• Indications:

  • bacterial infection in renal/genitourinary system, i.e., cystitis, pyelonephritis

  • other non-infectious inflammatory disorders, e.g., glomerulonephritis & lupus nephritis

  • presence of tumours and renal calculi

Pyuria

• excessive amount of WBCs in urine

  • 5 WBCs per high-powered field is considered abnormal

Proteins

• normal: only in trace amount (<150 mg/day or 10mg/dL)

• Indications:

  • physiological: strenuous exercise, dehydration

  • renal diseases/failure: e.g., nephrosis, glomerulonephritis, polycystic kidney disease

  • systemic disorders leading to increased level of serum proteins: e.g., multiple myeloma

Proteinuria (Albuminuria)

• elevated proteins in the urine

• ~1/3 of the total urinary proteins is albumin

• other proteins: Tamm-Horsfall mucoproteins (secreted by distal renal tubule), immunogloblin light chains, microglobulin, etc.

Glucose

• normal: negative

• Indications:

  • diabetes mellitus, Cushing;s syndrome, Fanconi’s syndrome, liver & pancreatic diseases

  • rare hereditary metabolic disorders

  • gestational diabetes

Glycosuria

• the presence of reducing sugars in urine

Glucosuria

• presence of glucose in urine (most common type of GLYCOSURIA)

Ketones

• normal: negative

• Indications:

  • pregnancy, ketogenic diets, compromised nutritional intake

  • uncontrolled diabetes mellitus (diabetic ketoacidosis), liver disease, certain forms of glycogen storage disease

Ketonuria

• high level of ketones in the urine

Bilirubin

• normal: negative

• Indications:

  • liver dysfunction (due to obstructive jaundice, cirrhosis, viral- or drug-induced hepatitis, hepatotoxic drugs, toxins)

  • biliary obstruction

  • congenital hyperbilirubinemia

Urobilinogen

• normal: 0.1mg/dL - 1.0 mg/dL or 4mg/day

• Indications:

  • ↑in hemolysis, hepatocellular disease (e.g., cirrhosis, hepatitis), severe infection

  • ↓in bile duct obstruction, renal insufficiency, with antibiotic use

Leukocyte esterase

• normal: negative

• Indications:

  • presence of neutrophils, either due to infection or other inflammatory processes, in urinary tract or kidneys

Nitrites

• normal: negative

• Indications:

  • presence of a significant number of bacteria, and a urine culture should be performed

  • UTI caused by nitrate reductase positive bacteria

Microscopical

• should be performed among those with persistent hematuria or proteinuria

Cells

red blood cells

• 0-5 cells/high power field

• confirming hematuria following positive dipstick results

• presence of dysmorphic red blood cells is suggestive of glomerular diseases

white blood cells

• 0-5 cells/high-power field (under high-power magnification)

• may also be examined under low-power magnification

• indicative of UTI, but culture is still needed for confirmation

epithelial cells

• increased squamous epithelial cells: originate from vagina, suggestive of contamination

• transitional epithelial cells: normal

• increased renal tubule cells: acute tubular necrosis & renal pathology associated to nephrotoxic agents

Casts

• formed in the lumen of distal convoluted tubules & collecting ducts

• via agglutination of protein cells or cellular debris

• coagulum consists of Tamm-Horsfall mucoprotein with or without additional elements

• prompt testing is mandatory (as it is dissolved in acidic urine within 30min or 10min in alkaline urine)

Crystals

• commonly found in urine; may or may not be pathologic

• supersaturation of solute componentys in urine initiates the crystallization

• acidic urine: calcium oxalate, uric acid & amorphous urate crystals

• alkaline urine: calcium phosphate, amorphous phosphate & ammonium magnesium phosphate crystals

• cystine crystals: abnormal; in those who have cystinuria & kidney stones

• tyrosine & leucine crystals: abnormal; suggestive of severe liver diseases

Bacteria

• absent in urine of normal healthy individuals

• reflects genitourinary tract infection or contamination of external genitalia

Dipstick

• results are available almost immediately

• convenient and cost-effective test to be performed at urgent care facilities, emergency departments, clinics or event at home

Fecal Analysis

• collected in a plastic hat-type receptacle

• should not be contaminated with urine or water

• should include any visible blood, mucus, pus, or parasites

• should be sent to the laboratory within 30-60 mins

Microscopial

Leukocytes

• especially neutrophils and monocytes

• as initial evaluation of diarrhoea of unknown aetiology/cause

Epithelial cells

• large amount indicates intestinal mucosa is irritated

Fats

• in the forms of triglycerides, fatty acids & fatty acid salts

• coupled with staining techniques prior to microscopic examination

• steatorrhea → excess fats in the stool (>60 fat droplets per high-power field)

• due to malabsorption syndromes or deficiency in pancreatic enzymes

• non-pathological: surgical resection of intestines & recent intake of excessive amounts of dietary fats

Meat fibers

• assess the efficiency of digestion

• presence in the stools indicates inadequate proteolysis

• usually correlates positively with steatorrhea

Parasites

• among individuals with intestinal disorders of unknown etiology or history of possible exposure to parasites

• i.e., roundworms, tapeworms, hookworms, & protozoa

• must be transported immediately to the lab

Chemical tests

Occult blood

• most frequently preformed

• to detect carcinoma

• numerous other pathological conditions, e.g., peptic ulcer, gastritis, inflammatory bowel diseases, diverticular diseases, hemmorrhoids, anorectal fissure, etc.

• stool samples are obtained after bowel movement or during rectal examination

• follow meat-free, high-bulk diet for 3 days before testing

• stop taking drugs that might alter the test results

Quantitative fats

• definitive test for excessive fecal fats

• evaluation is performed over 72-hour period

• controlled diet = percentage of solid material

• elevated level indicates intestinal malabsorption or pancreatic insufficiency

Trypsin

• normally not present in stool, except children <2 years old

• absence in children <2 years of age indicates pancreatic deficiency

Carbohydrates

• related to malabsorption disorders, e.g., celiac diseases

• excessive amounts appear in the stool

• evaluation: oral & intravenous (IV) glucose tolerance tests, and compare the results

• carbohydrate malabsorption syndrome

  • normal on IV but not on oral glucose tolerance test

Urobilinogen

• rarely assessed on stool sample

• blood and urine samples are more commonly used

• ↓ in liver & biliary tract disorders; ↑in hemolytic anemia

Bile

• absent in faeces of normal adults

• otherwise occurs with diarrhea & hemolytic anemias

Microbiologic

Stool cultures

• evaluate diarrhea of unknown etiology or other systemic infections

• identify pathological types of bacteria

• sampling via rectal swab or during bowel movement

• must not be exposed to air or room temperature more than necessary