URINALYSIS part I

STRUCTURE AND FUNCTION OF THE URINARY SYSTEM

Components of the Urinary System

The urinary system consists of several critical components:

  1. Kidneys

    • Bean-shaped organs measuring approximately 4.5 inches by 2-3 inches.

    • Located in the lumbar region.

    • Production of urine. Each kidney contains about 1 million nephrons, the functional units that filter blood and produce urine.

  2. Ureters

    10 to 12 inches in length and inch in diameter.

    Function: Propel urine from the kidneys to the bladder by force of gravity and peristaltic waves of the ureters.

  3. Urinary Bladder

    A hollow, muscular sac that can hold approximately 500 ml of urine that stores urine until expulsion.

  4. Urethra

    • Function: A tube that transports urine from the bladder to the outside. Urinary meatus is an external opening of the urethra

    • Males: urethra transports urine and reproductive secretions(semen).

    • Females: urethra transports urine only.

Function: Regulate fluid and electrolyte balance of the body and remove wastes

NEPHRON STRUCTURE AND FUNCTION

Components of Nephron

The nephron is the functional unit of the kidney, parts:

  • Glomerulus: A network (tuft) of capillaries that filters blood.

  • Tubules: Part of the nephron that reabsorbs essential substances, including water, glucose, and electrolytes.

Function of Nephrons

Nephrons filter waste from the blood, combine it with water to produce urine, and reabsorb substances needed by the body like water, glucose, and electrolytes.

Composition of Urine

  • Water: Approximately 95% of urine.

  • Organic and Inorganic Wastes: About 5% solutes including (urea, sodium, potassium, phosphate and sulfate ions, creatinine, uric acid)

  • Organic waste: including urea from the breakdown of proteins, Uric acid, Ammonia, creatinine,

  • Inorganic waste: Cl, Na, K, Mg, phosphates and sulfates.

Normal Urine Volume

Normal daily urine volume ranges from 750 to 2000 mL, varies based on the amount of fluid consumed, and lost through other means.

  • Polyuria: Increased urinary output, often due to excessive fluid intake Causes: caffeine, drugs, and pathological conditions(diabetes & renal diseases)

  • Oliguria: Decreased output (less than 400 mL/day), decreased fluid intake Causes: dehydration, profuse perspiration, vomiting/diarrhea, or kidney disease.

  • Anuria: No urine production.

  • Diuresis: Passage of a large amount of urine(urine passing through the system)

  • Dysuria: Difficulty/painful urination

  • Frequency: Condition of having to urinate often

  • Micturition: Act of voiding urine

  • Hematuria: blood in urine

  • Nocturia: excessive(voluntary) urination during night

  • Nocturnal enuresis: the inability of pt to control urine at night(bedwetting)

  • Pyuria: Pus in urine

  • Retention: inability to empty bladder

  • Urgency: immediate need to urinate

  • Urinary incontinence: inability to retain urine

GUIDELINES FOR URINE COLLECTION

  1. Obtain an adequate volume (30 to 50 ml).

  2. Properly label each specimen it will avoid a mix-up of specimens including the patient’s name, DOB, date and time, and type of specimen(example: urine)

  3. Record any medications a patient is taking on lab requisition and in the patient’s chart.

  4. Don’t collect specimens during menstruation.

  5. Be patient and relay understanding to the patient when collecting a sample.

  6. May be difficult to obtain from a child here are collection methods like urine collection bag, suprapubic aspiration, and catheterization.

URINE SPECIMEN COLLECTION METHODS

Type of test being performed: often dictates the collection method.

Example: Pregnancy test(first-voided morning specimen) or Identification of a UTI(clean-catch midstream collection)

  1. Random Specimen: Freshly voided specimen. MA instruct the patient to void into a clean, dry, wide-mouthed container. Urine tested immediately.

  2. First Voided Morning Specimen: Contains the greatest concentration of dissolved substances. Small amount of a substance are detected more easily. Instruct pt to collect the first specimen of the morning and preserver in refrigerator. Provide the patient with a specimen container.

  3. Clean Catch Midstream Specimen: Microorganisms are not normally present in the urinary bladder and most of the urethra. They are normally present in the Distal urethra and Urinary meatus.

    Clean catch prevents contamination of the specimen with normally present microorganisms ordered for the detection of a UTI and to evaluate the effectiveness of drug therapy for a UTI.

    • Clean catch procedure: Use a sterile container, prevent contamination of the specimen with normal flora. Microorganisms are removed from the urinary meatus by having the patient cleanse the area surrounding the urinary meatus and voiding a small amount into the toilet.

      Reduces the possibility of having to obtain urine specimen by:

      -Bladder catheterization: Passing of a sterile catheter through the urethra into the bladder.

      -Suprapubic aspiration of the bladder: Passing of a sterile needle through the abdominal wall into the bladder.

    • Guidelines: Provide complete instructions to prevent contamination of the specimen with bacteria, when collected MA should immediately cap and label the container with the patient’s name and DOB, date and time of collection, and type of collection(e.g. clean catch). Test the specimen immediately or refrigerate.

  1. 24-Hour Urine Sample: Used for quantitative measurement of specific urinary components. Increase accuracy. Can determine calcium, cortisol, lead, potassium, protein, and urea nitrogen. Use to determine the cause of kidney stone formation and to assist in the control or prevention of new stones.

    • Large container use: 3000mL.

    • To maintain the quality of the specimen must kept refrigerated, some containers also contain preservatives (instruct patient NO to discard or touch preservatives).

    • Provide patient containers to collect specimens. If the patient voids directly into the container with preservative could splash onto pt skin resulting in a chemical burn. Females: urine”hat” placed over commode under toiler seat. Males: collection cup.

    • MA should provide written and verbal instructions: Drink a normal amount of fluid during the collection period, avoid alcohol for 24hours before and during collection, choose 24hour period to be at home, DON’T perform during menstruation, and the physician may want to discontinue certain meds for 1 week before test.

ANALYSIS OF URINE

URINALYSIS

Consist of:

  • Physical Examination

  • Chemical Examination

  • Microscopic Examination

    Use: Screening part of the pt physical examination, Assist in DX, and evaluating the effectiveness of TX.

    Performed on a fresh preserved specimen. If can’t be tested within 1 hour needs to be refrigerated. Before testing return to room temperature and thoroughly mis specimen(rotate urine container).

    Changes that occur if a specimen stands out for more than 1 hour:

  • Bacteria from the environment will transform UREA to AMMONIA, and ammonia has a higher pH and may be a false positive for protein test.

  • Bacteria will multiply to cloudy and increase nitrites.

  • Bacteria will breakdown RBC, WBC.

  • Casts may be decomposed after several hours,

PHYSICAL EXAMINATION OF URINE

1- Color: Ranges from almost colorless to dark yellow.

  • Dilute urine: lighter yellow, occurs as day progresses and more fluids are consumed

Concentrated urine: darker yellow(e.g. first voided specimen) occurs because fluid consumption is decreased at night.

Color due to yellow pigment: urochrome from breakdown of hemoglobin.

Color varies among different shades of yellow throughout the day like light yellow, yellow, dark yellow, light amber, amber, and dark amber. Abnormal color may be due to the presence of hemoglobin or blood(reddish color), bile pigments(yellow-brown or greenish/liver not working well), fat droplets or pus(milky color), and some foods and meds.

2- Appearance: Fresh urine usually clear or transparent; becomes cloudy on standing out too long.

  • Cloudiness in freshly voided specimens has the presence of bacteria, pus, blood, fat, yeast, sperm, mucous threads, or fecal contaminants. A microscopic exam is required.

  • Classification used to describe appearance are clear, slightly cloudy, cloudy, and very cloudy.

3- Odor: Freshly voided urine has a slightly aromatic odor. Urine standing for long periods has an ammonia odor as a result of breakdown of urea by bacteria.

The urine of diabetic patients may have fruity odor because of the presence of ketone. Urine of patients with UTI has a foul-smelling odor. Certain foods like asparagus cause a musty smell. Odor is not generally used in the diagnosis of the patient’s condition.

4- Specific Gravity: Measures the weight of urine compared with the weight of an equal volume of distilled water(water with no sodium). Indicates the amount of dissolved substances present in urine. Provides information on the ability of the kidney to dilute or concentrate the urine

DECREASED SG

INCREASED SG

Chronic renal insufficiency Diabetes insipidus Malignant hypertension

Adrenal insufficiency Congestive heart failure Hepatic disease Diabetes Mellitus with glycosuria Condition causing dehydration(high)

  • Normal range for SG of urine: 1.003 to 1.030. Usually 1.010 to 1.025.

  • SG of distilled water: 1.000

  • Dilute urine: lower SG(fewer dissolved substances)

  • Concentrated urine: higher SG(more dissolved substances)

  • The urine is more concentrated in the morning and it’s more dilute after fluid consumption.

    - Measurement of SG: Reagent strip method most common method used to measure SG, has a color comparison determination, strip dipped in urine, and results compared with color chart.