IV. Urine Volume and Sample Handling

What is the normal range of urine output for 24 hours?

600 - 2000 mL per 24 hours

What 3 Factors affect urine volume?

1) Fluid intake and fluid loss related to non renal functions

2) Diuretics and antidiuretic hormone levels

3) Excretion of dissolved solids, including glucose and salts

What is referred to as Oliguria?

• decrease in urine output

  • could be due to dehydration

    • Ex. Vomiting, diarrhea, perspiration, and burns

What is referred to as Anuria?

• No urine output

  • Usually because of kidney damage or renal failure

What is referred to as Nocturia?

• Increased urine output at night

  • Can be caused by reduction in bladder capacity resulting from pregnancy, stones, or prostate enlargement

  • Also from increased fluid intake at night

What is referred to as Polyuria?

• Increased daily out; usually more than 3L/day

  • Causes:

    • Diabetes mellitus

    • Diabetes insipidus

    • Ingestion of diuretics, caffeine, alcohol

Although refrigeration can decrease bacterial growth, what is a negative effect?

Precipitation of amorphous phosphates/urates

If a chemical preservative is used on urine, how can the specimen be affected?

• It can kill bacteria but preserve elements

  • Should NOT generally cause interference

• HOWEVER, if the chemical preservative alters the pH, then interference occurs

What changes can occur in unpreserved urine?

• Increase in:

  • pH

  • Odor

  • Nitrite

  • Bacteria

  • Turbidity

• Decrease in:

  • Urobilinogen

  • Glucose

  • Ketones

  • Bilirubin

• Color change

• Cellular elements disintegrate

In unpreserved urine, how does color change and why?

• Color can darken

  • Due to oxidation or reduction of metabolites

What causes decreased clarity or increased turbidity in unpreserved urine?

• Bacterial growth and precipitation of amorphous material

What causes increased odor in unpreserved urine?

• Bacterial proliferation, causing breakdown of urea to ammonia

What causes pH to increase in unpreserved urine?

• Breakdown of urea to ammonia by urease-producing bacteria

• Loss of CO2

What causes decreased glucose in unpreserved urine?

• Glycolysis and bacterial use

What causes decreased ketones in unpreserved urine?

• Volatilization

• Bacterial Metabolism

What causes decreased bilirubin in unpreserved urine?

• Exposure to light, causing photooxidation to biliverdin

What causes decreased Urobilinogen in unpreserved urine?

• Oxidation to urobilin

What causes increased Nitrite in unpreserved urine?

• Multiplication of nitrate-reducing bacteria

What causes decreased cellular elements in unpreserved urine?

• Disintegration in dilute alkaline urine

What causes decreased Trichomonas in unpreserved urine?

• Loss of motility, death