Analysis of Urine

Flashcards for Experiment 6: Analysis of Urine

Functions of the Kidney

Excretion of wastes, regulation of blood volume and pressure, regulation of ion concentration, regulation of extracellular fluid pH, regulation of red blood cell synthesis, regulation of vitamin D synthesis.

Urinalysis

A simple and relatively inexpensive test that provides useful information about various diseases and conditions, often referred to as 'a poor man’s kidney biopsy'.

Urinalysis Sample Collection

30 to 60 mL clean catch or midstream urine collection, analyzed within one hour or refrigerated if delayed.

Types of Urinalysis Examinations

Physical, chemical, and microscopic examinations.

Normal Urine Composition

Water with 5% dissolved substances including ammonia, organic compounds (urea, uric acid), proteins, and ions.

Substances Not Normally Present in Urine

Serum proteins, glucose, ketones, bicarbonate ions, oxalate ions.

Physical Characteristics of Urine

Odor/smell, color, clarity, pH.

Urine Color Indications

Dark urine indicates dehydration, red urine indicates hematuria, orange or tea-colored urine may indicate muscle breakdown, and tea-colored urine may indicate liver disease.

Urine Clarity Indications

Cloudy urine indicates infection, very foamy urine indicates proteinuria.

Substances that Cause Cloudiness (Not Necessarily Unhealthy)

Mucus, sperm, prostatic fluid, cells from the skin, normal urine crystals, contaminants like body lotions and powders.

Substances that Cause Cloudiness (Requires Attention)

RBCs, WBCs, bacteria.

Normal Urine pH

Usually slightly acidic (~pH 6.0) but can range from 4.5-8.0.

Kidney's Role in pH Balance

The kidneys play an important role in maintaining acid-base balance in the body.

Test for Protein

Biuret Test using 6M NaOH and 5% CuSO4. Copper ions form a violet/blue violet-colored complex with the protein.

Proteinuria

Elevated urine protein; can be temporary or persistent due to stress, exercise, fever, aspirin therapy, or exposure to cold; may indicate kidney disease.

Urine Albumin Test

More sensitive test for small amounts of urine albumin.

Test for Sugar

Benedict’s Test using Benedict’s reagent (CuSO4 in citrate & carbonate); positive result is a brick-red precipitate.

Glucosuria

Presence of glucose in urine due to either excessive high glucose level in the blood or a reduction in the “renal threshold”.

Test for Ketone Bodies

Reagent is a 1:1 mixture of glacial acetic acid and 10% sodium nitroprusside; results in pinkish, red, or deep purple ring.

Ketone Bodies

Intermediate products of fat metabolism, produced when glucose is depleted as an energy source.

Ketonuria

Presence of high levels of ketones in urine; may be due to strenuous exercise, exposure to cold, vomiting, or several diseases.

Test for Bicarbonate

Test using 3M sulfuric acid (H2SO4); results in formation of gas bubbles.

Abnormal Bicarbonate Levels

Suggests the body's trouble in maintaining its acid-base balance; highly alkaline blood correlates with significant bicarbonate in urine.

Test for Chlorine

Test using nitric acid (HNO3) and silver nitrate (AgNO3); results in formation of white precipitate.

Chloride Function

Helps keep the balance of fluid inside and outside of the cells, maintains proper blood volume, blood pressure, and pH of the body fluids.

Test for Ammonia

Test using 6M sodium hydroxide (NaOH) and litmus paper; litmus paper color change from red to blue.

Purpose of Ammonia Test

To check how well the liver is working, to check success of treatment for severe liver disease, to help the identification and prognosis of a childhood disorder Reye syndrome.