Biochemistry I - Lecture 3

BIOCHEMISTRY I

Lesson 3

The Kidney and Urinalysis

Part I

Functions of the Kidney

1. Elimination of metabolic and toxic waste

products from the body

2. Regulation of acid-base balance (pH)

3. Regulation of the composition and volume of 3. Regulation of the composition and volume of

body fluids

4. Production of hormones necessary for proper

function of body tissues and organs

Hormones and the Urinary System

Hormones that affect kidney function:

Parathyroid hormone (PTH)

Calcitonin

Aldosterone Aldosterone

Antidiuretic hormone (ADH)

Atrial natriuretic peptide (ANP)

Hormones and the Urinary System

While kidney function is influenced by hormones such as ADH, which are produced by other organs (synthesized in the hypothalamus and released by the posterior pituitary gland), kidneys also produce hormones that influence kidneys also produce hormones that influence physiological processes in other parts of the body.

Hormones produced by the kidneys are: Erythropoietin

Renin

Active vitamin D

Renal Function Tests

Urinalysis

3 parts examination: physical, chemical and

microscopic

Creatinine and blood urea nitrogen (BUN) Creatinine and blood urea nitrogen (BUN)

Creatinine clearance test

Effect of Disorders and Diseases

Abnormal urinalysis results can be seen in:

Disorders or diseases of the urinary tract

Situations when disease in other parts of the

body affects kidney function or urine body affects kidney function or urine

composition

Effect of Disorders and Diseases

Disease can cause changes in the:

Urine volume

Urine colour

Urine transparency / clarity Urine transparency / clarity

Urine odour

Cells present in urine

Chemical constituents of urine

Urinary Tract Infections (UTIs)

Urine in urinary bladder is normally sterile

UTIs normally occur in the urethra and are

caused by bacteria, yeast (fungi) or protozoan

parasitesparasites

Untreated bacterial infections can spread to

urinary bladder causing cystitis

In severe cases it may involve the kidneys

resulting in pyelitis (inflammation of renal pelvis)

or pyelonephritis (inflammation of renal pelvis

and kidney)

Diseases of the Kidneys

1. Glomerulonephritis

2. Polycystic kidney disease

3. Tubular necrosis 3. Tubular necrosis

Glomerulonephritis

Inflammation of the glomeruli - due to

deposition of antibodies or immune complexes in

the glomeruli

Can develop due to:

infection in the body

autoimmune disease (a disease resulting from a

disordered immune reaction in which antibodies are

produced against ones own tissues, e.g. systemic

lupus erythematous or rheumatoid arthritis)

systemic disease in which capillary damage occurs

(glomeruli are made of capillaries)

Glomerulonephritis

Damage to the capillaries cause inefficient

filtering - protein and blood cells may be

present in urine, excess body fluid

accumulates (cause edema and hypertension)accumulates (cause edema and hypertension)

Post-streptococcal glomerulonephritis -

popular but infrequent occurring type of

glomerulonephritis

Polycystic Kidney Disease

Inherited condition where formation of

multiple cysts in kidney impair the

glomerulars function

Tubular Necrosis

Occurs when the blood supply to the kidney is

diminished, upon exposure to substances

which are toxic to kidney cells

The capacity of the tubules to concentrate

urine is affected

Systemic Diseases

Diabetes mellitus

Hypertension

Atherosclerosis

Autoimmune diseases Autoimmune diseases

e.g. rheumatoid arthritis which targets the lining,

synovium, that covers various joints

multiple sclerosis which targets nerve tissues of

the central nervous system

Systemic Diseases

Nephrotic syndrome

Abnormal condition where there is albumin

deficiency in blood due to altered permeability of

the glomerular basement membranes (as by toxic the glomerular basement membranes (as by toxic

chemical agent)

Malignancies

Can cause obstruction, abnormal urinalysis results

or the appearance of malignant cells in the urine

Collection and Preservation

Proper collection, labeling and handling of

urine specimens ensures reliable urine test

results

Different type of specimen are required for Different type of specimen are required for

different tests

Thus, it is important to know the proper urine

specimens that are used for urine tests and

the proper urine collection and handling

procedures for each

Types of Urine Specimens

Common types of urine specimens for

laboratory analysis are:

Random urine specimen

Fasting or first morning urine specimen

Should be collected by

midstream procedure

Fasting or first morning urine specimen

Clean-catch urine specimen

Timed urine specimen

24hr urine specimen

Midstream specimen - patient collects only the

middle portion of the urine flow

Should be collected by

midstream procedure

Specimens for Routine Urinalysis

Most preferred specimens for urine testing -

first morning specimen

Reason: Normally more concentrated with

acidic pH which helps to preserve any cells acidic pH which helps to preserve any cells

present

However, most routine urinalysis uses random

urine specimens

Timed Urine Specimen

Only for certain tests

e.g. screening test for diabetes - urine

collected 2 hr post-prandial (after eating) is

tested for glucosetested for glucose

Clean-Catch Urine Specimen

Required when urine is to be cultured for

microorganisms

When collecting this specimen, females

should avoid contaminating the specimen should avoid contaminating the specimen

with vaginal material which may contain

microorganisms

Reason: Normal vaginal microbe flora growth

on culture may interfere with the process of

identifying the microbe causing the infection

Clean-Catch Urine Specimen

The urine container should be labeled on the

outside (not on the lid) - name, identification

number and time of collection

The urine must be inoculated to culture media The urine must be inoculated to culture media

within 1hr of collection

If specimen is to be sent to a reference

laboratory, instructions and transport supplies

of that laboratory must be used

24hr Urine Specimen

Required in quantitative urine test to assess

kidney function

e.g. of analytes that can be measured using

this specimen - protein, creatinine, this specimen - protein, creatinine,

urobilinogen, calcium, etc.

Handling and Preserving

Random and first morning specimens - secure

lid containers large enough to store at least 50

mL

Clean-catch specimens - urine containers must Clean-catch specimens - urine containers must

be sterile

24hr urine specimens - large, opaque (not

clear) containers which can store 4L or more

(normally contain preservatives)

Labeling

Must be labeled clearly with the patients

name, date and time of collection

Labels must be on the container, not just on

the lidthe lid

Storage

Specimens (except 24hr tests) should be

examined within 1 hr of collection

If it is not possible, specimens must be stored in

dark, secure lid container at 2 - 8C for up to 4 hrdark, secure lid container at 2 - 8C for up to 4 hr

Urine placed at room temperature for an

extended time may cause bacterial

multiplication - increase pH (unpleasant

ammonia like odour)

Delay in testing also causes decomposition of

urine sediment components (e.g. casts and cells)

Preservation

Urine specimens that cannot be refrigerated or

need to be transported - preservatives added

(retards growth of bacteria)

Containers for 24hr urine specimens often have Containers for 24hr urine specimens often have

preservatives added before urine is collected

NO PRESERVATIVE of any kind should be added

to urine for BACTERIOLOGICAL CULTURE

Procedures for Collection

1. Safety precautions

All urine specimen must be submitted in clean,

non-leaking containersnon-leaking containers

Personal protective equipment (PPE) - gloves,

face protective equipment and a buttoned

fluid-resistant lab coat should be worn


Avoid splashes when pouring or discarding

urine

Spills must be wiped and disinfected Spills must be wiped and disinfected

Patients asked to collect 24hr urine specimens

should be given material safety data sheet

(MSDS) info or written instructions for safe

handling any preservatives in the collection

container


2. Quality assessment

Specimens collected must be labeled,

transported and stored as follows:

Give complete instructions to patients - collect Give complete instructions to patients - collect

specimens correctly

Written instructions - understandable by

patients

Specimen labeling - accurate and complete


Specimens delivered - logged in with time

received so testing can be done within the

excepted period

Label containers (never lids) with:

Patients name Patients name

Date

Time

Method of collection

Specimens cannot be tested within an hour of

collection must be stored in the dark with a lid

on at 2 - 8C


3. Midstream Urine Specimen

This method must be used for routine urinalysis

Patients should begin voiding into the toilet and

only collect middle portion of the urine streamonly collect middle portion of the urine stream

This method prevents contaminating the

specimens with epithelial cells, microbes or

mucus from the urethra

Used for first morning, fasting, random and

timed urine specimens


4. Clean-catch Urine Specimens

Used if urine is to be cultured for bacteria

Bacteria culture must be done first if the

specimen is to be used for routine urinalysis as specimen is to be used for routine urinalysis as

well - avoid contamination

Patients should be instructed to cleanse the

urethral opening using a kit with towelettes

before collecting midstream urine

Instructions must be understandable for all

patients


5. Drug screens

Use random urine specimen

A written protocol must be followed

Chain-of-custody of the specimen must be

documented


Requirements for urine drug-screen collection:

Photo identification verified

Signed consent of patient / donor obtained

Use of special collection kits provided by laboratory Use of special collection kits provided by laboratory

Inspection of bathroom before and after collection

Urine temperature measured and recorded right

after collection

Specimen labeled in presence of donor, seal in

outer container and secured under lock until

transported to testing agency


6. 24hr Urine Specimens

I. Specimen Containers

Container containing preservatives with 3 - 4 L

capacity will be provided by laboratory

Most test requires storage of specimens at 2 - 8C Most test requires storage of specimens at 2 - 8C

II. Instructions to Patients

24hr urine specimens - contain all the urine excreted

by patient in a 24hr period

Collection usually starts in the morning - patient

completely empty the bladder into the toilet on day

collection begins - this urine is NOT INCLUDED in the

24hr collection


III. Measuring Urine Specimens

Urine volume normally not measured in routine

urinalysis but must be recorded for 24hr urine

specimens because the volume is used in specimens because the volume is used in

calculating the test results

Total volume must be recorded on the specimen

label and the accompanying requisition form

Factors Influencing Urine Volume

1. Fluid intake

2. Diet

3. Fluid lost in inhalation and perspiration

4. Hormone levels4. Hormone levels

5. Status of renal and cardiac functions

Reference Ranges for 24hr Urine

Age Volume (mL / 24 hr)

Newborn 20 - 350

One year 300 - 600

Ten years 750 - 1500

Adult 750 - 2000

Terms

Common terms describing urine production:

1. Polyuria - consistent elimination of an

abnormally large volume of urine (>2000 mL)

in 24 hrs

2. Oliguria - excretion of an abnormally small 2. Oliguria - excretion of an abnormally small

volume of urine (

Biochemistry I - Lecture 3

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