Download Kidney and Urinalysis - Biomedic Generation | Sharing

Kidney and Urinalysis
Prepared by: Sr. Siti Norhaiza Hadzir
Functions of the kidney





Elimination of excess body water
Elimination of waste products of metabolism
e.g urea & creatinine
Elimination of foreign substances e.g drugs
Retention of substances necessary for normal
body function e.g protein, amino acids &
glucose
Regulation of electrolytes balance & osmotic
pressure of the body fluids.
The Nephron




The functional unit of the kidney.
Consists of renal corpuscle (glomerulus)
& renal tubule.
Structure of glomerulus
Structure of tubule
Kidney blood supply

Renal artery from aorta → afferent
arterioles → efferent arterioles → renal
vein → heart
Glomerular Filtration Rate

Normally this amounts to about 130mL
per minute (180 liters per 24 hours).
Renal Function Test

Falls into 2 major group:
i) Detect the presence of disease- not give
indication as to the degree of functional
impairment e.g proteinuria, cast,
hematuria, WBC
ii) Evaluate the degree of impairment e.g
BUN, creatinine
Test of Urinary tract involvement

Proteinuria
• Healthy glomerular permeable membrane passes only substances with MW
of less than 70 000.
• Excess small proteins are reabsorbed completely by proximal tubule
• Albumin is very close to cut off value (70000MW) can get access to the
urine in glomerular disease.
• Proteinuria are classified into 3:
Pre-renal- The glomerular membrane damage and tubular reabsorption
inefficiency e.g Bence Jones protein in multiple myeloma.
Renal- renal parenchyma disease e.g amyloidosis.
Postrenal- Urinary tract problem e.g inflammation
Figure 1:
Normal urine is compared with
proteinuria sample.
Note increase in turbidity in
proteinuria sample
Cast



Cast are precipitates of protein formed
in the distal convoluted and collecting
tubules of the kidney, where conditions
of filtrate flow and pH are optimal for
protein precipitation.
Normal condition-hyaline cast in small
number
Large number indicates active renal
disease.
Nature of cast

It is a muco-protein formed normally by the tubule; it
is not formed in plasma.

It is long, rod like, flexible molecule.

As the glomerular filtrate travels down the nephron
tubule, the concentrations of salts & H+ ↑.


At pH about 4.5, albumin and myoglobin change from
negatively to positively charge molecules, the mucoprotein is still negatively charge.
Opposite electric charge leads to precipitation and
the formation of casts.
Hematuria & hemoglobinuria



Presence indicate bleeding within the urinary
tract.
In acute glomerulonephritis there is
hemorrhage from the glomeruli, Hb is
convreted to hematin and methemoglobin.
These factors combine to give the “smoky”
red brown urine characteristic of the disease.
Figure 2:
The presence of blood
in the urine
White Blood Cells

An increased number of white blood
cells in a correctly collected specimen
indicates inflammation in the urinary
tract.
Test for Degree of Renal
Impairment




Test based on water elimination and
reabsorption
Blood Urea Nitrogen (BUN)
Creatinine
BUN: Creatinine
Test based on water
elimination and reabsorption


Normally, conservation of water is
reflected by concentrated urine with a
high specific gravity
Excretion of an excess of water is
illustrated by urine of low specific
gravity
Impaired concentrating power





Tubular damage e.g chronic
glomerulonephritis, polycystic disease
Severe potassium depletion
Hypercalcemia e.g due to vitamin D
intoxication, hyperPTH
Inborn defects of tubular function
Diabetes insipidus
Non-protein nitrogen in blood


It is heterogenous collection of
substances including urea, creatinine,
uric acid, nucleotides, glutathione.
Estimation of NPN was replaced by
determination of urea and creatinine,
more specific indicators of renal
condition, easily automated.
Blood Urea/BUN


Urea is the major excretion product of
protein catabolism.
After elaboration, urea is passed to the
blood and is excreted through the
glomeruli and partly reabsorbed in the
tubules.
Causes of ↑ BUN





Pre-renal: Circulation in the kidney is less
efficient e.g CCF
Renal: Renal parenchyma damage,
phylonephritis
Post-renal: Obstruction to the urinary tract
Presence of high level of urea is called
uremia.
Very high level of urea leads to azotemia with
kidney failure.
Creatinine


Nitrogenous substances found in
muscle.
Since creatinine is derived entirely from
endogenous metabolism (not form
dietary protein) and is not reabsorbed
by the renal tubules, its blood level; is a
reliable index to renal function.
BUN/creatinine ratio


Normal ratio is 10:1.
Ratio more than 10:1 occur in:
-Excessive turnover of protein (hemorrhage, burns and
infection)
- Reduced glomerular perfusion

Ration less than 10:1 occur in:
- Repeated dialysis
- Severe vomiting or diarrhea
- Liver failure
Routine urinalysis

The procedure
1. Urine collection and storage
2. Macroscopic examination
- Color
- turbidity and clarity (smoky. milky, cloudy)
- smell
- SG and osmolality
Color
Possible cause
Straw to amber
Normal
Orange
Concentrated urine
Greenish orange
bilirubin
Smoky
Red blood cells
Brown to black on
standing
Melanin or
homogentisic acid
Almost colorless
Dilute urine
Urine container
Centrifuge
tube
Pipetting the
supernatant
The procedure: cont;

-
Urine processing
Centrifuge
- Separate debris and supernatant
- Microscopic examination [cells (epithelium, RBC,
WBC, cast, mucus tread, ova and parasites,
crystals]
- Biochemical analysis (pH, protein, glucose,
ketones, bilirubin, blood, nitrite, urobinogen,
ascorbic acid)
Urine dipstick