kidney remove the metabolic waste products homeostatic function the kidney is an organ which does...
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The kidneykidney is an organ which does not simply remove the metabolic remove the metabolic waste productswaste products, but actually performs an important homeostatic homeostatic functionfunction.
It regulates the internal environment
of the body cells by 3 mechanisms3 mechanisms:
1) Glomerular filtrationGlomerular filtration..
2) Selective tubular reabsorptionSelective tubular reabsorption of substances that are necessary to maintain the internal environment; and
3) Tubular secretionTubular secretion of substances from the blood into the tubular lumen for excretion into the urine.
These 3 mechanisms result in urine formation.
7 ITEMS7 ITEMS1.1. VolumeVolume
2.2. Colour Colour
3.3. AspectAspect
4.4. Deposits Deposits
5.5. OdourOdour
6.6. ReactionReaction
7.7. Specific GravitySpecific Gravity
Volume:It ranges between 1 and 1.5 1 and 1.5 L/dayL/day.
The volume depends ondepends on water intake, external temperature, diet, mental and physical state of the individual.
Volume Volume
PhysiologicalPhysiological increaseincrease: In winter After excessive fluid intake- CoffeeNervousness or excitement
more than 2 L/day
N.B. N.B. Normally, more urine is excreted during the day than at night.
Abnormal increase Abnormal increase ((polyuria polyuria ):):
More than 3 L/day
diabetes mellitus (may reach 5 L/day)
diabetes insipidus (10-15 L/day)
hyperparathyroidism. Hypercalcemia -- Action of ADH
Physiological decreasePhysiological decrease: in summer due to increased
sweating during fasting or restricted
fluids in diet.
Volume
Volume
Abnormal decrease Abnormal decrease (Oliguria):
Less than 200 ml/dayacute nephritis, heart failure, shock, burns haemorrhage. vomiting and diarrhoea.
Volume
Anuria: No urine No urine at all (or < 50 ml /day)
late stages of renal failure and heart failure.
ColourNormal colour is amber amber yellow.yellow.
due to pigments called urochromesurochromes , urobilin or urobilinogen + peptide.
There are also other pigments (coproporphyrin, uroerythrin), but occur in small amounts.
The colour is changed
in the following conditions
Diabetes insipidusDiabetes insipidus: : colourlesscolourless or pale yellow.
FeverFever,, deep orange.Obstructive jaundiceObstructive jaundice: : Greenish
brown due to presence of cholebilirubin.
HaemorrhageHaemorrhage in urinary tract, reddish brown colour.
AlkaptonuriaAlkaptonuria: : Black (homogentisic acid is oxidized to give black colour when exposed to air.
Ingestion of : food coloured with dyes or
coloured drugs result in discolouration of urine.
Odour Fresh urine is normally aromatic (urineferousaromatic (urineferous).This odour is changed by:Different types of food: Cabbage, garlic, onion.Severe uncontrolled diabetes mellitus: Fruity
odourodour due to presence of acetone/acetoacetoacetic acid.
Contaminated urine: Ammoniacal odour odour. In stagnant urine, this odour is due to bacterial action, e.g. on urea which is converted into ammonia.
Putrefaction: Putrid odour odour due to bacterial growth in urinary infection.
Ammoniacal odour
Putrid odour
Fruity odour
Normally aromatic
(urineferous)Odour
Severe uncontrolled DM
BacteriaGrowthUrease
Reaction On mixed diet, it is acidic (pH acidic (pH is 6).is 6). It may be slightly acidic or slightly alkaline.
The urine pH depends on the ratio of acid phosphate (NaH2PO4) to alkaline phosphate (Na2HPO4). The kidney mainly excretes acid phosphate to preserve the alkali.
Reaction:
High protein diet gives acidic urine
due to excretion of excess phosphate and sulphate.
Reaction Vegetables and fruits give
alkaline urinedue to their high sodium and
potassium content with excretion of sodium and potassium bicarbonate in urine
ReactionAlkaline urineAlkaline urine
is passed an hour after a mealan hour after a meal,
this is the so called alkaline tidealkaline tide.
AspectAspectNormal urine is clear (transparent)clear (transparent)..
On standingstanding, it turns cloudycloudy due to precipitation of muco- and nucleoproteins and epithelial cells (present in traces in normal urine).
It becomes turbid and turbid and opaqueopaque due to presence of albuminalbumin.
Exposed urineExposed urine is a good medium for bacterial growth as its pH becomes alkaline, resulting in precipitation of phosphates.
DepositsDepositsNormal urine is: devoid from devoid from depositsdeposits.
In case of its presence, it depends on the colour and shape of deposit.
In order to examine the deposit, we make centrifugation to urine then microscopic examinationmicroscopic examination.
a) Crystals Crystals :: urates and oxalates (acid urine),
tripple phosphate (ammonium magnesium phosphate [NH2MgPO4]) (alkaline urine)
b) CastsCasts : : albuminoid substances released from epithelial
c) ParasiticParasitic ova ova ; and d) CellsCells :Pus cells or RBCs.
Microscopic examination of the solid parts of urine: the picture shows red blood cells (above), white blood cells (middle) and a cast of clumped-together white blood cells (below))..
A urinary A urinary castcast is a protein or is a protein or cellular debris, that forms within a cellular debris, that forms within a renal tubulerenal tubule . .
•The material or cells that form a cast The material or cells that form a cast may havemay have
come through a damaged come through a damaged glomerulus,glomerulus, been part of an interstitial been part of an interstitial inflammatory infiltrate,inflammatory infiltrate, have been dead tubular cells. have been dead tubular cells.
•The cast is expelled into the urine, and The cast is expelled into the urine, and maintains the shape of the tubule in maintains the shape of the tubule in which it formed. which it formed. •Casts reflect conditions of the kidney Casts reflect conditions of the kidney proper and not the lower urinary tract. proper and not the lower urinary tract. In most cases they are significant In most cases they are significant and must be explained. and must be explained.
Specific gravitySpecific gravity Normally, it ranges between
1.015 to 1.0251.015 to 1.025 It varies inverselyinversely with the volume
of urine, e.g.: In diabetes diabetes insipidusinsipidus, it is low (1.004).
In feverfever, it is high (more than 1.030) due to small amount of urine.
In diabetes mellitusdiabetes mellitus, the specific gravity is 1.40 due to the presence of glucose.
A diseased kidney loses its ability to dilute or concentrate urine
Water diuresis test
Evacuate The Bladder Then, Drink 1.5 L of water. Urine will be collected every half an
hour for 5 hours For each sample, determine
volume & specific Gravity. Normally, after 5 hours, shold void
at least 800 ml + Sp. Gravity < 1.010 If the distal tubules function is
impaired Diuresis doesnot occur & Sp. Gravity doesnot drop below 1.010
Water Concentration test
Evacuate The Bladder Then, No Drinking for 10-12 hours to
produce dehydration. At the end of the 12 hours Urine will
be collected determine volume & specific Gravity. Normally, Sp. Gravity shold rise to
1.025 If with dehydration, the Sp. Gravity
remains below 1.020 it indicates that the function of Loop of Henle & distal Tubules is inhibited