2. FUNCTIONS OF KIDNEY
Maintenance of homeostasis:
• The kidneys are responsible for the regulation of water, electrolyte &
acid-base balance in the body.
Excretion of metabolic waste products:
• The end products of protein & nucleic acid metabolism are
eliminated from the body. These include urea, creatinine, creatine,
uric acid, sulfate & phosphate
3. Retention of substances vital to body:
• The kidneys reabsorb & retain several substances of biochemical
importance in the body e.g. glucose, amino acids etc.
Hormonal functions:
• The kidneys also function as endocrine organ by producing hormones
4. Erythropoietin:
• A peptide hormone, stimulates haemoglobin synthesis and formation
of erythrocytes.
1,25-Dihydroxycholecalciferol (calcitriol):
• The active form of vitamin D is finally produced in the kidney. It
regulates calcium absorption from the gut.
5. Renin:
• A proteolytic enzyme liberated by kidney, stimulates the formation of
angiotensin II which, in turn, leads to aldosterone production.
Angiotensin II & aldosterone :
• These hormones involved in the regulation of electrolyte balance.
6. Indications for RFT
• High risk patient for CKD : To detect renal functional impairement at
an early stage and to detect degree of kidney damage
• Diagnosis of renal disease
• Follow the course of renal disease and asses the response of
treatement
• Plan for renal replacement therapy
• Adjust the dosage of certain drugs according to renal function
7. Classification of renal function test
• Glomerular function tests:
• clearance tests (inulin, creatinine, urea) are included in this group.
• Tubular function tests:
• Test to assess proximal tubular function : glycosuria , uricosuria
,generalised aminoaciduria, tubular proteinuria, fractional sodium
excreation
• Test to assess distal tubular function: specific gravity , water
deprivation test ,ammonium chloride load test
8. • Analysis of blood/serum:
• Estimation of blood urea, serum creatinine,microalbuminuria and
albuminuria are useful to assess renal function.
9. GFR
• Best test for assement of renal function in health and disease
• Varies according to the age, sex, and body weight of an individual a
normal GFR also depends on normal renal blood flow and pressure
• Normal GFR : 120-130 ml/min
• Creatinine clearance is commonly used for measurement of GFR
10. Creatinine clearance test
• Clearance is defined as the volume of plasma that would be
completely cleared of a substance per minute.
• Formula: clearance = UV/ P
• U: concentration of substance in urine in mg/dl
• V : volume of urine excreated in ml/ min
• P : concentration of substance in plasma in mg/ dl
• All clearance values are adjusted to a standard body surface area i.e.
1.73 sq. meter
11. • Agents used for measurement of GFR :
• Exogeneous : inulin , radiolebbled ethylenediaaminotetraacetic acid ,
I125-iothalamate , iohexol
• Enogeneous : creatinine , urea, cystatin c
12. Ideal agent used for measurement of GFR should have
following properties
• Physiological inert and preferably inert
• Freely filtered by glomeruli and should be neither reabsorbed nor
secreted by renal tubules
• It should not bind to plasma protein and should not be metabolized
by kidney
• It should be excreted by kidneys
• Currently substance of choice for measuring GFR are creatinine and
cystatin C
13. • Abnormal clearance seen in
• Prerenal factors – reduced blood flow due to shock , dehydration ,
and congestive cardiac failure
• Renal disease
• Obstruction to urinary outflow
14. Blood urea nitrogen
• Urea is produced in the liver from amino acid .
• The concentration of blood urea is usually expressed as blood urea
nitrogen
• Normal range: 7-8 mg/dl
• Causes of increased BUN :
• Prerenal azotemia : shock , congestive heart failure, salt and water
depletion
• Renal azotemia : impairment of renal function
• Postrenal azotemia : obstruction urinary tract
15. • Increased rate of production of urea : high protein diet , increased
protein catabolism , absorbtion of amino acid , peptides from a large
gastrointestinal hemorrhage or tissue hematoma
• Methods of estimation of BUN :
• Diaacetyl monoxime urea method : direct method
• Urea react with diaacetyl monoxime at high temp. in the presence of
a strong acid and an oxidizing agent . Reaction of urea and diaacetyl
monoxime produces a yellow diazine derivative . The intensity of
color is measured in a colorimeter or spectrophotometer .
16. Serum creatinine
• Serum creatine is more specific and more sensitive indicator of renal
function .
• causes of increased serum creatinine level :
• prerenal ,renal, and postrenal azotemia
• large amount of diatery cooked meat
• Muscular body habitus
• Active acromegaly and gigantism
17. • Causes of decreased serum creatinine level :
• Female
• Vegetarian diet
• Malnutrition and muscle wasting
• increasing age (reduction in muscle mass)
18. Methods
Jaffe’s reaction : (alkaline picrate reaction)
• Creatinine reacts with picric acid in an alkaline solution to produce a
red orange color . The color is measured with spectrophotometer at
485 nm .
Enzymatic method : enzymes that cleaves the creatinine , hydrogen
peroxide produced then reacts with phenol and a dye is produced , a
colored product is produced which is measured with
spectrophotometer .
20. proteinuria
Glomerular proteinuria:
• The glomeruli of kidney are not permeable to substances with
molecular weight more than 69,000 & plasma proteins are absent in
normal urine.
• When glomeruli are damaged or diseased, they become more
permeable & plasma proteins may appear in urine.
21. • The smaller molecules of albumin pass through damaged glomeruli
more readily.
• Albuminuria is pathological.
• Large quantities of albumin are lost in urine in nephrosis.
• Small quantities are seen in urine in acute nephritis, strenuous
exercise & pregnancy.
22. microalbuminuria
• It is also called minimal albuminuria or paucialbuminuria.
• It is identified, when small quantity of albumin (30-300 mg/day) is
seen in urine.
• The test is not indicated in patients with overt proteinuria (+ve
dipstick).
• Early morning midstream sample is preferred.
23. • Micro albuminuria is an early indication of nephropathy in patients
with diabetes mellitus & hypertension.
• All diabetics & hypertensive should be screened for
microalbuminuria.
• It is an early indicator of onset of nephropathy.
24. Test to evaluate tubular function
Proximal tubular function :
• Glycosuria
• Generalised aminoaciduria
• Tubular proteinuria
• Urinary concentration of sodium
• Fractional excreation of sodium
25. • Glycosuria :
• Proximal tubules efficeiently reabsorb 99% of the glomerular filtrate
to conserve essential substance like glucose , amino acid and water
• In renal glycosuria glucose is excreated in urine , while blood glucose
levels are normal
• Caused due to specific tubular lesion leading impairment of glucose
reabsorption
26. Test to asses the distal tubular function:
• Urine specific gravity
• Urine osmolality
• Water deprivation test
• Ammonium chloride loading test
27. • Water deprivation test:
• Procedure : water intake is restricted for 12-14 hrs and urine volume , urine
and serum osmolality and body weight is measured followed by
administration of vasopressin changes in urine and plasma osmolality is
noted
• Normal individual : reduction of urine volume and formation of
concentrated urine
• Central Diabetes insipidus : no significant abnormality , after
administration of vasopressin osmolality increases by 50%
28. • Nephrogenic diabetes insipidus: no significant increase in urine
osmolality even after water deprivation and vasopressin
administration
29. Renal biopsy
• Importance
• Establish the diagnosis
• Asses the severity and activity of the disease
• Asses the prognosis by noting the amount of scarring
• to plan the treatement and moniter response to therapy
30. • Indications :
• Nephrotic syndromes in adults with no evidence of systemic disease
• Nephrotic syndrome not responding to corticosteroids
• Acute nephritic syndrome for differential diagnosis
• Unexplained renal insufficiency with near normal kidney dimentions
on usg
• Asymtomatic hematuria , when other diagnostic test fail to to identify
the source of bleeding
• Isolated non nephrotic range proteinuria (1-3gm/24hrs) with renal
impairment
31. • Impaired functional renal graft
• Involvement of kidney in systemic diseases like SLE
• Complication :
• Hemorrhage
• Arteriovenous fistula
• Infection
• Accidental perforation of viscus
• Death (rare)
