This document discusses urea and creatinine, which are waste products excreted by the kidneys. It describes how urea is formed from ammonia in the liver and how defects in the urea cycle can cause metabolic disorders. It outlines methods for measuring blood urea and urine urea. Creatinine is formed from creatine in muscle and increased levels can indicate muscle or kidney issues. Methods for measuring serum and urine creatinine are provided. The document concludes by noting creatinine clearance is a sensitive indicator of kidney function.

1. Tapeshwar Yadav
(Lecturer)
BMLT, DNHE,
M.Sc. Medical Biochemistry

2.  Urea is the major end product of protein metabolism In
humans.
 Its formed in liver.
 Urea biosynthesis occurs in four stages:
(1) transamination,
(2) oxidative deamination of
glutamate,
(3) ammonia transport,
(4) reactions of the urea
cycle

4.  ammonia is produced in various ways by tissues are rapidly
removed from circulation by the liver and converted to urea.
This is essential, since ammonia is toxic to the central nervous
system.
 Urea is water soluble ,conversion of ammonia to urea is a kind
of detoxification.
 This is the importance of urea excretion and its estimation.

5.  Any defect in any of the enzyme function of urea cycle can lead
to various metabolic disorders.
 More than 90% of urea is excreted through the
kidneys(glomeruli), with losses through GIT and skin in minor
fraction.
 Determination of blood urea is important not only in many
diseases of kidney but in a wide range of conds which r not
primarily renal.

6. Causes of increase in serum urea
 Causes r divided in pre-renal , renal and post-renal
 PRE-RENAL :
dehydration
pyloric n intestinal obstruction with vomiting
sever n prolonged diarrhea
chrn intestinal obstruction without vomiting
ulcerative colitis with severe chloride loss
diabetic coma

7. RENAL :
 acute glomerulonephritis
 malignant hypertension
 chronic pyelonephritis
 hydronephrosis
 congenital cystic kidney
 renal tuberculosis
 calcium deposition in kidney in hyperthyroidism n
hypervitaminosis D.

8.  POST RENAL:
enlargement of prostate
stones in urinary tract
stricture of the urethra
tumors of the bladder affecting the ureter

9.  Cirrhosis of liver
 Acute yellow atrophy of liver
 Severe acidosis
 Nephritis
 Pregnancy

10.  BLOOD UREA:
Diacetyl monoxime method
principle
when urea is heated with diacetyl(,containing
two adjacent carbonyl group) under acidic
condition yellow coloured compound is
formed.the OD of the colour developed can be
read at 420 nm.intensity of the color depends
on conc of urea in serum.

11. additions BLANK STANDARD TEST
Protein free filtrate _ _ 1ml
Working standard _ 1ml _
Distilled water 1ml _ _
DAM reagent 0.4ml 0.4ml 0.4ml
Acid mixture 1.6ml 1.6ml 1.6ml

12. OD of the test × conc of standard × 100
OD of the standard
vol of the test
= T/S×100
BUN(blood urea nitrigen):
= blood urea level× 28/60
Normal value - 5 -20 mg/dl

13. Principle:
urease hydrolyses urea to ammonia and CO2.the
ammonia formed further reacts with a phenolic chromogen and
hypo chloride to form a green colored complex. Intensity of
colour is directly proportional to the amount of urea present in
the sample.
addition blank standard test
Working
reagent
1.0 ml 1.0ml 1.0ml
Distilled water 0.01ml - -
Urea standard - 0.01ml -
sample - - 0.01ml
Chorogen
reagent
0.2ml 0.2ml 0.2ml

14. calculation:
= T/S × 40
SERUM – 15 to 40mg/dl

15.  The hypobromite method
Principle:
the vol of nitrogen liberated by the action of
hypobromite on the urea present in the urine is measured. the
action is usually though not accurately, expressed
URINE - 15 to 30mg/day.

16.  Urea clearance is less than GFR.
Maximum urea clearance:
=U × V/P
U=mg of urea /ml of urine
p=mg of urea/ml of plasma
v=mg of urine excreted /minute
normal value - 75 ml /mint
Standard urea clearance:
u × √v/p
normal value - 54ml/mint

17.  Values below 75% is abnormal
 Values fall progressively with increasing renal failure
 Clearance values r the early indicator then plasma value
 creatinine clearance is more preferred
 Neither urea clearance nor blood urea r used as index of kidney
function today

18.  Creatine constitutes about 0.5% of total muscle weight.
 Its synthesized from 3 amino acids Glycine , Arginine &
Methionine.
glycine arginine
(occurs in mitochondia of kidney n pancreas)
Guanidoacetic acid ornithine
SAM (in liver)
SAH
Creatine creatine phosphate (ck is pesent in muscle brain n liver)
creatinine

19. CREATINE creatine kinase PHOSPHOCREATINE
SPONTANEOUS SPONTANEOUS
H₂O Pi
CREATININE

20.  Stored creatine phosphate which is a high energy compound,
stored in the muscle, serves as an immediate store of
energy.
 Inter conversion of phosphocreatine & creatine is an indicator
of metabolic process of muscle contraction.
 A particular proportion of muscle creatine is converted to
creatinine spontaneously everyday.
 So amount of creatinine produced in body is related to muscle
mass .
 Conc. Of creatinine in blood is mostly constant.
 Diet may influence the value with high meat intake.
 Its freely filtrated by glomerulus.
 Its an indicator of renal function.

21. Increased conc of creatine
 Muscular disorders
 Myasthenia gravis
 Different myositis
 Starvation
 High fever
 Diabetes mellitus
 Hyperthyroidism

22. Causes of increase in serum Creatinine
 Causes are divided in pre-renal , renal and post-renal
 PRE-RENAL :
 Dehydration
 Pyloric & intestinal obstruction with vomiting
 Severe n prolonged diarrhea
 Chronic intestinal obstruction without vomiting
 Ulcerative colitis with severe chloride loss
 Diabetic coma

23. RENAL :
 Acute glomerulonephritis
 Malignant hypertension
 Chronic pyelonephritis
 Hydronephrosis
 Congenital cystic kidney
 Renal tuberculosis
 Calcium deposition in kidney in hyperthyroidism &
hyper-vitaminosis D .

24.  POST RENAL:
Enlargement of prostate
Stones in urinary tract
Stricture of the urethra
Tumors of the bladder effecting the ureter

25. Increased conc of creatinine
 Conditions r same as increased urea conc.
 But in renal causes creatinine increases more than the
pre-renal causes.

26. Jaffe`s method (in urine)
principle:
creatinine in urine reacts with picric acid in
presence of NaOH to give orange colored compound.creatinine-
picrate color read at 500 nm.
addition BLANK
STANDARD
TEST
Distilled
water
3ml - -
Working
standard
- 3ml -
Diluted urine - - 3ml
Picric acid 1ml 1ml 1ml
0.75 N NaOH 1ml 1ml 1ml

27. calculation:
=gms of creatinine /lt
=T/S×0.03/1000×1000/0.03
=T/S gm/lt
Normal value – 1 - 1.5gm/lt

28. Modified jaffe`s reaction:
principle:
cretinine reacts with alkaline picrate to
produce a reddish color. Absorbance of the color is directly
proportional to creatinine conc in plasma n its measured in
500-520nm.
addition blank standard sample
Working
reagent
- 1000ùl 1000ùl
Standard - 100ùl -
serum - - 100ùl

29. Calculation:
=T/S ×conc of standard(mg/lt)(2mg/dl)
normal value – 0.7 -1.4mg/dl (male)
0.6 – 1.2 mg/dl (female)

30. Uncorrected clearance
=(u/p)× v
U=urinary creatinine conc.
p=plasma creatinine conc
v=urine flow in ml/min
Corrected clearance
=u×v×1.73
p×A

31. Normal value:
85-125 ml/min (male)
80-115 ml/min (female)
Clinical importance
 decreased creatinine clearance is an sensitive indicator of
GFR.
 UPTO 75% is nornal.
 Early detection of renal impairment
 Long term monitoring of renal patients
 Creatinine clearance is altered by body muscle mass
,drugs,age,sex