Urine Chemistry

Urine Chemistry

Urine

96% 4%

OrganicInorganic

Water

NORMAL CONSTITUENTS OF URINE

2A2U2C2P

Organic nitrogenous part:

It is also called non protein nitrogenous constituent = (NPN):

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1.Urea:

• 20 - 40 g/d.•Constitutes 85% of total urinary nitrogen excretion.

It is the principal end product of protein metabolism in mammals.

Urea excretion is directly proportional to protein intake.

Protein – rich Diet

More Urea excretion

Urea excretion is increased whenever protein catabolism is increased as in

fever, diabetes mellitus or excess adrenocortical activity.

Urea is synthesized in the liver, so decreased urea excretion is met with in advanced liver diseases.

Retention occurs in nephritis which results in smaller output and increase in urea concentration in the blood.

2. Ammonia:

0.8-1.2 g/day in urine. Its formation and excretion are important mechanisms that protect the body against acidosis.

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Ammonia is derived from glutamine by glutaminase enzyme in the kidney.

The formed ammonia drags with it H+ to be excreted as ammonium ions (NH4+) which is excreted in the urine in the form of NH4Cl.

3. Creatinine

It is the metabolic end product of creatine in muscles

Urinary creatinine is proportional to the muscle bulk , but regardless to the amount of protein in diet.

Urinary Cr. Excretion 1-1.8 g/day.

3. Creatinine

Creatinine level in blood and its Excretion in urine is a good index of kidney functions

3. Creatinine

(creatinine clearance).

4. Creatine:• 60-150 mg /day.

Urinary creatine represent 7% of total creatinine output.

Creatinuria 1. In pregnancy, 2. infancy - childehood3. Athletes

Physiological Creatinuria

in pathological states such as hyperthyroidism, starvation and

impaired carbohydrate metabolism in diseases involving loss of muscle

mass (myopathies).

0.8-1.2 g/day.The most important end product of oxidation of purines in the body

Occurs in urine in the form of urates. It is derived from

1. dietary nucleoproteins2. breakdown of cellular nucleoproteins.

5. Uric acid:

Soluble in alkaline urine, but it is precipitated in acid urine.

Increase in Urine In •Leukaemia•Gout•severe liver diseases and.

6. Hippuric acid:

0.7 g/day.It is formed by conjunction of benzoic acid with glycine.

Vegetables and fruits contain high content of benzoic acid.

Also, benzoic acid is derived from putrefaction of aromatic amino acids

from benzoate of preserved food.

7. Amino acids:

150-200 mg/day.

Aminoacidurias ???

Amino aciduriasOccur in case of extensive destruction of

the liver as in liver poisoning by: chloroform and tetrachlorocarbon

Also, inborn error known as (cystinuria) which is a tubular defect in reabsorption of cystine, arginine, lysine and ornithine.

8. Purines:Only traces.Several purines are found in urine

some of them are derived from the caffeine and theobormine found in coffee and tea.Methyl Xanthines

9. Indican:

It is a product of tryptophan putrefaction in gut ,

normally present in small amounts

and increases in constipation

Organic non-nitrogenous part:

1- Oxalic acid whose amount is very low. It is found as calcium oxalate crystals in

urinary deposits It is increased after ingestion of fruits and

vegetables of high oxalate content, is increased in inherited metabolic disease

(primary hyperoxaluria) large amount of oxalates may be continuously excreted.

2- Organic acids: These include citric acid, lactic acid and glucuronic acid.

Urinary Inorganic constituents

1. Chlorides: 9-16g/day. Next to urea, chlorides are the most abundant substances in urine

Mainly excreted as sodium chloride.

Its output depends upon its intake

2. Sulfates:2-3 g/day. These are derived mainly from sulfur containing amino acids of proteins.

Urinary sulfates can be divided into 3 forms:

a) Inorganic sulfates (85%): is proportional to the output of the total nitrogen since both originate from protein metabolism.

b) Ethereal sulfates (10%): Are esters of sulfuric acid with certain

phenols (e.g. indoxyl, indican, and other sulfur

conjuguates formed in detoxication).

c) Neutral sulfates (5%): This represents the unoxidized sulfur.

3. Phosphates:2-3 g/day.Relative proportions of NaH2PO4

determines the pH of urine.It is largely derived from the

ingested food, which contains inorganic & organic phosphate (e.g. nucleoproteins, phosphoproteins..etc).

Increases Phosphate level in hyperparathyroidism osteomalacia.

Decrease sometimes occurs in renal diseases and infectious diseaseshypoparathyroidism.

4. Cations: Sodium, Potassium, calcium, and magnesium are the 4 cations of the extracellular fluids present in urine.

ABNORMAL CONSTITUENTS OF URINE

Proteis Sugars Ketone Bodies Bile Blood Pophyrins

a) Proteins (proteinuria):1. Physiological (less than 500 mg/day) after severe

muscle excercise, after prolonged standing, after a high protein meal and during pregnancy.

2. Pathological: Prerenal: The primary causes are factors

operating before the kidney, e.g. heart failure. Renal: The lesion is intrinsic in the kidney, e.g.

nephritis and nephrosis. Postrenal: The lesion is in the lower urinary tract,

e.g. cystitis.

The increased amount of albumin in urine called albuminuria,

Microalbuminuria if 30-300 mg/day Macroalbuminuria if more > 300mg /day

• Albumin in urine is detected by heat coagulation test. • There are other types of protein which may appear in urine as Bence-Jones Proteins.

Bence-Jones proteins: These are abnormal globulins that

appear mainly in multiple myeloma which is a bone marrow cancer, also in leukemia and lymphosarcoma.

in such conditions, urine undergo 3 phases:

1. clotting when heated to 60°C, 2. undergoes redissolving at 100°C and 3. reclotting by cooling.

b) Sugar:Glucose (glucosuria): Normally not more than

1 g/day (many types of glucosuria).Fructose (fructosuria): It is a rare anomaly in

which the metabolism of fructose is disturbed. (Deficient Fructokinase)

Galaclose (galactosuria): May occasionally occur in infants and mothers, also in congenital galactosemia.

The renal threshold for glucose is 180 mg/dl

GlucosuriaA- Hyperglycemic glucosuria: It occurs when the blood glucose level exceeds

the renal threshold (180 mg/ dl). It is caused by: 1- Diabetes mellitus. 2- Epinephrine glucosuria: as emotional or stress

glucosuria or in case of pheochromocytoma 3- Alimentary glucosuria: It is due to increased rate of

glucose absorption as in cases of gastrectomy or gastrojejunostomy.

B- Normoglycemic or renal glucosuria: In these cases, the blood glucose is within normal range. 1- Congenital renal glucosuria (benign glucosuria or

diabetes innocens), due to congenital defects in renal tubular mechanism for reabsorption of glucose.

2- Acquired renal diseases as in nephritis.

Lactose (lactosuria): During pregnancy and lactation, may appear in mothers and infants.

Pentose (pentosuria): May occur after ingestion of food

containing large amounts of pentoses. Also appears in congenital pentosuria

due to inability to metabolise L-Xylulose.

c) Ketone bodies (ketonuria): They are acetone, aceto-acetate, & 3-

hydroxybutyrate. Normally 3-15 mg are excreted in urine per day. Ketonuria is the presence of excessive amounts

of ketone bodies in urine. This may occur in uncontrolled

diabetes mellitus and during prolonged starvation.

Aceto-acetate and 3-hydroxybutyrate are eleminated as salts thus depleting the alkali reserve which results in acidosis.

d) Bile:Bile pigments: They appear in urine, in hepatic, obstructive and haemolytic jaundice.

Bile salts: Bile salts appear only in obstructive jaundice.

e) Blood (haematuria): Due to

Bilharziasis,

Blood diseases, Renal stonesRenal tumoursHaemoglobinuria

f) Porphyrin:The occurrance of uroporphyrins

as well as increased amount of coproporphyrins in urine is termed porphyria.

(Defect in Haem Synthesizing Enzymes)