Chemical examination of urine, urinary sediment

Pavla Balínová

Kidney function

• maintenance of ECF and ICF volume, osmola r ity and pH of blood, electrolytes levels • elimination of wastes (urea, creatinine,…)

Glomerular filtration ,

occur in nephron.

tubular resorption

and

secretion

Nephron as a functional unit of the kidney

Figure was found at http://en.wikipedia.org/wiki/Renal_tubule#Renal_tubule

Production of urine

• glomerular filtration rate (GFR) is 2 mL of blood per one second = 120 mL/min → cca

160-180 liters of ultrafiltrate per day

• an adult human produces 0.5 – 2.0 L of urine per day (in average 1.5 L)

Composition of urine

● 95% of volume of normal urine is due to

water

Organic components:

● ●

urea urobilinogen

● ● ●

amino acids

●

metabolites of hormones

Inorganic components:

● ●

uric acid creatinine cations: Na + , K + , Ca 2+ , NH 4 + anions: Cl , SO 4 2 , HCO 3 , HPO 4 -

N-containing compounds in urine Urea

is synthesized in the liver - it is transported by free diffusion through membrane

Ammonia

is released from Gln - buffer function in the urine

Creatinine

is a product of muscle metabolism -it is not reabsorbed by the tubules →

creatinine clearance Uric acid

is a final product of endogenous and dietary purine degradation

Urobilinogen (UBG)

is formed from bilirubin in a small intestine - can be oxidized to urobilin in urine

N-containing compounds in urine

creatinine uric acid

Kidneys (and lungs) are the most important organs in maintenance of ABB Proximal tubule

• reabsorption of HCO 3 and secretion of H + • enzyme carboanhydrase (CA)

Distal tubule

• H + -ATPase catalyzes transport of H + into lumen of distal tubule • aldosterone increases H + secretion • H + in urine: – reacts with NH 3 – reacts with HPO 4 2-

BUFFER SYSTEMS

• urinary pH may range 4.5 – 8.0

Buffer systems in urine

Kidneys in metabolism

• • ATP for active transports comes from aerobic oxidation of lactate, glutamine and FA • tubular epithelia gluconeogenesis • kidneys take up are the main metabolic active cells (Gln, lactate, glycerol, Fru) is an important source of Glc during starvation

glutamine

from plasma ↓

glutaminase

glutamate + NH 3 URINE ↓

glutamate dehydrogenase

2-oxoglutarate + NH 3 URINE ↓ citric acid cycle

Determination of urine

Physical determination: • volume, density, colour, smell, foam, pH Chemical determination: • ion composition: Na (cells) + • creatinine clearance , K Functional test of kidney: + , Ca Microscopic determination: Microbiological determination: 2+ , Mg 2+ , Li + , Cl , phosphates • N-containing metabolites: urea, creatinine, uric acid • proteins, glucose, ketone bodies, enzymes, hormones • non-organ components (crystals of salts) and organ components ● apperance of bacteria, fungi or yeast

Pathological components of urine

• ↑

proteins → proteinuria

(glomerulonephrititis, bacterial infection, pregnancy) • 150 mg of proteins are excreted daily ● ↑

glucose → glycosuria

(diabetes mellitus, emotion stress) • renal threshold for Glc is around 10 mmol/L • ↑

ketone bodies → ketonuria

(starvation, diabetes, pregnancy) • other pathological components: bilirubin, blood (ery, Hb),…

Creatinine clearance test

• is a useful measure for estimating the creatinine per unit time (sec) glomerular filtration rate (GFR) of the kidneys in mL/sec • is the volume of blood plasma (mL) that is cleared of C cr (mL/s) = (c u /c s ) x V/t c u = creatinine concentration in urine sample c s = creatinine concentration in serum sample V/t = urine flow (mL/s)

Urinary sediment = microscopic examination of urine

• examination of urinary sediment evaluates the presence and number of organ components – cells (ery, leu, epithelial cell, bacteria) and nonorgan components (crystals) • crystals are mostly composed of calcium oxalate or calcium

phosphate

• urate stones (from uric acid) - gout, acidic pH of urine oxalate crystals uric acid crystals

Figures were assumed from http://mnof.cz/ sediment - Atlas močového sedimentu On-line