Chemical examination of urine,
urinary sediment
Pavla Balínová
Kidney function
• maintenance of ECF and ICF volume, osmolarity and
pH of blood, electrolytes levels
• elimination of wastes (urea, creatinine,…)
Glomerular filtration, tubular resorption and secretion
occur in nephron.
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
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95% of volume of normal urine is due to water
Organic components:
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urea
urobilinogen
uric acid
creatinine
amino acids
metabolites of hormones
Inorganic components:
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cations: Na+, K+, Ca2+, NH4+
anions: Cl-, SO4 2-, HCO3-, HPO4-
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 HCO3- 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:
BUFFER
– reacts with NH3
SYSTEMS
– reacts with HPO42• urinary pH may range 4.5 – 8.0
Buffer systems in urine
Kidneys in metabolism
• tubular epithelia are the main metabolic active cells
• ATP for active transports comes from aerobic
oxidation of lactate, glutamine and FA
• gluconeogenesis (Gln, lactate, glycerol, Fru) is an
important source of Glc during starvation
• kidneys take up glutamine from plasma
↓ glutaminase
glutamate + NH3
URINE
↓ glutamate dehydrogenase
2-oxoglutarate + NH3
URINE
↓
citric acid cycle
Note: glutaminase is located in the inner mitochondrial membrane
and it is activated by cortisol and catecholamines.
Determination of urine
Physical determination:
• volume, density, colour, smell, foam, pH
Chemical determination:
• ion composition: Na+, K+, Ca2+, Mg2+, Li+, Cl-, phosphates
• N-containing metabolites: urea, creatinine, uric acid
• proteins, glucose, ketone bodies, enzymes, hormones
Functional test of kidney:
• creatinine clearance
Microscopic determination:
• non-organ components (crystals of salts) and organ components
(cells)
Microbiological determination:
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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
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• ↑ ketone bodies → ketonuria (starvation, diabetes, pregnancy)
• other pathological components: bilirubin, blood (ery, Hb),…
Creatinine clearance test
• is a useful measure for estimating the glomerular
filtration rate (GFR) of the kidneys in mL/sec
• is the volume of blood plasma (mL) that is cleared of
creatinine per unit time (sec)
Ccr (mL/s) = (cu/cs) x V/t
cu = creatinine concentration in urine sample
cs = 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