The process of dialysis in glomerular

1. The rate of glomerular filtration: One of the two kidneys filter 180 liters of services, including 99% of services are reabsorbed in the tubules, forming only 1-1.5 liters of urine excreted with a product of decomposition of the body. In normal in 1 minute with 1200 ml of blood flow through the kidneys (containing 650 ml of plasma) by 21% cardiac output, but only 125 ml of plasma is filtered through the glomerular membrane in which Bowman. Thus, 125 ml of plasma is filtered through the glomeruli in 1 minute called glomerular filtration flow (or glomerular filtration rate). The process of glomerular filtration agents have similar mechanisms of metabolism at the capillary hydrostatic pressure instantly. It is a passive mechanism, depends on the pressure difference between inside and outside the circuit.

Pressure Filter (P¬L) really pushes service glomerular filtration membrane, calculated by the formula:

PL = PH - (PK + PB)

Among them:

PH: hydrostatic pressure of glomerular capillaries (normal is 60mmHg),

PK: glue pressure in the glomerular capillaries (normal is 32 mmHg),

P¬B¬: How Bowman pressure (normal is 18 mmHg).

Thus, the glomerular filtration rate depends primarily on three factors: pressure filter, filtering capabilities and areas of glomerular filtration membrane.

2. Mechanisms regulating glomerular filtration rate

There are two mechanisms regulating automatic glomerular filtration rate: Stretch arterioles to: the reduced glomerular filtration rate, decreased levels of sodium, chloride characteristics to macula DENSA plated layer. The decrease in the concentration of ions causes the arteries to relax, increasing blood flow to the glomeruli, glomerular filtration rate increases and vice versa. Regulating co arterioles go backwards when reduced renal blood flow, with less sodium and chloride to the macula DENSA, as glomerular cells secrete renin edge, leading to the formation of angiotensin II minimizing travel arterioles, increases in glomerular pressure and increased glomerular filtration rate.

Methods exploration of glomerular filtration function

Glomerular filtration rate was calculated using the formula:

MLCT (GFR) = Kf. PL = k.s.PL = Ki. (PH - PB - PK).

In that ultrafiltration coefficient Kf = ks (k: the ability of the membrane filter, s: is the membrane area). Pl is the pressure filter, PH: hydrostatic pressure of glomerular capillaries (normal is 60mmHg), PK: glue pressure in the glomerular capillaries (normal is 32 mmHg), P¬B¬: pressure how Bowman (normal is 18 mmHg).

In fact to calculate glomerular filtration rate it based on renal clearance with a reagent. The concept of clearance (Clearance) is Muler, Van Slyke first introduced in 1928 when the study of kidney function by determining the volume of blood is purified from urea. Clearance of a substance is the mass of purified plasma totally out of that substance in a unit of time. Van Slyke was formulated to evaluate glomerular clearance:

C: Clearance reagent (ml / h)

U: reagent concentrations in urine (mg%)

P: reagent concentrations in serum (mg%)

V: The volume (ml / min)

1.73: The surface area of the body at the high 1,70m, 70kg is 1,73m2.

S: surface area of the patient's actual body (m2)

Techniques to measure glomerular filtration rate requires the use of these substances freely filtered through the glomeruli, not protein bound, not being reabsorbed or excreted by the kidney tubules, and the substance is not metabolized by the kidney, as well as to collect blood and urine correctly in the given time. Inulin is a substance commonly used in the laboratory, but because of the difficulty of the technique should not be widely applied in clinical practice. Endogenous creatinine is now widely used in practice because of its simplicity and ability to perform easily, cheaply. However the downside is that the accuracy is not high in some cases severe renal impairment, children, the elderly ... Now to overcome the limitations of endogenous creatinine reagent, the authors recommend the use of substances cystatin C and beta testing is 2 microglobulin support for measurement using endogenous creatinine. However because of technical complexity, high cost, so they need time to be widely applicable.

Creatinine clearance with 24-hour urine flow (Clcre 24) is often chosen as the main criteria in clinical practice to assess glomerular filtration rate. The main disadvantage of this test is creatinine is excreted by the kidney tubules should add in creatinine clearance greater than 24 typically carry MLCT and retention of urine in 24 hours unavoidable errors.

There are four formulas are used to calculate the MLCT:

- Formula estimated by the Cockcroft Gault MLCT

eClcre CG (ml / min) = [(140- age) x weight (kg)] / (72 x creatinine HT) x 0.85 (for women)

- Recipe of the MDRD estimate MLCT

MDRD eGFR (ml / min / 1.73 m2) = 186 x (HT creatinine) -1.154 x (age) -0.203 x (0.742 if female) x (1.210 if black)

- Formula MLCT estimate of Japan has been modified MDRD

MDRD eGFR Japan (ml / min / 1.73 m2) = 194 x (HT creatinine) -1.094 x (age) -0.287 x (0.739 if female)

- Formula estimates of CKD-EPI MLCT

+ Female: If HT creatinine ≤ 0,7mg / dL: eGFR = 144 x (HT creatinine) -0.329 x (0.993) age; If HT creatinine> 0,7mg / dL: eGFR = 144 x (HT creatinine) -1.209 x (0.993), age

+ Men: If HT creatinine ≤ 0,9mg / dL: eGFR = 141 x (HT creatinine) -0.411 x (0.993) age; If HT creatinine> 0,7mg / dL: eGFR = 141 x (HT creatinine) -1.209 x (0.993), age

  Through a comparative study of formulas to estimate creatinine clearance, estimated creatinine clearance (eClcre) is the appropriate formula in practice on the Vietnamese people. In fact, computerized and not only give the results of blood creatinine but an MLCT help clinicians know directly the value of glomerular filtration function. Since it can be diagnosed early cases of kidney failure, timely intervention and reduced the proportion of patients with chronic end-stage renal failure.