Potassium in the urine
The excretion of potassium by the kidneys is subject to complex regulatory systems. Potassium is not only filtered and reabsorbed in the kidneys, but also excreted by the renal tubules.
The study of potassium in urine allows, in view of the amount of diuresis, to estimate the daily losses of this electrolyte. The results of this study are of great importance for resuscitation patients in severe condition when evaluating the effectiveness of the substitution therapy with potassium preparations.
Acute release of potassium in the urine is observed in the resolution of edema, the use of diuretics, with chronic nephritis accompanied by polyuria, with renal and diabetic acidosis. Elevated release of potassium in the urine is observed in malnutrition, fever and intoxication, diabetic coma. Hyperfunction of the adrenal cortex with increased production of aldosterone is accompanied by the most pronounced release of potassium, which was called "potassium diabetes."
The amount of potassium in the urine increases with renal hyperaminoaciduria, proximal tubular acidosis due to a defect in the proximal tubules, metabolic acidosis, hemorrhagic fever with renal syndrome, nephropathy, pyelonephritis, acute cauline necrosis, hyperaldosteronism, Cushing syndrome, Fanconi syndrome, alkalosis,administration of diuretics, etc.
Excretion of potassium in the urine decreases with glomerulonephritis, chronic pyelonephritis, extrarenal uremia, hyperaldosteronism( Addison's disease), acuidosis and hypoxia.
Determination of potassium and sodium in urine plays an important role in the differential diagnosis of prerenal and renal forms of arthritis. With prerenal form of OPN, the kidneys to reduce blood perfusion correspond to the enhanced retention of sodium and water. Sodium is saved by a low sodium content in the urine, as well as by an increase in the coefficient of K / N in the urine by 2-2.5 times( the norm is 0.2-0.6).The inverse ratio is observed in the renal form of OPN.
For the diagnosis of hyperkalemia due to aldosterone deficiency or resistance to it, as well as for non-specific reasons, a transanalian potassium gradient( TGG) is calculated - the indicator sec of
potassium distal nephron: TGC =( Km / Ks) x( Osms / Osm)where Km is the concentration of potassium in the urine;ะั - concentration of potassium in blood serum;Oms - osmolarity of blood serum;Osm - osmolarity of urine. Normally, THC is 6-12;if it is above 10, then the deficit of aldosterone or resistance to it can be excluded and look for the non-ulcerative cause of hyperkalemia;the THC value of less than 5 suggests an aldosterone deficiency or resistance to it. The value of THC above 10 indicates hypoaldosteronism, the absence of changes in THC indicates a defect( resistance) of the renal tubules. Patients with such a defect are resistant to any potassium-sparing diuretics.