From Big Medical Encyclopedia

DIURESIS (Greek dia-through, through + uresis an urination; synonym urination) — process of education and release of urine.

Total quantity of the urine emitted by the person in days fluctuates from 1000 to 1800 ml (0,7 — 1,2 ml in 1 min.), decreasing at restriction of ingress of water and increasing at reception of large amounts of liquid. The minimum size D. is defined by an amount of water and the salts necessary for maintenance of standard osmotic pressure of a blood plasma. At restriction of ingress of water and a protein-free diet of D. decreases to 300 ml a day. The amount of urine which is marked out by the healthy person per day — daily D. — considerably fluctuates depending on conditions of food, physical. loadings, temperature and humidity of the environment and other factors. On average the amount of water, entered with food and formed in an organism in the course of metabolism, makes apprx. 1000 ml (at combustion of 100 g of fat in an organism 100 ml of water, 100 g of protein — 40 ml, 100 g of carbohydrates — 60 ml of water are formed); apprx. 1500 ml comes to an organism in the form of liquids. In a temperate climate at usual conditions of food and moderate physical. the healthy person allocates to loading through skin on average 500 ml, through lungs — 400 ml, with a stake — 100 ml and with urine — 1500 ml of water, and 3/4 daily D. fall on day time. An essential role in daily D.'s regulation is played biological rhythms (see). Change of conditions influences size D. So, in the conditions of the desert with then it can be allocated up to 28 l of liquid. At the same time sharply falls, ud. the weight of urine can increase to 1,050, and the content of urea in it instead of usual of 1 — 2% increases to 6%. Moderate physical. work strengthens D.; at heavy physical. to D.'s loading decreases owing to reduction of a renal blood-groove and decrease in glomerular filtering. At disorders plentiful D. (so-called urina spastica), and sometimes and emotional is noted oliguria (see).

The volume of the excreted urine is a difference between amount of the liquid filtered in balls and which is soaked up back in tubules and the fornikalny device of kidneys. In proximal department of nephron as a result of the return absorption (reabsorption) the volume of urine decreases without essential change of its osmotic pressure. In distal departments of nephrons and collective tubules thanks to a separate reabsorption of water and osmotically active agents urine concentrates. At the same time the size of a reabsorption constantly changes, providing maintenance of osmolarity of internal environment of an organism.

Size D. depends on the regulatory systems protecting the volume and osmotic pressure of liquids of internal environment of an organism. Three mechanisms exert impact on amount of the urine which is emitted at change of volume of blood and an intercellular lymph: reflex, reninangiotenzinny and physical and chemical. The first two influence D. by means of change of a reabsorption of sodium and the related water, the last affects directly current of water and the salts dissolved in it.

Reflex regulation is carried out thanks to excitement of the volyumoretseptor localized in the right and left auricles on the course of carotid arteries and in a sinocarotid zone. On the wandering and sinocarotid nerves impulses come to the Hypothalamic centers, oppressing secretion vasopressin (see) and stimulating release of the natriuretic hormone suppressing a reabsorption of sodium in proximal tubules of kidneys. At increase in volume of blood secretion of hormone increases, sodium is late in a gleam of a tubule and connects an equivalent amount of water. The volume of canalicular liquid increases, and D. increases. Reduction of volume of blood causes opposite processes: secretion of vasopressin increases, the reabsorption of sodium and water increases, D. decreases, and urine concentrates a little.

Renin-angiotenzinny the mechanism of regulation of D. is closely connected with the ABP level. In walls of the bringing vessels of renal balls the cells cosecreting a renin which are a part of the juxtaglomerular device are localized. At increase in a renal blood-groove and stretching of walls of vessels secretion is suppressed renin (see), activity in blood of angiotensin II decreases (see. Angiotenzin ) also secretion decreases Aldosteronum (see) bark of adrenal glands. At reduction of a blood-groove secretion of a renin, a caption of angiotensin II and allocation of Aldosteronum increases. Under the influence of Aldosteronum in distal department of nephron the reabsorption of sodium and related water changes. At increase in volume of blood the reabsorption decreases and D. increases, at reduction the reabsorption increases and D. decreases.

Change of oncotic pressure of blood in peritubulyarny capillaries exerts impact on size D. when a large amount of protein-free liquid is entered into an organism. Decrease in oncotic pressure reduces a reabsorption of water and sodium through a wall of a proximal tubule and increases D.; increase in oncotic pressure strengthens a reabsorption of water and sodium, reduces.

Osmotic pressure of liquids of internal environment influences D. by turning on of the concentration mechanism localized in distal department of nephron and collective tubules. Change of osmotic pressure of intersticial liquid is perceived by the peripheral fabric and central osmoreceptors (a supraoptic kernel of a hypothalamus) having communication with a neurohypophysis (see. Hypophysis ). At increase in osmotic pressure secretion of vasopressin (hormone of a neurohypophysis) — the main regulator of a reabsorption of water increases in collective renal tubules. Under the influence of hormone permeability of their walls increases, water passes from a gleam of tubules into intersticial tissue of a kidney, urine concentrates and D. decreases. At reduction of osmotic pressure secretion of vasopressin is oppressed, permeability of collective tubules for water decreases, the reabsorption of water decreases and D. increases.

At the newborn child D. makes a day 200 ml on 1 sq.m of a body surface; by the end of the first month its size reaches 2500 ml on 1 sq.m a day and continues to increase to age of 2 — 4 months. The polyuria is a consequence of the weak concentrating ability of kidneys, and also feeding habits of newborns.

Disturbances of a diuresis

At various diseases size D. considerably fluctuates from sharp reduction — oliguria (see) and even complete cessation of an uropoiesis — anury (see) to polyurias (see), reaching sometimes 20 — 30 l and more per day. The polyuria usually is followed by the speeded-up urination — pollakiuria (see). Its qualitative changes are quite often combined with quantitative changes of D. In clinic the hyposthenuria, i.e. release of urine constantly low ud has special value. weight. In an origin of a hyposthenuria disturbance of the processes of concoction of urine depending on a condition of the canalicular device and an interstitium of a kidney and also from the increased concentration of osmotically active agents in primary urine which interfere with a reabsorption of water matters. Similarly speaks and Isosthenuria (see), at a cut ud. the weight of urine remains equal ud. to the weight of the blood serum exempted from protein.

The most considerable changes of D. are observed at diseases of kidneys, endocrine and cardiovascular systems, and also at other patol, states.

At diseases of kidneys size D. fluctuates very considerably — from an oliguria and an anury, napr, in an initial stage acute glomerulonephritis (see), to a polyuria — in an initial stage of a renal failure at hron, a glomerulonephritis. At an acute glomerulonephritis D.'s reduction is caused both by decrease in glomerular filtering, and strengthening of a canalicular reabsorption. Ud. the weight of urine in an initial stage of an acute glomerulonephritis is increased that allows to speak about giperstenurichesky type D. The heavy disturbances of glomerular filtering connected with big changes of balls owing to an inflammation can lead also to an anury that, however, is observed not often. At an acute glomerulonephritis and far come stage of adenoma of a prostate the nocturia — night D.'s dominance over day can be observed; the nocturia is usually combined with a cordial decompensation that allows to speak about a «cordial» nocturia in this case. At permission of an acute glomerulonephritis the polyuria with a bystry convergence of hypostases is observed.

At hron, a glomerulonephritis the oliguria is observed usually at an aggravation in a rise period of hypostases (see. Swelled ). The oliguria is especially persistent at nephrotic syndrome (see). It concerns not only hron, a glomerulonephritis, but also other diseases which are followed by damage of kidneys and a nephrotic syndrome: amyloidosis, system lupus erythematosus, other system vasculites, diabetic glomerulosclerosis. At the same diseases when the granular kidney develops, the polyuria which is combined with an isosthenuria or a hyposthenuria is observed.

The Gipostenurichesky type D. can be observed also at other diseases of kidneys — a nefroangioskleroza (see. Nephrosclerosis ), pyelonephritis (see), hydronephrosis (see), etc. In all these cases the gipostenurichesky type D. demonstrates considerable disturbances of renal processes and danger of development of a renal failure. A little differently D.'s disturbances at a sponge kidney proceed, at a cut mechanisms of concoction of urine are broken congenitally and D.'s disturbance (a hyposthenuria with a polyuria) a long time remains the only symptom.

At a hydronephrosis alternation of an oliguria and polyuria can be observed. D.'s increase is observed at canalicular damages of kidneys — Albright's syndrome (see. Laytvuda — Albright a syndrome ), at a renal glucosuria and other genetically caused disturbances of functions of tubules.

The acute renal failure, by whatever reason it was caused (e.g., disturbance of renal haemo circulation at shock, dehydration and owing to other reasons, poisoning with nefrotropny poisons, damage of kidneys at some infections), in most cases begins with falling of. At the same time ud. the weight of urine remains low; in further D. it is recovered, and the oliguria is replaced by a polyuria. The polyuria remains also in the period of recovery; concentration ability of kidneys and D.'s normalization are recovered gradually, several months later and more.

At hron, a renal failure in the course of conservative treatment D. Poliuriya's increase is observed is followed by reduction of a reabsorption not only water, but also urea and other subjects to removal of substances and can be considered as some compensatory mechanism. In this case use of diuretics for the purpose of

D. V increase of an end-stage hron is justified, a renal failure of D. decreases and it is essential to increase it diuretics it is not possible. The patient is transferred to treatment hemodialysis (see). A hemodialysis, reducing concentration of urea in plasma (therefore, and in a glomerular filtrate), is followed by some decrease D.

Otsenka of size D. is extremely important during the overseeing by activity of the replaced kidney. Quite often directly after change the transplantirovanny kidney passes a stage of an acute renal failure, edges is followed by D.'s disturbances from an anury and an oliguria to a polyuria. Overseeing of D. is important also after recovery of function of a transplant; sharp reduction of D. usually demonstrates the beginning crisis of rejection (see. Renal transplantation ).

D.'s changes at diseases of endocrine system have essential value. Especially expressed D.'s changes are observed at not diabetes mellitus, at Krom the polyuria is combined with pollakiuria (see) and a hyposthenuria it is also connected with decrease in products a back share of a hypophysis of antidiuretic hormone and disturbance of a reabsorption of water in distal department of nephron. The polyuria is characteristic also of a diabetes mellitus (see. diabetes mellitus ). Urine at it usually high specific weight owing to high content of sugar in it. Glucose works as osmotic diuretic and causes increase in. Owing to a diabetes mellitus develop glomerulosclerosis diabetic (see) or pyelonephritis (see), hyposthenuria. Considerable dominance of day D. is characteristic of a diabetes mellitus that is connected with day meal and bigger day hyperglycemia (see).

D.'s change in the form of a polyuria is characteristic also for hyperparathyreosis (see) is also one of early and most constant symptoms of this disease. Genesis of a polyuria at a hyperparathyreosis is not quite clear. It is probable that the increased release of calcium with urine (to 1500 mg instead of usual 200 — 300 mg) which is usually accompanying this disease influences function of distal department of nephron, breaking a reabsorption of water. At the same time there are data that parathormone is capable to cause the increased allocation by kidneys of water.

The hypercalcuria and a hyperphosphaturia at a hyperparathyreosis sometimes bring to to a nephrocalcinosis (see) and to formation of stones of kidneys which break functions of kidneys and.

D.'s change at other endocrine diseases is less characteristic.

Considerable changes of D. accompany heart failure (see). They are connected, on the one hand, with reduction of a renal blood-groove, a spasm of the bringing vessels of balls and reduction of glomerular filtering, and on the other hand — with strengthening of a canalicular reabsorption of water owing to secondary hyper aldosteronism (see) and increases in a reabsorption of sodium in tubules. Thus, at heart failure of disturbance of D. are expressed in an oliguria and increase ud. weight of urine. At the same time the nocturia is noted. Hard proceeding infectious diseases as a result of difficult neuroendocrinal shifts in the acute period are followed by an oliguria with a high ud. then during recovery is replaced the weight of urine, edge by a polyuria and a hyposthenuria.

Along with these causes of infringement of D. also nervnoreflektorny disturbances D. Tak are observed, in space flight in the conditions of D.'s weightlessness increases. At astronauts the polyuria was observed (D. increases for 25 — 75%); after return to D.'s Earth was returned to datum level. The polyuria probably arises reflex on redistribution of blood in an organism in the conditions of zero gravity and disturbance of normal functioning of volyumoretseptor.

D.'s disturbances can arise and for the second time owing to excitement of the center of thirst or polydipsias (see) at a number of diseases.

D.'s assessment in clinic is closely connected with studying of renal processes (a renal blood-groove, glomerular filtering, a canalicular reabsorption, canalicular secretion, concentration ability of kidneys etc.). So, during the conducting eurysynusic tests of Zimnitsky (see. Zimnitsky test ) and Reberg (see. Kidneys, methods of a research ) assessment of the received results depends on size D.

See also Clearance , Kidneys .

Bibliography: Ginetsinsky A. G. Physiological mechanisms of water-salt balance, M. — L., 1963, bibliogr.; Yu. V. Fiziologiya of a kidney, is ground by L., 1974; Fundamentals of nephrology, under the editorship of E. M. Tareeva, t. 1 — 2, M., 1972; Kidneys, under the editorship of F. K. Mostofi and D.E. Smith, lane with English, M., 1972; T a p e e in E. M. Nephrites, M., 1958, bibliogr.; De W and-dener of H. E. The kidney, L., 1967; D u t z H. u. M e b e 1 M. Die chronische Niereninsuffizienz, Lpz., 1973; Gilmore J. P. Renal physiology, Baltimore, 1972; Handbook of physiology, Sect. 8, Renal physiology, ed. by J. Orloff a. R. W. Berliner, Washington, 1973.

Ya. D. Finkinstein; V. V. Sura, H. A. Mukhin (pathology).