Functions of urinary system

• Volume regulation• Osmoregulatory function• Regulation of circulatory homeostasis (arterial pressure and

regional circulation)• Regulation of ion balance• Regulation of acidic balance• Excretory function• Metabolic function• Function of incretion (an active metabolite of vitamin D,

renin, angiotensin, erythropoetin)

Functional features of nephron in children

• Low glomerular filtration: hydrostatic pressure is lower, because arterial pressure is lower and owing to hypoproteinemia. In children filtering surface of capsule is less. Basal membrane is covered with a cubic or cylindrical epitheliumis till 2 years and in adults with a flat epithelium.

• Low secretion of alien high-molecular substances and reabsorbtion till 6 months : proximal and distal tubules in children is much shorter, and their lumen 2 times less, than in adults.

• Concentration function is low: Henle’s loop in children is short.• Reabsorbtion of glucose in children of early age makes only 25 %

from a level of the adult; glucosuria is possible. • Removing of excessive water: in newborn’s only 15 % during 2

hours, in adults 100%. • metabolic acidosis may develop, because in newborn removing

excess of acidic radicals 2 times slowly, than in adults.

Features of structure and function of urinary tract in children.

• Kidneys are posed relatively lower; it is possible to palpate a right kidney in children till 2 years.

• Kidneys have lobular structure; their cortical layer and connecting tissue are undeveloped.

• There is a close connection of lymphatic vessels of kidneys and an intestine.

• In children of early age the intrarenal locating of renal pelvis is observed.

• Muscular and elastic tissue of pelvis, ureters, bladder and urethra are bedly marked, mucous membrane has plentiful blood supply.

• Diameter of ureters is relative bigger; pleats of mucous are more expressed.

• The bladder is posed upper, easily palpated. Capacity of a bladder in newborns is 30 ml, on 1 year - 50 ml, on 10 years – 200 ml, in adults – 500 ml.

• The daily quantity of urine in 1 year – 600 ml, each next year till 10 years enlarges on 100 ml: V = 600 + 100 (n-1)

Dysuria• Enuresis – involuntary urination• Pollakiuria – frequent urination, daily quantity of urine is not

increased. Stranguria – a painful and difficult urination.• Polyuria – daily quantity of urine is 2 times more then the norm:

physiological in removing of edema, using of diuretics, increasing volume of taking water, pathological in acute and chronic renal failure, diabetes.

• Olyguria - decreasing of amount of daily urine 2 and more times in dehydratation, fever conditions and renal failure. Anuria – absence of urine, when its daily volume less than 1/15 of norm. In acute renal failure olygoanuria arise in the beginning of disease, at chronic – on final stage of disease.

• Ischuria – acute delay of urine in a bladder that can be caused by obstruction of urethra or have reflex character after operation, traumas.

Edema• Renal edema frequently connects with hypoproteinemia

and increased hydrophilic properties of tissues. • In the beginning edemas of renal parentage appear in the

morning and on the face, then can be distributed to a trunk, extremities. Ascites, hydropericardia, hydrothorax and anasarca can be present.

• For diagnostic of latent edemas test McClure – Aldridge can be used: 0.2 ml of physiological solution is introduced intracutaneously in a forearm. The blister forms and resolves in norm in adults in 40 minutes, in children of the first year of life in 20 minutes. Decrease of time of resorption of a blister testifies about presence of latent edemas, encreasing of body mass, decreasing of diuresis also testifies about latent edemas.

Symptoms

• Pallor is characteristic for renal diseases. It may be caused by vasospasm, compression of vessels because of presence of edemas, and also by anemia.

• Arterial hypertension in children has more often renal parentage. Rising of arterial pressure is accompanied with paleness and a headache. Thus shift of the left border of heart, intensifying of 1st tone on apex, accent of the second tone on aorta are observed. Rising of arterial pressure is typical of acute and chronic nephritises, anomalies of renal arteries, acute and chronic renal failure.

Urinary syndromeHematuria

• 0-1 erythrocytes in urinary sediment per microscopic field are in norm. According to Nechiporenko’s test - no more then 1000 erythrocytes in 1 ml of urine .

• Microscopic hematuria and macrohematuria (urine is from light pink to dark red)

• Hematuria is characteristic for nephritises, renal dysplasia and trauma of kidney. The suprarenal reasons of hematuria are coagulopathies and trombocytopathies. The subrenal hematuria takes place in urolithiasis, cystitis and urethritis.

Urinary syndrome• Leukocyturia. In norm in routine urinalysis in mycroscopic field no

more than 3 leucocytes in boys and no more than 6 leucocytes in girls. According to Nechiporenko in boys up to 2000 leucocytes, in girls up to 4000 in 1 ml of urine . If leucocytes cover all fields, speak about pyuria. Leukocyturia and a pyuria are characteristic for inflammatory diseases of urinary tract.

• Cylindruria. Cylinders – protein casts of renal tubules. In norm hyaline cylinders can be determined only. Hyaline casts more than 2 in m.f. (or more than 250 according to Nechiporenko), granular and waxy casts in any quantity speak about organic renal pathology

• Epihteliyria specifies hypovitaminosis A or inflammatory disease of urinary tract. In norm flat epithelium only determined and no more then 2 cells p/v, cubic and cylindrical epithelium is an attribute of pathology

Urinary syndrome• Proteinuria. urine contents no more than 0.033

g/l of protein (traces of protein) and daily proteinuria is no more than 30 mg in norm. Proteinuria connects with violation of glomerular filtration more often (glomerulonephritis), less often – with tubular reabsorbtion (interstitial nephritis). In norm orthostatic proteinuria can be present.

• Bacteriuria. In norm urine is sterile. The main pathogen is Esherihia coli. Diagnostic colony counts in 1 ml of urine makes 105 and higher.

Functional condition of kidneys on Zymnitsky’s test

• it is necessary to collect 8 portions of urine each 3 hours: 6-9, 9-12, 12-15, 15-18, 18-21, 21-24, 0-3, 3-6. The first 4 portions are daytime diuresis, the last 4 – night diuresis. In every portion determine amount and specific gravity (relative density) of urine.

• Estimation of the analysis. Diuresis. In norm it makes 600+100 (n-1) till 10 years, then 1.5-2 liters per a day.

• Ratio of night and daytime diuresis. If more than half quantity of urine excrets at night, speak about nocturia

• Specific gravity. If fluctuations of SG of urine is not less than 7-10 units, concentration ability of kidneys is not broken. Hyposthenuria – SG is lower then 1008, the isosthenuria – SG of urine is peer to relative density of a blood plasma: 1008-1010, fluctuations 1010-1030 – normosthenuria, higher then 1030 – hyperstenuria. Hypo- and an isosthenuria are observed in renal failure, diabetes insipidus, hyperstenuria – in diabetes mellitus, salt diathesis

Glomerulonephritis• - bilateral diffuse renal disease. There are 2 basic

mechanisms of defeat of basal membrane of glomeruli – formation of antibodies against basal membrane and bracing on it of immune complexes. Clinical displays are characterized:

• occurrence of signs of intoxication – rising of temperature, headache, poor appetite, weakness, pallor

• bilateral back pain • rising of arterial pressure• edema• urinary syndrome: hematuria, proteinuria, insignificant

leukocyturia is possible

Pyelonephritis• - inflammatory renal disease. Process can be both

unilateral, and bilateral. Penetration of microbes to renal parenhima is promoted by obstruction of urine flow at various levels of urinary tract – anomaly of a structure, a nephroptosis.

• At a clinical picture of disease occurrence of signs of intoxication – rising of temperature, headache, poor appetite, weakness, pallor

• bilateral or unilateral back pain• In urinary sediment combination of leukocyturia and

bacteriuria. The insignificant hematuria and proteinuria are possible.

Acute renal failure• The basic mechanism of acute renal failure is the ischemia of mainly

cortical nephrons. The reasons can be prerenal, renal and postrenal.

- Prerenal: dehydratation, shock, collapse and hemolytic disease. - Renal: acute renal diseases, renal toxins. - Postrenal: obstruction of urinary tract. • The basic symptoms of acute renal failure are olygo- and anuria.

The headache, thirst, nausea, vomiting, convulsions are marked. The mass of body quickly grows, the edemas appear. There is dermal itch, anorexia, dyssomnia.

• Azotemia, hyperkalemia, hypocalcemia, hypoproteinemia are observed. At favorable current in 3-4 days comes a stage of polyuria, edemas decrease, development of hypokalemia is possible.

Chronic renal failure

• Decrease of mass of working nephrons up to 25 %.• The reasons are chronic progressive renal diseases• Symptoms: thirst and polyuria, anemia, nocturia,

hyposthenuria or isosthenuria, decreasing of a level of electrolits in a blood. Patients are sleepy; headache, anorexia, dryness in a mouth, and weak contractions of muscles as result of a hypocalcemia mark.

• Later the uremia and olygoanuria with a clinical picture of hypervolemia, edema of lungs, of brain develops. In a blood the hypocalcemia, and hyperkalemia marks.