INTRODUCTION TO RENAL DISEASES
الدكتور خلدون ذنون- كلية طب نينوى- المرحلة الرابعةObjectives
The student is supposed to understand the following:1. Basic physiology and anatomy of the urinary system.
2. Cardinal features of the upper and lower urinary tract diseases.
3. The abnormal signs which are displayed by patients having various
diseases of the kidney, ureter and lower urinary tract.
PHYSIOLOGY OF THE KIDNEYS
Water&electrolytes balance (tubular function, renin-angiotensin-aldosterone system).GFR 120 ml/min. 170 L/day. Absorption& excretion.Acid-base balance.
Excretion of waste products e.g urea, toxins, drugs.
Erythropoietin, by interstitial peritubular cells, due to hypoxia
Hydroxylates 25-hydroxycholecalciferol to 1-25 HCC.
Renin secretion by juxtaglomerular apparatus in response to low afferent arteriolar pressure, sympathetic stimulation&changes of fluid composition in DCT at macula densa. Renin generates angiotensin 11 which constricts efferent arteriole,(glomerular filtration pressure, systemic vasoconstriction &(aldosterone. Renal ischaemia( systemic hypertension.
FUNCTIONAL ANATOMY
Adult kidney : 11-14cm(3 lumbar vertebral bodies),retroperit- oneal, right kidney lower, move up & down with respiration.1 million nephron in each kidney,receive 25% of cardiac output, Renal artery( intralobular branches( glom.afferent arteriole. Variation in caliber of afferent &efferent arteriole control filtration pressure at glomerular basement membrane which maintain GFR despite variation of systemic B.P&renal perfusion pressure. Angiotensin 11 control tone of efferent arteriole which supply distal nephron&medulla.
Glomerulus contains 3 main cell types : epithelial cells, endothel- ial cells & mesangial cells.GBM is produced by fusion of BM of epithelial & endothelial cells. endothelial cells contain pores (fenestrae).Epithelial cells (podocytes) have long foot processes which interdigitate with those of adjacent epithelial Cells.
Epithelial cells are non-dividing cells, their death lead to scar formation. normal filtration barrier requires integrity of these cells&their B.M.(size limit to glom.filtration).Albumin molecular Size = 67 kDa unable to pass.Those ( 20 kDa pass freely. Between 20-67 kDa there is a gradient of clearances related to shape &charge of molecules i.e Anionic proteins are less freely filtered than cationic proteins. Little lipid is filtered.
Mesangial cells simulates vascular smooth muscle cells i.e contractility & some macrophage like properties. Macrophages are also present.
Tubular cells: polarised, proximal tubular cells have brush border, function at their basal & apical surfaces.Interstitial cells between tubules(less well understood).
Erythropoietin: produced by fibroblast-like cells in the cortex. Lipid laden interstitial cells in the medulla produce prostaglandins.
Collecting system&lower urinary tract.
Continence mechanisms
Parasympathetic nerves : S2-S4 supply the detrusor muscle, contraction of which result in micturition.Sympathetic nerves: T10-L2 supply detrusor m.&bladder neck. Stimulation of B-adrenoceptors result in detrusor relaxation,while α-adrenoceptors stimulation causes bladder neck contraction.
Distal sphincter mechanism: S2-S4, somatic motor fibers through pelvic plexus or pudendal nerve.
Afferent sensory impulses pass to the cerebral cortex which suppresses detrusor contraction.
The micturition cycle A-storage(filling)phase
Detrusor m. compliance is high, bladder fills easily with out arise in intravesical pressure, as volume of urine ( stretch receptors cause reflex bladder relaxation & ( sphincter tone, at 75% of bladder capacity there is adesire to void, with further ( in capacity the next desire to void will occur.
B-voiding (micturition)phase
Act of micturition is initiated by voluntary & then by reflex relaxation of the pelvic floor & distal sphincter, followed by reflex detrusor contraction, the process is under the control of pontine micturition centre, intra vesical pressure remains greater than urethral pressure until the bladder is empty.
CARDINAL SYMPTOMS OF KIDNEY&URINARY TRACT DISEASES
Lower urinary tractInfection : Dysuria, frequency, urgency.
Bladder outflow obstruction: impaired urine flow, hesitancy, dribbling of urine, incomplete emptying of bladder.
Sphincter or bladder wall dysfunction, prostatic urethral obstruction( urinary retention, incontinence,enuresis.
Upper urinary tract
Loin pain & tenderness e.g pyelonephritis, glomerulonephritis, renal infarction, hydronephrosis.
Renal or ureteric colic: acute obstruction of renal pelvir& ureter by calculus or blood clot.
Abnormal urine volume : anuria, oliguria occur in acute renal failure & urinary tract obstruction. Polyuria or nocturia : failure of the kidney to concentrate urine e.g diabetes insipidus, chronic renal failure.
Uraemia
Diseases of the testis & epididymis Local swelling, pain & tenderness e.g orchitis,testicular torsion .
CLINICAL EXAMINATION
( Observation : in CRF (tiredness,(respiratory rate&depth(acidosis), pallor, yellow complexion, bruising, excoriation of
pruritus,(skin turgor in fluid depletion.
Hands (brown line pigmentation).
Blood pressure . JVP . Fundoscopy
Lungs : crepitation in fluid overload.
Heart : added sounds in fluid overload, pericardial friction rub.
Abdomen: bimanual kidney palpation, transplanted kidney, bladder distension, arterial bruit, inspect male genitalia, rectal exam.for prostate(BPH (smooth®ular) cancer:enlarged, hard & irregular.
Sacral & ankle edema.
Peripheral neuropathy
Urine exam.( protein; glomerular bleeding in Glomerulonephritis ( RBC cast & dysmorphic red cells including acanthocytes (tear drop forms), lower UT bleeding( normal RBC shape. Hyaline cast is a normal finding .
Diseases of kidney & UT are often clinically silent, diagnosis depends on biochemical testing & urine analysis. Presentation may be nonspecific.