Functions of the kidney:

Transcription

1 Diseases of renal system : Normal anatomy of renal system : Each human adult kidney weighs about 150 gm, the ureter enters the kidney at the hilum, it dilates into a funnel-shaped cavity, the pelvis, from which derive two or three main branches, the major calyces; each of these subdivides again into three or four minor calyces. On the cut surface, the kidney is made up of a cortex and a medulla. The medulla consists of renal pyramids, the apices of which are called papillae, each related to a calyx. Cortical tissue extends into spaces between adjacent pyramids as the renal columns. From the standpoint of its diseases, the kidney can be divided into four components: blood vessels, glomeruli, tubules, and interstitium. Functions of the kidney: 1. Excretion of waste products of metabolism. 2. Regulation of body water and salt. 3. Maintenance of acid base balance. 4. Secretion of various hormones as erythropoietin 1

2 Pathology: Diseases of the kidney are as complex as its structure, but their study is facilitated by dividing them into those that affect the four basic morphologic components: glomeruli, tubules, interstitium, and blood vessels. Clinical Manifestations of Renal Diseases: Azotæmia; is a biochemical abnormality that refers to an elevation of blood urea nitrogen (BUN) and Creatinine levels and is largely related to a decreased glomerular filtration rate (GFR). It could be caused by prerenal, renal and postrenal disorders. When azotemia becomes associated with a constellation of clinical signs and symptoms and biochemical abnormalities, it is termed uremia. Uremia is characterized not only by failure of renal excretory function, but also by a host of metabolic and endocrine alterations resulting from renal damage. the clinical presentations of renal disease / Major Renal Syndromes 1. Acute nephritic syndrome is a glomerular syndrome dominated by the acute onset of usually grossly visible hematuria (red blood cells in urine), mild to moderate proteinuria, and hypertension. 2. The nephrotic syndrome is characterized by heavy proteinuria (more than 3.5 gm/day), hypoalbuminemia, severe edema, hyperlipidemia, and lipiduria (lipid in the urine). 3. Asymptomatic hematuria or proteinuria, or a combination of these two, is usually a manifestation of subtle or mild glomerular abnormalities. 4. Acute renal failure is dominated by oliguria or anuria (reduced or no urine flow), with recent onset of azotemia. 5. Chronic renal failure, characterized by prolonged symptoms and signs of uremia, 2

3 6. Renal tubular defects are dominated by polyuria (excessive urine formation), nocturia, and electrolyte disorders (e.g., metabolic acidosis). They are the result of either diseases that directly affect tubular structure (e.g., medullary cystic disease) or defects in specific tubular functions. The latter can be inherited (e.g., familial nephrogenic diabetes, cystinuria, renal tubular acidosis) or acquired (e.g., lead poisoning). 7. Urinary tract infection is characterized by bacteriuria and pyuria (bacteria and leukocytes in the urine). The infection may be symptomatic or asymptomatic, and it may affect the kidney (pyelonephritis) or the bladder (cystitis) only. 8. Nephrolithiasis (renal stone) is manifested by renal colic, hematuria, and recurrent stone formation. 9. Urinary tract obstruction and renal tumors represent specific anatomic lesions with often varied clinical manifestations Congenital Anomalies: Agenesis of the Kidney. Total bilateral agenesis, which is incompatible with life, is usually encountered in stillborn infants. Unilateral agenesis is an uncommon anomaly that is compatible with normal life if no other abnormalities exist. Hypoplasia. Renal hypoplasia refers to failure of the kidneys to develop to a normal size. This anomaly may occur bilaterally, resulting in renal failure in early childhood, but it is more commonly encountered as a unilateral defect. Ectopic Kidneys abnormal position usually low level. Horseshoe Kidneys. Fusion of the upper or lower poles of the kidneys produces a horseshoe-shaped structure. 3

4 Glomerular diseases : The glomerular capillary wall is the filtering membrane and consists of the following structures: A. thin layer of fenestrated endothelial cells, B. glomerular basement membrane (GBM) with a thick electron-dense central layer, the lamina densa, and thinner electron-lucent peripheral layers, the lamina rara interna and lamina rara externa. The GBM consists of collagen (mostly type IV), laminin. C. The visceral epithelial cells (podocytes), are structurally complex cells that possess interdigitating processes embedded in and adherent to the lamina rara externa of the basement membrane. D. The entire glomerular tuft is supported by mesangial cells lying between the capillaries. Basement membrane-like mesangial matrix forms a meshwork through which the mesangial cells are centered. 4

5 5