Juxtaglomerular Apparatus +low BP & Ischaemia +Low NaCl
Renin-Angiotensin- Aldosterone System Ref:
Chronic Renal Disease Definition: Chronic renal disease (CRD) is a pathophysiologic process with multiple etiologies, resulting in the inexorable attrition of nephron number and function, and frequently leading to end-stage renal disease (ESRD). Irreversible deterioration in renal function (C.R.W.Edwards et al, 1998, pg.631) Ref: Harrison 15 th Ed.
Azotemia There is azotemia in chronic renal failure. Azotemia is the biochemical state in which there is an elevation of: 1. Blood urea nitrogen (BUN) and 2. Creatinine levels when there is a decreased glomerular filtration rate (GFR). Persistent azotemia gives rise to signs, symptoms and biochemical abnormalities, which is referred to as uremia.
Types of azotemia TypeFeature Pre-renal azotemia Due to hypoperfusion of kidneys. For e.g. in congestive heart failure, shock, hemorrhage, and dehydration. Post-renal azotemia Due to any obstruction to the urinary flow below the level of kidneys. [Note azotemia is not specific for chronic renal failure.]
Uremia Definition: Uremia is the clinical and laboratory syndrome, reflecting dysfunction of all organ systems as a result of untreated or under-treated acute or chronic renal failure. (CD-ROM 15th Harrison)
Pathogenesis Due to disturbances in water, electrolytes & acid-base balance. Accumulation of substances such as phosphate, parathyroid hormone, urea, creatinine, guanidine, phenols,& idoles.
End Stage Renal Disease (ESRD) In ESRD there is a degree of irreversible damage to the kidney and its function. The patient usually becomes dependent on renal replacement therapy (dialysis or transplantation) in order to avoid life- threatening uremia.
Clinical Features of Uraemia Anaemia Metabolic bone diseases(renal osteodystrophy) Neuropathy Myopathy Endocrine abnormalities Hypertension & atherosclerosis Acidosis Susceptibility to infection
Signs & Symptoms of Uraemia Vague-ill health Generalized weakness & lack of energy Breathlessness on exertion Anorexia Nausea & vomiting particularly in mornings Disordered intestinal motility Headaches Visual disturbances Pruritis Pallor Pigmentations Loss of libido
Laboratory Investigation Aim - Diagnosis and disease monitoring FBC - anaemia UEC – electrolyte imbalances, urea and nitrogen abnormalities Renal biopsy Others – Ca, phosphate, EPO, etc. Genetic & immunological studies - transplant
Chronic Renal Diseases - Causes The causes of chronic renal failure can be due to any disease process affecting the following structures: Glomeruli (glomerulonephritis) Tubules (reflex nephropathy) Interstitium (pyelonephritis, reflux nephropathy) Blood vessels (Hypertension)
Glomerular Diseases Types: Immune or Non-immune mediated injury
Immune mediated Glomerular Diseases Immune mechanism can be of antibody-associated injury. Two forms are known: Immune response resulting in injury due to deposition of soluble circulating antigen-antibody complexes in the glomeruli. Referred to as Circulating Immune complex injury. Immune response resulting injury due to antibodies reacting in situ within the glomerulus. Referred to as Cell Mediated Injury. Others may be due to cytotoxic antibodies directed against the glomerular cells.
Non-immune Mediated Glomerular Diseases 1. Metabolic glomerular injury. Diabetic nephropathy: the glomerular lesion is glomerulosclerosis whereby there is thickening of the glomeular basement membrane. 2. Hemodynamic glomerular injury. This is due to the high intra-glomerular pressure caused by systemic hypertension or local change in glomerular hemodynamics (glomerular hypertension). 3. Toxic glomerulopathies. The toxic verotoxic from the E.Coli is directly toxic to renal endothelium and induces hemolytic-uremic syndrome in patients with infective diarrhea caused by E.Coli.Verotoxic interacts with specific cell membrane receptor inducing thrombotic microangiopathy.
Non-immune Mediated Glomerular Diseases 4. Deposition disease. There is deposition of abnormal proteins in the glomeruli inducing inflammatory reaction or glomerulosclerosis. For e.g. amyloidosis, cryoglobulins, light and heavy chain deposition disease. 5. Infectious glomerulopathies. Infectious microorganisms can cause injury by: Direct infection of renal cell Elaboration of nephrotoxic e.g. E.Coli Intraglomerular deposition of immune complexes e.g. post-infectious glomerulonephritis. Providing chronic stimulus for amyloidosis. 6. Inherited glomerular diseases. A common e.g. is: Alports disease: Transmitted, as X-linked dominant trait. There is mutation in COL4A5 gene that encodes -5 chain of type IV collagen located on X-chromosome. The glomerular basement membrane (GBM) is affected.
The determinants of the severity of glomerular damage are 1. The nature of primary insult and secondary mediator system that evoke it. 2. The site of injury within the glomerulus. 3. The speed of onset, extend and intensity of disease.
Histological Types of GN Post-streptococcal GN Rapidly Progressive Glomerulonephritis Membranous GN Focal glomerulosclerosis Membranoproliferative GN
Post-streptococcal GN Normal glomerulusAcute proliferate GN Hypercellularity due to intercapillary leucocytes & proliferation of glomerular cells Ref: Robins Pathological Basis of Diseases, 6 th Ed. Fig 21.16
Rapidly Progressive (Crescentic) GN Ref:
Crescent GN Collapsed glomerular tufts Mass of crescent shaped proliferating cells & leucocytes Ref: Robins Pathological Basis of Diseases, 6 th Ed. Fig 21.17
Membranous GN Diffuse thickening of capillary wall without increase in number of cells Ref: Robins Pathological basis of Diseases, 6 th Ed. Fig Diagrammatic representation
Minimal Change Disease (Lipoid Nephrosis) Visceral epithelial cells show uniform and diffuse effacement of foot process Thin BN. No proliferation
Minimal Change Disease Normal glomerular tuft. No hypercellularity. Thin BM. Ref:
Focal Glomerular Sclerosis Sclerotic segment shows deposition of hyaline masses Lipid in sclerotic area (small vacuoles) Ref:www.med.niigata-u.ac.jp Foam cells
Membranoproliferative GN Ref: Robins Pathological Basis of Diseases, 6 th Ed. Fig Differentiation based on electron microscopy
Membranoproliferative GN Thickened in BM Proliferation of mesangial cells (glomerular cells) Leukocyte infiltration Ref: Robins Pathological Basis of Diseases, 6 th Ed. Fig 21.23
IgA Nephropathy (Berger Disease) IgA deposited within mesangium increasing its cellularity Immunofluorescence demonstrating positivity with antibody to IgA. Ref:
Focal Proliferative & Necrotising GN (Focal GN) Main differential diagnosis for Focal glomerulosclerosis as histological features very similar. Main lesions are predominantly proliferative. Focal necrosis & fibrin deposition often occur within lesions. Occur as part of a systemic disease (e.g. SLE), component of known glomerular disease (e.g. IgA nephropathy) or primary (cause unknown).
Blood Vessel Injury - Hypertension Atherosclerosis: Multifactorial The vascular injury is due to cholesterol- containing micro-emboli (atheroemboli) dislodged from atheromatous plaque in larger arteries. The micro-emboli occlude the small vessels in the kidney. Direct injury to blood vessel wall. It may result in renal artery stenosis and ischemic renal diseases.
Pathogenesis Of Disease Involving Blood Vessels Hypertension: The persistent exposure of renal circulation to intraluminal hypertension results in hyaline arteriosclerosis of the afferent arterioles and finally loss of function (nephrosclerosis). That is, Benign arteriolar nephrosclerosis: found in patients who are hypertensive for sometime with BP > 150/90 mmHg. Hypertension has not progressed to malignant form. Malignant arteriolar nephrosclerosis: found in patients who have long-standing benign hypertension and not known hypertensive. There is sudden elevation in BP (diastolic 130mmHg). There is accompanied papilledema, cardiac decompensation, CNS involvement, and progressive renal deterioration.