A variety of diseases occur in the kidneys and urinary tract. According to aetiology and location, they may be classified as: glomerular disease, tubulo-interstitial disorder, vascular damage, obstructive disease, congenital disease, tumor and so on. Glomerular disease is the most importamt and common.
Minimal change disease affects all ages, but is much more common and is the commonest cause of nephrotic syndrome in children. The pathological feature is that no significant abnormalities can be detected in glomeruli by light microscopy and immunofluorescence techniques. The loss of epithelial foot processes is evident only by electron microscopy. Tubular epithelium may show accumulation of lipid, giving rise to the alternative name of lipoid nephrosis. Nephrotic syndrome responsive to steroid therapy is the classical presentation. The prognosis in children is good.
Membranous nephropathy affects all age groups, but adults are affected more commonly.Males are affected more than females. Capillary wall thickening without proliferation or inflammation is present in all glomeruli. Light microscopy reveals characteristic spikes on the thickened capillary wall by PASM staining. Electron microscopy reveals the immune complexes deposited on the epithelial side of the basement membrane and new basement membrane around immune complex deposits. There are four pathological stages. The clinical feature is heavy proteinuria or nephrotic syndrome. Membranous nephropathy is one of the most important causes of the nephrotic syndrome in adults. About 50% of the patients develop chronic renal failure over a period of about 10 years.
Endocapillary proliferative glomerulonephritis is caused by the deposition of immune complexes in glomeruli, with a preceding infection, especially β- haemolytic streptococcal infection. Light microscopy reveals that all of the glomeruli are hypercellular and the increase in cellularity is due to the proliferation and swelling of mesangial and endothelial cells, together with a variable infiltration of polymorphonuclear leucocytes. Ultrastructurally, electron dense deposits on the side of epithelial cells of the basement membrane, referred to as humps, are the main feature. Clinical manifestation is acute nephritic syndrome.
Membranoproliferative glomerulonephritis(MPGN) is a diffuse , global pattern of glomerulonephritis with features of both proliferation and membrane thickening. Primary MPGN is subdivided into two types, according to clinical and pathological features. Type Ⅰ MPGN is characterized by subepithelial immune complex deposits, proliferation of mesangial cells and reduplication of the basement membrane. The feature of Type Ⅱ MPGN is dense continuous linear deposition of C3 by immunofluorescence technique. Ultrastructurally, large electron-dense ribbon-like deposits are seen in the basement membrane and the alternative name –dense deposit disease- is preferable. The two types have many clinical similarities and majority of patients present with nephrotic syndrome, but some have haematuria.
Crescentic glomerulonephritis is a manifestation of severe glomerular injury characterized by the presence of crescents composed of epithelial cells and macrophages within the Bowman’s space. The crescents are seen in the majority of the glomeruli and eventually compress the glomeruli, resulting in glomerular ischaemia. The salient clinical feature is rapidly progressive renal failure. The prognosis is poor.
IgA disease is one of the common causes of renal failure throughout the world. There is a geographical localization, with the highest incidence in the Asia-Pacific area. Serum IgA level is increased and IgA with C3 is deposited in the mesangium and the junction between the mesangium and basement membrane. A wide spectrum of changes is seen histologically.
Sclerosing glomerulonephritis may be caused by many types of glomerular diseases at their end-stage. Histologically, there is diffuse glomerular hyalinization with tubular atrophy and interstitial fibrosis. Affected kidneys are small and contracted, with granular appearance of external surface. The patients present with chronic renal failure.