Conventional site for taking biopsy In secondary amyloidosis is?

The amyloidoses are a group of acquired and hereditary disorders characterised by extracellular deposition of insoluble proteins . These complex deposits consist of fibrils of the specific protein involved, linked to glycosaminoglycans, proteoglycans and serum amyloid P (SAP). Protein accumulation may be localised or systemic, and the clinical manifestations depend upon the organ(s) affected. The diagnosis of amyloidosis should be considered in all cases of unexplained nephrotic syndrome ,cardiomyopathy and peripheral neuropathy. Diagnosis The diagnosis is established by biopsy, which may be of an affected organ, rectum or subcutaneous fat. The pathognomonic histological feature is apple-green birefringence of amyloid deposits when stained with Congo red dye and viewed under polarised light. Immunohistochemical staining can identify the type of amyloid fibril present. Quantitative scintigraphy with radio-labelled SAP is a valuable tool in determining the overall load and distribution of amyloid deposits DAVIDSON&;S 22nd EDITION;PAGE NO 86