Glomerulonephropathies


Amyloidosis

Introduction:

Amyloidosis is a progressive disease that often leads to chronic renal failure. It is mostly seen in dogs, and is rare in cats. Glomeruli are the most common site for amyloid deposition; however, amyloid is often deposited within the medullary interstitium in cats. Renal amyloidosis may occur in association with other diseases, or may be idiopathic. A hereditary predisposition for amyloidosis has been reported in Abyssinian cats and Chinese Shar Pei dogs.

Pathophysiology:

Amyloidosis is usually associated with an underlying inflammatory or neoplastic process, but in some cases, no underlying cause is found. Amyloid is deposited extracellularly within several organs, not just the kidneys. In dogs, amyloid deposits usually are within the glomerlui and leads to proteinuria and nephrotic syndrome.  In cats, amyloid deposits are usually found in the medullary interstitium, but may occur within the glomeruli. The systemic reactive form of amyloid contain the amyloid protein AA, which is a fragment of the acute phase protein serum amyloid A protein that is produced by hepatocytes in response to injury. Glomerulary amyloidosis is a protein-losing nephropathy that causes proteinuria and uremia, and may result in the nephrotic syndrome. Renal biopsies are needed to differentiate renal amyloidosis from immune complex-mediated glomerulonephritis (ICGN).

Gross Pathology:

pale tan accumulation of amyloid Kidneys are pale, enlarged, with large tan deposits of amyloid. The amyloid within the glomeruli may appear as tan dots on the capsular and cut surfaces.

http://www.vetmed.wsu.edu/medsci520/inflamm.htm

 WSU/UI Medical Science 520
 Robert Wilson, PhD, DVM

 

 

amyloid stained brown with iodine Treatment with an iodine stain, such as Lugol's, stains the amyloid brown.

http://www.vetmed.wsu.edu/medsci520/inflamm.htm

WSU/UI  Medical Science 520
Robert Wilson, PhD, DVM
 

Histopathology:

eosinophilic amyloid deposits Amyloid deposits have an eosinophilic appearance when stained with H&E and viewed by light microscopy.

 http://www.vetmed.wsu.edu/medsci520/inflamm.htm

 WSU/UI Medical Science 520
Robert Wilson, PhD, DVM
 

 

amyloid as green with Congo red and polarized light Amyloid appears as green birefringence when stained with Congo red and viewed under polarized light.

 http://www.vetmed.wsu.edu/medsci520/inflamm.htm

WSU/UI Medical Science 520
Robert Wilson, PhD, DVM
 


Clinical signs:

The nephrotic syndrome is usually the first sign of disease, and then followed by chronic renal failure. Other signs related to renal failure, such as oral ulceration, vomiting, dehydration, and emaciation, may be seen. Other presenting signs may be present related to the primary inflammatory or neoplastic process.

For more information:

Carlton, W.W., and McGavin, M.D. 1995. Amyloidosis: Chapter 5: The Urinary System. In: Thompson's Special Veterinary Pathology. Mosby pp 228-229.


Nelson, R.W., Couto, C.G., et al. 1998. Glomerulonephropathies. In: Small Animal Internal Medicine. Mosby pp. 607-608.
 

Tilley, L.P., and Smith, F.W. 2000. Amyloidosis. In: The Five Minute Veterinary Consult Canine and Feline. Williams and Wilkins pp.338-339.

Pubmed:

"renal amyloidosis in cats" search

"renal amyloidosis in dogs" search