Glomerulonephritis


Introduction

The term glomerulonephritis refers to primary inflammation of the glomeruli. Glomeruli might also suffer damage secondary to tubular disease or pyelonephritis.

Glomerulonephritis is generally a diffuse condition affecting most if not all glomeruli in the kidney, although not all glomeruli are affected to the same extent.

In the early stages, the changes are confined to the glomeruli and associated with the deposition of immune complexes in the basement membrane. In some cases, proliferative changes in the mesangium and wall of the Bowman's capsule may accompany it.

This gives rise to the two types of pathology generally encountered in the various species: membranous and membrano-proliferative.

The membranous form is seen predominantly in cats, and the membrano-proliferative form is the most common form in dogs.

Glomerulonephritis can be found on histopathological examination of ruminants and horses but it is only rarely a cause of clinical disease.

Aetiology

The aetiology is often obscure, but its incidence has increased in recent years due to better recognition of the disease and a reduction in the incidence of chronic interstitial nephritis in dogs due to vaccination. It has also been suggested that the increased use of modified live vaccines may produce a sustained low level stimulation of the antigenic response in vaccinated individuals.

Various other causes have been implicated:

Hereditary/familial aetiology:

dogs: Samoyed, Elkhound and Doberman (expressed as renal failure in 4-14 months)
sheep: Finnish Landrace Sheep

Viral:

dogs: Infectious Canine Hepatitis
cats: Feline Infectious Peritonitis, Feline Leukaemia Virus
ox: Bovine Viral Diarrhoea
pig: Classical Swine Fever

Bacterial:

Pyometra and endocarditis

Autoimmune diseases

Systemic Lupus Erythematosus

Clinical Signs and Pathology

Animals with idiopathic glomerulonephritis (>50% of cases) usually have signs of renal disease, whereas secondary glomerulonephritis is often a relatively minor part of a more serious disease.

Gross pathology: acute cases have swollen, tense kidneys with pinpoint red dots in the cortex representing individual glomeruli. Chronic cases have shrunken, pitted kidneys with a granular appearance.

Histopathology:

Membranous glomerulonephritis: diffuse and even thickening of the basement membrane
Membranoproliferative: thickening of the basement membrane and proliferation of the mesangial cells and the parietal epithelium (crescent formation) with adhesions between the vascular tuft and Bowman's capsule.

The glomerulus becomes progressively obliterated, accompanied by periglomerular fibrosis. Reduction in blood supply to the nephron also causes damage to the tubules and provokes an interstitial nephritis in the later stages.

There is persistent proteinuria and the nephrotic syndrome can develop as a consequence.

Diagnosis

Diagnosis of the condition is by renal biopsy in the live animal, or histopathology of the kidney at post-mortem examination.

A careful search should be made for an inciting disease process. Abdominal and thoracic radiographs, ultrasonography, and specialized serologic tests can rule out various inflammatory, infectious, and neoplastic diseases. In dogs, this includes tests for SLE (eg, antinuclear antibody titre) and appropriate antigen or antibody screening tests for other infectious agents; in cats, tests for infection with FeLV, FIV, FIP and SLE should be included.

Treatment

If a cause for immune-complex disease can be identified it should be treated.

If the nephrotic syndrome is manifested, it should be treated with diuretics and through dietary salt restriction.

Antithrombotics may have to be considered in those animals with a very low albumin.

If no known cause of the glomerulonephritis is found, efforts should be made to reduce the magnitude and consequences of immune-complex deposition, and immuno-suppressive drugs such as azathioprine, cyclophosphamide and chlorambucil can be considered in dogs, although results are variable.

Chronic kidney disease when it develops should be managed in accordance to the stage of the disease.

Prognosis for animals with glomerulonephritis is poor, with a mean survival time of 87 days in dogs.


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References

Kahn, C. (2005) Merck Veterinary Manual Merck and Co

Carlyle Jone, T. (1997) Veterinary Pathology Wiley-Blackwell

Smythe, B. (2009) Urogenital System, urinary tract pathology Royal Veterinary College student notes




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