Rapidly Progressive Glomerulonephritis

Anatomy

The kidneys are paired organs. The structural and functional unit of the kidney is the nephron. Each kidney contains up to one million nephrons. A nephron consists of two main components: the glomerulus, a network of capillaries surrounded by Bowman’s capsule, and the renal tubules (proximal and distal convoluted tubules, and straight tubules). Filtration of blood occurs in the glomerulus, while the renal tubules are responsible for the reabsorption of water and solutes and the secretion of substances into the tubular fluid.

Description

Rapidly progressive glomerulonephritis (RPGN) is a clinical syndrome characterized by rapidly progressive loss of kidney function. Histologically, it is characterized by crescent formation within the glomeruli, as demonstrated on kidney biopsy. Crescent formation disrupts normal glomerular filtration, and as the number of crescents increases, renal function progressively declines. RPGN develops rapidly, and end-stage kidney failure may occur within weeks to months after symptom onset.

This condition develops in approximately 10–15% of patients with glomerulonephritis and most commonly affects individuals between 25 and 50 years of age.

Cause

Rapidly progressive glomerulonephritis may result from several different underlying diseases and is classified into three major types:

• Idiopathic rapidly progressive glomerulonephritis, in which the underlying cause is unknown.
• Type I. Caused by anti-glomerular basement membrane (anti-GBM) antibody disease, such as Goodpasture syndrome. In this form, autoantibodies target the glomerular basement membrane rather than foreign antigens.
• Type II. Caused by immune complex-mediated diseases. It may occur in systemic lupus erythematosus, poststreptococcal glomerulonephritis, infective endocarditis, and other immune complex disorders.
• Type III. Associated with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides, including microscopic polyangiitis, granulomatosis with polyangiitis (formerly Wegener’s granulomatosis), eosinophilic granulomatosis with polyangiitis (formerly Churg-Strauss syndrome), and other related disorders.

Symptoms

The disease is characterized by nephritic syndrome, including proteinuria and hematuria. Clinical manifestations may include edema affecting the ankles, wrists, periorbital region, or abdomen. Hypertension is common. Fever and flank pain may also occur. Symptoms develop rapidly because renal function deteriorates quickly. Urine output progressively decreases, and in severe cases, oliguria or anuria may develop if treatment is not initiated promptly.

Diagnosis

Blood and urine tests are performed to evaluate kidney function and identify evidence of nephritic syndrome. Renal ultrasonography is used to exclude other causes of kidney disease. The diagnosis is confirmed by kidney biopsy with histopathological examination of the tissue.

Treatment

Treatment depends on the underlying cause of rapidly progressive glomerulonephritis. In anti-glomerular basement membrane disease (Type I), plasma exchange is used to remove circulating pathogenic antibodies. Glucocorticoids are commonly used in immune-mediated forms of the disease, often in combination with other immunosuppressive agents. Treatment typically continues for approximately six months. If end-stage kidney disease develops, kidney transplantation may be required.

Early diagnosis and prompt initiation of treatment are essential for improving the prognosis.

Source | Author Doctor Nikas Samuolis, reviewed by Prof. Virginijus Šapoka | Vilnius University | Faculty of Medicine | Head of the Department of Internal Medicine, Family Medicine, and Oncology