Proteinuric Syndrome

Idiopathic Primary Renal Hematuric/Proteinuric Syndrome

 

Definition

This syndrome includes a group of disorders characterized by blood and protein in the urine and by damage to the kidney glomeruli (filtering structures) that may lead to kidney failure.

Description

This syndrome, also known as Berger's disease or IgA nephropathy, arises when internal kidney structures called glomeruli become inflamed and injured. It can occur at any age, but the great majority of patients are 16-35 when diagnosed. Males seem to be affected more often than females, and whites are more often affected than blacks. Blood in the urine (hematuria), either indicated by a visible change in the color of the urine or detected by laboratory testing, is a hallmark of this syndrome, and it may occur continuously or sporadically. The pattern of occurrence is not indicative of the severity of kidney damage.

Causes and symptoms

The glomeruli are the kidney structures that filter the blood and extract waste, which is then excreted as urine. The barrier between the blood and the urine side of the filter mechanism is a membrane only one cell layer thick. Anything that damages the membrane will result in hematuria. Symptoms of idiopathic primary renal hematruic/proteinuric syndrome are caused by inflammation of the glomeruli and deposit of IgA antibodies in kidney tissue. Although a genetic basis for this syndrome is suspected, this has not been proven. Symptoms often appear 24-48 hours after an upper respiratory or gastrointestinal infection. Symptoms of the syndrome include:
  • blood in the urine (hematuria)
  • protein in the urine (proteinuria)
  • pain in the lower back or kidney area
  • elevated blood pressure (20-30% of cases)
  • nephrotic syndrome (less than 10% of cases)
  • swelling (occasionally)
This condition usually does not get worse with time, although renal failure occasionally results. In patients with large amounts of IgA deposits in their glomeruli, the long-term prognosis may not be favorable. The syndrome can go into remission spontaneously, although this is more common in children than in adults.

Diagnosis

One of the objectives of diagnosis is to distinguish glomerular from non-glomerular kidney diseases. Idiopathic primary hematuric/proteinuric syndrome involves the glomeruli. The presence of fragmented or distorted red blood cells in the urine is evidence of glomerular disease. A high concentration of protein in the urine is also evidence for glomerular disease. The hematuria associated with this syndrome must be distinguished from that caused by urinary tract diseases, which can also cause a loss of blood into the urine. Biopsy of the patient's kidney shows deposits of IgA antibodies. Detecting IgA-antibody deposits rules out thin membrane disease as the cause of the hematuria and proteinuria. Test values are normal for ASO, complement, rheumatoid factor, antinuclear antibodies, anti-DNase, and cryoglobulins, all of which are associated with different types of kidney disease. A diagnosis of idiopathic primary renal hematuric/proteinuric syndrome is largely made by ruling out other diseases and their causes, leaving this syndrome as the remaining possible diagnosis.

Treatment

Many patients do not need specific treatment, except for those who have symptoms indicating a poor prognosis. Oral doses of corticosteroids are effective in patients with mild proteinuria and good kidney function. Other treatments, such as medications to lower blood pressure, are aimed at slowing or preventing kidney damage. If kidney failure develops, dialysis or kidney transplantation is necessary.

Prognosis

Idiopathic primary renal hematuric/proteinuric syndrome progresses slowly and in many cases does not progress at all. Risk for progression of the disorder is considered higher if there is:
  • high blood pressure
  • large amounts of protein in the urine
  • increased levels of urea and creatinine in the blood (indications of kidney function)
About 25-35% of patients may develop kidney failure within about 25 years.

Prevention

Since the underlying causes of this syndrome are so poorly understood, there is no known prevention.

Resources

Books

Greenberg, A. Primer on Kidney Diseases. San Diego: Academic Press, 1998.

Organizations

IgA Nephropathy Support Network. 964 Brown Ave., Huntington Valley, PA 19006. (215) 663-0536.
National Kidney Foundation. 30 East 33rd St., New York, NY 10016. (800) 622-9010. http://www.kidney.org.

Key terms

Glomeruli (singular, glomerulus) — Filtering structures in the kidneys.
Hematuria — The presence of hemoglobin or red blood cells in the urine.
Idiopathic — Refers to a disease that arises from an obscure or unknown cause.
Nephrotic syndrome — A kidney disorder characterized by fluid retention (edema) and proteinuria. It is caused by damage to the kidney glomeruli.
Proteinuria — The presence of protein in the urine exceeding normal levels.