Thursday, March 30, 2017

Management of Nephrotic Syndrome in Adult

Nephrotic Syndrome
By Laurie Barclay, MD

Recommendations for primary care clinicians regarding the diagnosis and treatment of nephrotic syndrome in adults are reviewed in the November 15 issue of the American Family Physician.

"In nephrotic syndrome, a variety of disorders cause proteinuria, often resulting in marked edema and hypoalbuminemia," write Charles Kodner, MD, from the University of Louisville School of Medicine in Louisville, Kentucky. "Hyperlipidemia is a common associated finding. Family physicians may encounter persons with nephrotic syndrome from primary (idiopathic) renal disease or a number of secondary causes, and should initiate appropriate diagnostic workup and medical management pending specialist consultation."

Nephrotic syndrome may be classified as primary (or idiopathic) renal disease, or it may be secondary to various causes. The most common primary causes in adults are focal segmental glomerulosclerosis and membranous nephropathy.

Focal segmental glomerulosclerosis accounts for approximately one third of cases of primary nephrotic syndrome and for approximately 3.3% of new cases of end-stage renal disease, and it is the leading cause of idiopathic nephrotic syndrome in adults. It is characterized by sclerosis and hyalinosis of segments of less than 50% of all glomeruli on electron microscopic studies. Clinical features may include hypertension, renal insufficiency, and hematuria.

In membranous nephropathy, electron microscopic study reveals thickening of the glomerular basement membrane, and immunofluorescent staining shows immunoglobulin G and C3 deposits. This form of nephrotic syndrome, which also accounts for approximately one third of cases of primary nephrotic syndrome, is most often diagnosed at ages 30 to 50 years. Patients may have microscopic hematuria, and roughly one quarter have systemic lupus erythematosus, hepatitis B, malignant disease, drug-induced nephrotic syndrome, or other underlying systemic disease.

Another form of primary nephrotic syndrome is minimal-change disease, which together with immunoglobulin A nephropathy is responsible for approximately one quarter of cases of idiopathic nephrotic syndrome. It is diagnosed from normal-appearing glomeruli on renal biopsy microscopic examination with effacement of foot processes on electron microscopic studies. After upper respiratory tract infection or immunization, relatively mild or benign cases of minimal-change disease may develop.

Secondary causes of nephrotic syndrome include diabetes mellitus, which is the most common secondary cause. Other causes are systemic lupus erythematosus, hepatitis B or C, use of nonsteroidal anti-inflammatory drugs, minimal-change disease, amyloidosis, multiple myeloma, HIV, or preeclampsia.

Typical presenting features of nephrotic syndrome are marked edema, proteinuria, hypoalbuminemia, and usually hyperlipidemia.

Possible complications of nephrotic syndrome are venous thromboembolism. Although acute renal failure and serious bacterial infection may occur, they are much less common.

To date, there are no established guidelines regarding diagnostic evaluation of patients with nephrotic syndrome. To diagnose specific disorders, blood tests should be used selectively, but a broad-ranging or unguided workup is not recommended. Imaging studies are seldom necessary. In some cases, however, renal biopsy may help confirm an underlying disease or identify idiopathic disease that has a greater probability of responding to corticosteroids.

Professional organizations have also not yet issued recommendations for treatment of nephrotic syndrome. Most patients should be treated with fluid and sodium restriction, oral or intravenous diuretics, and angiotensin-converting enzyme inhibitors.

"Diuretics are the mainstay of medical management; however, there is no evidence to guide drug selection or dosage," Dr. Kodner writes. "Based on expert opinion, diuresis should aim for a target weight loss of 1 to 2 lb (0.5 to 1 kg) per day to avoid acute renal failure or electrolyte disorders. Loop diuretics, such as furosemide (Lasix) or bumetanide, are most commonly used."

In persons with nephrotic syndrome, angiotensin-converting enzyme inhibitors have been shown to decrease proteinuria and lower the risk for progression to renal disease.

Although corticosteroid treatment may benefit some adults with nephrotic syndrome, research evidence supporting this therapy is limited. At present, intravenous albumin, prophylactic antibiotics, and prophylactic anticoagulation are not advised.

Key Recommendations

Key clinical recommendations for practice, and their accompanying level of evidence rating, are as follows:

* To evaluate the extent of proteinuria, persons with nephrotic syndrome should undergo measurement of random urine protein-to-creatinine ratio (level of evidence, C).
* Although renal biopsy may help guide diagnosis and management in selected patients, it is not recommended for all persons with nephrotic syndrome (level of evidence, C).
* Most persons with nephrotic syndrome should be treated with sodium and fluid restriction and high-dose diuretic therapy (level of evidence, C).
* Most persons with nephrotic syndrome should be treated with angiotensin-converting enzyme inhibitors (level of evidence, C).
* Despite the lack of evidence that corticosteroid treatment has any proven therapeutic benefit for nephrotic syndrome, some physicians recommend it for persons who are refractory to conservative management (level of evidence, C).

"In most cases, family physicians should consult specialists in renal medicine about the need for renal biopsy in individual patients," Dr. Kodner concludes.

"There are no clinical guidelines and few high-quality studies on the management of nephrotic syndrome in adults. Recommendations are based primarily on early case series, other observational studies, and expert opinion."

Dr. Kodner has disclosed no relevant financial relationships.

Am Fam Physician. 2009;80:1129-1134. Abstract

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