Introduction to Nephrotic Syndrome

Nephrotic syndrome (or nephrosis) is characterized by marked proteinuria, hypoalbuminemia, hyperlipemia, and edema. Although nephrotic syndrome isn’t a disease itself, it results from a specific glomerular defect and indicates renal damage. The prognosis is highly variable, depending on the underlying cause. Some forms may progress to end-stage renal failure.

Causes
About 75% of nephrotic syndrome cases result from primary (idiopathic) glomerulonephritis. 

Classifications include the following:

• With minimal change disease (lipid nephrosis or nil disease)—the main cause of nephrotic syndrome in children—the glomeruli appear normal by light microscopy. Some tubules may contain increased lipid deposits.
• Membraneous glomerulonephritis—the most common lesion in patients with adult idiopathic nephrotic syndrome—is characterized by uniform thickening of the glomerular basement membrane containing dense deposits. It can eventually progress to renal failure.
• Focal glomerulosclerosis can develop spontaneously at any age, follow kidney transplantation, or result from heroin abuse. Lesions initially affect the deeper glomeruli, causing hyaline sclerosis, with later involvement of the superficial glomeruli. These lesions generally cause slowly progressive deterioration in renal function. Remissions occur occasionally.
• With membranoproliferative glomerulonephritis, slowly progressive lesions develop in the subendothelial region of the basement membrane. These lesions may follow infection, particularly streptococcal infection. This disease occurs primarily in children and young adults.
• Other causes of nephrotic syndrome include metabolic diseases such as diabetes mellitus; collagen-vascular disorders, such as systemic lupus erythematosus and polyarteritis nodosa; circulatory diseases, such as heart failure and sickle cell anemia; nephrotoxins, such as mercury, gold, and nonsteroidal anti-inflammatories; allergic reactions; infections, such as tuberculosis or hepatitis B; preeclampsia toxemia; hereditary nephritis; multiple myeloma; and other neoplastic diseases. These diseases increase glomerular protein permeability, leading to the increased urinary excretion of protein, especially albumin, and subsequent hypoalbuminemia.

Signs and symptoms
The dominant sign of nephrotic syndrome is mild to severe dependent edema of the ankles or sacrum, or periorbital edema, especially in children. Such edema may lead to ascites, pleural effusion, weight gain, and high blood pressure.
Accompanying signs and symptoms include orthostatic hypotension, lethargy, anorexia, depression, and pallor. Major complications are malnutrition, infection, coagulation disorders, thromboembolic vascular occlusion, and accelerated atherosclerosis.

Diagnosis
Consistent proteinuria in excess of 3.5 g/24 hours strongly suggests nephrotic syndrome; examination of urine also reveals an increased number of hyaline, granular, and waxy, fatty casts, and oval fat bodies. Serum values that support the diagnosis are increased cholesterol, phospholipid, and triglyceride levels and decreased albumin levels. Histologic identification of the lesion requires a kidney biopsy.

Treatment
Effective treatment of nephrotic syndrome necessitates correction of the underlying cause, if possible. Supportive treatment consists of protein replacement with a nutritional diet of 1 g protein/kg of body weight, with restricted sodium intake; a diuretic for edema; and an antibiotic for infection. Immunosuppressants, antihypertensives, and diuretics can also help control symptoms. Angiotension-converting enzyme inhibitors can decrease protein loss in urine.
Some patients respond to a course of corticosteroid therapy (such as prednisone), followed by a maintenance dose. Patients with chronic nephrotic syndrome that’s unresponsive to therapy may require vitamin D replacement.

Special considerations

• Frequently check urine protein levels. (Urine containing protein appears frothy.)
• Measure blood pressure while the patient is in a supine position and also while he’s standing; be alert for a drop in blood pressure that exceeds 20 mm Hg.
• If the patient has had a kidney biopsy, watch for bleeding and shock.
• Monitor intake and output, and check weight at the same time each morning—after the patient voids and before he eats—and while he’s wearing the same kind of clothing.
• Ask the dietitian to plan a high-protein, low-sodium diet.
• Provide good skin care because the patient with nephrotic syndrome usually has edema.
• Watch for and teach the patient and family how to recognize adverse reactions to drug therapy.
• Offer the patient and family reassurance and support, especially during the acute phase, when edema is severe and the patient’s body image changes.