6.5 Additional Reading:Nephrotic Syndrome in Adult...
Nephrotic syndrome is a group of symptoms that indicate your kidneys are not working properly.In nephrotic syndrome，a variety of disorders cause proteinuria，often resulting in marked edema and hypoalbuminemia.Hyperlipidemia is a common associated finding.
Causes
Most cases of nephrotic syndrome appear to be caused by primary kidney disease.Membranous nephropathy and focal segmental glomerulosclerosis（FSGS）each account for about one third of cases of primary nephrotic syndrome；however，FSGSis the most common cause of idiopathic nephrotic syndrome in adults.Minimal change disease and（less commonly）immunoglobulin A（IgA）nephropathy cause approximately 25 percent of cases of idiopathic nephrotic syndrome.Other conditions，such as membranoproliferative glomerulonephritis，are less common.FSGS accounts for approximately 3.3 percent of new cases of end-stage renal disease.A large number of secondary causes of nephrotic syndrome have been identified，with diabetes mellitus being the most common.
Pathophysiology
The underlying pathophysiology of nephrotic syndrome is not completely clear.Although the more intuitive“underfill”mechanism of edema from reduced oncotic pressure caused by marked proteinuria may be the primary mechanism in children with acute nephrotic syndrome，edema in adults may be caused by a more complex mechanism.Massive proteinuria causes renal tubulointerstitial inflammation，with resulting increased sodium retention that overwhelms the physiologic mechanisms for removing edema.Patients may have an“overfilled”or expanded plasma volume in addition to expanded interstitial fluid volume.This may be clinically important if over-rapid diuresis leads to acute renal failure from reduced glomerular blood flow，despite persistent edema.
Clinical features
Progressive lower extremity edema，weight gain，and fatigue are typical presenting symptoms of nephrotic syndrome.In advanced disease，patients may develop periorbital or genital edema，ascites，or pleural or pericardial effusion.Persons who present with new edema or ascites，without typical dyspnea of congestive heart failure or stigmata of cirrhosis，should be assessed for nephrotic syndrome.Nephrotic-range proteinuria is typically defined as greater than 3 g to 3.5 g of protein in a 24-hour urine collection；however，not all persons with this range of proteinuria have nephrotic syndrome.Although a urine dipstick proteinuria value of 3＋is a useful semiquantitative means of identifying nephrotic-range proteinuria，given the logistic difficulties of collecting a 24-hour urine sample，the random urine protein/creatinine ratio is a more convenient quantitative measure.The numeric spot urine protein/creatinine ratio，in mg/mg，accurately estimates protein excretion in g per day per 1.73 m2 of body surface area，so a ratio of 3 to 3.5 represents nephrotic-range proteinuria.Low serum albumin levels（less than 2.5 g per dL）and severe hyperlipidemia are also typical features of nephrotic syndrome.Possible complications of nephrotic syndrome include venous thromboembolism caused by loss of clotting factors in the urine，infection caused by urinary loss of immunoglobulins，and acute renal failure.Thromboembolism has long been recognized as a complication of nephrotic syndrome.Renal venous thrombosis is a possible complication of nephrotic syndrome，but was uncommon in this case series.Arterial thrombotic complications can occur，but are rare.Infection is also a possible complication of nephrotic syndrome；however，this risk appears primarily in children and in persons who have relapses of nephrotic syndrome or who require longer-term corticosteroid therapy.Invasive bacterial infections，especially cellulitis，peritonitis，and sepsis，are the most common infections attributable to nephrotic syndrome.The mechanisms of infection are unclear，but may relate to the degree of edema，loss of serum IgG with overall proteinuria，effects of corticosteroid therapy，reduced complement or T cell function，or impaired phagocytic function.The risk of serious bacterial infection attributable to nephrotic syndrome in adults in the United States is unclear，but seems low.Acute renal failure is a rare，spontaneous complication of nephrotic syndrome.Although older persons，children，and those with more profound edema and proteinuria are at highest risk，there are many possible causes or contributing factors to acute renal failure in this setting.Excessive diuresis，therapeutic drug complications，sepsis，renal venous thrombosis，renal interstitial edema，and marked hypotension may cause or contribute to acute renal failure.
Diagnostic evaluation
Typical clinical and laboratory features of nephrotic syndrome are sufficient to establish the diagnosis of nephrotic syndrome.The diagnostic evaluation focuses on identification of an underlying cause and on the role of renal biopsy.However，there are no published practice guidelines available for the diagnostic evaluation of persons with nephrotic syndrome.(https://www.daowen.com)
Initial investigation should include history，physical examination，and a serum chemistry panel.Given the large number of potential causes of nephrotic syndrome and the relatively nonspecific aspect of therapy，the diagnostic evaluation should be guided by clinical suspicion for specific disorders，rather than a broad or unguided approach to ruling out multiple illnesses.
Imaging studies are generally not helpful in assessing persons with nephrotic syndrome.Renal ultrasonography may identify renal venous thrombosis if suggestive features，such as flank pain，hematuria，or acute renal failure，are present.
Renal biopsy is often recommended in persons with nephrotic syndrome to establish the pathologic subtype of the disease，assess disease activity，or confirm the diagnosis of diseases，such as amyloidosis or systemic lupus erythematosus.There are，however，no clear guidelines on when renal biopsy is indicated or whether it is needed in all persons with nephrotic syndrome.For example，in diabetic nephropathy，the leading cause of secondary nephrotic syndrome，renal biopsy may not be necessary if the patient has enlarged kidneys，bland urinary sediment without cellular casts，or other evidence of microvascular disease，such as proliferative retinopathy or peripheral neuropathy.Although renal biopsy is often recommended to assess the likelihood that nephrotic syndrome will respond to corticosteroid treatment，there are no biopsy findings that accurately predict corticosteroid responsiveness.
Management
The nephrotic syndrome is a combination of physical signs and biochemical abnormalities which are the direct consequence of heavy proteinuria.Symptomatic treatment is appropriate for most patients.It consists of a diet rich in protein and low in salt，together with the administration of varying combinations of diuretics and the control of hypertension.Logically，treatment should also be aimed at correcting the underlying renal disease.
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Task 9 Identify the word elements and define the meaning of each medical term.
