Nephrotic Syndrome (NS)

• Def  massive proteinuria

  • >3-3.5g/day in adults

  • 40mg/m²/hr for children

• Causes  Many dz’s 

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• Mechanism 

  • Selective Proteinuria  Loss of negative charge in BM w/ Ig/Alb <0.1>

    • Uniquely associated w/ MCD

  • Nonselective proteinuria  Ig/Alb >0.5

    • Disorders of BM structure  hereditary nephritis or Alport’s syndrome

    • Disorders of BM biochemistry  DM & MN

• Hypoalbuminemia (<3g/dl)

  • Only some get it  b/c liver’s large reserve makes up for the loss of albumin

    • young pt w/ healthy liver make up to 12g/d albumin

    • elderly w/  liver fn & nutritional status  gets it

  • Causes  edema  b/c low oncotic pressure  causes Na & H₂O retention in conn tiss

    • BUT this does not explain all cases of edema b/c 50% of pts have  normal to high blood volume

• Hyperlipidemia

  •  hepatic synthesis or decrease catabolism of lipids   chol, phospholipids, LDL, VLDL & chylomicrons  accelerate atheroscerosis

    •  hepatic synthesis  b/c shunting of intermediate products more to lipid prod’s rather than albumin

  • In NS  lipiduria due to more lipid in blood  present as

    • free fat

    • fatty casts 

      • are oval fat bodies  which are degen’d renal tubular cells containing cholesterol esters

      • Maltese cross pattern under polarized light

• Complications 

  • Malnutrition  b/c uncomp’d protein loss in urine

  • Hypercoagubility  b/c 

    •  levels of factors V, VIII & fibrinogen

    • levels of antithrombin 3 & antiplasmin.

    • Hypercoag leads to thromboembolic events

    • Hypercoag causes  renal vein thrombosis  MOST assoc’d w/ MN & MPGN

  • Acute renal failure  renal perfusion  acute tubular necrosis

    • Also in drug induced intersitial nephritis

      • diuretics will cause it  thiazides

    • Another drug mech is NSAIDS inhibit formation of prostaglandins (fn: vasodilators) vasoconstriction & renal perfusion acute tubular necrosis

  • Infx  b/c  Ig’s

  • Proximal tubular dysfn 

    • called Fanconi syndrome (aminoaciduria, glucosuria, phosphaturia & proximal tubular acidosis)

      • cause  protein metab in the tubules

  • Osteomalacia & 2 hyperparathyroidism  b/c loss of trace metals such as Fe, Cu, Zn, & Vit D

Category: Nephrology Notes