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Back to Basics Nephrology 2010

Back to Basics Nephrology 2010. Major issues in Nephrology, Electrolytes, Acid-base disturbances. CKD. K/DOQI Classification of Chronic Kidney Disease. Stage GFR ( ≥ 3mo) Description (ml/min/1.73m 2 )

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Back to Basics Nephrology 2010

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  1. Back to BasicsNephrology2010 Major issues in Nephrology, Electrolytes, Acid-base disturbances

  2. CKD

  3. K/DOQI Classification of Chronic Kidney Disease Stage GFR (≥3mo) Description (ml/min/1.73m2) 1 90 Damage with normal GFR 2 60-90 Mild  GFR 330-59 Moderate  GFR 4 15-29 Severely  GFR 5 <15 Kidney Failure

  4. In this K/DOQI staging, “kidney damage” means: • Persistent proteinuria • Persistent glomerular hematuria • Structural abnormality: • such as PCKD, reflux nephropathy

  5. CHRONIC KIDNEY DISEASE • Diagnosis: • Acute vs. chronic: • Small kidneys on U/S or unenhanced imaging mean CKD • Diabetic CKD may still have normal sized kidneys

  6. CHRONIC KIDNEY DISEASE • Common causes of CKD: • Diabetic nephropathy • Vascular disease • GN • PKD

  7. CHRONIC KIDNEY DISEASE • Causes of CKD: • Best to divide as proteinuric or non-proteinuric CKD • Proteinuric is much more likely to have deterioration in GFR and higher cardiovascular morbidity and mortality

  8. CHRONIC KIDNEY DISEASE • Treatment • Delay progression: • Treat underlying disease i.e. good glucose control for DM • BP control to 130/80, (the current target) • ACEI or ARB has extra benefit for proteinuric CKD • Lower protein diet…maybe

  9. CHRONIC KIDNEY DISEASE • Treatment of the consequences of decreased GFR: • PO4: • decrease dietary intake • PO4 binders such as CaCO3 • Hypocalcemia: • CaCO3, 1,25 OH D3

  10. CHRONIC KIDNEY DISEASE • Treatment of the consequences of decreased GFR: • Anemia: • Erythropoetin current target Hb 105-115

  11. CHRONIC KIDNEY DISEASE • Uremic Complications: Major: • Pericarditis • Encephalopathy • Platelet dysfunction

  12. ARF

  13. ARF • Pre renal and ATN most common causes (quoted at 70% of cases of ARF) • DDx: • Pre Renal • Intra Renal • Post Renal

  14. Urine: Pre-Renal vs. RenalAssessment of Function U Na U Osm Fe Na • Pre-Renal • ATN < 20 > 500 < 1% > 40 < 350 > 2% U/P Na U/P Cr Fe Na= X 100 • Pigmented granular casts found in up to 70% of cases of ATN

  15. Urine: Pre-Renal vs. RenalAssessment of Function Fe Urea • Pre-Renal • ATN < 35 U/P Ur U/P Cr Fe Urea= X 100 > 55 • FeUrea might be useful to Dx pre renal ARF in those who received diuretics…but not all studies support its use.

  16. ARF • Investigations: • Pre Renal: Urine tests as noted and responds to volume • Intra-Renal: look for GN, interstitial nephritis as well as ATN • Post Renal: Imaging showing bilateral hydronephrosis is highly specific for obstruction causing ARF

  17. Dialysis: Who Needs It? • If cannot control these by other means: Hyperkalemia Pulmonary edema Acidosis Uremia • (GFR < 10-15% for CRF)

  18. Dialysis: Who Needs It? • Hemodialysis is also used for intoxications with: • ASA • Li • Alcohols: i.e. methanol, ethylene glycol • Sometimes theophylline

  19. Na+

  20. Hyponatremia • Pseudo: • If total osmolality is high: hyperglycemia/ mannitol • If total osmolality is normal, could be due to very high serum lipoprotein or protein

  21. Hyponatremia • Volume status: • Hypovolemic: high ADH despite low plasma osmolality • High total volume: CHF/ cirrhosis have decreased effective circulating volume and high ADH despite low plasma osmolality

  22. Hyponatremia • Volume status: • If volume status appears normal: • If urine osmolality is low: normal response to too much water intake…”psychogenic polydipsia” • If urine osmolality is high: inappropriate ADH

  23. Hyponatremia • Treatment: • Hypovolemic: • Replace volume • Decreased effective volume: • Improve cardiac output if possible • Water restrict • SIADH: • Water restrict

  24. Hyponatremia • Treatment: • Rate of correction of Na: • Not more than 10 mmol in first 24 h and not more than 18 mmol over first 48 h of treatment • Or Central Pontine Myelinosis may occur

  25. Potassium

  26. Hyperkalemia • Real or Not: • Hemolysis of sample • Very high WBC, PLT • Prolonged tourniquet time

  27. Hyperkalemia • Shift of K from cells: • Insulin lack • High plasma osmolality • Acidosis • Beta blockers in massive doses

  28. Hyperkalemia • Increased total body K: • Decreased GFR plus: • High diet K • KCl supplements • ACEI/ARB • K sparing diuretics • Decreased Tubular K secretion

  29. TTKG • Requirements: • Urine osmolality > 300 • Urine Na+ > 25 • Reasonable GFR • TTKG = U/P K+/U/P Osm [urine K+ (urine osmol/serum osmol)] serum K+ <7, esp < 5 = hypoaldosteronism

  30. Hyperkalemia • Treatment • IV Ca • Temporarily shift K into cells: • Insulin and glucose • Beta 2 agonists (not as reliable as insulin) • HCO3 if acidosis present • Remove K

  31. GFR

  32. ASSESSMENT OF GFR:

  33. ASSESSMENT OF GFR: • Cockroft-Gault estimated Creatinine clearance • UCr x V • PCr Creatinine clearance formula: • (140-age) x Kg x1.2 • Creat • (x .85 for women) Need a Steady State for these to be valid

  34. MDRD eGFR • Labs now calculate this for anyone who has a serum creatinine checked • Use serum creatinine, age, gender

  35. MDRD eGFR GFR, in mL/min per 1.73 m2   =(170 x (PCr [mg/dL])exp[-0.999]) x (Age exp[-0.176]) x ((Surea [mg/dL])exp[-0.170]) x ((Albumin [g/dL])exp[+0.318]) where SUrea is the serum urea nitrogen concentration; and exp is the exponential. The value obtained must be multiplied by 0.762 if the patient is female or by 1.180 if the patient is black. Simplified: GFR, in mL/min per 1.73 m2 = 186.3 x ((serum creatinine) exp[-1.154]) x (Age exp[-0.203]) x (0.742 if female) x (1.21 if African American) Do NOT memorize this formula

  36. Limitations of GFR estimates:Not reliable for: extremes of weight or different body composition such as post amputation, paraplegia acute changes in GFR use in pregnancy eGFR greater than 60ml/min/1.73m2

  37. Proteinuria

  38. Proteinuria • Albumin vs. other protein • Dipstick tests albumin

  39. PROTEINURIA • Quantitative: • 24 hour collection • ACR: random albumin to creatinine ratio • PCR: random protein to creatinine ratio

  40. PROTEINURIA • Microalbuminuria: less than dipstick albumin • Can use albumin to creatinine ratio on random urine sample… best done with morning urine sample

  41. Nephrotic Syndrome • Definition: • > 3 g proteinuria per day • Edema • Hypoalbuminemia • Hyperlipidemia and lipiduria are also usually present

  42. Nephrotic Syndrome • Causes: • Secondary: DM, lupus • Primary: • Minimal change disease • FSGS • Membranous nephropathy

  43. Nephrotic Syndrome • Complications: • Edema • Hyperlipidemia • Thrombosis…with membranous GN and very low serum albumin

  44. Nephrotic Syndrome • Treatment: • Treat cause if possible • Treat edema, lipids • Try to decrease proteinuria

  45. Hematuria

  46. Hematuria • Significance: ≥3 RBC's per hpf • DDx: Is it glomerular or not? • Glomerular: • RBC casts • Dysmorphic RBCs in urine • Coinciding albuminuria may indicate glomerular disease

  47. Hematuria • Other investigation: • Imaging of kidneys • Serum creatinine • Age over 40-50 rule out urologic bleeding, i.e. referral for cystoscopy

  48. Hematuria • For glomerular hematuria without proteinuria DDx includes: • IgA nephropathy • Thin GBM disease • Hereditary nephritis

  49. Ca++, PO4, Mg++

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