Nephrology

• Most common cause AKI in Outpatient is pre renal : hypotension, vomiting, diarrhea, gastroenteritis
• Most common hospital acquired AkI is Acute tubular necrosis bec medication or prolonged pre renal
• Two drugs cause AKI

  • NSAID: vasoconstriction afferent so dec blood flow to renal
  • ACEI: vasodilation efferent so inc blood flow from renal
• Pathophysiology of AKI


  • Pre-renal (If prolonged will lead to acute tubular necrosis)
  • Renal
  • Post-renal (Obstruction at any site from renal tubule to the urethra)

  
• Increased BUN:creatinine ratio


  > 20
• FENa (%) (fractional excretion of Na)


  < 1%
• Decreased BUN:creatinine ratio


  FENa (%) (fractional excretion of Na) > 2%
• Causes of decreased blood flow to kidneys

  • Stenosis
  • Obstruction blood flow of kidney
  • Hemorrhage shock
  • Hypovolemic shock
  • Heart failure
  • Sepsis
• Normally function of renal reabsorption of Na and excretion K
• Creatinine


  Measured function renal self
• BUN


  Increased by pre-renal bec dehydrate
• FENa


  Excretion of Na and reabsorption K
• Isolated high BUN with normal creatinine is due to Upper GI Bleeding
• Increased BUN : Creatinine ratio >20


  Due to crush injury, marathone runners
• Acute tubular necrosis is the most common cause of hospital acquired AKI
• Acute tubular necrosis


  • Due to drug, toxin or prolonged pre-renal state
  • Presence of Muddy brown cast or granular cast
  • Urine Na high
  • FeNa > 2%
• RBCs Cast or dysmorphic red cells indicates glomerulonephritis
• Muddy brown or granular cast in ATN
• Hyaline cast in pre-renal causes
• WBC cast indicates infection or interstitial nephritis
• Fatty cast in nephrotic syndrome
• Waxy cast in chronic kidney disease
• Acute interstitial nephritis


  • Triad of eosinophilia, fever and rash
  • Presence of pyuria and eosinophiluria
• Eosinophiliuria DDx:- AIN and cholesterol emboli
• Rhabdomyolysis causes dark tea color urine with dipstick +ve for blood but no erythrocyte on UA
• Rhabdomyolysis follows heat exposure or crush injury
• Rhabdomyolysis has High CK level
• Treatment of Rhabdomyolysis is IV fluid
• Contrast induced nephropathy causes increased serum creatinine within 24 to 48 hours following contrast exposure
• High risk for CIN:- recent AKI, eGFR < 30
• Only approved prophylaxis for CIN is IV 0.9 saline and use of iso-osmolar or low osmolar contrast
• No benefit of N-acetylcystine, dialysis post-contrast or sodium bicarbonate infusion for CIN
• Indications for renal replacement therapy

  • Refractory hyperkalemia
  • Refractory fluid overload
  • Refractory acidosis
  • Uremic pericarditis or uremic encephalopathy
  • Intoxication
• Acute Renal replacement therapy


  Replaces nonendocrine kidney function in patients with renal failure. Techniques include intermittent hemodialysis, continuous hemofiltration and hemodialysis, and peritoneal dialysis
• Small kidneys on ultrasound suggest chronicity except in DM, HIV, Polycystic kidney disease, Amyloidosis

  
• Most common cause of death in ESRD patient is cardiovascular diseases
• Diabetic nephropathy


  Protein > 3.5 Gm in diabetic patient, Clinical diagnosis, absence of diabetic retinopathy make it unlikely cause of proteinuria
• Screen for diabetic nephropathy with albumin/creatinine ratio annually starting from time of diagnosis for Type 2 DM and 5 years after diagnosis for Type 1 DM

  
• Treatments to delay progression of CKD

  • BP control
  • Glycemic control
  • ACEi in case of proteinuria
  • SGLT-2 inhibitors (Empagliflozin)
  • Low protein diet (but not restricted and not in case of nephrotic syndrome)
  • Sodium bicarbonate only in case of metabolic acidosis
• Anemia in chronic kidney disease

  • Anemia of chronic inflammation, treated with SC Erythropoietin
  • Iron deficiency anemia should be ruled out first and if present to be treated first
  • Transferrin saturation < 20% + Ferritin < 100 à Iron supplement
  • Transferrin saturation > 20% + Ferritin > 100 à SC Erythropoietin
  • EPO in contraindicated in case of malignancy
  • Target hemoglobin in CKD:- 10 – 11.5
  • One of side effects of EPO is hypertension