Renal
Tubular & Interstitial Renal Disease + RTAs
Renal

Tubular & Interstitial Renal Disease + RTAs

ATN, AIN, PKD, RTA types, contrast nephropathy.

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◆Acute tubular necrosis (ATN)

  • •Most common intrinsic AKI
  • •Causes: ischemia (sepsis, surgery, shock), nephrotoxins (aminoglycosides, vancomycin, IV contrast, cisplatin, amphotericin B), pigment (rhabdomyolysis, hemolysis)
  • •Phases: initiation → maintenance (oliguric) → recovery (polyuric — watch for hypoK)
  • •Urine: muddy brown granular casts; FENa >2%; urine osm ~300
  • •Supportive; dialysis if AEIOU criteria

◆Acute interstitial nephritis (AIN)

  • •Drug-induced hypersensitivity: PPI, NSAIDs, β-lactams, sulfa, allopurinol
  • •Triad (often incomplete): fever + rash + eosinophilia
  • •Urine: WBC casts + sterile pyuria + eosinophiluria (Hansel stain)
  • •Stop offending drug; steroids if persistent

◆Polycystic kidney disease

  • •ADPKD: most common; PKD1/PKD2; presents adulthood; bilateral cysts + flank pain + hematuria + HTN; berry aneurysms + mitral valve prolapse + hepatic cysts; ESRD often by 60s
  • •ARPKD: infantile; oligohydramnios → Potter sequence + hepatic fibrosis

◆Contrast-induced nephropathy

  • •Risk: CKD, diabetes, HF, dehydration, age
  • •Prevent: IV isotonic saline pre/post; minimize contrast volume; hold metformin (avoid lactic acidosis)
  • •N-acetylcysteine evidence weak

Renal tubular acidosis types

TypeDefectUrine pHK+Associations
1 (distal)Cannot secrete H+ in distal tubule>5.5LOWCalcium phosphate stones, Sjogren, amphotericin, lithium
2 (proximal)Cannot reabsorb bicarb in proximal tubule<5.5 (variable)LOWFanconi syndrome (multiple myeloma, Wilson, lead), acetazolamide
4 (hypoaldo)Aldosterone resistance/deficiency<5.5HIGH (hyperK)Diabetes (most common), ACEi/ARB, heparin, NSAIDs

High-yield pearls

  • ◆Type 1 RTA + nephrolithiasis = calcium PHOSPHATE stones (alkaline urine)
  • ◆Type 2 RTA = Fanconi syndrome (also glucosuria, phosphaturia, aminoaciduria)
  • ◆Type 4 RTA = diabetic kidney; hyperK + non-anion gap acidosis + low aldosterone
  • ◆AKI from rhabdomyolysis: ↑CK + heme positive UA without RBCs + brown urine; aggressive fluids
  • ◆Hepatorenal syndrome: cirrhosis + AKI + no other cause; albumin + terlipressin; definitive = liver transplant
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