Acute Kidney Injury Flashcards
What are the main causes of acute tubular necrosis?
- Ischemia (hypovolemia, post-op)
2. Toxins: exogenous (dyes) and endogenous (pigments)
What is the pathophysiology of ATN?
- Tubular back leak of filtrate into blood
- Abnormal ultrafiltrate (Na+ increased, shuts down nephron)
- Lumin obstruction (from cells and pigments)
What are the clinical signs of ATN?
- Decreased urine output
2. Increased serum creatinine
What will investigations show for ATN?
- Urinalysis: dysmorphic blood, heme granular casts, epithelial casts
- Lytes: >40, FeNa> 2%, may have hyperkalemia
How can we differentiate ATN from pre-renal causes of AKI?
- ATN: slowly reversible, urine not bland, Uosm=Posm, FENa>2%, urine Na>40. INTRINSICALLY DAMAGED
- Pre-renal: quickly reversible, urine bland, increase Uosm, FENa
How is AKI treated?
- Stop any nephrotoxic drugs (metformin, fibrates, LMW heparin)
- Decrease salt intake
- Maintain eletrolytes (watch for hyper K)
- Treat uremia if present (hemodialysis)
- IV saline prior to any IV contrast
What causes acute interstitial nephritis?
- Drugs* (beta lactams, abx, NSAIDS)
- Infections
- Autoimmune
- Tubular obstruction causing inflammation (multiple myeloma, calcium oxalate, uric acid)
How does acute interstitial nephritis present?
- May be delayed from first exposure to drug (shorter latency with second exposure)
- Triad: fever, rash, eosinphilia
What do investigations show in IN?
- Urinalysis: pyuria/eosinophils, hematuria, WBC casts
- FENa>1%
- Biopsy would show lymphocytic infiltrate
How do we treat IN?
- Stop causal drug
- Course of prednisone
usually kidneys recover
What would investigations show in glomerulonephritis?
- Urinalysis: RBC casts, proteinuria, eosinphilia, dysmorphic RBCs
- Serological analysis: ANCA , anti-GBM ab, immune complexes
What causes pre-renal AKI?
- Cardiac: MI/CHF/valves/shock
- Decreased SVR: sepsis/cirrhosis
- Volume depletion
- Decreased autoregulation: NSAIDS, ACEi
What do investigations show in pre-renal AKI?
- Urinalysis: bland, hyaline casts,
2. FENa
What are the causes of a rapidly progressive glomerulonephritis?
- Wegener’s
- Goodpasture’s
- Post-strep
- Anti-GBM nephritis
- IgA nephropathy
- Lupus
What urinalysis findings indicate glomerulonephritis?
- RBC casts
- proteinuria
- Dysmorphic RBCs
Active urine
- Dysmorphic RBC and or casts +/- proteinuria
2. Means glomerulonephritis
Diamond/rhomboid crystals
Uric Acid
Envelope shaped crystals
Calcium oxalate* common!
Needle shaped crystals
Calcium oxalate formed in ethylene glycol overdose
Coffin shaped crystals
Struvite (from chronic bacterial infections). May form staghorn calculi
How do we differentiate causes of glomerulonephritis based on serology?
- ANCA ab= polyarteritis nodosa, granulomatosis with polyangitis
- Anti-GBM= goodpastures, anti GBM nephritis
- Low C3= lupus nephritis, anti-strep, cryoglobulinemia
- Normal C3= IgA nephropathy
