Nephrology
7 high-yield topics. Open a topic to review its pearls.
Acute Renal Failure
Prerenal, intrinsic, postrenal
Classification
- Prerenal: BUN:Cr over 20, FeNa under 1 percent, hyaline casts
- Intrinsic (ATN): FeNa over 1 percent, muddy brown casts
- Postrenal: obstruction, hydronephrosis on ultrasound
ACE-I and NSAIDs
- ACE-I: relaxes efferent arteriole, precipitates ARF in renal artery stenosis
- NSAIDs: constrict afferent arteriole
- If both and creatinine rises: d/c NSAID first
- NSAIDs cause interstitial nephritis (no eosinophils)
ATN Causes
- Ischemic: hypovolemia, muddy brown casts
- Contrast: within 12h, vasoconstriction (FeNa under 1), prevent with IVF
- Amphotericin B: after days, vasoconstriction (FeNa under 1)
- Aminoglycosides: non-oliguric, days to weeks
- Rhabdomyolysis: dipstick positive blood, no RBCs, high CK
Urgent Dialysis (AEIOU)
- Acidosis, Electrolytes (hyperkalemia), Incoherence (encephalopathy), Overload, Uremic symptoms
Glomerulonephritis
Nephritic and nephrotic
ABC of GN
- A = ANCA GN (Wegener, microscopic polyangiitis, Churg-Strauss)
- B = anti-GBM (Goodpasture with lung hemorrhage)
- C = immune complex (lupus, post-infectious, IgA, MPGN)
Low vs Normal Complement
- Low: PSGN, SLE, cryoglobulinemia, MPGN
- Normal: IgA, Goodpasture, Wegener, PAN, HSP, TTP/HUS
Nephrotic Syndromes
- Minimal change: Hodgkin/NSAIDs, most common in children, steroids
- Membranous: solid tumors, Hep B, most common in adults, renal vein thrombosis
- FSGS: African American, HIV, heroin
- MPGN: Hep C, low complement, tram track
Nephritic Syndromes
- Post-strep: 6-10 days after infection, low C3, subepithelial humps
- IgA nephropathy: young male 24h after sore throat, normal complement
- Goodpasture: hemoptysis + hematuria, linear IgG, anti-GBM
- Wegener: sinusitis + lung nodules + c-ANCA
Electrolyte Disorders
Sodium and potassium
Hyponatremia
- Check urine osm, volume status, urine Na
- Euvolemic: SIADH, hypothyroid, drugs
- Hypervolemic: CHF, cirrhosis, nephrotic
- Hypovolemic: renal (diuretics) vs extrarenal (diarrhea)
- Treatment: hypertonic saline if seizures; correct under 12 mEq/24h
Hyperkalemia
- EKG: peaked T waves, widened QRS, sine wave
- Calcium gluconate first (membrane stabilization)
- Insulin/glucose, beta agonists, bicarbonate (shift)
- Kayexalate, diuretics, dialysis (removal)
Chronic Kidney Disease
Staging and complications
Features
- Small kidneys (under 9-10 cm), anemia, low Ca/high PO4
- Prior elevated creatinine, subperiosteal erosions
Treatment
- ACE inhibitors for HTN
- Correct acidosis (HCO3/CaCO3)
- Phosphate binders for hyperparathyroidism
- Erythropoietin for anemia
Dialysis Indications
- Pericarditis, fluid overload, uremic encephalopathy
- Neuropathy, GFR under 10, bleeding diathesis
Renal Tubular Acidosis
Types I, II, IV
RTA Types
- Type I (distal): cant secrete H, urine pH over 5.5, stones, low K, Sjogren
- Type II (proximal): decreased HCO3 absorption, urine pH under 5.5, low K, Fanconi/MM
- Type IV: defective NH4, urine pH under 5.5, HIGH K, hypoaldosteronism/diabetes
Nephrolithiasis
Stone types and treatment
Stone Types
- Calcium oxalate: most common
- Struvite: staghorn, urea-splitting organisms (UTI)
- Uric acid: allopurinol + alkalinize urine
- Cystine: cystinuria
Metabolic Treatment
- Hypercalciuria: thiazide diuretics
- Hyperoxaluria (Crohn): do NOT restrict calcium
- Hypocitraturia: potassium citrate
Renovascular and Hepatorenal
Special syndromes
Renovascular HTN
- Best screen: renal scan before/after captopril
- Treatment: surgery or angioplasty + stent if gradient over 1.5
Hepatorenal Syndrome
- Functional renal failure with advanced liver disease
- Does NOT respond to volume replacement
- Cause of death is liver failure
- Only effective treatment: liver transplant
ADPKD
- Cysts in cortex and medulla
- Associated with intracranial aneurysm (screen if symptomatic + family history of bleed)
- Hepatic cysts, MV/AV prolapse