NEPHROLOGY
Definition and classification/staging classification/staging system for acute kidney injury (AKI) AKI stage •
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Creatinine criteria
Urine output criteria
AKI stage I
Increase of serum creatinine by ≥ 0.3 mg/dl (≥ 26.4 μmol/L) μmol/L) or increase to ≥ 150% – 200% from baseline < 0.5 ml/kg/hour for > 6 hours -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------AKI stage II
Increase of serum creatinine to > 200% – 200% – 300% from baseline < 0.5 ml/kg/hour for > 12 hours -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------AKI stage III
increase of serum creatinine to > 300% from baseline or serum creatinine ≥ 4.0 mg/dl ≥ 354 μmol/L) μmol/L) after a rise of at least 44 μmol/L μmol/L or treatment with renal replacement replacement therapy
< 0.3 ml/kg/hour for > 24 hours or anuria for 12 hours
ATN vs. Prerenal Azotemia Indices
Prerenal
ATN
UNa
< 20
> 40
FeNa
< 1%
> 4%
U/PCreat
> 40
< 20
FeUN
< 35%
>70%
Urinary Sediment Findings in Intra-Renal Acute Renal Failure Intra-renal Acute Renal Failure
Albuminuria
Dysmorphic Hematuria Red cell casts
Glomerulonephritis Atheroembolic disease Thrombotic microangiopathy
Oval fat bodies Fatty Casts
Minimal change disease Focal segmental glomerulosclerosis
Tubular proteinuria
Muddy brown casts Renal tubular epithelial cells and casts
White cells White cell casts Eosinophiluria
Tubular epithelial injury -Ischemic -Nephrotoxic
Interstitial nephritis Urinary tract infection
Crystalluria
Drug toxicity Urate crystals -Urate nephropathy Calcium oxalate crystals -ethylene glycol
Acute Renal failure Introduction to casts Hyaline Casts: •
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Better seen with low light. Non-specific.
Composed of Tamm-Horsfall mucoprotein.
Acute Renal Failure Granular Casts: •
Represent degenerating cellular casts or aggregated protein.
Nonspecific. Waxy Casts: •
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Smooth appearance.
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Blunt ends.
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May have a “crack”.
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Felt to be last stage of degenerating cast – representative of chronic
Acute Renal Failure Fatty Casts: •
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Seen in patients with significant proteinuria. Refractile in appearance. May be associated with free lipid in the urine. Can see also “oval fat bodies” – RTE’s that have ingested lipid. Polarize – demonstrate
Acute Renal Failure Muddy Brown Casts: •
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Highly suggestive of ATN. Pigmented granular casts as seen in hyperbilirubinemia can be confused for these.
Acute Renal Failure White Blood Cell Casts: •
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Raises concern for interstitial nephritis. Can be seen in other inflammatory disorders. Also seen in pyelonephritis.
Acute Renal Failure •
Hematuria
Nonglomerular hematuria: •
Urologic causes.
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Bladder/Foley trauma.
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Nephrolithiasis.
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Urologic malignancy.
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May be “crenated” based upon age of urine, osmolality NOT dysmorphic.
Acute Renal Failure Dysmorphic Red Cells: •
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Suggestive of glomerular bleeding as seen with glomerulonephritis. Blebs, buds, membrane loss. Rarely reported in other conditions – DM, ATN.
Red Blood Cell Casts: •
Essentially diagnostic of vasculitis or glomerulonephritis.
Acute Renal Failure Crystals – Pretty and important. Uric acid crystals: •
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Seen in any setting of elevated uric acid and an acidic urine. Seen with tumor lysis syndrome.
Calcium oxalate crystals: •
Monohydrate – dumbell shaped, may be needle-like.
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Dihydrate – envelope shaped.
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Form independent of urine pH.
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Seen acutely in ethylene glycol
Conditions that Lead to Pre-renal Acute Renal Failure Intravascular Volume Depletion Large-vessel Renal Vascular Disease
Decreased Effective Circulating Volume CHF Cirrhosis Nephrosis
Medications CYA, Tacrolimus ACE inhibitors NSAIDS Radiocontrast Amphotericin B Aminoglycosides
Hepatorenal Syndrome
Generalized or Localized Reduction in Renal Blood Flow
Renal Artery Thrombosis Renal Artery Embolism Renal Artery Stenosis or Crossclamping
Sepsis
Small-vessel Renal Vascular Disease Vasculitis Atheroemboli Thrombotic Microangiopathies Transplant Rejection
Ischemic Acute Renal Failure
Common Causes of Drug Induced AIN •
NSAIDS
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Antibiotics –
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Penicillins •
methacillin
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Ampicillin, amoxacillin, carbenacillin, oxacillin
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Cephalosporins
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Quinolones (ciprofloxacin)
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Anti-tuberculous medications (rifampin, INH, ethambutol)
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Sulfonamides (TMP-SMX, furosemide, thiazides)
Miscellaneous –
Allopurinol, cimetidine, dilantin
Acute Glomerulopathies •
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RPGN most commonly seen with: –
Lupus nephritis (DPGN, class IV)
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Pauci-immune GN (ANCA associated)
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Anti-GBM disease
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less commonly: IgA, post-infectious
Nephrotic presentations of ARF –
Collapsing FSGS (HIV nephropathy)
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Minimal change disease with ATN
Thrombotic microangiopathies (HUS, TTP, malignant hypertension, scleroderma kidney, pre-eclampsia)
Hepatorenal Syndrome - Major Criteria •
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Chronic or acute liver disease with advanced hepatic failure and portal hypertension Low GFR, as indicated by a serum creatinine >1.5 mg/dL or a creatinine clearance < 40 mL/min Absence of shock, ongoing bacterial infection, fluid loss, and current or recurrent treatment with nephrotoxic drugs. Absence of gastrointestinal fluid losses (repeated vomiting or intense diarrhea) or renal fluid losses (as indicated by weight loss > 500 gm/d for several days in patients with ascites without peripheral edema or > 100 gm/d in patients with peripheral edema) No sustained improvement in renal function (decrease in serum creatinine to 1.5 mg/dL or less or increase in creatinine clearance to 40 ml/min or more) after withdrawal of diuretics and expansion of plasma volume with 1.5 L of isotonic saline Proteinuria < 500 mg/d and ultrasonographic evidence of obstructive uropathy or parenchymal renal disease.
Hepatorenal syndrome - Minor Criteria •
Urine volume < 500 mL/day
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Urine sodium < 10 mEq/L
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Urine osmolality > plasma osmolality
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Urine red blood cells < 50 per high-power field Serum sodium concentration < 130 mEq/L
CURRENT STAR MCQS •
Abdominal Compartment Syndrome –
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Acute Phosphate Nephropathy –
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AKI from Oxalate nephropathy due to enhancing oxalate absorption with increased urinary excretion.
IVIG associated AKI –
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AKI from Nephrocalcinosis after use of oral sodium phosphate (phospho soda) for colonoscopy.
Orlistat associated AKI –
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Presence of IAP >20 that is associated with a single or multiple organ system failure. Causes severe oliguric or anuric renal failure. Tx: surgical decompression.
AKI from osmotic nephrosis from sucrose-containing formulation.
Herbal, Home remedies –
Arsenal X, Chromium picolinate, Chineses Herb Xi Xin with aristolochic acid; tea from Mouring Cypress, Snake gallbladder, Star fruit (oxalate), Ma Huang (ephedra), Noni
Definition of CKD-Mineral and Bone Disorder A systemic disorder of mineral and bone metabolism due to CKD manifested by either one or a combination of the following: •
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Abnormalities of calcium, phosphorus, PTH, or vitamin D metabolism Abnormalities in bone turnover, mineralization, volume, linear growth, or strength Vascular or other soft tissue calcification
Mechanism of Cyst Formation
1. Mutation(s) leads to changes in epithelial cell behavior 2. Tubule epithelial cells proliferate to form cyst 3. Electrolytes and water accumulate in cyst lumen
Cystic diseases of kidney •
ADPKD
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ARPKD
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VHL : AD,hemangioblastoma, RCC (40-70%)
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TS: angiomyolipomas in CNS
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MSK : AD, 3rd & 4th decade, stones, recurrent hematuria.
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NPH =3 types:juvenille,infantile,adolescent. AR. Cerebellar ataxia , hepatic fibrosis MCK = AD. 3rd & 4th decade.
