Definition of acute kidney injury
Abrupt (w/i 48 hours) reduction in kidney function defined as:
- An absolute increase in creatinine of >0.3 mg/dL or a percentage increase more than 50%
- Or a reduction in Urinary Output (UOP) (<0.5 ml/Kg/h for more than 6 hours)
Major cause of acute renal failure in hospital setting
Acute tubular necrosis
Prerenal presentation and treatment
Normal physiologic response to renal hypo perfusion to impair GFR. Renal parenchyma is normal. If not treated can lead to ATN.
Treat: Fluid repletion
Rate of rise of plasma creatinine in ATN vs. Prerenal
ATN: rise progressively at a rate greater than 0.3 to 0.5 mg/dL per day.
Prerenal disease: Slower rate of rise with periodic downward fluctuation
UA in ATN and Prerenal
- Normal in Prerenal disease
- In ATN: Muddy brown granular and epithelial cell casts and free epithelial cells.
Fractional excretion of sodium (FENa) in prerenal and ATN
Prerenal disease: 2%
Fractional excretion of urea (FEurea) in prerenal patients
<35%
Diagnosis of Prerenal Azotemia
- Normal renal US
- UA-normal
- Low urine Na, FENa<35%
- No proteinuria, no albuminuria
- Reversible with hydration
Glomerular Disease as a cause of Acute Kidney Injury presentation
- Most of time rapidly progressive GN
- Normal Renal US- large kidney
- UA- hematuria, RBC CASTS, dysmorphic RBCs
- Proteinuria ~1-2 g/day
- FENa can be <1%
Tubular Diseases- ATN presentation
Renal US: Normal
UA: Muddy brown granular casts, epithelial cell, epithelial cell casts, hematuria- no dysmorphic RBCs
-Subnephrotic proteinuria
-FENA >2%
ATN management
Conservative: Avoid hypotension, fluid depletion, nephrotoxic medication. Use renal replacement therapy when needed (dialysis).
Interstitial Kidney Disease presentation
-Symptoms and/or signs of allergic-type reaction: Rash, fever, eosinophilia, or triad of three
-Renal US: normal
-UA: White cells, red cells, WBC casts. Mild increase in protein. EOSINOPHILURIA (75% in 1st week).
-Nephrotic syndrome due to minimal change disease can be seen with NSAIDS
FENa >2%
AIN- Acute interstitial nephritis causes
Drugs with antibiotics responsible for 1/3 of these cases.
- Infection related
- Idiopathic
- Tubulointerstitial nephritis and uveitis syndrome
- sarcoidosis
AIN management
Identify and stop medication causing disease.
-Severe: prednisone- make sure infection has been excluded before starting therapy
Tests to be ordered with acute renal failure
1) Renal Ultrasound with Doppler
2) UA with microscopic exam
3) Spot urine proteins/creatinine ratio
4) Spot urine albumin/ creatinine ratio
5) Urine Na, urea
Postrenal causes
- Ureteral obstruction
- Bilateral ureteral obstruction (stone, retroperitoneal fibrosis, pelvic masses)
- Urethral obstruction: BPH, Prostate cancer
Renal US with Doppler can tell you…
- Kidney size
- Renal perfusion
- Measures the resistive indexes
- Renal echogenicity
- Ureteral obstruction
- Bladder obstruction, masses, postvoid residue
- prostate size and shape
- possible other organs pathology
Increased renal echogenicity seen often in what?
Chronic renal disease
UA with microscopic exam:
1) Glomerular problem
2) Prerenal
3) ATN
1) Hematuria (dysmorphic RBC) and proteinuria
2) Normal
3) Muddy brown granular casts
Urine protein/creatinine and urine albumin/creatinine for glomerular (not NS), ATN, Interstitial disease
1-3.5 g of proteins/day
> 3.5 g protein/day is
NS or nephrotic range proteinuria
Indications to start RRT (Dialysis)
- Severe acidosis
- Severe hyperK
- Fluid overload not responding to diuretics
- Uremic symptoms
- Uremic pericarditis
- BUN ~80 mg/dL
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Overview- Sasek3
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Common Pediatric Disorders- Villanueva27
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Urolithiasis - Thierfelder32
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HIV/AIDS - Sandkovsky34
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Microhematuria - LaGrange8
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UTI - Brown33
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Prostate Cancer - Hill (Bishay)16
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BPH - Bishay27
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Incontinence - Bishay23
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Intro to Nephrology5
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Diabetic Nephropathy/ Glomerular Diseases35
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Acute Renal Failure- Florescu22
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Pediatric Nephrology37
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Renal Failure and Transplant13
