Renal Failure - GU Flashcards
Acute Renal Failure
- Worsening of renal function over hours to a few days
- Retention of nitrogenous wastes such a urea nitrogen and creatinine in the blood
- This is called azotemia
- Oliguria: urine output <400 ml/day
- 5% of hospital admissions and 30% of ICU admissions have acute renal failure
- Sudden decrease in renal function resulting in an inability to maintain fluid and electrolyte balance and to excrete nitrogenous wastes
- Serum Creatinine acutely increases by more than 0.5mg/dL and more than 50% over baseline levels
Chronic Renal Failure
- Loss of renal function over months to years
- Typically see anemia in the setting of chronic renal failure
- Small kidneys
Signs and Symptoms of ARF
- Nausea
- Vomiting
- Malaise
- Altered sensorium
- Arrhythmias in setting of hyperkalemia
- Pericardial Effusion
- Nonspecific abdominal pain
- Evaluate BUN (blood urea nitrogen) and creatinine
- Decreased GFR (glomerular filtration rate)
- Hyperkalemia
3 Categories of ARF
- Prerenal Azotemia
- Postrenal Azotemia
-Intrinsic Renal Disease
Acute Tubular Necrosis
Acute Glomerulonephritis
Acute Interstitial Nephritis
Prerenal Azotemia
-Most common cause of ARF
Due to renal hypoperfusion
- Decrease in intravascular volume
- Change in vascular resistance
- Low cardiac ouput
- common in heart failure patients
Sxs: tachycardia and hypotension
Causes that change Vascular resistance
-Sepsis
-Anaphylaxis
-Anesthesia
After-loading medications:
-Ace-inhibitors (lisinopril) ARB’s (losartan)
-NSAID’s
-Renal Artery Stenosis
Low cardiac output is a state of hypovolemia
-Cardiogenic Shock
-CHF (congestive heart failure)
-Pulmonary Embolus
-Pericardial tamponade
-Arrhythmias and Valvular Disease
Prerenal AzotemiaLab Findings
Serum BUN:Cr Ratio >20:1
Fractional excretion of sodium is low 500
Decreased urine sodium
Treatment of Prerenal Azotemia
- Depends on the cause
- Maintain euvolumic state
- Monitor potassium levels
- Avoid nephrotoxic medications
-Monitor cardiac function, volume status, and medication usage
Postrenal Azotemia
-Least common cause of acute renal failure
-Occurs when urinary flow from both kidneys is obstructed
Causes:
-Urethral obstruction
-Bladder Dysfunction or obstruction
-Obstruction of both ureters or renal pelvis
-In men, BPH (benign prostatic hypertrophy) is common
-Bladder, prostate or cervical cancers
Lab Findings with postrenal azotemia
- Serum BUN:Cr ratio > 20:1
- Urine Osmolality <400
- Urine sediment: normal or red cells, white cells, or crystals
Treatment for postrenal azotemia
Evaluate and treat obstruction promptly and this can result in complete reversal of the acute process
Intrinsic Renal Failure
- Accounts for 50% of all cases of ARF
- Consider this after you have ruled out pre and postrenal azotemia
- Acute tubular Necrosis
- Acute Glomerulonephritis
- Acute Interstitial Nephritis
Acute Tubular Necrosis
-ARF due to tubular damage
Causes:
-Ischemia: causes tubular damage from state of prerenal azotemia
-Nephrotoxin exposure (aminoglycosides, contrast):
Nephrotoxins (exogeneous):
-Aminoglycosides (gentamicin)
-Amphotericin B
-Vancomycin
-Cephalosporins
-Contrast Dye (usually occurs 24-48 hours after contrast)
Nephrotoxins (endogenous)
-myoglobinuria as a consequence of rhabdomyolysis (Rhabdomyolysis occurs with an elevated serum creatine kinase)
-Bence Jones protein seen in conjunction with multiple myeloma
Lab Findings in Acute Tubular Necrosis
- Brown urine
- Serum BUN:Cr <20:1
- Urinary sediment shows granular casts
- Urinary osmolality 250-300
Treatment of ATN
-Loop Blocking Diuretics
Dialysis indications:
- life threatening electrolyte disturbances
- volume overload unresponsive to diuresis - worsening acidosis - uremic complications: encephalopathy, pericarditis, seizures