TOC |  STAT | Kidney

ACUTE RENAL FAILURE (ARF)           LAB  | DIFF-DX |  RX

REF: Acute Renal Failure     |  Normotensive Ischemic Acute Renal Failure 2007
Cleveland Clinic J of Med  July 2002 Vo. 69:569 - Joseph V. Nally (www.ccjm.org)

RX of the complications of intrinsic Acute Renal Failure:

1. Rx for fluid overload:  fluid & salt restriction, diuretics, dialysis or ultrafiltration.
2. Rx for hyponatremia:  water intake restriction
3. Rx for hyperkalemia:  K diet restriction, avoid K+ sparing diuretics, Kayexalate 30 g 3-4x/d PO + 100 mL 20% sorbitol to prevent constipation (or 30-50 g in 200 mL sorbitol rectal enema q6h), Ca-gluconate 10% 10 mL amp over 5 min (be careful if pt on digoxin), NaHCO3 7.5% 1-2 amp + insulin 10-15 u in 500 mL D5W over a couple hours; IV Furosemide 40-80 mg; Florinef (fludrocortisone 0.1-1 g/d.)
   *   Dialysis !
4. Rx for Metab. acidosis:  restrict diet protein <40-60 g/d; NaHCO3, Dialysis.
5. Hypocalcemia Rx:  CaCO3, or Ca-gluconate 10% 10-20 mL
6. Hyperphosphatemia Rx:  restrict diet phosphate intake, phosphate binding agents (CaCO3, Al-OH)
7. Hypermagnesemia Rx:  avoid Mg++ containing antacids
8. Hyperuricemia Rx:  usually not needed if < 15 mg/dL
9. Nutrition Rx:  diet protein 0.5 g/kg/d, carbohydrate 100 g/d
10. Drug dosage:  adjust for degree of renal impairment.
11. Dialysis for intractable fluid overload, hyperkalemia, metab. acidosis, & uremic symptoms & signs.
    

Measures to prevent acute renal failure in hospitalized patients:

• Prevent hypotension, & correct it rapidly when it does occur
• Evaluate renal function before any surgery
• Avoid prescribing nephrotoxic drugs
• Correct volume deficits or electrolyte imbalances, esp. before surgery
• Replace traditional contrast agents with non-ionic contrast, & use contrast sparing (good hydration before contrast-procedure)
• Treat infection quickly
• Treat oliguria quickly

How to evaluate patients wirh Acute Renal Failure

Review records perform history & physical examination

• Findings that suggest prereanl causes: volume depletion (hypotension), CHF, severe liver disease or other edematous states
• Findings that suggest postrenal causes: palpable bladder or hydronephrotic kidneys, enlarged prostate, abnormal pelvic examination, large residual bladder urine volume, history of renal calculi; hydronephrosis on renal ultrosonography.
• Findings that suggest intrinsic renal disease: hypotension, exposure to nephrotoxi drugs, recent radiographic procedures with contrast

Examine the urine sediment

• If no abnormalities;: suspect prerenal or postrenal azotemia
• If eosinophils: suspect acute interstitial nephritis
• If red bllod cell casts: suspect glomerulonephritis or vasculitis
• If renal tubular epithelial cells & muddy brown casts: suspect acute tubular necrosis

Calculate urinary indices

• Findings that suggest prerenal azotemia or glomerulonephritis
• • Urin [Na] < 20 mEq/L
  • Urin:plasma creatinine ratio > 30
  • Renal failure index < 1
    (Renal failure index = { Urin [Na] / urin [Creatinine]}X plasma [Creatinine]
  • Urine osmolalitiy > 500
• Findings that suggest acute tubular necrosis or postrenal azotemia
  • Urin [Na] > 40 mEq/L
  • Urin:plasma creatinine ratio < 20
  • Renal failure index >1
    (Renal failure index = { Urin [Na] / urin [Creatinine]}X plasma [Creatinine]
  • Urine osmolalitiy < 400

Urine findings in Prenal azotemia vs Acute Renal Failure

Laboratory Tests	Prenal azotemia  or   Glomerulonephritis	Acute renal failure or  Postrenal azotemia
Specfic gravity	>1.018	<1.012
Urine osmolality	> 300 - 500	< 300 - 400
Urine Na (meq)	< 20 meq/l	> 40 meq/l
Urine/plasma creatinine	> 40	< 20
Renal failure index (U Na/ U/P creat)	< 1	>2
Fractional excreation Na (U/P Na/ U/P creat)x100	<1	>2
Response to fluid challenge	++	?
Urine sediment	normal	hyaline cast brown granular casts, cellular debris

Differential Diagnosis of Acute Renal Failure - 3 Types

A. PRERENAL AZOTEMIA (due to underperfusion of an otherwise normal kidney)

1. Hypovolemia: hemorrhage, GI fluid losses, diuretics, third spacing (pancreatitis, peritonitis, burns, traumatized tissue)
2. Heart failure: CHF, MI, pericardial tamponade, acute PE
3. Peripheral vasodilatation: bacteremia, antihypertensive medications
4. Increased renal vascular resistance: anesthesia, surgical operation, hepatorenal syndrome.
5. Renovascular obstruction, bilateral: thromboembolism

B. POSTRENAL AZOTEMIA  (due to obstruction of the urinary tract)
      - diagnosed by renal ultrasonography  to detect the Urinary Tract Obstruction.

1. Urethral/bladder obstruction: prostate enlargement, plugged Foley catheter, stone, trauma, tumor(cancer), spasm, swelling (inflammation or infection), neurogenic bladder (+/ ganglionic blocking agents)
2. Bilateral ureter obstruction a. Intraureteral: blood clots, sulfonamide & uric acid crystals, pyogenic debris, stones, edema, necrotizing papillitis. b. Extraureteral: tumor (cervix, prostate, endometriosis), periureteral fibrosis, accidental ureteral ligation during pelvic operation.

C. RENAL DISORDERS/ AZOTEMIA

1. Nephrotoxins, including hypersensitivity reactions
   a. Antibiotics: aminoglycosides, amphotericin B, vancomycin, sulfa, tetracycline, pesticides, fungicides; cephalosporin, pentamidine, Foscanet, Acyclovir, Indinavir, Ritonavir.  
   b. X ray contrast media or toxins  (esp. in Diabetes Mellitus)
   c. Heavy metals: mercury, lead, arsenic, bismuth, uranium, cadmium
   d. Ethylene glycol poisoning, carbon tetrachloride, other oranic solvents, pesticides, fungicides
   e. Other drugs & chemical agents: ACE Inhibitors; anesthetics (methoxyflurane, enflurane),  phenacetin, diphenylhydantoin, phenylbutazone, uric acids, calcium, poisonous mushroom, venom, NSAID, methotrexate, cis-platinum, cyclosporin, etc.
   
2. Ischemic disorders - Acute Tubular Necrosis (ATN)
   • Shock or hypotensive episodes: hypovolemia, hemorrhage, sepsis, cardiac failure, neurogenic shock, third spacing, etc.
   • Major trauma, burn, crush syndrome, rhabdomyolysis, myoglobinuuria
   • Transfusion reactions, hemolysis
   • Postoperative, esp. after cardiac, aortic, biliary surgery.
     
3. Major blood vessel disease:
   renal artery thromboembolism, stenosis, bilateral renal vein thrombosis, dissecting aortic aneurysm.
   
4. Diseases of glomeruli & small blood vessels:
   • Acute posotstreptococcal glomerulonephritis
   • Idiopathic rapidly progressive glomerulonephritis
   • Postpartum renal failure
   • SLE glomerulonephritis
   • Vasculitis: polyarteritis nodosa, Schonlein Henock purpura, TTP, Goodpasture's syndrome, Wagener's granulomatosis, mixed essential cryoglobulinemia,  drug related vasculitis, serum sickness, subacute bacterial endocarditis, hemolytic uremic syndrome
   • Malignant hypertension
   • Renal failure of pregnancy
     
5. Interstitial nephritis:
   a. Drugs as Penicillin semisynthetic analogues, sulfonamides, tetracycline, cephalosporin, rifampin, coumadin, lasix, thiazide, azathioprine, allopurinol, phenytoin, tagamet, acyclovir.
   b. Diffuse infection
   c. Hypercalcemia  or hyperuricemia nephritis
   d. Postpartum renal failure
   e. SLE glomerulonephritis
   f . Vasculitis: polyarteritis nodosa, Sarcoidosis
   
6. Renal allograft rejection

(REF: Harrison's Med Text )

REF:

Acute Renal Failure
Cleveland Clinic J of Med  July 2002 Vo. 69:569 - Joseph V. Nally

Acute Renal Failure
Naveen Singri, MD; Shubhada N. Ahya, MD; Murray L. Levin, MD
JAMA Feb.12, 2003 Vol. 289:747  

ACP Best Dx/Best Rx 2007

Acute Renal Failure

Mary Jo Shaver, M.D., Sudhir V. Shah, M.D.
University of Arkansas for Medical Sciences

Definition/Key Clinical Features  

* An abrupt decrease in renal function occurring over hours to days sufficient to result in retention of nitrogenous waste

* Usual criteria are as follows:

• Increase in serum creatinine of 0.5 mg/dl or

• 25% increase in serum creatinine or

• 25% decrease in glomerular filtration rate (GFR)

* Epidemiology

• Incidence: 1% of hospital admissions

• Affects 2% to 5% during hospitalization

• Affects up to 20% of patients in intensive care units

• Occurs in 4% to 15% of patients after cardiovascular surgery

* Prognosis

• Mortality: 50% to 80% in acute renal failure (ARF) associated with sepsis, hypotension, and respiratory failure

• Complete recovery of renal function in most survivors

• Small percentage of patients with acute tubular necrosis (ATN) may require long-term dialysis

* Clinical manifestations

• Fatigue

• Weakness

• Nausea

• Vomiting

• Loss of appetite

• Metallic taste in mouth

• Itching

• Confusion

• Fluid retention

• Hypertension

Differential Diagnosis

* Prerenal azotemia

• Absolute decrease in effective blood volume

• Relative decrease in blood volume (ineffective arterial volume)

• Arterial occlusion

* Renal azotemia

• Vascular causes

• Acute glomerulonephritis

• Acute interstitial nephritis

• Acute tubular necrosis

  • Ischemia

  • Sepsis syndrome

  • Nephrotoxicity

    • Exogenous nephrotoxins

    • Endogenous nephrotoxins

* Postrenal azotemia (obstruction of collecting system)

Best Tests for Acute Renal Failure

* History

• Previous renal function

• Nephrotoxins

  • Medications

    • NSAIDs

    • Aminoglycosides

    • Amphotericin B

    • Cisplatin

    • Angiotensin-converting enzyme inhibitors (in volume-depleted patients)

  • Radiocontrast agent

  • Ethylene glycol

  • Rhabdomyolysis

  • Hyperuricemia (tumor lysis syndrome)

  • Hepatorenal syndrome

• o Surgery

  • Type and duration

  • Hemodynamics

  • Blood loss

  • Anesthetic used

• Infection or sepsis

* Physical examination

• Fever

• Volume status

  • Orthostatic hypotension

  • Edema

  • Jugular venous distention

  • Crackles

  • S3 gallop

• Skin

  • Diffuse rash (drug reaction)

  • Livedo reticularis

  • Atheroemboli

• Bladder

  • Suprapubic fullness

  • Bladder catheterization to assess postvoid residual volume and to relieve bladder obstruction

* Laboratory studies

• Blood urea nitrogen (BUN)

• Serum creatinine

• Electrolytes

• Urinary volume

• Urinalysis and urine sediment

• Urinary indices

  • Used to differentiate between prerenal azotemia and ATN

  • Urinary sodium: prerenal azotemia, < 20; ATN, > 40

  • Urine osmolarity: prerenal azotemia, > 500; ATN, < 450

  • Fractional excretion of sodium: prerenal azotemia, < 1%; ATN, > 1%

  • BUN-to-creatinine ratio: prerenal azotemia, > 20:1; ATN, NA

  • Urine creatinine–to–plasma creatinine ratio: prerenal azotemia, > 40; ATN, < 20

* Imaging studies

• Indications

  • Diagnosis uncertain, clinical situation suggests other possibilities (e.g., obstruction, vascular accident)

  • Clinical findings make diagnosis of prerenal azotemia or ATN less likely

  • Oliguria persists > 4 wk

• Renal ultrasonography

  • Initial imaging procedure of choice

• High-resolution CT

  • Test of choice for suspected urinary tract calculi

• Radionuclide methods

  • Assessing renal blood flow and excretory function

• Magnetic resonance angiography

  • Evaluation of renal arterial or venous thrombosis or obstruction  

Best Therapy for Acute Renal Failure

Prevention of Acute Renal Failure

* Identify patients with risk factors

• Advanced age

• Abnormal renal function or diabetes

• Volume depletion

• Recent vascular surgery

• Recent trauma

* Avoid nephrotoxic agents

* Apply preventive strategies in specific circumstances

• Use of contrast media

  • Hydration with normal saline 1 ml/kg/hr 8–12 hr before and 8–12 hr after procedure

  • Limit volume of contrast used

  • Iso-osmolar contrast for high-risk patients

  • Acetylcysteine, 600 mg p.o., b.i.d., day before and day of procedure

• Tumor lysis syndrome

  • Hydration and forced diuresis

    • Infuse normal saline to maintain urine output 3–5 L/day

  • Urinary alkalization

    • Infuse 100–150 mEq sodium bicarbonate to maintain urine pH > 7

    • Infuse acetazolamide 1 g/m2

    • Avoid significant metabolic alkalosis

  • Allopurinol, 300–600 mg/day, starting 3 days before chemotherapy; adjust dose for renal impairment

* Rhabdomyolysis

• Hydration

  • Infuse normal saline to replace any volume depletion, then infuse at 200–300 ml/hr and follow hemodynamic status

• Pharmacologic treatment

  • Mannitol (25 g/100 ml) + sodium bicarbonate (100 mEq/100 ml) + 800 ml 5% dextrose in water

  • Infuse at 250 ml/hr

  • Monitor fluid intake, urine output, basic metabolic panel

  • If urine output good, continue infusion until myoglobinuria resolves

  • If patient oliguric (urine output < 400 ml/24 hr), stop infusion, manage as established renal failure

• Surgical procedures

  • Recognize patients with high-risk conditions

  • Avoid volume depletion

  • Avoid hypotension

  • Avoid nephrotoxic agents

Management of Acute Renal Failure

* Emergent intervention

• Severe hyperkalemia

• Marked fluid overload with pericardial tamponade

• Extreme metabolic acidosis

* Dialysis

• Severe hyperkalemia, acidosis not easily controlled by medical treatment, or both

• Fluid overload not responsive to fluid restriction, diuretics, or both

• Signs or symptoms of uremia (e.g., pericardial friction rub, asterixis, mental status changes, seizure)

* Supportive therapy

• Nutritional support in patients with ATN

* Treatment of complications

• Volume overload

• Hyponatremia

• Hyperkalemia

• Acidosis

• Calcium and phosphate imbalances

• Anemia

Best References

• Blantz RC: Kidney Int 53:512, 1998 [PMID 9461116]

• Brivet FG, et al: Crit Care Med 24:192, 1996 [PMID 8605788]

• Kandzari DE, et al: Am J Cardiovasc Drugs 3:395, 2003 [PMID 14728060]

• Sheridan AM, et al: Curr Opin Nephrol Hypertens 9:427, 2000 [PMID 10926180]