Acute Renal Failure (ARF)
Acute Renal Failure (ARF)
Acute renal failure is the rapid loss your kidneys’ ability to remove waste and help balance fluids and electrolytes in your body. In this case, rapid means within 7 days.
Causes of Acute Renal Failure (ARF)
Acute Renal Failure
Pre-renal causes
Prerenal causes include systemic causes, such as low blood volume, low blood pressure, heart failure, liver cirrhosis and local changes to the blood vessels supplying the kidney. The latter include renal artery stenosis, or the narrowing of the renal artery which supplies the kidney with blood, and renal vein thrombosis, which is the formation of a blood clot in the renal vein that drains blood from the kidney.
Renal ischaemia ultimately results in functional disorder, depression of GFR, or both. These causes stem from the inadequate cardiac output and hypovolemia or vascular diseases causing reduced perfusion of both kidneys. Both kidneys need to be affected as one kidney is still more than adequate for normal kidney function.
Volume contraction (diarrhoea, vomiting, sweating, burn)
Hypotension, shock, septicemia
Severe heart failure and myocardial infarction.
Intra – renal causes
(1) Arteriolar injury
Accelerated hypertension
Polyarteritis nodosa and SLE
Thrombotic thrombocytopenic purpura
Haemolytic uremic syndrome
(2) Glomeruonephritis (GN)
Rpgn(Rapidly Progressive Glomerulonephritis), post streptococcal N,Vaculitis, SLE, Goodpasture syndrome
(3) Tubulo-interstitial injury
Allergic, drug induced, toxin induced, contrast media induces, Intra-renal deposition of myeloma protein and uric acid.
(4) Hepato renal syndrome (including Weil’s disease)
Post-renal causes
1. Urethral obstruction : Clot, calculus, tumor, external compression.
2. Bladder outlet obstruction, Neurogenic bladder, Prostatic hypertrophy, Carcinoma, Calculus, Stricture urethra
3. Obstruction to renal arteries and veins
Acute Renal Failure causes
Findings in Acute Renal Failure
Pre-renal
Urinary sodium < 10 mEq /l
Urinary osmolality > 500 mosm / l
Urine : plasma osmolality 1.1
Urine : plasma cretinine concentration > 20
ATN
Urinary sodium > 20 mEq/l
Urinary osmolality < 400 mosm / l
Urine : plasma osmolality 0.9 – 1.05
Urine : plasma cretinine concentration < 15
Non-Oliguric renal failure occurs in
Shock, Aminoflycosides, Radiographic contrast material,Toxemia of pregnancy, Crush injuries, Analgesic nephropathy.
Clinical features of Acute Renal Failure
Polyguric phase
Lethagy, headache, nausea, etc. due to water retention
Oliguric phase
Vomiting, abdominal pain, adynamic ileus, acidotic reath, kussmaul’s breathing, drowsiness, confusion, agitation, cramps, twitching, chest pain (Pericarditis), neuropathy, hypertension, dypnoea, tremor.
Diruetic phase
Polyuria, dehydration, fever, aggravation of uremic symptoms.
Investigations of Acute Renal Failure
Urine exmamination, specifc gravity of urine,CVP (central Venous Pressure) measurement
Blood urea, creatinine, electrolytes
HBSAg, HBC Ab
Renal ultrasound
ASO titre, throat swab culture
Auto antibody screen, (SLE) C3
Renal biopsy if (1) cause of ARF uncertain (2) failure of ARF to resolve in 6-8 weeks.
Treatment for Acute Renal Failure
Incipient ARF
1. Correction of hypotension by saline infusion and vasopressors (doapamine), donot use RL or DNs
2. Lasix 2 mg / kg IV, two doses
3. Treatment of heart failure by diuretic, dialysis, ultrafiltraiton.
4. Treatment of metabolic acidosis by sodium bicarbonate.
5. Treatment of hyperkalemia by 50% IV glucose 100 ml + 25 units Sol. Insulin.
Estabilised ARF
1. Fluid management (500 ml plus urine output)
2. Diet including
Calori 25-50 kcal / kg / d
Protein restriction to 0.5g / kg / d
Salt restriction 2- 4 g / d
Potassium 50 mEq/d
3. Phosphate and calcium : product maintained at < 70.
4. Allupurinol 200 mg. Orally daily if serum uricaid > 10 mg/dl
5. Correction of acidosis, hyperkalemia, prophylactic antibiotics
6. Drug dosage modifications
7. Dialysis-peritoneal (PD) or haemodialysis (HD)
Indications for Dialysis
Volume overload
BUN over 150 mg %
Hyperkalemia (serum K+ > 7.0 mEq/L
Severe acidosis (serum HCO3 < 12 mEq /L)
Neurologic symptoms (encephalopathy)
Uremic pericarditis
Excessive catabolism
Aggressive protein restriction not possible
Before diagnosis of ARF do renal Ultra Sound. If both kidneys are shrunken then you are dealing with acute on cronic renal failure. Such patients may have features of renal ostedystrophy.
Fluid management is very crucial in ARF. The IV line can be a death line. Patients of diarrhoea and vomiting with ARF receiving too much of Ringer lactate, ORS and orange juice often die of fatal hyperkalemia
Prognosis of Acute Renal Failure
Post trauma ARF mortality – 60%
Post surgery ARF mortality – 40%
Obstetric ARF mortality – 40%
Complications of Acute Renal Failure
1. Infections of a urinary tract, abdomen, septicemia.
2. Hypertension
3. G.I. bleeding
4. Anaemia : due to (a) shortened RBC survival
(b) Decreased Red Blood Cell production
(c) Increased Red Blood Cell loss
5. Neurologic abnormalities
6. Uremic pericarditis, Paralytic ileus
7. Metabolic disturbances – Hyperphosphatemia,
Hyperkalemia,
Hypocalcemia,
Hyperurecemia and Metabolic acidosis
