Renal disease in a child: Acute Renal Failure Flashcards
Define acute renal failure.
A significant deterioration in renal function occurring over hours or days, resulting in increased plasma urea, creatinine and oliguria. Complete recovery of renal function usually occurs within days/weeks.
What are some pre-renal causes of acute renal failure?
- Hypovolaemia: Haemorrhage, GI losses, DKA, burns, diarrhea, septic shock.
- Cardiac failure: Severe coarctation, hypoplastic left heart, myocarditis.
- Hypoxia: Pneumonia, RDS.
What are some intrinsic renal causes of acute renal failure?
- Acute tubular necrosis (ATN) (80% of intrinsic renal causes) due to circulatory compromise or nephrotoxic drugs (paracetamol, aminoglycosides)
- Acute GN
- Acute interstitial nephritis: Infection, drugs: NSAIDS, frusemide, penicillin
- Small/large vessel obstruction: Renal artery/vein thrombosis, vasculitis, HUS, TTP
What are some post-renal (obstructive) causes of acute renal failure?
- Neuropathic bladder: May be acute in transverse myelitis, spinal trauma.
- Stones: Bilateral pelvicureteric junction or ureteral.
- Urethral prolapse of bladder ureterocele
- Iatrogenic: Catheters, stents, nephrostomy or surgery
What is the pathophysiology of acute tubular necrosis?
Macro: Enlarged kidneys with pale cortex.
Micro: Swelling and necrosis of the tubular cells, interstitial oedema with macrophage and plasma cell infiltration.
Summarise the epidemiology of acute renal failure.
0.8/100,000 children
What are symptoms of acute renal failure?
Vomiting
Anorexia
Oliguria
Convulsions
Previous sore throat and fever (post-streptococcal GN)
Bloody diarrhoea and progressive pallor (HUS)
Drug history
What are signs of acute renal failure?
Assess intravascular volume status: Volume depleted (cool peripheries,tachycardia, postural hypotension) or overloaded (oedema, weight gain, pulmonary oedema)
Septic
Obstruction
Examine abdomen for palpable bladder
What are appropriate investigations for acute renal failure?
Bloods: Decreased Hb (hypovolaemia/haemorrhage), increased WCC, increased CRP, blood cultures (sepsis), increased urea, increased creatinine, increased potassium, increased phosphate, decreased calcium, decreased magnesium, LFTs, venous capillary blood gas, clotting (DIC), ASOT (post-streptococcal GN)
Blood film: HUS/TTP (RBC fragmentation).
Urine: Urinalysis for blood, protein (GN), glucose (interstitial nephritis), microscopy for casts (GN), urine Na+, urea, creatinine, osmolality to differentiate between pre-renal and instrinsic renal failure
ECG: Signs of hyperkalaemia; tall tended T wave; small or absent P waves; increased P-R interval; widened QRS complex; sine wave pattern; asystole.
CXR: Signs of pulmonary oedema
Renal USS: In ARF, kidneys appear normal or increased in size and echogenicity, may detect stones or clot in renal vein thrombosis (RVT)
Renal biopsy: If diagnosis has not been determined
Monitor: Daily U&E, temperature, PR, RR, BP, O2 saturation, strict input/output (need to catheterize), daily weights
What is the management for acute renal failure?
Resuscitate: Especially in pre-renal causes of ATN
Fluids: Allow insensible losses (400 ml/m2) + ml for ml replacement of urine output in acute phase
Treat the cause
What are indications for acute dialysis?
- Severe extracellular fluid volume overload, increase BP, pulmonary oedema not responding to diuretics
- Severe increase in K+; not responding to medical treatment
- Severe systematic uraemia
- Severe metabolic acidosis, not controllable with IV bicarbonate
- Removal of toxins (drugs, poisons)
What are complications associated with acute renal failure?
Heart failure and pulmonary oedema (volume overload)
GI bleeding (gastric ulceration and platelet dysfunction)
Muscle wasting due to hypercatabolic state
Uraemic encephalopathy
What is the prognosis of acute renal failure?
Depends on the causative factor.
Recovery of renal function following ARF is most likely following pre-renal causes, HUS, ATN, acute interstitial nephritis or uric acid nephropathy.
