Acute on Chronic Renal Failure

Any sudden decline in renal function in patients with known chronic renal failure requires rapid assessment, diagnosis and appropriate management to prevent an accelerated and possibly irreversible decline in renal function. The patient may be known to have chronic renal failure or may be presenting for the first time, having been previously not known to have chronic kidney disease. Management is directed towards identification and treatment of the underlying cause of the acute deterioration of renal function, and treatment for acute renal failure.

The most common causes are infection (e.g. UTI, chest infection, central line), drugs (e.g. diuretics, ACE inhibitors), dehydration, urinary tract obstruction or renal vein thrombosis (particularly in patients with nephrotic syndrome). Likely causes include:

• Renal hypoperfusion:
  • Dehydration from diarrhoea, diuretics, surgery
  • Cardiac failure
  • Pericardial tamponade
  • Aortic dissection
  • Renal vascular disease
  • Drugs, especially ACE inhibitors, NSAIDs
  • Systemic infection, septicaemia
• Obstruction and infection of the urinary tract: urinary retention, e.g. due to spinal cord compression or neurogenic bladder, and asymptomatic infection (particularly common in the elderly) are easy to miss and should always be considered as a possible cause of acute on chronic renal failure. Possible underlying causes of urinary retention and/or infection include:
  • Papillary necrosis and sloughing
  • Stones
  • Pelvic malignancy
  • Bladder cancer
  • Polycystic cysts
  • Clot in the ureter
• Metabolic and toxic:
  • Diabetic ketoacidosis, hyperosmolar coma
  • Hypercalcaemia
  • Hyperuricaemia
  • Contrast media (especially in diabetes)
  • Drugs, especially aminoglycosides
• Progression of underlying diseases, e.g. relapse of glomerulonephritis
• Development of accelerated-phase hypertension
• Renal vein thrombosis: usually occurs in chronically nephrotic patients
• Pregnancy: at the end of the pregnancy or after delivery (e.g. in patients with reflux nephropathy), pre-eclampsia, eclampsia

The patient may present with the cause of the exacerbation (e.g. local infection), features of chronic failure or may present with acute renal failure.

Clinical assessment should include:

• Identifying possible causes of acute exacerbation, e.g. drug history, signs of infection evidence of prostatic hypertrophy.
• Identifying any degree of urinary tract obstruction.
• Assessment of pre-existing renal function and whether episode represents acute on chronic renal failure or acute renal failure in patient with previously normal renal function (see separate articles on Chronic Renal Failure and Acute Renal Failure).
• Assessment of blood pressure and general cardiovascular status.

Investigations

• Serial assessment of renal function: serum urea, creatinine and electrolytes.
• Urine: urinalysis, microscopy, electrolytes and protein excretion.
• Full blood count.
• Infection swabs and cultures as appropriate.
• ECG: evidence of hyperkalaemia, myocardial infarction.
• Ultrasound of urinary tract and lower abdomen to identify urinary tract obstruction or urinary tract abnormalities
• Further investigations and management will depend on wellbeing of the patient, likely cause of the exacerbation and current renal function.
• A full assessment as described in the article on acute renal failure may be required.
• Renal biopsy may also be required.

Other causes of raised urea and creatinine:

• Raised urea can also be caused by intravascular volume depletion, diuretics, congestive heart failure, gastrointestinal bleeding, corticosteroids and tetracyclines.
• Creatinine levels can be increased by muscle damage (rhabdomyolysis) and decreased tubular secretion, e.g. cimetidine, trimethoprim.
• Ingestion of cooked meat and severe exercise cause a rapid but temporary rise in serum creatinine.

• Management involves treatment of the underlying cause and management of acute renal failure.
• Depending on the nature and certainty of the cause, clinical wellbeing and underlying renal function, patients often require referral to hospital for full assessment and appropriate management.
• However some patients with an obvious cause and who are clinically stable may be safely managed at home.