Indications for Dialysis

Dialysis is a renal replacement therapy used to remove waste products, correct electrolyte and acid base derangement, and manage fluid balance when native kidney function is insufficient to do so, whether in the context of acute kidney injury or end stage chronic kidney disease.

The two principal modalities are:

• Hemodialysis, in which blood is circulated through an external filter against a dialysate fluid across a semipermeable membrane, typically performed several times weekly in a dialysis unit or, in selected patients, at home.

• Peritoneal dialysis, in which the patient's own peritoneal membrane serves as the filtering surface, with dialysate instilled into and drained from the peritoneal cavity, typically performed daily at home either manually or via an automated overnight cycler.

The indications for urgent dialysis in acute kidney injury are commonly recalled using the mnemonic AEIOU, reflecting the specific, time critical complications that dialysis is used to correct when they fail to respond to medical management.

• Acidosis, specifically severe metabolic acidosis that is refractory to medical correction, is an indication, since uncorrected severe acidosis carries significant cardiovascular and metabolic risk.

• Electrolyte abnormality, most commonly severe or refractory hyperkalemia not adequately controlled by medical measures (calcium, insulin and glucose, salbutamol, potassium binders), is one of the most common acute indications given the immediate arrhythmic risk of significant hyperkalemia.

• Intoxication with a dialyzable substance, such as certain overdoses (for example lithium, salicylates, or methanol and ethylene glycol among others), is an indication where dialysis can meaningfully accelerate toxin clearance.

• Overload of fluid, causing pulmonary edema refractory to diuretic therapy, particularly in an oliguric or anuric patient where diuretics have limited further effect, is an indication.

• Uremia, specifically the clinical complications of uremia rather than a biochemical urea level in isolation, including uremic encephalopathy, uremic pericarditis, and significant uremic bleeding tendency, is an indication, since these represent the clinical manifestations that dialysis is specifically intended to reverse.

Dialysis initiation in progressive chronic kidney disease is generally guided by a combination of eGFR trajectory and the development of specific symptoms or complications, rather than by an eGFR threshold in isolation. Timing of initiation based on symptoms rather than a fixed number has been shown not to disadvantage patients and avoids unnecessarily early initiation.

Indications include the same AEIOU categories when they occur in the context of progressive, irreversible chronic kidney disease rather than resolving acute injury.

Further indications are:

• significant uremic symptoms (nausea, anorexia, pruritus, cognitive change);
• malnutrition attributable to advanced renal failure;
• an eGFR that has fallen to a very low level (generally in the range of 5 to 10 mL per minute per 1.73 m squared), even in the relative absence of overt symptoms.

This is given the recognized risks of delaying initiation too long in this setting.

Chronic dialysis planning includes the choice of modality and, for hemodialysis, the creation of vascular access such as an arteriovenous fistula well in advance of anticipated need. Planning should ideally begin once a patient's chronic kidney disease trajectory suggests dialysis is likely to be required within the coming months to a year or so.

Late referral and unplanned dialysis initiation, often via an emergency central venous catheter, carry worse outcomes than planned initiation with established access.

The choice between hemodialysis and peritoneal dialysis is guided by a combination of patient preference, lifestyle, comorbidity, and specific contraindications.

• Peritoneal dialysis is generally contraindicated or relatively unsuitable in patients with extensive prior abdominal surgery, significant abdominal wall hernia, or an inability to manage the technique either independently or with adequate support.

• Hemodialysis requires adequate vascular access and the ability to attend a dialysis unit regularly, unless home hemodialysis is being pursued.

Renal transplantation remains the optimal form of renal replacement therapy where feasible, offering superior long term survival and quality of life compared with either dialysis modality. It should be actively considered and discussed with suitable candidates, ideally well before dialysis becomes necessary, to allow for pre-emptive transplantation where a suitable donor is available.

Referral: nephrology for planning of renal replacement therapy in progressive chronic kidney disease, ideally well in advance of anticipated need; urgent nephrology involvement for any acute indication for dialysis in the context of acute kidney injury.