What is uraemic pruritus?
Uraemic pruritus is also called chronic kidney disease associated pruritus (CKD-associated pruritus). Uraemia refers to excessive urea in the blood, and occurs when both kidneys stop working (renal failure). Pruritus, or itch, is a common problem for patients with chronic renail failure or end stage renal disease. It affects about one-third of patients on dialysis and is more common with haemodialysis than continuous ambulatory peritoneal dialysis (CAPD).
Uraemic pruritus is not associated with gender, age, ethnicity, duration of dialysis, or cause of renal failure. Pruritus does not arise when uraemia is due to acute renal failure.
What are the signs and symptoms?
Uraemic pruritus is characterised by daily bouts of itching that tend to worsen at night and may prevent sleep. The itch may be generalised or localised to one area, most often the back, abdomen, head and /or arms. In haemodialysis patients, the pruritus is lowest the day after dialysis and peaks 2 days afterwards.
The skin may appear normal or dry (xerosis), with few to numerous scratch marks and/or picked sores.
What are the complications of uraemic pruritus?
Uraemic pruritus can be very unpleasant; about half of affected individuals become agitated or depressed. Uraemic pruritus in haemodialysis patients is associated with a 17% increase in mortality.
What causes uraemic pruritus?
Uraemic pruritus is thought to be due to a combination of factors including:
- Dry skin
- Reduced sweating
- Abnormal metabolism of calcium and phosphorus / raised parathroid hormone
- Accumulation of toxins
- Sprouting of new nerves
- Systemic inflammation
- Co-existing medical problems, particularly diabetes and liver disease.
Some patients have acquired perforating collagenosis.
What is the treatment of uraemic pruritus?
The first step in treatment is optimising dialysis efficacy. It is also important to attempt to reduce serum parathyroid hormone to normalise calcium / phosphorus.
Menthol and camphor may be added to an emollient to cool the skin and relieve the itch. Localised itch may be reduced by frequent applications of topical capsaicin, if tolerated.
Other treatments that have been reported to help some individuals include:
- Gabapentin and pregabalin
- Nalfurafine (opioid agonist)
- Activated charcoal
Kidney transplantation usually results in resolution of uraemic pruritus.