From the Guidelines
Generalized pruritus can be provoked when blood urea nitrogen (BUN) levels exceed approximately 50-100 mg/dL, though this threshold varies between individuals. This is based on the understanding that uremic pruritus, the itching associated with elevated BUN levels, typically occurs in advanced kidney disease when the kidneys cannot effectively filter waste products from the blood 1. The mechanism involves uremic toxins irritating nerve endings in the skin, mast cell proliferation, and immune system dysregulation.
Key Points to Consider
- Uremic pruritus is a common feature of patients with end-stage renal disease (ESRD) or chronic kidney disease, affecting approximately 42% of patients on haemodialysis 1.
- The severity of pruritus is lower in ESRD treated with peritoneal dialysis, rather than haemodialysis 1.
- Dry skin (xerosis) is the most common cutaneous sign in patients on dialysis, although this does not necessarily correlate with pruritus 1.
- Management focuses on treating the underlying kidney disease, optimizing dialysis if applicable, and symptomatic relief with moisturizers, topical corticosteroids, antihistamines, or gabapentin.
Treatment Strategies
- Ensuring adequate dialysis, normalizing calcium–phosphate balance, controlling PTH to accepted levels, correcting any anaemia with erythropoietin, and using emollients (for xerosis) are common practices before using other treatment strategies 1.
- High-flux haemodialysis is more effective in treating uraemic pruritus than haemodialysis filtration 1.
- Oral antihistamines, such as ketotifen or doxepin, may be effective in uraemic pruritus, but their use should be cautious due to potential side effects like drowsiness and the risk of dementia with long-term sedative antihistamines 1.
From the Research
BUN Level and Generalized Pruritis
- The provided studies do not directly mention a specific BUN level that can provoke generalized pruritis 2, 3, 4, 5, 6.
- However, it is known that uremic pruritus is a common symptom in patients with end-stage renal disease (ESRD) and those undergoing dialysis, suggesting a link between kidney function and pruritis 2, 3, 5, 6.
- The pathophysiology of uremic pruritus is not fully understood, but it is thought to involve an imbalance of μ and κ-opioid receptor activity, as well as a chronic inflammatory state and altered immune signaling 5.
- Treatment options for uremic pruritus include gabapentin, which appears to be the most evidence-based widely available treatment, as well as other agents such as difelikefalin and nalfurafine 2, 3, 5.
- The lack of awareness and underdiagnosis of uremic pruritus can lead to unsuccessful treatment, highlighting the need for increased awareness and effective treatment algorithms 6.