Uremic pruritus – a review Prasad PVS*, Kaviarasan PK, Nethra T and Kannambal

Uremic pruritus remains a frequent concern for hemodialysis patients with the most frustrating and disabling symptoms. The word uremic may denote that patients suffer from acute renal injury. Hence it is preferred to use the recent term “chronic kidney disease associated pruritus” (CKDassociated pruritus). The prevalence of CKD-associated pruritus in patients ranges from 15%-90% in various studies. Interestingly, in CKD associated pruritus the skin lesions are not found. The various skin lesions which range from excoriations, impetigo, linear crusts, papules and ulcers are secondary. Other co-existing diseases like cardiovascular diseases, diabetes, hypothyroidism, chronic liver or hematological diseases may challenge the diagnosis and management. The pathophysiology remains unexplained. There may be an imbalance between the antagonistic activities of μand] κ-opioid receptors. Itch sensation are correlated with the activation of certain areas in the brain, spatial and temporal aspects may be processed in the primary somatosensory cortex, planning of scratch response in the pre-motor and supplementary motor cortices, and affective and motivational aspects in the anterior cingulate cortex. A number of different mechanisms have been proposed like xerosis, transdermal water loss, accumulation of pruritogenic substances, increase in parathyroid hormone levels, high levels of urea, calcium, phosphate, β-2 microglobulin but none are convincing. Because of the poorly understood patho-physiological mechanisms the treatment of this condition, have been largely empirical. Reduced hydration may be alleviated by simple emollient therapy. Antihistamines have been widely prescribed in spite of lack of best evidence. UVB phototherapy helps many patients. Anti convulsant, gabapentin may have beneficial effect. Other ole remedies include fish oil, omega 3 fatty acids, IV heparin, thalidomide, lidocaine and mexitine. Recent studies demonstrated that nalfurafine as a systemic agent for two weeks would benefit most patients. All these treatment modalities are best only in addition to the dialysis related treatment like renal dialysis, erythropoietin and renal transplantation. Introduction Uremic pruritus with the most frustrating and disabling symptoms is a challenge to dermatologist, physician and nephrologist. The term “uremic pruritus” has been replaced by Patel etal.in the recent times as pruritus in these patients is not directly linked to acute kidney injury. Hence new term has been proposed as “Chronic Kidney Disease” (CKD) associated pruritus [1-4]. Patients with CKD not only suffer from pruritus but also from other co morbid conditions like drug induced reactions, diabetes mellitus, hypo/hyper thyroidism, lympho proliferative tumours and other neurologic, gastrointestinal and cardiovascular complications which may further complicate the treatment of pruritus [5]. CKD associated pruritus remains a frequent and sometimes a tormenting problem in patients with end stage renal disease (ESRD). Many studies were done in depth to analyze the factors behind this itch. All these were more contradictory rather than contributory. During the last two decades much importance were given for metabolic derangements and involvement of immune systems. Based on these findings, CKDassociated pruritus is now considered as systemic rather than an isolated skin disease. Hence understanding the pathophysiology will help in our concepts of management [6]. Pathophysiology The various factors are given in Table 1. Xerosis: Dry skin is present in the majority of patients undergoing dialysis. This could be due to atrophy of sweat or sebaceous glands or both. Some studies confirmed the findings that patients with CKD associated pruritus and level of hydration. There are contradictory reports in one study which claimed that the trans epidermal water loss is also normal in CKD associated pruritus patients [7-10]. Parathyroid hormone levels: Parathyroid hormones are not directly pruritogenic but it causes itching by a high calcium phosphorus product, precipitation of calcium and phosphorus in the skin and by causing mast cells to release histamine [11]. Disappearance of itching after parathyroidectomy is and evident for its involvement [12]. Correspondence to: Prasad PVS, Retd Professor & Dean, Rajah Muthiah Medical College, Annamalai University, Annamalai Nagar, Tamil Nadu, India, India 608002, Tel: 919894380771; E-mail: [email protected] Received: October 27, 2015; Accepted: November 30, 2015; Published: December 03, 2015 1. Xerosis 2. Parathyroid hormone levels