SALIVA COMPOSITION AND UPPER GASTRO-INTESTINAL SYMPTOMS IN CHRONIC KIDNEY DISEASE

Abstract

Many chronic kidney disease (CKD) patients experience uraemic symptoms including dry mouth, taste changes, nausea, vomiting and dry retching. Saliva is composed of a number of active compounds that play vital roles in taste stimulation. Salivary composition differs in CKD and patients have an impaired ability to recognise basic tastes. The purpose of this cross-sectional study was to determine any associations between changes in salivary composition, upper gastrointestinal (GI) symptoms and altered taste perceptions in chronic renal failure patients. Thirty CKD patients (24 males, 6 females, age 69.7 ± 14.2yrs, glomerular filtration rate <25mL/min) were recruited from the Austin Health outpatient renal clinic. A saliva sample was collected to determine biochemical composition. Participants performed a taste identification task to assess perception of the five basic tastes and completed a symptom questionnaire regarding taste changes and upper GI symptoms experienced. Only 3 (10%) CKD patients reported no upper GI symptoms while 63% complained of a dry mouth, 56% had a changes in taste, 30% complained of nausea and 20% vomited or dry retched. Saliva bicarbonate concentration was inversely related to both dry mouth (p<0.003) and dry retching. (p<0.01) Nausea was reported with higher saliva sodium levels (p<0.03) and a higher saliva sodium/potassium ratio (p<0.02). Correlation analysis revealed saliva bicarbonate concentration was inversely related to liking and intensity of glutamate taste and to the intensity of sour taste (p<0.05). Salivary urea was linked to the perceived intensity of bitter taste (p<0.05). Forty-three percent of patients indicated their symptoms contributed to decreased food intake. In conclusion this study provides evidence that active compounds are present in the saliva and impact upper GI symptoms in CKD. In particular lower saliva concentrations of bicarbonate are associated with dry mouth and retching, while higher sodium levels and a greater sodium/potassium ratio are associated with nausea. Saliva bicarbonate and urea are associated with taste perception, especially for glutamate and may influence taste function. Further research is required to clearly establish if changing saliva composition improves uraemic symptoms, taste sensitivity and food intake in CKD patients.