Saliva composition and upper gastrointestinal symptoms in chronic kidney disease

To investigate self-reported upper gastric symptoms experienced by patients with chronic kidney disease (CKD) and compare associations between uraemic symptoms and saliva composition.

In a cross-sectional observational study, 30 patients with Stages 4 and 5 CKD were selected from a tertiary hospital renal outpatient clinic. Subjects answered a questionnaire to assess upper gastrointestinal (GI) symptoms. A saliva sample was collected to determine biochemical composition. Possible associations between saliva composition and uraemic upper GI symptoms were assessed.

Only 3 (10%) patients reported no upper GI symptoms whilst 19 (63%) complained of a dry mouth, 16 (56%) had a change in taste, 9 (30%) had nausea, 7 (23%) vomited and 7 (23%) dry retched. Lower saliva bicarbonate concentration related to both dry mouth (p < 0.003) and dry retching (p < 0.01). An elevated level of saliva calcium was also implicated in a dry mouth sensation (p < 0.01). Nausea was associated with higher saliva sodium levels (p < 0.03) and a higher saliva sodium/potassium ratio (p < 0.02).

Altered saliva composition in patients with Stages 4 and 5 CKD may be associated with uraemic upper GI symptoms. In particular, lower saliva concentrations of bicarbonate are associated with dry mouth and retching. Higher saliva calcium levels are also related to a dry mouth whilst higher saliva sodium levels and a greater sodium/potassium ratio are associated with nausea. Further studies investigating strategies to improve uraemic symptoms via changes in saliva are required.