Impact of sex and psychological factors on the water loading test in functional dyspepsia.

BACKGROUND: The pathogenesis of upper abdominal symptoms in patients with functional dyspepsia (FD) is still unclear. The water loading test (WLT) is a new method for evaluation of gastric function. Our aim was to determine the impact of sex, age and psychological factors on the results of WLT in FD patients, FD-subgroups and healthy controls (HCs), and to evaluate the safety of the test.
METHODS: Fifty-six HCs and 35 consecutive patients with FD drank mineral water (100 ml/min) until intolerable. Serum samples for sodium, potassium and creatinine was taken before and after drinking. Water quantity was registered and symptoms were assessed after maximal water intake and 30 min later using a VAS scale. Participants also completed questionnaires measuring psychological general well-being (PGWB) and gastrointestinal symptoms (GSRS and Mearin score).
RESULTS: Healthy men drank more than healthy women, 2350 +/- 105 ml versus 1860 +/- 100 ml (P < 0.01), and the same gender difference was noted in FD patients, 1770 +/- 115 ml versus 1180 +/- 110 ml (P < 0.01). Maximal water intake was significantly higher in HC than in FD patients, both in males (P < 0.001) and females (P < 0.0001). Age had no impact on drinking capacity. FD patients had more symptoms 30 min after maximal water intake than HCs. Serum sodium decreased from 141 +/- 0.3 mmol/l to 138 +/- 0.5 mmol/l. Two of the assessed psychological factors, general health and depressed mood, correlated with water intake in FD patients (Rho = 0.47, P < 0.01 respectively Rho = 0.41, P < 0.05).
CONCLUSION: WLT is a useful, simple and safe test for evaluating symptoms in FD patients. Sex, but not age affects the results of the WLT. Furthermore, psychological factors must also be taken into consideration when interpreting the WLT.