Dyspeptic patients with visceral hypersensitivity: sensitisation of pain specific or multimodal pathways?

Background and aims: Patients with functional dyspepsia who have hypersensitivity to gastric distension have more prevalent pain, suggesting the presence of hyperalgesia. It is unclear whether this reflects activation of pain specific afferent pathways or multimodal afferent pathways that also mediate non-painful sensations. In the former case, hyperalgesia should occur when intensity of non-painful sensations is still low. The aim of the study was to analyse whether the symptom profile during gastric dissentions in functional dyspepsia patients with hyperalgesia reflects sensitisation of pain specific or multimodal pathways. Methods: Forty eight consecutive dyspeptic patients (35 female) underwent gastric sensitivity testing with a barostat balloon using a double random staircase protocol. At the end of every distending step, patients scored perception of upper abdominal sensations on a graphic 0-6 rating scale and completed visual analogue scales (VAS 0-100 mm) for pain, nausea, satiety, and fullness. The end point was a rating scale of 5 or more. Results: Hypersensitivity was present in 20 patients (40%); gastric compliance did not differ between normo- and hypersensitive patients. At maximal distension (score 5 or more), hypersensitive patients had significantly lower distending pressures and intra-balloon volumes, but similar VAS scores for pain, nausea, satiety, and fullness compared with normosensitive patients. In both normosensitive and hypersensitive patients, elevation of pain VAS scores with increasing distending pressures paralleled the elevation in VAS scores for nausea, satiety, and fullness. Conclusions: Hypersensitive dyspeptic patients reach the same intensity of painful and non-painful sensations as normosensitive patients but at lower distending pressures. Hyperalgesia occurs in hypersensitive dyspeptic patients at distending pressures that also induce intense non-painful sensations. These findings argue against isolated upregulation of pain specific afferents in functional dyspepsia patients with visceral hypersensitivity.