Pain and biomechanical responses to distention of the duodenum in patients with systemic sclerosis

Abnormalities of the small intestine have been indicated in systemic sclerosis. The aim was to use a new method to study the active-passive mechanical and sensory properties of the duodenum in these patients.

A volume-controlled ramp-distention protocol was used in the duodenum in 9 patients and 8 healthy controls. The nonpainful/painful sensations, pressure, cross-sectional area, wall tension, and strain were evaluated. Using butylscopolamine for muscle relaxation, the active (contractile muscular component) and passive (other mechanical tissue components) were computed.

The contraction amplitude was smaller and the cross-sectional area higher in the patients (P < 0.05). Both the active and passive tension as function of strain was translated to the left in the patients, indicating a stiffer wall. The maximum active tension and the corresponding strain were 62% and 69% lower in the patients (P < 0.05). An association was found between the duration of the disease and the strain (P < 0.05). The perception score was higher as function of pressure, tension, and strain (P = 0.01, P = 0.03, and P < 0.01, respectively) in the patients than in the controls, with strain as the most sensitive variable to describe the sensory response. In 5 patients who complained of regular clinical symptoms, the referred pain area to distention was enlarged.

Systemic sclerosis resulted in increased stiffness and impaired muscle function of the duodenum. The pain evoked by a controlled strain of the gut was increased and can explain many of the symptoms reported in the clinic.