Effects of fractionated abdominal irradiation on small intestinal motility--studies in a novel in vitro animal model

Disordered small intestinal motility occurs frequently during acute radiation enteritis. However, the characteristics and time course of the motor dysfunction are poorly defined. These parameters were assessed in a novel animal model of radiation enteritis. Ileal pressures were recorded in vitro with perfused micromanometric catheter using an arterially perfused ileal loop in 22 ferrets following fractionated abdominal irradiation (9 doses 2.50 Gy thrice weekly for 3 weeks). Tissue damage was graded histologically. Studies were performed 3 to 29 days after irradiation. Tissue from 7 control animals was also studied. All treated animals developed diarrhoea. Histology showed changes consistent with mild to moderate radiation enteritis. Following irradiation, there was an initial increase in frequency followed by a non-significant reduction in the frequency, but not the amplitude of ileal pressure waves. The frequency of pressure waves showed an inverse relationship with time after radiation (r = -0.634, p < 0.002). There was no relationship between motility and histology. We conclude that abdominal irradiation is associated with a time-dependent reduction in ileal motility which does not correlate with light microscopic changes.