Theoretical modeling of the resistance to gastric emptying and duodenogastric reflux due to pyloric motility alone, presuming antral and duodenal quiescence.

A theoretical model of the pyloric channel, approximated as a two-dimensional tube with sinusoidal corrugation, is developed to estimate the degree of resistance offered by the pylorus to transpyloric flow (gastric emptying and duodenogastric reflux) in the viscous regime. Study indicates that the resistance of the channel depends on pressure gradient, flow behavior index and channel diameter. Flow is majorly determined by the extent of luminal opening; since they scale to fourth power of the diameter for Newtonian flow, with the exponent being higher for pseudoplastic and lesser in case of dilatants relative to Newtonian fluid. At zero pressure difference, across the channel, the closing pylorus drives the aborad propulsion of the contents at the intestinal end, and at the gastric end the flow is driven along the orad direction. While no transfer of contents occur at the centre of pylorus due to zero pressure gradients, it is essential to have a non-zero pressure difference to drive the flow through the channel. The extent of pressure difference is found to linearly relate to the transpyloric flow rate. The resistive function of the pyloric channel is observed at a higher occlusion where there is a development of higher pressure barrier that is sensitive to the flow behavior index, frequency, occlusion, and contraction length.