M R Cox1, S J Franzi, C J Martin. 1. Department of Surgery, St Vincent's Hospital, Fitzroy, Victoria, Australia. cox@mis.net.au
Abstract
BACKGROUND: A canine model was used to define whether Nissen fundoplication inhibits gastro-oesophageal reflux by inhibiting transient lower oesophageal sphincter relaxations (TLOSR) or by creating a pressure barrier at the gastro-oesophageal junction. METHODS: Four surgical models were studied pre-operatively and postoperatively. These were: (i) the surgical mobilization required for fundoplication (sham fundoplication, n = 5); (ii) a standard fundoplication (n = 4); (iii) anterior and posterior myotomy of the lower oesophageal sphincter (LOS; cardiomyotomy, n = 4); and (iv) combined cardiomyotomy and fundoplication (n = 4). Each operative procedure was assessed for its effect on the incidence of TLOSR and gas reflux events, the mean LOS pressure and the LOS pressure profile during swallow events. RESULTS: Sham fundoplication reduced the rate of evoked TLOSR in response to gaseous gastric insufflation from 9.8+/-1.6/h (mean +/- SEM) to 5.4 +/-1.5/h. The mean LOS pressure was reduced from 25.1+/-2.6 to 18.5+/-2.1 mm Hg but nadir LOS pressure during swallowing was not altered. Nissen fundoplication virtually abolished evoked TLOSR from 10.4+/-1.2/h to 0.4+/-0.4/h, increased mean basal LOS pressure from 19.8+/-2.1 to 27.0+/-1.1 mm Hg and increased the nadir pressure on swallowing from 3.4+/-1.0 mm Hg to 14.4+/-1.0 mm Hg. Cardiomyotomy was associated with a near continuous leakage of gas across a chronically hypotensive LOS. Cardiomyotomy reduced the resting LOS pressure from 14.7+/-1.2 mm Hg to 2.3+/-1.0 mm Hg. Cardiomyotomy with fundoplication was associated with no loss of LOS competence. No gas venting episodes occurred either by passive leakage or by TLOSR. Cardiomyotomy with fundoplication was associated with a fall in mean LOS pressure from 14.3+/-1.5 mm Hg to 7.1+/-1.8 mm Hg but no LOS relaxation occurred during swallowing. CONCLUSION: Nissen fundoplication is highly effective in preventing reflux across a normal or chronically hypotensive LOS. Fundoplication results in a constant, measurable pressure barrier at the lower end of the oesophagus that is not due to a change in intrinsic LOS tone. Following fundoplication TLOSR are prevented by the constant low-pressure barrier.
BACKGROUND: A canine model was used to define whether Nissen fundoplication inhibits gastro-oesophageal reflux by inhibiting transient lower oesophageal sphincter relaxations (TLOSR) or by creating a pressure barrier at the gastro-oesophageal junction. METHODS: Four surgical models were studied pre-operatively and postoperatively. These were: (i) the surgical mobilization required for fundoplication (sham fundoplication, n = 5); (ii) a standard fundoplication (n = 4); (iii) anterior and posterior myotomy of the lower oesophageal sphincter (LOS; cardiomyotomy, n = 4); and (iv) combined cardiomyotomy and fundoplication (n = 4). Each operative procedure was assessed for its effect on the incidence of TLOSR and gas reflux events, the mean LOS pressure and the LOS pressure profile during swallow events. RESULTS: Sham fundoplication reduced the rate of evoked TLOSR in response to gaseous gastric insufflation from 9.8+/-1.6/h (mean +/- SEM) to 5.4 +/-1.5/h. The mean LOS pressure was reduced from 25.1+/-2.6 to 18.5+/-2.1 mm Hg but nadir LOS pressure during swallowing was not altered. Nissen fundoplication virtually abolished evoked TLOSR from 10.4+/-1.2/h to 0.4+/-0.4/h, increased mean basal LOS pressure from 19.8+/-2.1 to 27.0+/-1.1 mm Hg and increased the nadir pressure on swallowing from 3.4+/-1.0 mm Hg to 14.4+/-1.0 mm Hg. Cardiomyotomy was associated with a near continuous leakage of gas across a chronically hypotensive LOS. Cardiomyotomy reduced the resting LOS pressure from 14.7+/-1.2 mm Hg to 2.3+/-1.0 mm Hg. Cardiomyotomy with fundoplication was associated with no loss of LOS competence. No gas venting episodes occurred either by passive leakage or by TLOSR. Cardiomyotomy with fundoplication was associated with a fall in mean LOS pressure from 14.3+/-1.5 mm Hg to 7.1+/-1.8 mm Hg but no LOS relaxation occurred during swallowing. CONCLUSION: Nissen fundoplication is highly effective in preventing reflux across a normal or chronically hypotensive LOS. Fundoplication results in a constant, measurable pressure barrier at the lower end of the oesophagus that is not due to a change in intrinsic LOS tone. Following fundoplication TLOSR are prevented by the constant low-pressure barrier.