Fundoplication reduces the volume of the stomach and uses most of the proximal stomach to create a wrap around the lower part of the esophagus that results in an increase in LES pressure and in the esophagogastric junction contractile integral of 26.3 % [2, 4, 5, 8–10]. The surgery can have a major impact on gastric function, and may explain some of the postoperative symptoms that can be encountered [11]. There have been a few studies that have evaluated gastric accommodation, sensation, and emptying in children and adults after fundoplication. Mousa et al. [5] studied gastric compliance and gastric sensory function before and after Nissen fundoplication in children. They performed barostat studies in 13 children before surgery and repeated the test after surgery in 8. After fundoplication, patients had significantly higher minimal distending pressure values, reduced gastric compliance, and significantly higher pain scores. These indicate that gastric compliance was reduced, and presumably that lead to stimulation of visceral afferents and the heightened perception they noted. Zangen et al. [12] showed that in 12/14 children there was a decrease in gastric volume capacity that produced retching.

Findings of abnormal gastric accommodation have also been reported in adults. In a case controlled study proximal gastric function was studied with the use of barostat in 12 adult patients that underwent fundoplication and compared with 12 controls [13]. They found that there was no difference between groups in compliance during fasting. However the adaptive relaxation in the fundoplication group was significantly less than that in controls after ingestion of a liquid meal [13]. They also showed that the fundal wrap is not afunctional and is still able to accommodate to pressure increments, that the stomach relaxation after a meal occurs normally, but that in the patients there was a decrease in receptive relaxation. Similar findings related to accommodation were reported by Vu et al. [14] who studied with a barostat 12 adult patients before and after Nissen fundoplication and compared the results with the findings on 12 healthy adults and 12 adults with GERD who did not undergo surgery. The sensation of fullness was increased in the postoperative patients. Again post-Nissen patients had normal compliance, but reduced postprandial gastric accommodation and accelerated gastric emptying.

Other less invasive methods that indirectly assess gastric function have also been used to study gastric function after surgery. By using single photon emission computed tomography with three-dimensional analysis, Bouras et al. [15] showed that patients post-fundoplication had a postprandial/fasting gastric volume ratio that was lower than in healthy controls, again suggesting impaired gastric accommodation. By using the water load test Remes-Troche et al. [16] found that asymptomatic subjects after surgery had higher scores for bloating, nausea, and abdominal pain compared to controls. They found that patients with dyspeptic symptoms after fundoplication had a significantly lower drinking capacity and higher symptoms scores than controls, including patients that were asymptomatic after fundoplication [16]. Their scores were similar than those of patients without surgery and functional dyspepsia, while the scores of asymptomatic fundoplication patients were similar than those of healthy controls [16].

Visceral hypersensitivity has been associated with abnormal gastric accommodation and hyperalgesia, and cofactors of this hypersensitivity are likely to be wall tension and the function of visceral afferents [17]. Therefore it is possible that patients who do not develop dyspeptic symptoms after fundoplication may have a nearly normal gastric function [16].

The exact mechanism by which these changes in accommodation occur is not clear. There may be alterations in the proximal gastric wall function, the abnormalities may be secondary to vagal dysfunction, or to the mechanical effects of the fundoplication per se [5, 8, 11, 18]. A recent meta-analysis showed that rates of adverse results involving dysphagia, gas-bloat syndrome, inability to belch, and reoperation due to severe dysphagia were significantly higher after laparoscopic Nissen as compared with Toupet fundoplication, suggesting the type of gastric manipulation has an effect on prognosis [1]. The proximal gastric wall seems to work normally as gastric compliance, tone and volume waves have been found to be normal [13, 14]. It is then possible that surgical manipulation itself could impair autonomic pathways affecting the gastric sensorimotor function and that changes in postprandial relaxation after reflux surgery could result from alterations in neurohormonal control [11, 18]. Vagal nerve function after fundoplication has been evaluated by using different methods. By using sham-feeding-stimulated pancreatic polypeptide (PP) test before and after surgery Devault et al. [18] showed that 5/12 with normal testing before the surgery developed evidence of vagal dysfunction after surgery. Interestingly here was no correlation between PP tests and the development or worsening of symptoms after surgery. In another study that evaluated vagal function by seeing PP response to insulin-induced hypoglycemia, Vu et al. found that 11 of their 12 patients responded normally [14]. Given the information described above it appears that the reduced gastric accommodation is probably mechanical in origin [13, 14].