Introduction: Vagal nerve injury may lead to symptoms of nausea, vomiting, abdominal discomfort, and bloating. Be it by injury or an infiltrative process, vagal nerve function is difficult to assess. Measuring pancreatic polypeptide (PP) following a sham meal may serve as a surrogate marker of vagal nerve function. Our aim was to assess vagal nerve integrity using sham feeding, in addition to evaluating the relationship of symptoms with PP levels and gastric emptying.
Methods: This was a retrospective study of patients who underwent sham feeding at Mayo Clinic Florida from 2018 to 2024. We collected demographic and clinical data, sham feeding results, and gastric emptying data. A 50 % increase in PP level within 30 mins compared to baseline after sham meal was considered normal. A gastric emptying scan was classified as delayed if < 75% of the material emptied at 4 hours.
Results: 36 patients were included (58.3% F) with a mean age of 56.4 years. Most patients were white (n=30), and the mean BMI was 26.9 kg/m2. The main GI symptoms were nausea and vomiting (14, 38.9%) and diarrhea (11, 30.6%). The average weight loss from the onset of symptoms was 32.6 lb. 28 of 36 patients had a history of abdominal surgery, with hiatal hernia repair (HHR) and HHR with Nissen fundoplication being the two most common surgeries (5, 17.8%). The mean baseline PP level of normal vs abnormal was 107.3 pg/mL and 128.79 pg/mL, respectively (p=0.34). The mean peak PP level of normal vs abnormal was 201.1 pg/mL and 128.8 pg/mL, respectively (p< 0.05). Symptoms of nausea and vomiting were found to have a robust correlation with a positive sham feeding result (15, 83.3%), compared with gastric emptying scintigraphy (12, 66.7%) (Figure 1). In patients with symptoms of nausea and vomiting but with normal gastric emptying study, the sham feeding tests were all abnormal. There was no correlation between sham feeding result with symptoms of abdominal pain and GER. The care after apparent vagus nerve injury required significant medical resources, including an average of 3.7 visits and 7.1 tests per patient to evaluate key GI symptoms.
Discussion: Sham feeding is an underused method to measure vagus nerve injury. sham feeding were consistently abnormal in patients with predominant symptoms of nausea and vomiting while the correlation between gastric scintigraphy result and gastroparesis symptoms was not significant. Sham feeding may be a valuable test when assessing patients with symptoms of nausea and vomiting.
Figure: Figure 1. Percentage of abnormal study in patients with nausea and vomiting
Disclosures:
Tian Li indicated no relevant financial relationships.
Sabrina Billings indicated no relevant financial relationships.
Antonia Vineyard indicated no relevant financial relationships.
Timothy Woodward indicated no relevant financial relationships.
