Patients have often suffered symptoms for up to three years before presentation. Dehydration and any electrolyte imbalances should be addressed immediately, as these can lead to further complications. As fluid losses can exceed 20 litres daily, central venous pressure should monitored. The diarrhoea can be treated with adenylate cyclase inhibitors, which prevent the secretion of fluid into the intestine. Lithium, phenothiazines and indomethacin may also be used. Octreotide will inhibit secretion caused by VIP, and will enhance salt absorption. This has proved effective in 90% of people. It may also help shrink the tumour.
Surgical excision of the tumour is the only curative treatment. This is appropriate for benign lesions and malignant tumours that have not yet metastasised. When a VIPoma is diagnosed but its exact location is not clear, a 'blind' laparotomy is done in order to localise the tumour. Such a technique may use intraoperative ultrasound, operative endoscopy with transillumination or simple palpation. This method is normally successful, however if the tumour can't be localised the treatment may involve removing two thirds of the pancreas, or rejecting surgical therapy and opting for medical treatment. This is also the case with microadenomas and multifocal tumours, which make up 20% of VIPomas, where surgery will only be curative if a large amount of pancreas is removed.
50% of cases have metastases at the time of presentation, and in this case debulking of the tumour is indicated, as this may help relieve symptoms by decreasing the amount of VIP-producing tissue.
Chemotherapy has been shown to relieve VIP syndrome in 90% of patients, using Streptozotocin and 5-fluorouracil. Human leukocyte interferon has been shown to reduce tumour size in 50% of cases, with a median response of lasting 8.5 months. This particular drug is not used frequently however, as its side effects include influenza-like symptoms, anaemia, altered liver function, thrombocytopenia and granulocytopenia.