Severe hypokalaemia and secretory diarrhoea secondary to a vasoactive intestinal peptide-secreting tumour (VIPoma).

A woman in her 60s presented to the emergency department with an 18-month history of chronic secretory diarrhoea and 8 kg weight loss. She had multiple previous presentations to healthcare for dehydration, weakness and severe hypokalaemia (serum potassium <2.5 mmol/L) over the preceding 18 months. Previous colonoscopy and workup for infectious and inflammatory causes had not yielded a diagnosis. At presentation, her serum potassium was 2.1 mmol/L (reference 3.5-5 mmol/L) with evidence of muscle weakness and volume depletion. A CT of the abdomen and pelvis demonstrated an 8 cm mass in the pancreatic tail. Endoscopic biopsy demonstrated well-differentiated pancreatic neuroendocrine tumour. Serum vasoactive intestinal peptide (VIP) was elevated eightfold above the upper limit of normal, in keeping with the diagnosis of VIPoma. Long-acting somatostatin analogue (SSA) was initiated. The patient underwent surgical resection of the primary tumour for symptom control. Following surgery and ongoing SSA use, diarrhoea and hypokalaemia have resolved.