Pancreatic Vasoactive Intestinal Peptide-Producing Tumor as a Rare Cause of Acute Diarrhea and Severe Hypokalemia

Abstract

Pancreatic vasoactive intestinal peptide-producing tumor (VIPoma) is a rare functional neuroendocrine tumor most commonly presenting with watery diarrhea and electrolyte abnormalities that include hypokalemia, hypercalcemia and metabolic acidosis. This type of tumor has usually insidious clinical behavior that is characterized by chronic secretory diarrhea, lasting usually from months to years before diagnosis, not responsive to usual medical or dietary treatment approaches. Given the resemblance of VIPoma with other more common causes of chronic watery diarrhea, the final diagnosis is often delayed and the tumors are usually large and metastatic at the time of detection. Our case of pancreatic VIPoma demonstrates an unusual clinical course for this type of tumor with acute refractory diarrhea and rapid deterioration of patient’s clinical and biochemical status that required emergent in-hospital diagnosis and treatment. Our patient is a 45-year-old woman who presented with abrupt, watery diarrhea during the past 24 h before admission accompanied with severe hypokalemia as well as hyponatremia, hyperglycemia and hypercalcemia. Despite aggressive management with fluid administration and electrolyte replenishment, no significant improvement in patient’s symptoms and electrolyte imbalance was observed. After exclusion of other causes of acute diarrhea from the medical history and the laboratory tests, the clinical suspicion of a functional neuroendocrine tumor was raised. After the establishment of final diagnosis of pancreatic VIPoma with biochemical tests and magnetic resonance imaging (MRI), somatostatin analogues were prescribed and the patient underwent distal pancreatectomy and splenectomy with no signs of lymph node and splenic metastases. Few days after the surgical resection of the tumor, the patient readmitted to our hospital with tarry stools and severe anemia. The abdominal computed tomography (CT) revealed a retroperitoneal cystic lesion. The gastrointestinal bleeding gradually recessed after endoscopic hemostasis of duodenal ulcer lesions whereas the cystic lesion (postoperative lymphocele) was successfully drained under CT-guidance before discharge. After almost 10 years postoperatively, the patient is still asymptomatic with no signs of relapse or metastasis of the disease in the periodic laboratory and imaging follow-up. In conclusion, pancreatic VIPoma can sometimes manifest symptoms of abrupt onset and rapid progression that require high clinical suspicion, appropriate diagnostic workup and aggressive management.

Longterm outcome of rare functioning pancreatic neuroendocrine neoplasms

“…In the present cohort, all rf-pNENs could be visualized by preoperative imaging with either CT or MRI because of the large tumor size, as reported in previous series [37,39,40,41]. EUS was used in only half of our patients and had an additional value in only one patient with 12 mm glucagonoma in the pancreatic head.…”

“…Thus, the discussion of the possible advantages and disadvantages of individual treatments and their sequence is somewhat vague and is beyond the scope of this article. However, somatostatin analogs, were used as the mainstay treatment in several other series [11,32,37,41] when curative surgery was not an option. They can control symptoms caused by excessive hormone secretion and prolong progression-free survival [46].…”

A Rare Presentation of Lymph Node Metastasis of VIPoma After Three Years of Resection: A Case Report

“…It is usually diagnosed at late stages due to its insidious onset and the non-specific nature of the symptoms [ 5 ]. The disease usually presents itself with intractable watery diarrhea, electrolyte abnormalities such as hyponatremia and hypokalemia, and metabolic acidosis which initially lead to investigation of other etiologies of watery diarrhea such as colitis and small bowel disorders [ 3 ]. Due to late diagnosis of the disease, it becomes an already distant organ metastasis, mostly liver, and in late stages, this limits resectability and decreases survival [ 5 ].…”

“…Despite being rare, it presents with insidious and comorbid symptoms such as intractable diarrhea and electrolyte abnormalities such as hypokalemia and hyponatremia due to the oversecretion of vasoactive intestinal peptide (VIP) from the tumor [ 2 ]. Due to its insidious onset, the disease is usually detected in late stages with distant organ metastasis with lymph node metastasis being extremely rare [ 3 ]. In this paper, we represent the first case of VIPoma with metachronous lymph node metastasis in a 60-year-old patient three years after the resection of the primary tumor.…”