Can Neuroendocrine Tumors Cause These Gastroduodenal Findings?
Yes, neuroendocrine tumors can cause hematin (blood) throughout the stomach and proximal duodenum with erythema, and they commonly present with minimal diarrhea and acid reflux, though nasal regurgitation is not a typical NET manifestation and suggests severe gastroesophageal reflux disease. 1
Gastric and Duodenal NETs: Direct Mucosal Effects
Gastric NETs and Upper GI Bleeding
Gastric NETs can directly cause mucosal bleeding and hematin, particularly Type 3 (sporadic) gastric NETs which are more aggressive and can ulcerate, leading to hematemesis or melena. 1, 2
Type 1 and Type 2 gastric NETs (hypergastrinemic types) are typically smaller and less likely to cause significant bleeding unless they are larger than 2 cm or have invaded deeper layers. 1, 3
The presence of hematin throughout the stomach suggests either diffuse mucosal injury from acid hypersecretion (if Type 2/gastrinoma-associated) or bleeding from the tumor itself. 1, 3
Duodenal NETs and Proximal Findings
Duodenal NETs can cause local mucosal erythema and bleeding, especially when located in the duodenal bulb or proximal duodenum where they may ulcerate or cause inflammatory changes. 1, 4
Duodenal NETs are increasingly discovered incidentally at endoscopy and can present with upper GI bleeding as a primary manifestation. 2, 4
Functional Syndromes Explaining Acid Reflux and Diarrhea
Gastrinoma (Zollinger-Ellison Syndrome)
If this is a gastrinoma, it would perfectly explain the constellation of findings: severe acid reflux, hematin from acid-induced gastroduodenal injury, erythema in the proximal duodenum, and diarrhea. 1, 3, 5
Gastrinomas cause diarrhea in 50-65% of patients through gastric acid hypersecretion, with one-half presenting with chronic diarrhea as the chief complaint rather than peptic ulcer symptoms. 5
Diagnosis requires fasting serum gastrin levels measured after discontinuing proton pump inhibitors for at least 1 week; levels >1000 pg/mL strongly suggest gastrinoma, though comparable elevations occur with pernicious anemia or atrophic gastritis. 1, 5
A combination of fasting serum gastrin level greater than 10 times elevated and gastric pH less than 2 is diagnostic of gastrinoma. 1
Carcinoid Syndrome (Less Likely Here)
Carcinoid syndrome causes diarrhea in 50-70% of patients but typically requires hepatic metastases to allow bioactive products to bypass hepatic metabolism. 5, 6
The "minimal diarrhea" described is more consistent with gastrinoma than carcinoid syndrome, which typically produces more prominent secretory diarrhea. 5
Carcinoid syndrome would not directly explain the hematin and proximal duodenal findings unless there were concurrent peptic disease. 1, 6
Nasal Regurgitation: Not a NET Feature
Nasal regurgitation is NOT a recognized manifestation of NETs and instead indicates severe gastroesophageal reflux with regurgitation reaching the nasopharynx, or potentially a motility disorder. 1
This symptom should prompt evaluation for complications of severe GERD or alternative diagnoses affecting esophageal/pharyngeal function. 1
Diagnostic Algorithm
Immediate Endoscopic Assessment
Document the size, number, and location of any visible lesions in the stomach and duodenum, as this determines classification (Type 1,2, or 3 gastric NET) and management. 1, 3
Perform endoscopic biopsy of any visible lesions and adjacent mucosa to establish histologic diagnosis and obtain tissue for immunohistochemistry. 1
Biochemical Evaluation
Measure fasting serum gastrin (after stopping proton pump inhibitors for 1-2 weeks) and gastric pH to evaluate for gastrinoma/Zollinger-Ellison syndrome. 1, 3, 5
Measure chromogranin A as a general NET marker, though levels can be spuriously elevated with proton pump inhibitor use, renal/liver failure, or chronic gastritis. 1
Consider 24-hour urinary 5-HIAA if carcinoid syndrome is suspected (flushing, more prominent diarrhea), though this seems less likely given the presentation. 1, 5
Imaging for Staging
Obtain multiphasic CT or MRI to assess for primary tumor location (if not visible endoscopically), lymph node involvement, and distant metastases. 1
Somatostatin receptor scintigraphy (octreoscan) should be performed for staging, as most NETs express high-affinity somatostatin receptors. 1
Management Considerations
Symptom Control
Somatostatin analogues (octreotide or lanreotide) are first-line for managing hormonal symptoms including diarrhea and can help prevent carcinoid crisis during procedures. 7, 6
For gastrinoma-related acid hypersecretion, high-dose proton pump inhibitors are essential for symptom control and healing of acid-induced mucosal injury. 1, 3
Definitive Treatment
For hypergastrinemic tumors ≤2 cm, options include endoscopic resection (if feasible), observation, or octreotide/lanreotide for symptom control. 1, 3
For tumors >2 cm or Type 3 gastric NETs, surgical resection with regional lymphadenectomy is indicated due to higher malignant potential. 1, 3
Duodenal NETs may require endoscopic resection if feasible, or transduodenal local excision with lymph node sampling for larger lesions. 1
Critical Pitfall to Avoid
Do not measure gastrin levels while the patient is on proton pump inhibitors, as this will cause spuriously elevated results and confound the diagnosis of gastrinoma. 1, 3
Most patients with elevated gastrin do NOT have gastrinoma but rather have achlorhydria or are receiving acid suppression therapy. 1