CASE A 69-year-old woman presented to the ED with a 4-hour history of intractable nausea and vomiting, diffuse colicky abdominal pain, and obstipation.FigureHistory The patient had a history of recurrent small bowel obstructions, eight within the past 3 years. Accustomed to her symptoms, the patient feared another obstruction. Each past obstruction had a similar presentation, necessitated hospitalization for IV fluid replacement and electrolyte repletion, and resolved with nasogastric bowel decompression. The patient's past surgical history was notable for two uncomplicated cesarean deliveries at 29 and 32 years of age and an elective laparoscopic cholecystectomy at age 54. Her past medical history was significant for hypertension managed with atenolol-chlorthalidone; hyperlipidemia managed with atorvastatin; hypothyroidism managed with levothyroxine; gastroesophageal reflux disease managed with omeprazole; chronic nausea managed with ondansetron; and a stable adrenal nodule. Her family history was negative for inflammatory bowel disease (IBD) and hereditary cancer syndromes. The patient denied previous and current use of tobacco, alcohol, and recreational substances. She had no known drug allergies. Physical examination Upon arrival at the ED, the patient was hypertensive but otherwise afebrile with a normal heart rate and respiratory rate. Her vital signs were blood pressure, 141/96 mm Hg; heart rate, 80 beats/minute; respiratory rate, 20 breaths/minute; Spo2, 96% on room air; and oral temperature, 98.0 °F (36.7 °C). Her weight was 175 lb and height was 62 inches for a BMI of 32. She was alert, oriented, and well-nourished without signs of nutritional deficiency. She appeared uncomfortable but was in no acute distress. Her skin was moist and pink without rash or jaundice. Cardiopulmonary examination revealed regular heart rate and rhythm without murmurs, and her lungs were clear to auscultation bilaterally. Abdominal examination revealed a distended abdomen with well-healed scars, decreased bowel sounds, and tympany throughout. The patient's abdomen was diffusely tender upon light and deep palpation without signs of peritonitis, palpable masses, or hepatosplenomegaly. No abdominal hernias were appreciated. DIFFERENTIAL DIAGNOSIS Adhesive disease IBD Crohn disease Ulcerative colitis Malignancy Cancers within the small and large bowel OUTCOME Historically, medical and surgical consultants attributed the patient's recurrent obstructions to adhesive disease, based on abdominopelvic CT scans demonstrating varying transition points—reflective of the dynamic nature of fibrous tissue formation—as well as the patient's therapeutic response to diatrizoate meglumine and diatrizoate sodium. IBD and malignancy were less of a concern due to a prior negative luminal evaluation through small bowel imaging and bidirectional scopes. Notably, a barium small bowel series performed after the patient's first obstruction, 3 years prior to her current presentation, was negative for intraluminal filling defects, including bowel wall thickening, narrowing, strictures, nodularity, and masses. An esophagogastroduodenoscopy and colonoscopy performed after her fifth obstruction, 2 years prior to her current presentation, was negative for mucosal abnormalities or masses. Advanced diagnostics and surgical exploration were deferred due to the prior negative luminal evaluation and concern that further intervention could exacerbate any underlying adhesive disease. The patient was admitted to medicine service. Upon consultation for her ninth obstruction, the newly involved senior surgeon was not convinced that adhesive disease was the sole cause. The lack of significant abdominopelvic surgical history combined with a consistent transition point observed in the right lower quadrant on both the current and most recent previous scan, performed 4 months earlier, elicited concerns and warranted closer examination. Upon review of both scans, the surgeon noted an intraluminal lesion that had not been documented in the radiology reports. The lesion was relatively unchanged in size and near the transition point, raising suspicion for a slow-growing neoplasm. The patient showed improvement with conservative measures and, following resolution of the obstruction, was discharged on day 3 and scheduled for an elective exploratory laparotomy, which was performed 8 weeks later. The laparotomy revealed a 2-cm lesion 3 ft proximal to the ileocecal valve and a 1-cm lesion 1 ft proximal to the ileocecal valve. Additionally, an enlarged 2.5-cm lymph node was identified at the root of the mesentery. There was no evidence of adhesive disease, despite previous speculation. The patient underwent a small bowel resection of 30 in and tolerated the procedure well. Pathology revealed a well-differentiated grade 1 neuroendocrine tumor (NET) extending to the serosal surface with negative margins of resection. Three of 20 lymph nodes revealed metastatic carcinoid tumor. Medical oncology subsequently evaluated the patient with a positron emission tomography (PET)-CT scan and deemed that surgical resection had achieved definitive cure of the small bowel neuroendocrine tumor (SBNET); they recommended surveillance imaging thereafter. DISCUSSION NETs arise from various anatomic sites, including but not limited to the gastrointestinal tract, lungs, and pancreas.1 They are primarily sporadic but may be associated with inherited genetic syndromes such as multiple endocrine neoplasia.1 NETs are classified by origin, histology, and stage.1 Histologically, they are classified by tumor differentiation and grade: low-grade (G1), intermediate-grade (G2), and high-grade (G3).1 Tumor differentiation and grade are determined by mitotic count and Ki-67 proliferation index; a higher mitotic rate and elevated Ki-67 index are associated with a more aggressive clinical course and worse prognosis.1 NETs are staged I to IV based on the tumor (T), node (N), and metastasis (M) staging system developed by the American Joint Committee on Cancer.1 SBNETs are epithelial neoplasms arising from enterochromaffin cells located in the submucosa.2-4 They primarily arise in the jejunoileum, are midgut in embryologic origin, and commonly occur within 100 cm of the ileocecal valve.4,5 SBNETs are typically diagnosed in adults in their sixth or seventh decade of life.2-8 Diagnosis is often delayed due to SBNETs' nonsecretory/nonhormonal function, indolent growth, and small size, which limit clinical suspicion and hinder early identification on imaging.2-4,7,9 Individuals are often asymptomatic until mass effect—which can manifest as obstruction, intussusception, mesenteric ischemia, and/or carcinoid syndrome—develops from advanced disease.2,5,8,9 Diagnostic testing Chromogranin A, serotonin, and 24-hour urine 5-hydroxyindoleacetic acid may assist in the evaluation of patients with symptoms suggestive of hormone hypersecretion such as secretory diarrhea or flushing, but providers should be conscious of their variable performance characteristics.2,5,6 Cross-sectional imaging can help identify nodal or mesenteric metastasis, but may not localize a primary SBNET.5 Direct optical visualization with an ileocolonoscopy may miss lesions that are inaccessible relative to the ileocecal valve.4,5 Video capsule endoscopy and small bowel enteroscopy offer comprehensive mucosal views of the small bowel, but they are invasive, pose a risk of capsule retention, and are operator-dependent, limiting their use and influencing diagnostic yields.2,5,7 Advanced functional imaging with a PET-CT scan using dodecane tetraacetic acid is faster, less expensive, has less radiation exposure, and is more sensitive in detecting NETs than an octreotide scan.5,6 Exploratory laparotomy can be diagnostic, therapeutic, and curative for SBNETs.4 Diagnosis and treatment At diagnosis, mean tumor size is approximately 2 cm with invasion of the muscularis propria and metastasis to regional lymph nodes.4,7,8 Segmental surgical resection of the primary tumor, nodal metastases, and mesenteric masses, when feasible, is considered first-line treatment.2-7 Adjuvant therapy, including somatostatin analogues, may be considered for patients with residual or unresectable disease and/or carcinoid syndrome to help control hormonal symptoms.4-6,8 The distinctive behaviors and characteristics of SBNETs contribute to their diagnostic complexities. In this patient's case, diagnosis was delayed due to a low index of clinical suspicion and oversight on interpretation of CT scans. The surgeon's keen insight in challenging the original assumption of adhesive disease and conducting a secondary review of radiological images ultimately led to the discovery of this patient's SBNET, which exhibited similar features including nonsecretory function, distal ileum location, size, obstructive mass effect, mucosal invasion, and metastasis to regional lymph nodes. CONCLUSION Small bowel obstructions are primarily due to adhesive disease secondary to surgical intervention, but recurrent obstructions in the absence of significant abdominopelvic surgical history should prompt further investigation. This case underscores the importance of refining the differential diagnosis as presentations evolve; considering rare pathologies when explanations fail to account for the full clinical picture; and remaining vigilant against anchoring a diagnosis based on previous circumstances.
Kimberly A. Carter (Thu,) studied this question.