Imaging Pearls ❯ Small Bowel ❯ Neuroendocrine tumor
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- This cancer forms in tissues of the small intestine (the part of the digestive tract between the stomach and the large intestine). The most common type is adenocarcinoma (cancer that begins in cells that make and release mucus and other fluids). Other types of small intestine cancer include sarcoma (cancer that begins in connective or supportive tissue), carcinoid tumor (a slow-growing type of cancer), gastrointestinal stromal tumor (a type of soft tissue sarcoma), and lymphoma (cancer that begins in immune system cells).
SEER Cancer Stat Facts: Small Intestine Cancer. National Cancer Institute.
Bethesda, MD https://seer.cancer.gov/statfacts/html/smint.html - Neuroendocrine neoplasms (NENs) of the small bowel are typically slow-growing lesions that remain asymptomatic until reaching an advanced stage. Imaging modalities for lesion detection, staging, and follow-up in patients with known or suspected NEN include CT enterography, MR enterography, and PET/CT using a somatostatin receptor analog. FDG PET/CT may have a role in the evaluation of poorly differentiated NENs. Liver MRI, ideally with a hepatocyte-specific contrast agent, should be used in the evaluationof hepatic metastases. Imaging informs decisions regarding both surgical approaches and systematic therapy (specifically, peptide receptor radionuclide therapy).
Imaging of Small-Bowel Neuroendocrine Neoplasms: AJR Expert Panel Narrative Review
Patrick J. Navin, Eric C. Ehman, Jason B. Liu et al.
AJR 2023; 221:289301 - Most NENs are sporadic. Approximately 5% of patients with NENs have associated clinical syndromes such as multiple endocrine neoplasia type 1, von Hippel-Lindau syndrome, neurofibromatosis type 1, or tuberous sclerosis; NENs with associated symptoms are described as gastroenteropancreatic NENs. NENs have historically been described in certain contexts as carcinoid or neuroendocrine tumors. However, according to the WHO classification system, all variations of lesions with neuroendocrine differentiation should be described as NENs.
Imaging of Small-Bowel Neuroendocrine Neoplasms: AJR Expert Panel Narrative Review
Patrick J. Navin, Eric C. Ehman, Jason B. Liu et al.
AJR 2023; 221:289301 - Mean age at SBNEN diagnosis is 65 years, with no significant sex or race predilection. Owing to slow growth, SBNENs, particularly those that are hormonally inactive, often remain asymptomatic until presentation with metastatic disease. Patients with NENs experience diagnostic delays, with a mean patient-reported time from first symptom onset to diagnosis of 52 months and a mean of 11.8 health care visits before diagnosis. A third of patients reported diagnostic delay of at least 5 years. Specifically, for SBNENs, reported median symptom duration to diagnosis is 3.4 months, with approximately 4.5% ofpatients receiving diagnosis after at least 5 years of symptoms.
Imaging of Small-Bowel Neuroendocrine Neoplasms: AJR Expert Panel Narrative Review
Patrick J. Navin, Eric C. Ehman, Jason B. Liu et al.
AJR 2023; 221:289301 - Initial suspicion for SBNEN is sometimes raised during interpretation of a routine portal venous phase abdominopelvic CT owing to presence of mesenteric hyperenhancing lymph nodes and/or desmoplastic reaction, despite nonvisualization of the primary neoplasm. However, routine abdominopelvic CT is not optimized for detection of SBNEN, and without high index of suspicion, SBNENs are often missed. For example, in one study, SBNENs were prospectively missed on at least one examination in 64% of patients who had identifiable tumors at retrospective review.
Imaging of Small-Bowel Neuroendocrine Neoplasms: AJR Expert Panel Narrative Review
Patrick J. Navin, Eric C. Ehman, Jason B. Liu et al.
AJR 2023; 221:289301 - High-quality evidence regarding the accuracy of CTE or MRE in detecting SBNEN is scant. In a study from 2022, CTE had per-lesion sensitivity of 5053% and specificity of 8793%. Manymissed lesions were in patients with multifocal disease, emphasizing the importance of a thorough investigation of the entire length of small bowel when NEN is suspected. Other retrospective research has shown CTE to have per-patient sensitivity for SBNEN detection of 9193%. In addition, a prospective analysis found MRE to have a sensitivity of 74% on a per-lesion basis and 95% on a per-patient basis using surgical exploration and histology as the reference standard.
Imaging of Small-Bowel Neuroendocrine Neoplasms: AJR Expert Panel Narrative Review
Patrick J. Navin, Eric C. Ehman, Jason B. Liu et al.
AJR 2023; 221:289301 - On CTE, SBNENs typically show intense early (arterial and/or enteric) hyperenhancement . SBNENs show three distinct morphologies: nodular or polypoid mucosal or submucosal lesion, plaquelike mural thickening often with associated serosal puckering, or carpet lesion with segmental submucosal spread. The latter morphology can mimic ileal Crohn disease on imaging. Multifocality is present in approximately 54% of patients with SBNENs. In patients with extraserosal extension, a fibrotic desmoplastic reaction occurs in the small-bowel mesentery. The fibrotic reaction may be associated with small-bowel distortion and angulation and can cause small-bowel obstruction .
Imaging of Small-Bowel Neuroendocrine Neoplasms: AJR Expert Panel Narrative Review
Patrick J. Navin, Eric C. Ehman, Jason B. Liu et al.
AJR 2023; 221:289301 - Abdominopelvic CT, often with concurrent chest CT, is commonly used to evaluate for metastatic disease in patients with known SBNEN. Metastatic lymph nodes from SBNEN often hyperenhance similar to the primary small-bowel lesion. Nodal metastases may calcify in up to 70% of patients. Mesenteric nodal metastases often incite an intense fibrotic desmoplastic reaction with a sunburst appearance and may encase or occlude mesenteric vessels,which in turn may result in engorged and/or varicose veins peripherally. Single-phase CT has sensitivity of 6070% and specificity of 87100% for detecting lymph node metastases.
Imaging of Small-Bowel Neuroendocrine Neoplasms: AJR Expert Panel Narrative Review
Patrick J. Navin, Eric C. Ehman, Jason B. Liu et al.
AJR 2023; 221:289301 - At multiphase CT, hepatic metastases from SBNEN often show arterial phase hyperenhancement and may become iso- or hypoattenuating on subsequent portal venous or delayed phases; thus, multiphase imaging is essential for detecting hepatic metastases. As with nodal metastases, hepatic metastases may calcify; in addition, cystic change has been rarely reported. Multiphase CT has mean sensitivity and specificity for diagnosing hepatic metastases of 84% and 92%, respectively. Peritoneal metastatic disease can display a similar fibrotic reaction as seen with mesenteric metastases and can lead to small-bowel tethering and obstruction. Peritoneal metastases are present in approximately20% of patients with metastatic SBNENs. Osseous metastatic disease is present in up to 30% of patients with midgutNENs, with osseous lesions often appearing sclerotic on CT.
Imaging of Small-Bowel Neuroendocrine Neoplasms: AJR Expert Panel Narrative Review
Patrick J. Navin, Eric C. Ehman, Jason B. Liu et al.
AJR 2023; 221:289301 - Carcinoid tumor arises from the chromaffin cellsat the base of the crypts of Lieberkόhn. It mostfrequently arises in the distal ileum, Meckel diverticulum, or appendix and can be multifocal. Carcinoid tumor represents 25% of primary tumors of the small bowel, and 90% of small bowel carcinoid tumors arise in the distal ileum. Detection of primary carcinoid tumor in the small bowel is difficult with conventional imaging owing to the small size of the primary tumor(often less than a centimeter) and its location in the submucosa. More often, a spiculated mesenteric mass from metastatic disease is detected with imaging.
Small Bowel Neoplasms: A Pictorial Review
Rahul Jasti, Laura R. Carucci,
RadioGraphics 2020; 40:10201038 - The primary carcinoid lesion may show avid arterial enhancement at CT enterography or MR enterography. Rarely, the primary lesion appears as an ulceratingmass in the small bowel. More often, a spiculatedmesenteric mass is found at CT or MRI andrepresents mesenteric metastatic disease. The mesenteric mass may contain calcifica-tions and often appears desmoplastic. This mass can stimulate a fibrotic reaction in the surrounding tissues and lead to bowel obstruction,ischemia, or vascular compromise.
Small Bowel Neoplasms: A Pictorial Review
Rahul Jasti, Laura R. Carucci,
RadioGraphics 2020; 40:10201038 - Carcinoid tumors are a type of neuroendocrine tumor (NET) that arises from the enterochromaffin (or Kulchitsky) cells and can affect virtually any organ system in the body. Although at times the terms carcinoid and neuroendocrine tumor are used interchangeably, not all neuroendocrine cell tumors are carcinoids . Although considered rare, the reported age-adjusted incidence of carcinoid tumors has increased in the United States. This increase is partly due to increased detection at radiologic imaging and endoscopy . Thereis significant diversity in clinical presentation, incidence at specific anatomic sites, biologic behavior, hormone production, morphologic characteristics, metastatic disease, and immunophenotypes, all of which mostly depend on site of origin and cell type .
Multimodality Imaging Findings in Carcinoid Tumors: A Head-to-Toe Spectrum
Ameya Jagdish Baxi, Kedar Chintapalli, Amol Katkar, et al
RadioGraphics 2017; 37:516536 - Approximately 2%8% of gastrointestinal NETs occur in the duodenum . They arise from either the gastrinproducing G cells or somatostatin-producing D cells. The majority (62% of cases) arise from G cells of the duodenum and result in duodenal gastrinomas, of which approximately one-third develop signs and symptoms of Zollinger-Ellison syndrome. G cell tumors may be sporadic or associated with MEN1 . When associated with MEN1, they can be multiple and located in the proximal duodenum. Carcinoid tumors arisingfrom D cells are located in the periampullary region and result in duodenal somatostatinomas. These lesions can cause biliary obstruction and can manifest as jaundice and/or pancreatitis. They are strongly associated with NF type1.
Multimodality Imaging Findings in Carcinoid Tumors: A Head-to-Toe Spectrum
Ameya Jagdish Baxi, Kedar Chintapalli, Amol Katkar, et al
RadioGraphics 2017; 37:516536 - At imaging, duodenal carcinoids can have the appearance of intraluminal polyps and mural masses. They show early arterial enhancement at CT with delayed washout, which sometimes can help to differentiate them from adenomas and periampullary adenocarcinoma, which typically do not show enhancement in the arterial phase. At MR imaging, the lesions are hypointense on T1-weighted images and heterogeneously hyperintense on T2-weighted images and show heterogeneous enhancement . Tumors greater than 2 cm infiltrating the muscularis propria and with high mitotic activity are more prone to metastases. However, even 1-cm tumors can have distal metastases at the time of diagnosis . Nodal and distant metastases are uncommon and are seen in up to 9%10% of cases.
Multimodality Imaging Findings in Carcinoid Tumors: A Head-to-Toe Spectrum
Ameya Jagdish Baxi, Kedar Chintapalli, Amol Katkar, et al
RadioGraphics 2017; 37:516536 - At imaging, small bowel carcinoids can be solitary or multifocal, mucosal or submucosal, polypoid or plaquelike masses with size usually under 2 cm. They show early arterial enhancement at multidetector CT. The primary tumor rarely exceeds 3.5 cm. Metastases in the liver, lymph nodes, or mesentery can attain larger size, often overshadowing the primary tumor. The polypoid mass can serve as the lead point for intussusceptions.
Multimodality Imaging Findings in Carcinoid Tumors: A Head-to-Toe Spectrum
Ameya Jagdish Baxi, Kedar Chintapalli, Amol Katkar, et al
RadioGraphics 2017; 37:516536 - The tumors secrete serotonin, which causes a local desmoplastic reaction, which at multidetector CT gives a characteristic appearance of bowel kinking, tethering, angulation, and at times obstruction. Mesenteric involvement is seen as an oval soft-tissue mesenteric mass with radiating linear strands and thickened adjacent bowel loops . The extent of mesenteric vasculature involvement can be well depicted at CT angiography and thus provide a road map for surgical planning.
Multimodality Imaging Findings in Carcinoid Tumors: A Head-to-Toe Spectrum
Ameya Jagdish Baxi, Kedar Chintapalli, Amol Katkar, et al
RadioGraphics 2017; 37:516536 - Calcification is seen in 70% of mesenteric masses, with three patterns described: small stippled, coarse dense, and diffuse calcification. Necrosis is rare in mesenteric carcinoids due to high vascularity and small size; however, it can be seen in large tumors. The differential diagnosis of mesenteric carcinoid includes retractile mesenteritis, desmoid tumor, treated lymphoma, metastatic disease (eg, to the ovary or colon), and peritoneal mesothelioma.
Multimodality Imaging Findings in Carcinoid Tumors: A Head-to-Toe Spectrum
Ameya Jagdish Baxi, Kedar Chintapalli, Amol Katkar, et al
RadioGraphics 2017; 37:516536 - Differential Diagnosis
The imaging findings can sometimes mimic other conditions, notably:
Sclerosing Mesenteritis: Also shows a "misty mesentery" and fibrotic mass, though it often lacks the hypervascularity and primary bowel mass seen in carcinoid. Mesenteric Lymphoma: Usually presents with larger, bulkier nodes that do not typically cause the intense desmoplastic tethering seen in carcinoid. - Carcinoid Tumor: CT Findings
Primary mass in bowel or in the mesentery
Desmoplastic reaction in the mesentery
Calcification of mesenteric mass
Liver metastasis (hypervascular) - Conclusion and Summary from Gemini
Small bowel carcinoid tumors (now more commonly referred to as well-differentiated neuroendocrine tumors or NETs) present with a classic "classic" appearance on CT, though the primary tumor itself is often small and difficult to detect. - Key CT Imaging Features
The Primary Tumor: Often appears as a small, hyperenhancing (bright on arterial phase) submucosal mass or polypoid lesion, most commonly located in the distal ileum. It is frequently less than 2 cm in size and can be easily missed on standard CT. AJR Online
The Mesenteric Mass: This is often the most prominent finding. It typically manifests as an enhancing soft-tissue mass within the mesentery, representing nodal metastasis. - Key CT Imaging Features
Desmoplastic Reaction: The tumor secretes serotonin, which causes a characteristic intense fibrotic reaction. On CT, this appears as:
"Sunburst" or "Spoke-wheel" Appearance: Linear strands of soft tissue radiating from the mesenteric mass into the fat. AJR Online
Bowel Tethering: Small bowel loops may be kinked, angulated, or pulled toward the central mesenteric mass.
Calcification: Roughly 70% of mesenteric masses show stippled or coarse calcifications. AJR Online
Vascular Involvement: The desmoplastic reaction can encase or pull on mesenteric vessels, potentially leading to bowel ischemia or congestion. RadioGraphics
- “Conventional CT has lower sensitivity for detecting the primary tumor primary tumor, although oral contrast may improve detection. The tumor is often initially missed, and identified retrospectively, highlighting the need for high level of suspicion in patients presenting with longstanding nonspecific abdominal complaints. The addition of late arterial phase imaging to leverage the increased vascularity of NENs increases tumor conspicuity. Similarly, the use of CT enterography allows for better small bowel distention with neutral oral contrast medium. This improves tumor-to background contrast resolution and improves the sensitivity for detecting small bowel tumors to over 90%. Combining multiphase imaging with enterography further improves the detection of NET. This approach has been comparable to, if not better than video capsule endoscopy, which may be more limited in identifying submucosal lesions such as NEN.”
Small bowel neuroendocrine neoplasm: what surgeons want to know
Akshya Gupta et al.
Abdominal Radiology (2022) 47:4005–4015 
Small bowel neuroendocrine neoplasm: what surgeons want to know
Akshya Gupta et al.
Abdominal Radiology (2022) 47:4005–4015- “Desmoplastic reaction in the mesentery can lead to spiculation and fibrosis with a classic sunburst appearance or spoke wheel appearance on both CT and MRI . T2-hypointensity in some cases reflects the underlying fibrosis. Calcifications are common, seen in up to 70% of nodal metastases, with stippled, coarse, and diffuse patterns identified. Smaller metastatic lymph nodes may be more challenging to identify on conventional anatomic imaging. DOTATATE PET-CT offers improved sensitivity (92% versus 64%) and specificity (83% versus 59%) for the detection of nodal metastases on a per patient basis.”
Small bowel neuroendocrine neoplasm: what surgeons want to know
Akshya Gupta et al.
Abdominal Radiology (2022) 47:4005–4015 - “Small bowel neuroendocrine neoplasms have been increasingly identified and are now the most common small bowel tumor. Although frequently metastatic at presentation, initial surgical cytoreduction has demonstrated a survival benefit in well differentiated NET and may aid in symptom control. The radiologic findings of the primary tumor, nodal spread of disease, and distant metastases have significant impact on the management of these patients. A multimodality and interdisciplinary approach are necessary to determine the ideal treatment strategy for patients with small bowel NEN.”
Small bowel neuroendocrine neoplasm: what surgeons want to know
Akshya Gupta et al.
Abdominal Radiology (2022) 47:4005–4015
- “Small bowel neuroendocrine neoplasms (SB-NENs) are now the most common small bowel tumor, surpassing adenocarcinoma and comprising almost 40% of small bowel malignancies. Historically known as “carcinoid” tumors, the classification of NENs has evolved over the years, with increased recognition of their diverse clinical and pathologic profile. SB-NENs were previously classified as foregut duodenal or midgut jejunoileal neoplasms. Using this prior framework, duodenal NENs are uncommon, accounting for less than 3% of gastrointestinal neuroendocrine tumors, and are most often identified incidentally. Most are non- functional, and a small minority are associated with multiple endocrine neoplasia type 1 (MEN 1), MEN type 4, or neu- rofibromatosis type 1 syndromes. In comparison, jejunoileal tumors are much more common, with more than 70% of tumors originating within 100 cm of the ileocecal valve.”
Small bowel neuroendocrine neoplasm: what surgeons want to know
Akshya Gupta et al.
Abdominal Radiology 2022(in press) - "Patients with SB-NENs are most often diagnosed in the sixth decade, without a gender predilection, and often incidentally on imaging. If patients present with symptoms, the clinical presentation in large part relates to the site of origin as well as underlying tumor burden. Patients with jejunoileal tumors may be asymptomatic, have long standing vague abdominal symptoms, or present with complications of local tumor progression or distant metastases, including carcinoid syndrome. The clinical and imaging findings of early stage disease can be subtle. Most jeju- noileal NETs are typically grade 1 or 2 tumors, with a more indolent course; this can lead to significant diagnostic delays. Duodenal tumors are more heterogeneous and even well differentiated tumors may present with early metastatic disease.”
Small bowel neuroendocrine neoplasm: what surgeons want to know
Akshya Gupta et al.
Abdominal Radiology 2022(in press) - “Small bowel NENs almost always produce biologically active peptides such as serotonin, histamine, and neurokinin A. However, these peptides are normally metabolized by the liver. The classic flushing, diarrhea, and bronchospasm of carcinoid syndrome occurs in up to 20% of patients, almost exclusively when liver and other distant metastases are present.”
Small bowel neuroendocrine neoplasm: what surgeons want to know
Akshya Gupta et al.
Abdominal Radiology 2022(in press) - “Functional imaging has evolved and now primarily consists of positron emission tomography (PET) CT. Newer radiotracers take advantage of the high degree of somatostatin receptor expression exhibited by well differentiated NETs, and offer improved sensitivity for detection of disease. Gallium (68Ga) labelled octreotide analogs are widely in use, with the FDA having approved 68Ga-DOTA- octreotate (DOTATATE) for imaging of NETs. Fluorode- oxyglucose (FDG) 18 PET CT has a limited role in the assessment of grade 1 and 2 well differentiated neuroen- docrine tumors. However grade 3 NETs and PDNECs have variable somatostatin receptor expression, higher mitotic rates, and higher glucose utilization. Therefore, these tumors are often better imaged with conventional FDG 18 PET CT as opposed to DOTATATE PET CT.”
Small bowel neuroendocrine neoplasm: what surgeons want to know
Akshya Gupta et al.
Abdominal Radiology 2022(in press) - "Similarly, the use of CT enterography allows for better small bowel distention with neutral oral contrast medium. This improves tumor-to- background contrast resolution and improves the sensitivity for detecting small bowel tumors to over 90%. Combining multiphase imaging with enterography further improves the detection of NET. This approach has been comparable to, if not better than video capsule endoscopy, which may be more limited in identifying submucosal lesions such as NEN.”
Small bowel neuroendocrine neoplasm: what surgeons want to know
Akshya Gupta et al.
Abdominal Radiology 2022(in press) - "While tumor size, grade, and serosal invasion all play a role in the likelihood of developing metastases, almost half of patients with primary tumors under one centimeter in size still have mesenteric disease. The most relevant imaging finding in the setting of nodal disease, is whether involved lymph nodes are within the potential surgical field. Cytoreductive operations for jejunoileal NENs include resection of these locoregional mesenteric nodal metastases both for accurate staging and symptomatic improvement.”
Small bowel neuroendocrine neoplasm: what surgeons want to know
Akshya Gupta et al.
Abdominal Radiology 2022(in press) - "Small bowel neuroendocrine neoplasms have been increasingly identified and are now the most common small bowel tumor. Although frequently metastatic at presentation, initial surgical cytoreduction has demonstrated a survival benefit in well differentiated NET and may aid in symptom control. The radiologic findings of the primary tumor, nodal spread of disease, and distant metastases have significant impact on the management of these patients. A multimodality and interdisciplinary approach are necessary to determine the ideal treatment strategy for patients with small bowel NEN.”
Small bowel neuroendocrine neoplasm: what surgeons want to know
Akshya Gupta et al.
Abdominal Radiology 2022(in press)
- “Neuroendocrine tumors occur most commonly in the small bowel, especially the distal ileum; 40% of them are found within 60 cm of the ileocecal valve. Arterial phase CT scanning is useful for the detection of small bowel neuroendocrine tumors, because the tumors usually present with small hyperenhancing masses (30% of these are multiple at diagnosis). Neuroendocrine tumor cells tend to show infiltrative growth through the small bowel wall into the adjacent mesentery, causing mesenteric fibrosis with the encasement of mesenteric vessels that subsequently results in bowel ischemia. If the primary tumor is larger than 2 cm, nodal metastasis and liver metastasis occur in more than 80% and 40% of tumors, respectively.”
Tumors of the jejunum and ileum: a pattern‐based imaging approach on CT
Kim SW et al.
Abdominal Radiology (2019) 44:2337–2345 - "Several small bowel tumors, such as hemangiomas, small GISTs, neuroendocrine tumors, and malignant gastrointestinal neuroectodermal tumors (GNETs), usually appear as well-enhanced masses. Because the imaging features of metastases usually depend on those of the primary tumor, hypervascular small bowel masses may be metastases of hypervascular primary cancer.”
Tumors of the jejunum and ileum: a pattern‐based imaging approach on CT
Kim SW et al.
Abdominal Radiology (2019) 44:2337–2345 - “Emergent biphasic MDCT demonstrated low but non-trivial yield (11.1%) for the depiction of suspected acute mesenteric ischemia but was particularly low for occlusive venous AMI (0.9%). The relationship between serum lactate elevation and positive MDCT findings of AMI in our study conforms to prior work and cautiously suggests value in routine serum lactate assessment preceding imaging for patient prioritization.”
Utility of biphasic multi-detector computed tomography in suspected acute mesenteric ischemia in the emergency department
Gopee-Ramanan P et al.
Emergency Radiology (2019) 26:523–529 - “In light of serum lactate as an established prognosticator for increased all-cause mortality and emerging as a generally concerning metric when suspecting AMI, consistent ordering of serum lactate prior to MDCT assessment for AMI may potentially help expedite triaging of sicker patients. For example, knowledge of patients’ serum lactate elevation at the time of protocolling and performing emergent MDCTs from the ED for suspected AMI could expedite preferential diagnostic reporting of the given patients’ scans at the console or at the workstation by the responsible radiologist, thereby minimizing time to management.”
Utility of biphasic multi-detector computed tomography in suspected acute mesenteric ischemia in the emergency department
Gopee-Ramanan P et al.
Emergency Radiology (2019) 26:523–529 - “The approach to assessment of the utility of MDCT of AMI in the ED setting is highly relevant to daily practice. The combination of a low but non-trivial yield of biphasic MDCT for AMI of 11.1% and only a 0.9% yield for venous-occlusive ischemia at our institution lays ground- work for further investigation into CT protocols to possibly further reduce patient radiation dose, reduce the numbers of images to review, and reduce unnecessary delays in patient work-up and in surgical versus non-surgical management.”
Utility of biphasic multi-detector computed tomography in suspected acute mesenteric ischemia in the emergency department
Gopee-Ramanan P et al.
Emergency Radiology (2019) 26:523–529
- “Neuroendocrine tumors occur most commonly in the small bowel, especially the distal ileum; 40% of them are found within 60 cm of the ileocecal valve. Arterial phase CT scanning is useful for the detection of small bowel neuroendocrine tumors, because the tumors usually present with small hyperenhancing masses (30% of these are multiple at diagnosis). Neuroendocrine tumor cells tend to show infiltrative growth through the small bowel wall into the adjacent mesentery, causing mesenteric fibrosis with the encasement of mesenteric vessels that subsequently results in bowel ischemia. If the primary tumor is larger than 2 cm, nodal metastasis and liver metastasis occur in more than 80% and 40% of tumors, respectively.”
Tumors of the jejunum and ileum: a pattern‐based imaging approach on CT
Kim SW et al.
Abdominal Radiology (2019) 44:2337–2345 - "Several small bowel tumors, such as hemangiomas, small GISTs, neuroendocrine tumors, and malignant gastrointestinal neuroectodermal tumors (GNETs), usually appear as well-enhanced masses. Because the imaging features of metastases usually depend on those of the primary tumor, hypervascular small bowel masses may be metastases of hypervascular primary cancer.”
Tumors of the jejunum and ileum: a pattern‐based imaging approach on CT
Kim SW et al.
Abdominal Radiology (2019) 44:2337–2345 - “Emergent biphasic MDCT demonstrated low but non-trivial yield (11.1%) for the depiction of suspected acute mesenteric ischemia but was particularly low for occlusive venous AMI (0.9%). The relationship between serum lactate elevation and positive MDCT findings of AMI in our study conforms to prior work and cautiously suggests value in routine serum lactate assessment preceding imaging for patient prioritization.”
Utility of biphasic multi-detector computed tomography in suspected acute mesenteric ischemia in the emergency department
Gopee-Ramanan P et al.
Emergency Radiology (2019) 26:523–529 - “In light of serum lactate as an established prognosticator for increased all-cause mortality and emerging as a generally concerning metric when suspecting AMI, consistent ordering of serum lactate prior to MDCT assessment for AMI may potentially help expedite triaging of sicker patients. For example, knowledge of patients’ serum lactate elevation at the time of protocolling and performing emergent MDCTs from the ED for suspected AMI could expedite preferential diagnostic reporting of the given patients’ scans at the console or at the workstation by the responsible radiologist, thereby minimizing time to management.”
Utility of biphasic multi-detector computed tomography in suspected acute mesenteric ischemia in the emergency department
Gopee-Ramanan P et al.
Emergency Radiology (2019) 26:523–529 - “The approach to assessment of the utility of MDCT of AMI in the ED setting is highly relevant to daily practice. The combination of a low but non-trivial yield of biphasic MDCT for AMI of 11.1% and only a 0.9% yield for venous-occlusive ischemia at our institution lays ground- work for further investigation into CT protocols to possibly further reduce patient radiation dose, reduce the numbers of images to review, and reduce unnecessary delays in patient work-up and in surgical versus non-surgical management.”
Utility of biphasic multi-detector computed tomography in suspected acute mesenteric ischemia in the emergency department
Gopee-Ramanan P et al.
Emergency Radiology (2019) 26:523–529
- Neuroendocrine Tumors of the Duodenum: Facts
Duodenal neuroendocrine tumors (NETs) comprise 2–3% of all GI endocrine tumors and are increasing in frequency. These include gastrinomas, somatostatinomas, nonfunctional NETs, gangliocytic paragangliomas, and poorly differentiated NE carcinomas. Although, the majority are nonfunctional, these tumors are a frequent cause of Zollinger-Ellison syndrome and can cause other clinical hormonal syndromes (carcinoid, Cushing's, etc.). 
- “Duodenal carcinoid tumors commonly appear as an enhancing mass in either the arterial or venous phases. If a primary tumor is not seen in the duodenum, adjacent enhancing lymphadenopathy can be a clue to the presence of a duodenal carcinoid tumor.”
Duodenal neuroendocrine tumors: retrospective evaluation of CT imaging features and pattern of metastatic disease on dual-phase MDCT with pathologic correlation.
Tsai SD, Kawamoto S, Wolfgang CL, Hruban RH, Fishman EK
Abdom Imaging. 2015 Jun;40(5):1121-30 - The incidence of neuroendocrine tumors of the GI tract has increased in the last few decades which may in part be due to the increased detection of tumors with wider availability of thin-section multi-detector computed tomography (CT) and endoscopy. For instance, a study based on a national population-based cancer registry in England found the incidence rate of neuroendocrine tumors in the GI tract increased 3- to 4-fold from 1971 to 2006 with an increase of fivefold in the duodenum in men and 6.7-fold in the duodenum in women. This underscores the importance of imaging tests in the primary diagnosis and staging of GI neuroendocrine tumors.
Duodenal neuroendocrine tumors: retrospective evaluation of CT imaging features and pattern of metastatic disease on dual-phase MDCT with pathologic correlation.
Tsai SD, Kawamoto S, Wolfgang CL, Hruban RH, Fishman EK
Abdom Imaging. 2015 Jun;40(5):1121-30 - Most duodenal carcinoids are sporadic but may be associated with clinical syndromes such as multiple endocrine neoplasia type 1 (MEN-1) and neurofibromatosis type 1(NF-1) . Two-thirds of duodenal neuroendocrine tumors are gastrinomas and one-third of these are functioning tumors manifesting as Zollinger–Ellison syndrome (ZES). The next most common type (20%) of duodenal neuroendocrine tumors is somatostatinomas. Other more rare types of neuroendocrine tumors are nonfunctioning serotonin-, gastrin-, or calcitonin-producing tumors and gangliocytic paragangliomas. Somatostatinomas are strongly associated with NF-1 as up to 50% of patients with somatostatinomas have NF-1. Somatostatinomas associated with NF-1 are usually found around the ampulla, and they histologically often contain psamomma bodies.
Duodenal neuroendocrine tumors: retrospective evaluation of CT imaging features and pattern of metastatic disease on dual-phase MDCT with pathologic correlation.
Tsai SD, Kawamoto S, Wolfgang CL, Hruban RH, Fishman EK
Abdom Imaging. 2015 Jun;40(5):1121-30 - Our results show that duodenal carcinoid tumors enhance during the arterial phase of intravenous-contrasted enhanced CT and although they do lose contrast enhancement during the venous phase (30.4%) as has often been previously reported; however, in a significant percentage (60.9%), there was an increase in contrast enhancement during the venous phase and no change in contrast enhancement in the venous phase in 8.7% of patients. Early-phase arterial enhancement pattern is an important criterion in distinguishing a duodenal carcinoid tumor from other duodenal masses such as adenocarcinoma which is usually hypovascular, adenomas, or other peri-ampullary masses.
Duodenal neuroendocrine tumors: retrospective evaluation of CT imaging features and pattern of metastatic disease on dual-phase MDCT with pathologic correlation.
Tsai SD, Kawamoto S, Wolfgang CL, Hruban RH, Fishman EK
Abdom Imaging. 2015 Jun;40(5):1121-30 - In conclusion, carcinoid tumors of the duodenum most often present as a focal polypoid mass, but may present as an area of wall thickening or intramural mass with the primary tumor not well defined. Regional lymphadenopathy may be more pronounced than the primary lesion in the duodenum. The CT features of an enhancing duodenal mass can be suggestive of a carcinoid tumor. Duodenal carcinoid tumors are most common in the proximal duodenum and may present with metastatic disease as evidenced by regional enhancing lymphadenopathy or hypervascular liver lesions.
Duodenal neuroendocrine tumors: retrospective evaluation of CT imaging features and pattern of metastatic disease on dual-phase MDCT with pathologic correlation.
Tsai SD, Kawamoto S, Wolfgang CL, Hruban RH, Fishman EK
Abdom Imaging. 2015 Jun;40(5):1121-30
- “ Patients with metastatic MNETs often die of local complications of the primary tumor, such as small bowel obstruction or ischemia. These complications van potentially be avoided by resection of the primary tumor, with recent literature showing that resection has a survival benefit.”
Midgut Neuroendocrine Tumors: Imaging Assessment for Surgical Resection
Woodbridge LR et al.
RadioGraphics 2014; 34:413-426 - “ MNETs can release local growth factors and other substances, resulting in extensive mesenteric fibrosis, or desmoplasia. Desmoplasia leads to fixation of the mesentery with multiple fibrous bands and can cause small bowel obstruction and vascular occlusion. Regions of dysplasia should be resected to prevent development of an obstruction in the small bowel. ”
Midgut Neuroendocrine Tumors: Imaging Assessment for Surgical Resection
Woodbridge LR et al.
RadioGraphics 2014; 34:413-426
- “ The most common clinical signs and symptoms of gastrointestinal neuroendocrine carcinomas are intermittent intestinal obstruction, vague abdominal pain, hematemesis, or hematochezia.”
CT and enhanced CT in diagnosis of gastrointestinal neuroendocrine carcinomas
Wang D et al.
Abdom Imaging (2012); 37:738-745 - “ Most gastrointestinal neuroendocrine carcinomas are hypervascular and will be best seen in the arterial phase moderately or obviously enhanced. However, in some cases, portal venous phase imaging best demonstrates the tumors.”
CT and enhanced CT in diagnosis of gastrointestinal meuroendocrine carcinomas
Wang D et al.
Abdom Imaging (2012); 37:738-745