In addition, different histologic tumor subtypes have a predilection for different segments of the small bowel: adenocarcinoma is most frequent in the duodenum and jejunum, and carcinoid tumor most commonly occurs in the ileum. The frequency of small bowel tumors decreases from the proximal to distal small bowel (ie, frequency greater in duodenum than in jejunum, frequency greater in jejunum than in ileum). In addition, symptoms of bowel obstruction are more likely with larger tumors. Symptomatic tumors are more commonly malignant. Small bowel neoplasms can lead to complications including jaundice, gastrointestinal bleeding, obstruction, and perforation. Small bowel neoplasms can be asymptomatic even when symptomatic, they often have a vague and nonspecific clinical manifestation, with symptoms including intermittent abdominal pain, nausea, vomiting, and weight loss ( 6– 9). Reasons for delayed diagnosis include failure to order appropriate diagnostic tests and misinterpretation of imaging studies. The mean symptom-to-diagnosis interval approaches 3 years for benign tumors and can approach 2 years for malignant tumors ( 5). Most small bowel tumors are clinically silent for a long period, and nearly half are found incidentally during surgery or at imaging performed for other reasons. Diagnosis is a challenge owing to the nonspecific clinical manifestation, rare occurrence, and low index of clinical suspicion. Their rarity is despite the fact that the small bowel accounts for the majority (>90%) of the gastrointestinal surface area. Small bowel neoplasms are rare, accounting for 0.5% of all cancers and approximately 3% of all gastrointestinal tumors in the United States, and their incidence is rising-in particular, there is a rising incidence of small bowel carcinoid tumor ( 1– 4). The authors review the imaging features of common benign and malignant small bowel neoplasms to aid the radiologist in diagnosis of small bowel tumors. Most small bowel tumors are clinically silent for long periods, and nearly half of the benign tumors are found incidentally during surgery or at cross-sectional imaging performed for other reasons. Understanding the imaging features of small bowel neoplasms is important to improve the radiologist’s ability to diagnose and characterize small bowel neoplasms. Yet, various small bowel neoplasms have characteristic imaging features at CT and MRI when optimal distention of the small bowel is achieved, correlating well with features seen in gross specimens. Diagnosis is a challenge owing to nonspecific clinical manifestation, rare occurrence, and low index of clinical suspicion. This may in part be due to small bowel lesion identification in an increasing number of cross-sectional imaging studies performed for other indications as well as increased use of advanced imaging techniques to assess specifically for small bowel disease. The incidence of small bowel neoplasms is rising-in particular, there is a rising incidence of small bowel carcinoid tumors. Small bowel tumors are rare and account for approximately 3% of all gastrointestinal tumors in the United States.
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