A 29-year-old male patient with no known comorbidities presented to our hospital with pain in the abdomen for the past 3 months, which had increased over the past 2 weeks, and complaints of vomiting and decreased appetite. Physical examination revealed right hypochondriac tenderness without guarding or rigidity; no mass was palpable. Ultrasonography revealed an intussuscepted small bowel loop [Figure 1]. Contrast-enhanced computed tomography revealed an ileo-ileal intussusception with an avidly enhancing intraluminal mass in the proximal ileum with resultant upstream dilatation of the small bowel loops [Figure 2a], [Figure 2b], [Figure 2c], [Figure 2d].
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DIFFERENTIAL DIAGNOSIS AND FURTHER MANAGEMENT
The radiological differentials considered were lymphoma, carcinoma, gastrointestinal stromal tumor, metastases from an unknown primary tumor, and neuroendocrine tumor. Enlarged mesenteric, retroperitoneal, and left supraclavicular nodes along with hypoattenuating liver lesions made the provisional diagnosis of small bowel lymphoma or metastases from an unknown primary tumor more likely. A histopathological evaluation by immunohistochemistry was performed, which showed neural cell adhesion molecule/CD56, S100 calcium-binding protein P (S100P), epithelial membrane antigen, synaptophysin, and anaplastic lymphoma kinase 1 positivity. These findings favored the diagnosis of gastrointestinal neuroectodermal tumor. After discussion in a multidisciplinary tumor board meeting, conservative management was initiated, and the patient was referred to the medical oncology department for chemotherapy.
Gastrointestinal neuroectodermal tumor presenting as small bowel intussception
Intussusception is defined as the prolapse (telescoping) of a bowel loop with its mesentery into the lumen of the contiguous distal bowel segment. The entering segment is called the intussusceptum and the receiving segment is called the intussuscipiens. The vague presentation with intermittent abdominal pain, nausea, and vomiting in adults often leads to a delayed and incidental diagnosis, as clinical suspicion is less likely. The clinically silent nature of small bowel neoplasms is yet another reason why cross-sectional imaging is not routinely performed. Multidetector computed tomography imaging plays an important role in diagnosing and delineating the features and ability to differentiate between the presence and absence of intussusception lead point in adults, thus guiding their management and helping in the selection of candidates eligible for surgery.
Intussusception is less common among adults and differs from childhood intussusception in its presentation, etiology, and treatment. In adults, 90% of the cases occur in either the small or large bowel and about 10% involve the stomach or postoperative stoma sites. Obstructive mass lesions in lead point intussusceptions, altered peristaltic forces causing an imbalance between the longitudinal and radial smooth muscles of the intestine leading to invagination of one segment into the other and the nitric oxide hypothesis causing increased production of nitric oxide in the ileocecal region due to inflammatory mediators leading to smooth muscle relaxation and predisposition to intussusception are some of the suggested pathophysiologies for underlying intussusception.
The etiological spectrum of intussusception includes benign, malignant, and idiopathic causes, such as inflammatory bowel disease, neoplasms, congenital conditions (Meckel's diverticulum, venous malformations, or hereditary conditions like Henoch Schönlein purpura), post-surgical adhesions, and trauma (intramural hematoma or submucosal hemorrhage). Among adults, neoplastic causes of intussusception are far more common than other benign entities. In more than 90% of adults, intussusception has a definite underlying cause; more than 65% of intussusceptions among adults are caused by tumors. Bowel neoplasms presenting with intussusceptions include both benign and malignant cancers, with lymphomas and metastases being the most common. Adenocarcinomas account for 30% of all adult small intestine intussusceptions and 66% of colonic intussusceptions. Histopathological examination of the lead point lesion in our case confirmed the diagnosis of gastrointestinal neuroectodermal tumor. Malignant gastrointestinal neuroectodermal tumor is a rare entity with only a few cases described in the literature. Gastrointestinal neuroectodermal tumors are known for their aggressiveness with poor prognosis and histopathological diversity. The diagnosis of gastrointestinal neuroectodermal tumor requires histopathologic, immunohistochemical, and molecular testing. Gastrointestinal neuroectodermal tumors are most commonly seen in the small intestine (67%), followed by the stomach (13.8%) and colon (9.6%). These are aggressive neoplasms that are usually metastatic at presentation. They are hypervascular, with mesenteric, nodal, and liver metastases. They pose a diagnostic challenge to clinicians and pathologists, as they show both melanocytic and neural differentiation. Moreover, there is an urgent unmet need to improve the survival outcomes of patients with gastrointestinal neuroectodermal tumors. Other neoplasms that can clinically present as intussusception are described in Table 1.
The imaging pattern for intussusception depends on its anatomical location, the axis of the section, bowel wall thickness, and luminal patency. Depending on the severity and the orientation to the scanning axis, intussusception may have three different CT patterns as described in Table 2. Key information revealed by multidetector computed tomography for bowel intussusception is provided in Table 3. A thorough investigation of adult patients with intussusception is required to determine the underlying neoplastic process. Cross-sectional CT imaging of the thorax, abdomen, and pelvis plays a vital role not only in locating and characterizing the primary neoplasm in the bowel but also in screening for other similar lesions or distant metastases. In our case, the patient presented with metastatic disease. The presence of metastases points toward a malignant etiology underlying the intussusception and helps in narrowing down the differentials. CT helps in identifying and locating the primary tumor, distant metastases, and complications if any, and plays a key role in guiding the medical and surgical oncology teams to come to a consensus about the management strategy. Early identification of complications on CT can also help expedite optimal management.
Presentation of intussusception can be quite variable based on the underlying cause, duration, and symptoms. Intussusception detection rates in incidental cases have dramatically increased over the past two decades, with the help of multi-detector tomographic technology. CT plays an important role in differentiating lead point from non-lead point intussusceptions. Transient intussusceptions usually present with vague abdominal pain and are self-resolving. Non-lead point intussusceptions are commonly seen in children; they are also reported in adults with Crohn's disease, celiac disease, and other causes related to dysrhythmic contractions. Observation and conservative management are sufficient in these cases. Lead-point intussusceptions present with episodic cramp-like abdominal pain with vomiting. On CT, identification of the bowel-within-bowel configuration, degree of bowel wall edema, invagination of mesenteric vessels, and fat stranding are the key imaging features to look for, which can guide further management. Unlike hydro-reduction in children, adult intussusception almost always requires surgical intervention. The surgical approach is based on the site involved, vascular status, and preoperative planning for enterostomy whenever required.
Adult intussusception flags an underlying sinister etiology. Compared to ultrasonography and colonoscopy, CT imaging offers higher detection rates for intussusception and can determine its cause more accurately. CT plays an important role in both the detection and characterization of lead point intussusception. It provides additional information about the associated vascular compromise and ischemic/gangrenous changes, if any, thus guiding preoperative planning. Intussusceptions in adults require a thorough diagnostic work up, as more than 65% of the cases are associated with underlying neoplasms. Early identification of the cause and complications can expedite optimal management.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published, and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed.
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Conflicts of interest
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