Ileo-Ileal Intussusception Secondary to Neuroendocrine Tumor in Adult Patient

Introduction

Intussusception occurs when a proximal region of the intestine telescopes into a distal region, thus causing obstruction, ischemia, or perforation. It is more common in pediatric patients, with only 5% of cases occurring in the adult population [1]. The most frequent causes of adult intussusception are malignancy, polyps, or diverticula [2]. In particular, a gastroduodenal intussusception can be seen following certain types of bariatric surgery [3]. Of those caused by malignancy, the most commonly seen is metastatic disease from melanoma, colon, lung, or renal cancer. Lymphomas and primary adenocarcinoma are other common etiologies [4]. Some very rare causes of adult intussusception are neuroendocrine tumors (NETs) and gastrointestinal stromal tumors [5,6].

NETs are a diverse group of neoplasms that arise from endocrine cells throughout the body [7]. The first description of small bowel NET was made in 1867 and was described as a polypoid tumor of the small intestine [7]. NETs were initially classified by their embryologic origin into foregut, midgut, and hindgut, but this distinction was made for convenience rather than being of fundamental importance [7]. As a result, the World Health Organization published a classification system in 1980, in which most NETs were classified as carcinoid tumors [7]. Due to the increasingly imprecise use of the term “carcinoid” and the fact that most of these tumors were not actually associated with carcinoid syndrome, Capella et al proposed the use of NET to refer to all neoplasms of the neuroendocrine system [7,8]. Here, we present a case of a patient who presented with ileo-ileal intussusception due to a T3N1 NET, grade 1.

Case Report

A 60-year-old man with a past medical history of peptic ulcer disease presented to the Emergency Department for evaluation of lower abdominal pain, several dark “maroon” colored bowel movements, and hematemesis for the past 2 days. He had associated palpitations and shortness of breath, which quickly resolved upon arriving to the hospital. He reported using Goody’s powder, an over-the-counter aspirin/paracetamol/caffeine-based powdered pain reliever, daily. He admitted to drinking alcohol occasionally and smoking 2 packs of cigarettes per day for the past 40 years. He denied any family history of malignancies. His last colonoscopy was 10 years ago and was unremarkable.

On presentation, his vital signs were stable. Physical examination was notable for mild tenderness across the lower abdomen. Initial laboratory test results were significant for a hemoglobin level of 12.3 g/dL and hematocrit of 36%. The remainder of his laboratory work was unremarkable. Computed tomography (CT) of the abdomen and pelvis with intravenous contrast showed ileo-ileal intussusception in the right lower quadrant. Just distal to this segment, there was an irregular area of mucosal/submucosal thickening, suspicious for an underlying small bowel mass, with no signs of intestinal obstruction (Figures 1, 2).

General Surgery was consulted for further evaluation of peptic ulcer disease and his ileo-ileal intussusception. As his hemoglobin level remained stable and he had no additional episodes of hematemesis, they recommended outpatient follow-up for esophagogastroduodenoscopy. He was taken to the operating room for an exploratory laparotomy where he was found to have a small bowel mass approximately 30 cm from the ileocecal valve, serving as the lead point for his intussusception. There was also a small palpable lymph node in the associated mesentery. Approximately 15 cm of small bowel and 13 lymph nodes, including the palpable lymph node, were resected and sent for pathological analysis. No abnormalities were seen on the liver.

Subsequent histopathological examination confirmed a well-differentiated 1.2-cm NET with spread to 1 lymph node, with surgical margins clear of the tumor (Figures 3–5). The Ki-67 stain was positive for less than 1% of cells. The final diagnosis was an ileo-ileal intussusception secondary to a T3N1 NET, grade 1. The patient was subsequently referred to the Oncology Department as an outpatient. As his grade 1 NET was resected with clear margins and there were no signs of carcinoid syndrome, no additional surveillance was recommended. His postoperative course was complicated by the development of an ileus, which quickly resolved on its own following conservative management.

Discussion

Intussusception in adults usually presents with vague gastrointestinal symptoms, such as nausea, vomiting, abdominal distension, and intermittent constipation within the first 24 to 48 h [9]. Almost 90% of adult intussusception is due to a pathological lead point, most commonly a malignancy [1]. In pediatric patients, the diagnosis relies heavily on ultrasound and barium-enema studies. However, as this is not suitable for adults, CT scan is the main diagnostic tool and will typically show the pathognomonic “target” sign, which was seen in our patient, as shown in Figure 2 [10]. Treatment involves immediate surgical exploration and resection of the involved bowel. In cases of suspected malignancy, reduction of intussusception should be avoided, due to increased risk of perforation. One notable exception is in the case of Peutz-Jeghers syndrome [11]. Local lymph nodes should also be resected, as the risk of an associated malignant lesion is up to 50% [2].

As mentioned earlier, NETs are a very rare cause of adult intussusception [5]. NETs can occur throughout the body, but we will focus this discussion on small bowel NETs, which are located anywhere from the ligament of Treitz to the ileocecal valve. Since 1973, there has been a 6.4-fold increase in the incidence of small bowel NETs, which is now 1.05 per 100 000 persons in the United States [12]. It is unclear to what degree the incidence has actually increased versus just being an apparent increase because of more frequent imaging and endoscopy, coupled with more clinician awareness [7]. Although NETs are regarded as rare malignancies, their increasing incidence and relatively indolent course has led to a prevalence that exceeds that of many other gastrointestinal malignancies [7].

The terms NET and carcinoid tumor have been used interchangeably for many years, with current literature favoring NET. This is mainly due to the fact that only a minority of NETs actually present with carcinoid syndrome. Carcinoid syndrome is classically described as flushing, diarrhea, valvular heart disease, and bronchospasm, in order of decreasing frequency [7,13]. Other clinical signs can also be present, such as telangiectasias, cyanosis, pellagra-like dermatitis, arthritis, myopathy, edema, and ascites [7,13]. These additional clinical signs, however, are not due to excess hormone secretion, but rather to hepatic tumor replacement and carcinoid heart disease [13]. Carcinoid syndrome is caused by the secretion of hormones such as serotonin, neurokinin A, histamine, and others [7,14]. The reason that most of the small bowel NETs do not present with carcinoid syndrome is because these hormones are secreted directly into the portal system and get inactivated by the liver, thereby delaying the onset of carcinoid syndrome until after the NET metastasizes to bypass the portal circulation [13]. As a result, patients with small bowel NETs usually present with nonspecific abdominal pain instead of symptoms of excess hormone secretion [13]. This leads to a delay in diagnosis, with the reported duration of symptoms preceding small bowel NET diagnosis ranging from a median of 4.3 months to 9.2 years [14]. Our patient’s palpitations were likely secondary to his vomiting and abdominal pain, as his liver examination during his exploratory laparotomy was unremarkable.

Conclusions

In adult patients presenting with nonspecific abdominal pain and concern for small bowel obstruction, a CT scan can be helpful in diagnosing intussusception. When dealing with adult intussusception, the etiology needs to be carefully investigated, as an underlying malignancy is more likely. In rare occasions, small bowel NETs can be the cause of intussusception, in which case, they can be identified early, before they metastasize and present with carcinoid syndrome. Surgical intervention is often recommended for adult intussusception, as a majority of cases have a pathologic lead point, which requires further workup.