Small bowel carcinoids
What is the treatment of small bowel carcinoids? Are there any preoperative considerations?
Patients with a small intestinal neuroendocrine tumor undergo an exploratory laparotomy. The primary tumor is identified and the entire small intestine is examined for synchronous neuroendocrine tumors which are present in 30% of patients. Twenty-nine percent of patients will have synchronous or metachronous non-carcinoid tumors, most commonly adenocarcinoma of the colon. The small bowel mesentery is examined for lymphadenopathy and the liver is examined for metastatic disease. Intraoperative ultrasound exam of the liver is also of value in determining the extent of metastatic involvement of the liver. Approximately one-third of patients with small intestinal neuroendocrine tumors will have metastases to the liver. The metastatic potential of small bowel neuroendocrine tumors best correlates with the size of the primary tumor.
Figure 3: Segment of small intestine and its mesentery containing a primary neuroendocrine tumor( single arrow) and a bulky lymph node metastasis (multiple arrows). (From McHenry CR and Mittendorf EA. Gastrointestinal carcinoid tumors. General Surgery Board Review Manual;7(4): 1-12,2001 with permission)
Surgical treatment of the primary tumor consists of a segmental resection of the involved small intestine along with its mesentery (Figure 3). It is important to pay close attention to the adequacy of the resection margins of the small intestine and the lymphatic drainage of the tumor, and preserve the blood supply to the bowel margins. Intraoperative lymphatic mapping using lymphazurin blue dye has been used to map the subserosal lymphatic channels for the purpose of ensuring adequate resection margins and preserving the ileocecal valve when conditions permit.
In patients with known liver metastases, resection of the involved segment of small bowel and its associated mesentery is recommended for palliation of abdominal pain and prevention of vascular compromise and small bowel obstruction. Most patients who have small bowel neuroendocrine tumors will eventually be treated with octreotide, which is known to be associated with a high incidence of gallstones. As a result, a removal of the gallbladder should be considered in patients undergoing exploratory laparotomy for treatment of a small bowel neuroendocrine tumor.
Surgical resection of liver metastases can improve survival in selected patients. A wedge resection or lobectomy is indicated for patients with metastases confined to one lobe of the liver. In patients with diffuse hepatic metastases, tumor debulking may help ameliorate symptoms of carcinoid syndrome. Hepatic artery chemoembolization and radiofrequency ablation are therapeutic options when liver metastases are not amenable to complete surgical resection.
Long acting somatostatin analog, administered two to three times per month, is useful for helping control hormonal symptoms. It may also have an antitumor effect, slowing tumor growth and stabilizing disease. The perioperative use of somatostatin analog has also been shown to prevent the development of carcinoid crisis, an uncommon life threatening manifestation of carcinoid syndrome. Carcinoid crisis can be precipitated by tumor manipulation, medications that promote histamine release or that stimulate the autonomic nervous system, hypotension, hypercapnea, and hypothermia. Intraoperatively, it is manifested by tachycardia, arrhythmias, blood pressure lability, and cardiovascular collapse. Carcinoid crisis is best treated by tumor removal and intravenous octreotide therapy.