Intraoperative Consultation During Intestinal, Appendiceal, and Proximal Colonic Surgery, Including Neuroendocrine Tumors

Neoplastic causes of Stricture/Obstruction

Adenocarcinomas account for the majority of the malignant neoplasms of the small intestine. Most tumors are located in the duodenum and proximal jejunum. Occasionally, adenocarcinoma may develop in patients with Crohn disease. These patients tend to be younger, and the ileum is the most common site of involvement. Adenocarcinomas arising from the small bowel often present with vague symptoms, and therefore it is not uncommon for these tumors to present at an advanced stage with carcinomatosis/liver metastasis. In these cases, an intraoperative evaluation of the metastatic deposit may be performed to confirm the presence of malignancy. In less advanced cancers, distinguishing a neoplastic stricture from nonneoplastic stricture is critical. A common clinical scenario is that of a patient with small bowel Crohn disease, who is brought to the operating room because of obstructive symptoms that have not responded to medical therapy. In these cases, the surgeon is sometimes faced with multiple small bowel strictures scattered over a significant length of intestine. As “bowel conservation” is a guiding principle in Crohn disease surgery, strictureplasty techniques may be employed to avoid precipitating short bowel syndrome (Dietz et al, 2001). Because strictureplasty does not remove the strictured segment, in theory, a malignant stricture could go undetected and be left in situ. There have been case reports describing adenocarcinoma involving small bowel strictures in Crohn disease. Our policy is to biopsy all such strictures in the operating room prior to performing strictureplasty (Marchetti et al, 1996; Jaskowiak and Michelassi, 2001; Partridge and Hodin, 2004). If adenocarcinoma is identified, strictureplasty is contraindicated, and radical resection of the strictured segment to include its draining mesentery is performed.

Most adenocarcinomas are easy to recognize and show deeply infiltrating neoplastic glands surrounded by desmoplastic stromal response. Rarely, the tumors may be extremely well differentiated (especially those arising from the duodenal/periampullary region), and may be difficult to distinguish from misplaced epithelium in a benign stricture ( Figure 12-1 ). Features that support the presence of misplaced epithelium include lobular glandular architecture, extravasated mucin with inflammatory reaction, hemorrhage and hemosiderin-laden macrophages, and the presence of lamina propria around the glands. In most instances, these glands may be present underneath an ulcer and are lined by cells that lack cytologic dysplasia. In some instances, the glands may be cystically dilated (enteritis cystica profunda). In contrast, neoplastic glands usually demonstrate an irregular, infiltrative growth pattern with angulated glands. Careful examination of the epithelium shows a monotonous population of cells with nuclear enlargement and hyperchromasia. Mitotic figures, especially atypical mitoses, indicate a malignant process.

Nonneoplastic causes of Stricture/Obstruction

Besides strictures related to adhesions and prior surgeries, Crohn disease, ischemic enteritis, diverticular disease, and radiation enteritis should be considered in the differential diagnosis of nonneoplastic strictures.

Crohn disease accounts for approximately 5% of all causes of small bowel obstruction. A subset of patients with long-standing Crohn disease may develop complications related to strictures and need surgical resection. The primary purpose of intraoperative consultation (IOC) is to exclude a neoplastic process as discussed above. Grossly, the serosal aspect of bowel involved with Crohn disease characteristically shows "fat-wrapping." The mucosal surface shows longitudinal, serpiginous ulcers associated with cobblestone appearance of the surrounding mucosa. Histologically, the diagnostic features of Crohn disease include patchy chronic active enteritis with transmural lymphoid aggregates and mural fibrosis ( Figure 12-2 ). Noncaseating epithelioid granulomas are often distributed throughout the bowel wall.

Ischemic enteritis can present as strictures or masslike lesions and mimic a neoplastic process. Preoperative imaging and clinical history of a cardiovascular condition are helpful in establishing a diagnosis. Histologic sections often show mucosal ulceration, submucosal edema, and a variable amount of mural fibrosis. Branches of mesenteric vessels may show organizing thrombi or vasculitis.

Diverticular disease of the small bowel is much less common compared to colon. Excluding congenital diverticula (Meckel diverticulum), the duodenum is more commonly affected compared to the jejunum or ileum. Complications related to inflammation and abscess formation may cause marked thickening of the bowel wall and subsequent obstruction. In these cases, careful gross examination of the specimen often reveals an inflamed diverticulum in association with the mass or stricture-like lesion.

Radiation enteritis typically occurs in patients who have received adjuvant therapy for abdominal or pelvic cancers. Chronic radiation injury (usually after a period of 30 days) results from damage to the blood vessels, causing radiation vasculopathy and progressive "ischemic"-type injury to the bowel. Stricture formation and fistulas are commonly observed in these patients. Intraoperative sampling of the affected bowel shows prominent submucosal fibrosis with characteristic hyalinization of the blood vessels. The stromal and epithelial cells may show bizarre nuclear atypia that may be difficult to distinguish from a carcinoma or sarcoma on a frozen section. Knowledge of radiation history and random distribution of cellular atypia with intact mucosal architecture help in distinguishing radiation-related atypia from a neoplastic process. This is important because radiation strictures are sometimes treated with strictureplasty in an attempt to avoid short bowel syndrome (Dietz et al, 2001). Excluding cancer by frozen section examination during surgery is mandatory in this situation.