Crohn disease can affect any segment of the intestinal tract, and the colon will be involved in approximately half of afflicted patients. Crohn disease of the colon can entail disease of the large bowel alone or of the large bowel plus the terminal ileum. The behavior of the disease varies and can be categorized as predominantly inflammatory, stricturing, or penetrating. Furthermore, disease of the anal canal or perineum can complicate any of these behavior patterns. Understanding the distribution and behavior of the disease is critical to the creation of an individualized treatment plan that usually begins with medical therapy but ultimately includes surgery in many patients.
The appropriate treatment of a patient with Crohn disease of the colon or ileocolon generally begins with individual or combination medical therapy in the form of antibiotics, 5-aminosalicylic acid (5-ASA) compounds, glucocorticoids, immunomodulators, or biologic agents. The 5-ASA compounds and glucocorticoids can be orally or topically delivered, depending on the disease location. The medications are conventionally prescribed in an escalating or “bottom-up” fashion in which the next level of medication is implemented when the disease shows itself to be unresponsive to the current therapy. However, more recent studies suggest that early aggressive or “top-down” treatment might be more effective with quicker and greater control of mucosal inflammation and disease symptoms. Regardless of the medical treatment, surgery is ultimately required in many patients with large bowel disease. The incidence of surgery, however, is lower than that for terminal ileal or small bowel Crohn disease.
The indications for surgery in a patient with Crohn disease are generally categorized as failed medical therapy or disease-associated complications. Medication failure can be defined as the persistence of symptoms despite appropriate medical therapy, failure as a result of poor compliance, intolerance of medications, debilitating adverse effects, or concern for potential risks/complications. Disease complications can be classified as acute (e.g., abscess, free perforation, hemorrhage, and severe colitis) or chronic (e.g., growth retardation, neoplasia, and obstruction).
Any patient requiring surgery for large bowel disease requires routine laboratory studies to exclude anemia and electrolyte abnormalities. Assessment of nutrition-related proteins (e.g., albumin, transferrin, and prealbumin) is reserved for a patient with recent poor caloric intake or substantial weight loss (>10% of the patient’s weight when well). Simple deficits such as hemoglobin less than 7. 0 g/dL, hypokalemia, and hypomagnesemia should be corrected. Malnutrition secondary to systemic inflammatory mediators will not improve with hyperalimentation, but 7 to 10 days of parenteral nutrition should be considered in elective situations if the cause of malnutrition is poor caloric intake. Smoking cessation should be strongly encouraged and supported when appropriate because of the negative impact of smoking on operative morbidity and disease recurrence. Regardless of the setting, a patient who may or will require fecal diversion should undergo marking in at least one abdominal quadrant in an area that is easily visible and remote from bony structures, scars, and creases despite the patient’s position (e.g., lying, sitting, and standing). A patient with anorectal sepsis in whom a proctectomy is planned will usually benefit from preliminary drainage of the sepsis.
A patient scheduled for elective surgery should generally undergo endoscopy and selective imaging if these investigative studies have not been performed recently. Colonoscopy is warranted to determine the distribution of disease, but upper endoscopy is usually not necessary. Magnetic resonance imaging or computed tomography (CT) enterography is performed to evaluate small bowel involvement in a patient with suggestive symptoms. Rectal compliance and anal sphincter function should be assessed if preservation of the rectum and anal canal is considered. The compliance and sphincter strength can be objectively measured using anorectal physiology testing and subjectively assessed by observing distensibility of the rectum with insufflation during endoscopy and digital examination. A patient who can retain a 150-mL saline enema for at least 5 minutes should experience minimal problems with urgency or seepage after an operation that spares the rectum and anal canal.
The colon is responsible for absorption of water and salt from stool, and the majority of this activity occurs in the midgut portion of the large bowel. This physiologic role helps protect patients against dehydration and electrolyte imbalances. Although the large bowel is dispensable and patients undergoing a colectomy have a normal life expectancy, attempts at preservation of the colon are justified.
Laboratory, endoscopic, and imaging studies are used to plan the operation so that unanticipated findings are rare. However, patients with large bowel disease must be emotionally prepared for the possibility of a permanent stoma during their lifetime. The incurable nature of the disease causes physicians and surgeons to redirect efforts toward safely restoring a normal quality of life, and many patients equate this goal with avoidance of a permanent stoma. Patient education or experience with a temporary ileostomy often helps alter a patient’s outlook and enables her or him to appreciate that a permanent stoma does not negatively affect quality of life for most ostomates.
A laparoscopic approach to large bowel Crohn disease is associated with an acceptable conversion rate and is generally favored in the elective setting for a patient undergoing a first-time operation for uncomplicated disease. Compared with a conventional open procedure, this laparoscopic approach is associated with reduced postoperative pain, lessened operative morbidity, better cosmesis, and decreased length of stay without an increased risk for disease recurrence.
The surgical options that are used for large bowel Crohn disease include resection with or without fecal diversion. Diversion (i.e., an ileostomy or colostomy) can be temporary or permanent. A temporary ileostomy is used to avoid or protect an anastomosis in a patient with coagulopathy, debilitating comorbid conditions, high-dose glucocorticoid usage, or severe malnutrition, as well as someone requiring an operation associated with undrained sepsis, purulent or feculent peritonitis, or excessive blood loss. Unlike in persons with small bowel Crohn disease, strictureplasty is not generally advocated for large bowel strictures because approximately 7% of colonic strictures harbor a malignancy and colonic strictureplasty does not provide better postoperative function or quality of life compared with resection.
Disease of the Colon Alone
Colonic disease can be managed by segmental resection with creation of a primary anastomosis or by a total colectomy with construction of an ileorectal anastomosis.
Disease that is limited to the ascending colon with or without terminal ileum involvement is best treated by resection, but the resultant anastomosis can abut against the second portion of the duodenum and expose the patient to risk of a complex fistula involving the duodenum or retroperitoneum if disease recurs at the ileocolic anastomosis. Accordingly, omentum is interposed between the anastomosis and duodenum or the distal resection margin is moved into the mid transverse colon to create separation from the duodenum.
Disease affecting the ascending colon and transverse colon is also managed with limited resection, but a tension-free anastomosis is best assured by rotating the midgut mesentery counterclockwise to bring the terminal ileum into close proximity of the descending colon. The small bowel will accordingly lie medial to the hindgut mesentery and occupy the right side of the abdomen.
Disease of the transverse colon, descending colon, and sigmoid colon can be treated by either segmental resection with creation of a colorectal anastomosis or a total colectomy with construction of an ileorectal anastomosis. The latter approach is generally preferred, but a more limited resection is favored if the patient is older (>50 years) or has undergone significant (>50 cm) small bowel resection. In both scenarios, preservation of the ascending colon may significantly improve the patient’s function because absorptive colonic mucosa is retained. Problems with reach of the colonic segment associated with a limited resection can be overcome by passing the colon through a window created between the superior mesenteric and ileocolic vessels in the midgut mesentery ( Fig. 43-1 ).