Ulcerative colitis—diagnosis and surgical treatment

AORN Journal,  August, 2004  by Patricia Stein

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Ulcerative colitis is a serious illness affecting the colon. It can be managed medically, but surgery is the only definitive way to remove the disease in its entirety. Ulcerative colitis is an inflammatory bowel disease (IBD) that invariably involves the rectum and may involve all or part of the colon but not the small intestine. Although the disease is mild in some patients, ulcerative colitis increases patients' risk of cancer, depending on the duration and extent of the disease.

Ulcerative colitis is a continuous disease extending in a retrograde fashion from the rectum, so there are no intervening normal areas of colon. Ulcerative colitis is in the same category as Crohn's disease, another type of IBD. Crohn's disease may occur as patchy ulcerations in the small or large bowel and can affect the entire gastrointestinal (GI) tract from mouth to anus. The entire bowel wall is affected in Crohn's disease, whereas ulcerative colitis affects only the mucosa (ie, inner lining) of the colon and rectum. indeterminate colitis describes the category of conditions in which distinguishing between Crohn's disease and ulcerative colitis is impossible.

The incidence of ulcerative colitis is eight to 15 people per 100,000 in the United States and Northern Europe. (1) The lowest rate (ie, 0.34 per 100,000) occurs in Japan? The incidence of ulcerative colitis peaks during the third decade of life and again during the seventh decade. (1)

NORMAL BOWEL PHYSIOLOGY

Normal physiological bowel processes promote defecation and normal health and flora of the bowel. These processes include water, sodium, and ammonia absorption; fatty acid, mucous, and gas production; maintenance of colonic bacteria; and motility.

WATER AND SODIUM ABSORPTION. The colon is the major site of water absorption and electrolyte exchange in the body. Approximately 90% of the fluid contained in the ileum (ie, distal portion of the small intestine) is absorbed in the colon. This amounts to 1,000 mL to 2,000 mL per day. The entire colon can absorb up to 5,000 mL of fluid daily. As much as 400 mEq of sodium is actively absorbed. Water absorption occurs passively as it follows the transported sodium. Potassium transport also is passive. Absorption of fluid is not equal throughout the colon. The right colon absorbs more salt and water than the distal colon; thus, a patient undergoing a right hemicolectomy is more likely to have diarrhea than a patient undergoing a left hemicolectomy. (2)

AMMONIA ABSORPTION. Ammonia in the colon is derived, to some extent, from dietary nitrogen, epithelial cells, and bacterial debris. Ammonia absorption depends partially on intraluminal pH. Patients taking broad-spectrum antibiotics have decreased amounts of colonic bacteria, decreased intraluminal pH, or both, which decreases ammonia absorption. This is important for patients with impaired kidney function or liver failure who cannot clear the extra ammonia.

FATTY ACIDS PRODUCTION, The production of short-chain fatty acids provides an important source of energy for the colonic mucosa. Metabolism of these fatty acids by the colonocytes provides energy for processes, such as active sodium transport. Some short-chain fatty acids are produced by bacterial fermentation of dietary carbohydrates. Mucosal atrophy may result when dietary sources of fatty acids are lacking or when the fecal stream is diverted by an ileostomy or colostomy. In patients with such diversions, this is known as diversion colitis.

MUCUS PRODUCTION. Mucus is secreted in the lumen of the colon. The epithelium contains large numbers of mucus-secreting cells. Even if feces are diverted by an ileostomy or colostomy, mucus will continue to be produced and secreted by the distal bowel.

GAS PRODUCTION. Intestinal gas arises from swallowed air, diffusion from the blood, and intraluminal gas production. The major components of gas are nitrogen, oxygen, carbon dioxide, hydrogen, and methane. The GI tract usually contains between 100 mL and 200 mL of gas, and 400 mL to 1,200 mL is released as flatus, depending on the type of food ingested. (1) Nitrogen and oxygen come largely from swallowed air, but carbon dioxide is produced by the reaction of bicarbonate and hydrogen ions. The digestion of triglycerides to fatty acids also produces these ions. Hydrogen and methane gases are produced by colonic bacteria.

COLONIC BACTERIA MAINTENANCE. Approximately 30% of fecal dry weight is bacteria (ie, [10.sup.11] to [10.sup.12] bacteria per gram of feces). (1) The most common bacteria are anaerobes, of which the Bacteroides species predominates. Eschericia coli are the most common aerobes. Endogenous microflora are crucial for carbohydrate and protein breakdown. They also participate in bilirubin, bile acid, estrogen, and cholesterol metabolism. Additionally, colonic bacteria are necessary for vitamin K production and suppression of pathogenic microorganisms (eg, Clostridium difficile). Conversely, a high colonic bacterial load may contribute to sepsis in critically ill patients. In a surgical patient, wound infection can occur after a colectomy procedure.