Ulcerative colitis typically occurs in patients between 20 and 50 years of age and may present as an early acute fulminating attack or may follow a rather indolent and often chronic course. Approximately 70% of patients will have complete symptomatic remissions between intermittent attacks. Ten percent of patients will have one initial attack and will experience no subsequent attacks, and 15–20% will be troubled by continuous symptoms that occur without remission.

The initial and most common symptom of ulcerative colitis is rectal bleeding. A blood stain on the toilet tissue or the appearance of bloody mucus on the surface of stools is usually the first symptom noticed. This initial bleeding is often mistaken for bleeding from hemorrhoids. Indeed, this first evidence of blood may follow a bout of constipation, which can sometimes be the presenting complaint. When constipation is the presenting complaint, the colitis is most often associated with disease limited to the rectum, where spasm prevents feces from entering the area involved. Hence, initial constipation or normal bowel habits may be the hallmark of ulcerative proctosigmoiditis.

Diarrhea occurs with more extensive colonic involvement, and blood is usually mixed with the feces. The principal mechanism responsible for diarrhea in ulcerative colitis is exudation with resultant secretion of interstitial fluids and loss of mucosal surface area for absorbing fluid and electrolytes and water. In addition, involvement of the rectum prevents this segment of the colon from acting as a reservoir for fecal contents prior to defecation. This rectal irritability causes frequent bowel evacuation of minute amounts of blood and mucus, an activity that can be termed “pseudodiarrhea.”

Since the severity of the disease will affect the therapeutic approach and, indeed, the prognostic implications, it is important for the physician to assess the severity of the disease for every patient. The best indices of severity are clinical signs and symptoms. Large volumes of diarrhea indicate that the colonic mucosa has been involved to the extent that sodium and water absorption are significantly impaired. Frequency, however, is an unreliable indicator of severity because frequent bowel movements can indicate either large-volume diarrhea or rectal irritability. Large quantities of blood in the stools, a fallen hemoglobin concentration, and hypoalbuminemia as a consequence of loss of albumin into the stool are signs of widespread disease. Elevated erythrocyte sedimentation rate, fever, and abdominal pain and tenderness may point to transmural extension of the disease and the development of severe ulcerative colitis.

Ulcerative colitis can be classified according to grade of clinical severity:
1. Severe. Diarrhea comprising six or more movements per day, macroscopic blood in the stools, fever, tachycardia greater than 90/min, anemia and an elevated erythrocyte sedimentation rate.
2. Moderate. Diarrhea comprising four or fewer movements per day, small amounts of macroscopic blood in stools, no fever, no tachycardia, mild anemia and a minimally elevated erythrocyte sedimentation rate.
3. Mild. Diarrhea comprising fewer than four bowel movements per day without anemia, fever, tachycardia, weight loss or hypoalbuminemia.

Severe ulcerative colitis, the least common form of the disease, occurs in 15% of all patients with ulcerative colitis. This form of the disease may be the initial presentation or may represent a progression from a less severe attack. Diarrhea is profuse and rectal bleeding is constant and severe. Fever is marked and sustained, and appetite and weight are both severely diminished. Abdominal cramps are severe and tenderness may be localized, indicating impending perforation. Leukocytes greater than 10,000, severe anemia, and hypoalbuminemia resulting from low protein intake (anorexia) and increased chronic loss of albumin are hallmarks of this form of the disease.

Medical therapy is often ineffective for this type of patient, and colectomy is often required.

Moderate ulcerative colitis affects 25% of all patients with ulcerative colitis. Diarrhea is the major symptom, and it occurs three to four times per day. Invariably, the diarrhea contains macroscopic amounts of blood. Abdominal pain may occur and may awaken the patient at night; usually the cramps are relieved by defecation. Low-grade fever may exist, and the patient may complain of fatigue, anorexia and some mild weight loss.

Generally, moderate ulcerative colitis responds quickly to appropriate therapy. Immediate mortality in this group is low. However, the long-term prognosis is for repeated attacks of equal or greater severity, and the risk of ultimately developing cancer in the affected colon is appreciable. As well, at any time during the moderate attack of ulcerative colitis, the patient may become severely ill, developing a severe fulminant colitis characterized by high fever, profuse diarrhea, progressive dilation of the colon (toxic megacolon) and rapid deterioration.

Mild ulcerative colitis is the most common form of the disease, occurring in 60% of patients. In 80% of those affected with mild disease, the ulcerative colitis will be limited to the distal colon (sigmoid and rectum); in the other 20% the whole colon will be involved. The age, sex and familial incidence of ulcerative colitis are the same for mild disease as for severe disease. As well, the number of patients who have only one attack, intermittent attacks, or continuous disease is the same for both mild and severe ulcerative colitis.

In the case of mild disease limited to the rectal sigmoid, most often the disease will remain in this area; however, in 10% of these patients it will eventually involve the entire colon and bring about the simultaneous development of severe diarrhea and bleeding.

Neither colonic bleeding nor diarrhea is severe in mild ulcerative colitis, and the systemic complications of anorexia, weight loss and fatigue are not seen. Occasionally, the patient may suffer from a few days of crampy lower abdominal pain; however, hospitalization is usually not required and mild ulcerative colitis responds rapidly to therapy.

For patients who have mild ulcerative colitis, particularly proctosigmoiditis, the rate of colonic cancer is similar to that of control populations. Thus, colonic cancer occurs in mild cases of ulcerative colitis only one-fifth as often as in the more severe forms of the disease.

The diagnosis of ulcerative colitis is made on the basis of the clinical symptoms listed above, on physical findings, and on the results of laboratory and endoscopic investigations.

Physical examination during mild ulcerative colitis or between attacks may yield completely normal findings. In contrast to Crohn’s disease, there are no palpable masses and no specific areas of tenderness, unless serosal involvement, peritoneal irritation or impending perforation (toxic megacolon) exists. Occasionally, the liver is palpable because of fatty infiltration or other hepatic abnormality. Auscultation of the abdomen may reveal increased bowel sounds and audible borborygmi. With toxic megacolon, bowel sounds are quiet or absent.