Ulcerative colitis (UC) is a chronic inflammatory condition that targets the lining of the large intestine, or colon. The most commonly recognized symptom of active UC is frequent, often bloody, diarrhea, resulting from the accelerated movement of waste through the inflamed bowel. Given this typical presentation, it may seem contradictory that many individuals with UC also experience difficulty with bowel movements. This apparent paradox, where a disease known for causing diarrhea can also lead to constipation, is a recognized phenomenon that requires a closer look at how UC affects the colon.
Typical Symptoms of Ulcerative Colitis
The symptoms of ulcerative colitis are directly linked to inflammation and ulceration of the colon’s inner layer. This inflammation causes the body to struggle with water reabsorption, leading to loose stools and an increased frequency of bowel movements. Patients often report finding blood or mucus in their stool, a result of the damaged lining of the colon.
The irritation caused by the inflammation also creates a strong sensation of urgency, making it feel like a bowel movement must happen immediately. This intense need to evacuate, sometimes without passing much stool, is a common symptom. These symptoms are more pronounced when the disease is active, or in a “flare.”
Mechanisms Behind Constipation in Ulcerative Colitis
The occurrence of constipation in UC is a complex issue driven by several factors related to the disease’s location and long-term effects. A key mechanism involves inflammation limited to the very end of the large intestine, a condition known as proctitis or distal colitis. When the rectum is severely inflamed, it becomes hypersensitive and painful, leading to tenesmus—the painful feeling of needing to pass stool despite the bowel being empty.
To avoid the pain and discomfort associated with this intense urge, patients may consciously or unconsciously withhold stool. This causes fecal matter to back up into the less-inflamed, more proximal parts of the colon. This functional withholding allows the stool to dry out and harden in the upstream colon, resulting in true constipation even while the rectum remains irritated. Up to half of UC patients may experience constipation symptoms at some point.
Chronic inflammation can also lead to permanent changes in the colon’s structure and function. Recurring cycles of severe inflammation and healing can cause the intestinal wall to develop scarring, known as fibrosis. This scarring can lead to the formation of a stricture, which is a narrowing of the colon that physically impedes the passage of stool. In addition, the chronic inflammatory state may also damage the nerve cells that control the rhythmic muscle contractions of the colon, slowing down the movement of waste and contributing to fecal stasis.
Medication and Diet Factors Affecting Bowel Movements
Constipation in UC patients is not always a direct result of inflammation; it can also be a side effect of necessary treatments and behavioral changes. Several medications commonly used to manage UC can slow down the digestive system. For example, certain 5-aminosalicylate (5-ASA) medications, which are often the first line of treatment for mild to moderate UC, have been reported to cause constipation in some patients.
Patients who experience anemia due to chronic blood loss may be prescribed iron supplements, which are known for causing hard stools and constipation. Opioid-based pain medications, used for severe abdominal discomfort, directly slow down gut motility and are a significant cause of constipation.
Dietary adjustments made by patients can also inadvertently contribute to constipation. Many individuals with active UC follow a highly restrictive diet, often cutting back on fiber, fruits, and vegetables. They do this out of fear that these foods will trigger or worsen diarrhea and cramping. This reduced intake of dietary fiber, which provides bulk and helps retain water in the stool, can easily lead to constipation, especially when the disease is in remission. Dehydration is also a common challenge, and inadequate fluid intake alone can cause stools to become dry and difficult to pass.
Recognizing Signs of Severe Bowel Complications
While mild constipation can often be managed with simple adjustments, severe or sudden constipation, especially when accompanied by other symptoms, can signal a serious complication. One severe complication is toxic megacolon. This life-threatening condition occurs when inflammation is so intense that it paralyzes the muscle layer of the colon, causing the large intestine to dilate rapidly and significantly.
Symptoms of toxic megacolon include severe abdominal distension, fever, a rapid heart rate, and signs of shock. In this scenario, the colon stops contracting effectively, leading to a dangerous buildup of gas and waste, which increases the risk of perforation.
Another complication is a complete bowel obstruction, which can be caused by a severe stricture or a large accumulation of hardened stool. Signs of an obstruction include persistent vomiting, an inability to pass gas, and intense, cramping abdominal pain. Any sudden change in bowel habits, particularly a severe inability to pass stool or gas accompanied by systemic symptoms like fever and extreme pain, requires immediate medical attention.