Why Does Diarrhea and Constipation Occur in Alternation?

Normally, everyone will defecate, and most people have regularity in defecation, once a day or every other day. If diarrhea and constipation alternate, it will disrupt the regularity of defecation, leading to irregular bowel movements. Especially when diarrhea and constipation alternate frequently, it needs to be taken seriously as it is usually caused by intestinal diseases. It is necessary to go to the hospital promptly to clarify the cause and treat it accordingly.

1. Anal and rectal diseases: Although changes in defecation patterns and stool characteristics are warning signs of colorectal cancer, hemorrhoids, anal fistulas, and other anal and rectal diseases can also cause symptoms such as blood in the stool and changes in defecation patterns. Mild cases may manifest as local fullness and a sense of falling, while severe cases may include urgency, frequent squatting in the toilet, and persistent heaviness after defecation, which can be very painful and not uncommon in clinical practice. When constipation and diarrhea alternate, it is often overlooked, as people may not consider it a serious problem and may not associate it with cancer. This can lead to missed opportunities for early diagnosis and treatment.

2. Colorectal cancer: The large intestine is the "terminal station" of the digestive tract. After food is digested and absorbed by the digestive organs such as the mouth, esophagus, and stomach, it forms stool in the large intestine and is excreted regularly. After developing colorectal cancer, the shape of the stool may become thinner and may contain mucus. Besides changes in the nature of the stool, the timing of defecation may also change. Sometimes there is constipation, with bowel movements every 3-4 days; sometimes there is diarrhea, with 4-5 bowel movements per day or even more; or constipation and diarrhea may alternate; or there may be a sensation of incomplete evacuation or difficulty defecating after bowel movements. This alternating pattern of constipation and diarrhea is an important warning sign of colorectal cancer and requires prompt medical attention. The cure rate for early-stage colorectal cancer can reach 90% once it is detected, but the five-year survival rate for late-stage colorectal cancer is as low as 10%.

If any of the above situations occur, it is advisable to promptly undergo a medical examination to facilitate early detection and treatment. For example, people who have always had regular bowel movements and recently experience changes in their bowel habits, such as diarrhea, constipation, or alternating diarrhea and constipation, with a sense of incomplete evacuation; changes in stool characteristics, such as loose stool, mucus, bloody stool, or stool with fresh red or jam-colored blood, should be taken seriously and promptly examined and treated.