What are the characteristics of anal pain in rectal cancer?

Generally, rectal cancer is a malignant tumor occurring above the dentate line of the rectum up to the junction of the rectum and sigmoid colon. Anal pain caused by rectal cancer is characterized by persistent pain, progressively worsening pain, increased pain during defecation, pain accompanied by a sensation of pressure or heaviness, and radiating pain. The specific features are as follows:

1. Persistent pain: Anal pain in patients with rectal cancer occurs due to continuous compression and invasion of surrounding tissues by the tumor. As tumor cells proliferate, they compress nerves, muscles, and other tissues around the anus. This physical pressure continuously stimulates nerve endings, resulting in uninterrupted pain signals.

2. Progressively worsening pain: As rectal cancer progresses, the tumor increases in size, gradually expanding its invasion to surrounding anal tissues. Initially affecting only the local mucosa and superficial tissues, the tumor progressively invades deeper layers such as the muscular layer, nerve plexuses, and even surrounding organs. Additionally, the tumor may trigger local inflammatory reactions, releasing inflammatory mediators such as prostaglandins and histamines, which further stimulate nerve endings and intensify the pain.

3. Increased pain during defecation: During defecation, the increased pressure within the rectum places additional pressure on the tumor. Simultaneously, the passage of stool through the rectum and anus causes friction and compression of the perianal tissues already affected by the tumor, thereby exacerbating the pain. Moreover, the contraction and relaxation of the anal sphincter muscles during defecation stimulate nerves surrounding the tumor.

4. Pain accompanied by a sensation of pressure or heaviness: The presence of a rectal tumor can cause a feeling of pressure or heaviness in the rectal and anal areas. This sensation is partly due to the weight and volume of the tumor itself, creating a downward pressure in the anal and rectal regions. Additionally, the tumor may cause local congestion, edema, and inflammatory reactions, all of which contribute to a feeling of discomfort characterized by pressure or heaviness in the anal area, often occurring simultaneously with pain.

5. Radiating pain: When rectal cancer invades the nerve plexuses around the anus, pain signals travel along nerve fibers. This results not only in localized anal pain but also in pain radiating to surrounding areas. This occurs because nerve fibers are interconnected, and tumor-induced nerve stimulation causes pain sensations to spread across the nerve distribution areas.

The presence of anal pain does not necessarily indicate rectal cancer; it could also be caused by other anorectal diseases such as hemorrhoids or anal fissures. Therefore, if related symptoms occur, timely medical consultation is recommended for accurate diagnosis and appropriate treatment.