A meatball on the outside of the anus is mainly caused by lesions in the anus and rectum. The main causes of this symptom include hemorrhoids, perianal abscesses, and sinusitis. First of all, this symptom is often seen in patients with hemorrhoids, both internal and external hemorrhoids, which can cause a meatball on the outside of the anus. Internal hemorrhoids are mainly due to the prolapse of the nucleus from the anus, while external hemorrhoids are mainly a symptom manifested by the formation of venous blood clots. Next, the possibility of a perianal abscess should be considered. A perianal abscess can lead to lesions in the mucosa of the lower rectum, causing tissue fluid to leak out of the anus and converge around the anus to form lumps, which can appear as meatballs. Finally, sinusitis can also cause this symptom, as the anal sinus can become inflamed due to fecal and bacterial stimulation, become edematous and prolapse through the anus, and the meatballs that appear in this symptom have a distinct root.