Anal Fistula 

An anal fistula, also called fistula-in-ano, is a small tunnel that develops between the inside of the anus and the skin around the anus. It's usually caused by an infection near the anus that results in a pus-filled cavity called an abscess. When the pus drains away, it can leave a small channel behind, which is the fistula. 

 Anal Fissure

An anal fissure is a small tear or split in the thin, moist tissue lining the anus. It can be seen as a crack in the skin when the area is stretched. Anal fissures are very common and can occur in people of any age or gender. They can be caused by passing large or hard stools, or by constipation 

 Piles (haemorrhoids)

 Piles, also known as haemorrhoids, are swollen veins in the anus and lower rectum that can be internal or external:

• External haemorrhoids: Form under the skin around the anus
• Internal haemorrhoids: Form in the lining of the anus and lower rectum