Nitricum acidum:
This acid has a marked affinity for the margins of the outlets, especially of the anus, mouth. Rectum feels torn, violent cutting pains after stools, lasting for hours. Pain as from splinters. Discharges are acrid, thin, and offensive and the orifices are red, swollen and cracked. Stools tear the anus even though soft.

Silicea:
Fistula in ano with spasm of sphincter. Rectum feels paralyzed. Stool comes down with great difficulty; when partly expelled,recedes again. Faeces remain for a long time in the rectum. Fistula in ano alternates with chest symptoms.

Ratanhia peruviana:
Anal and rectal symptoms are very marked. Sharp splinter like pain in rectum, excruciating pains after stool, burning after soft stool which is relieved temporarily by cold water.

Causticum:
Fistula, with pulsation and pain in perineum. Stool hard, tough, covered with mucus; small shaped; expelled after much straining, or only on standing. Rectum insensible to solid stool.

Kali carbonicum:
Stitching pain in the rectum an hour before stool; anal fistula. Large quantity of blood is discharged with stool. Burning in the rectum and anus.

Berberis vulgaris:
Fistula ani with chest complaints, itching.Violent pain in anus.Parts around the anus feels sore. Tearing around the anus.Hard, scanty stools, like sheep dung.

Paeonia officinalis:
Fistula ani, diarrhoea, with burning in the anus and internal chilliness. Oozing offensive moisture on the perineum. Excruciating pains at anus, continues long after stool; must rise and walk about at night.

Calcarea Phosphorica:
Calcarea Phosphorica: Useful in cases of fistula; and when fistula has been operated on and symptoms have appeared elsewhere; fistula in ano, alternating with chest symptoms. Fistula; in persons who have pains in joints with every spell of cold,stormy weather.

Calcarea Sulph
Painful abscess about the fistula.

Fluoric acid:
Fistula with syphilitic and psoric, history of tuberculosis .