The anal sinus is located in the dentate line of the anal canal, between the bases of the two adjacent anal columns, shaped like a half-moon, with an upward opening, concave as a pocket, and 3-5 mm deep. It has an opening for the anal glands at its base. Sinusitis, also known as anal saphenous fossa, is an inflammatory lesion of the anal saphenous fossa at the dentate line of the anus. Sinusitis often causes perianal abscesses and other infectious anal diseases. The common site of onset is the anus. Common symptoms Pain in the anus when defecating Causes Due to the special anatomical form of the anal sinus, the sinus is prone to accumulation of feces or blockage by secretions, resulting in infection and inflammation. In addition, dietary factors may also cause anal sinusitis, such as fried and spicy foods, seafood, etc. Clinical manifestations 1. anal pain during defecation, and the localization is very clear. It is often posterior to the anus because it is the highest pressure point in the anal canal. 3. In addition, it is accompanied by anal foreign body sensation, discomfort, anal canal downward feeling and anal purulent discharge. Examination 1.Anal finger examination Tension of sphincter, hardness and tenderness of anal sinus and papilla. 2.Anoscopic examination Anal sinus and anal papillae are congested and red and swollen. Diagnosis Diagnosis should be made based on clinical symptoms and relevant examinations. Differential diagnosis 1.Anal fissure Anal fissure is characterized by periodic anal pain and constipation with blood in the stool. The degree of pain is heavier than that of anal fossa and the pain lasts longer. 2.Perianal abscess is the result of the further development of anal fossa inflammation, mainly manifested by the gradual increase of perianal pain, peck-like pain when pus is brewed, accompanied by vicious chills and fever, etc. The white blood cell count increases significantly and the neutrophils also increase in routine blood tests. Treatment 1, conservative treatment of anal sinusitis at the beginning or when the symptoms are mild, more can be used drug therapy, sitz bath. 2, surgical treatment anal sinusitis by drug treatment is not effective, or the anal sinus has become an abscess, or with anal papillary hypertrophy and hidden fistula patients, it is appropriate to use surgical treatment, treatment methods are anal sinus incision and anal sinus excision.