Perianal rectal abscess Perianal rectal abscess is an infection in the rectal rectal tissue or in the interstitial space around it that develops into an abscess, and most abscesses form an anal fistula after penetration or incision. (I) Etiology and pathology Most of the infections originate in the wall of the anorectal canal, such as anal cryptitis, and sharp foreign bodies in feces can damage the intestinal wall and cause infection. A few perianal rectal abscesses can be secondary to trauma, inflammatory lesions or drug injections; infection of hair follicles and sebaceous glands in the perianal skin can also form abscesses, and finally, anal fistulas can also be formed. The pathogenesis can be divided into three stages: ①Anal saphenous stage, where the infection occurs and the exudate accumulates in the saphenous fossa. (2) Perianal rectitis stage, in which the anal glands deep in the saphenous fossa or the lymph invade into the surrounding cellular tissue, forming perianal rectitis. ③ abscess stage, if the inflammation continues to develop, abscesses are formed, in the perianal subcutaneous for perianal subcutaneous abscesses; in the perianal space below the anal raphe, for sciatic rectal fossa abscess; above the anal raphe, on both sides of the rectum, below the pelvic peritoneum, for pelvic rectal abscesses, and in the sacral anterior rectum, between the ligaments on both sides, for posterior rectal fossa abscess. (2) Clinical manifestations 1. perianal abscess Local persistent throbbing pain, aggravated by defecation, superficial systemic symptoms of abscess are not obvious. If the abscess is not treated in time, the abscess can pierce through the skin by itself and form an external fistula or drain into the anal sinus and form an internal fistula. 2.Sciatorectal fossa abscess is more common. The abscess is larger and deeper, the symptoms are more severe, the whole body can be feverish, chill, and the local pain is persistently swollen and gradually worsens to throbbing pain, and defecation can be aggravated, and sometimes there is difficulty in urination and urgency. When examining the perianal area, there are no obvious signs at the beginning of the disease, but later redness, swelling and pressure pain appear, and soft, fluctuating and painful masses can be found on rectal finger examination, and pus can be extracted by puncture. 3.Pelvic rectal fossa abscess is deeper and the systemic symptoms are more obvious while the local symptoms are light, which makes the diagnosis difficult. There are persistent high fever, headache, nausea, etc., local anal swelling, incomplete bowel movement, discomfort in urination, etc. There are no abnormal findings in the perianal area on examination, and there is a raised mass or fluctuating sensation outside the rectal sidewall on finger examination, and the diagnosis is confirmed by puncture and pus extraction. 4.Other such as posterior rectal fossa abscess, rectal submucosal abscess, etc., the diagnosis is more difficult because of deeper location and local symptoms are not obvious. Patients have different degrees of systemic infection symptoms as well as local swelling, often with bowel movements, etc. In case of large abscesses, painful masses can be found. (iii) Treatment Once an abscess is diagnosed, it mostly requires surgical incision and drainage. If the infection has not formed abscess, non-surgical treatment can be used: ① application of antibacterial drugs, depending on the condition, 1 to 2 kinds of antibiotics or Chinese medicine to clear heat and detoxify dampness; ② hot water sitz bath; ③ local physiotherapy; ④ oral laxative to reduce the patient’s pain during defecation. The method of surgical incision and drainage varies depending on the location of the abscess. In superficial cases, it is performed under local anesthesia, and a perianal radial incision is made centered on the obvious site of fluctuation, which should be large enough to ensure unobstructed drainage. For abscesses in the colorectal fossa, the site is deeper and the scope is larger, so the incision should be made under saddle anesthesia for drainage, and the incision should be 3-5 cm from the anal verge, curved and slightly posterior, with a large incision so that the operator’s fingers can enter the abscess cavity and ensure unobstructed drainage. For pelvic rectal fossa abscesses, the pus cavity should be drained under puncture guidance due to the anal raphe interval, and the incision through the anal raphe must be large enough.