Abscess around lower rectum and anal canal are known as anorectal abscess. These are important as this often culminates in fistula-in-anus. The causative organism is usually E. coli, less commonly staphylococcus aureas, bacteroids, streptococcus, B. proteus etc. In 90% of cases, it is caused by blood borne infection e.g. extension of a cutaneous boil etc.
Types of Anorectal Abscesses
3. Sub-mucous and
Of these perianal (60%) and ischio-rectal (30%) are the common abscesses.
Perianal abscesses Causes
Majority of these abscesses arise from acute inflammation of anal gland. The pus collects within the internal sphincter and gradually paves its way between the internal sphincter and conjoined longitudinal muscle to tract down and comes superficial in the perianal region. Infection of thrombosed external pile may also result in perianal abscess.
Clinical symptoms of Perianal Abscesses
Patient complains of throbbing pain around anus. This pain becomes aggravated during defecation. Some constitutional symptoms such as fever, headache may be associated with this condition. On inspection, an acute reddish lump may be seen at the anal margin. Sometimes this might not be seen, but felt on anal examination. It is a very tender cystic lump.
Treatment for Perianal Abscesses
Treatment is incision and drainage of the pus. This should be done immediately under antibiotic cover. The cavity is packed and healing will start granulation tissue.
Ischio-rectal abscess Causes
- Common cause is extension of anal gland inflammation laterally through the external sphincter.
- Infection may be through blood or lymph.
- Penetrating injury causing direct infection from outside.
- Extension from pelvi-rectal abscess through hiatus of Schwalbe.
Clinical features of Ischio-rectal abscess
Patient presents with acute pain by side of the anus. Pain becomes exuberant during defecation. Constitutional symptoms and fever may be present. On examination, a brawny indurated swelling is seen and felt superficial to the ischio-rectal fosse on one side of the anus.
Treatment of Ischio-Rectal Abscess
Under general anesthesia, early incision and drainage of the abscess is the main theme of the treatment. The wound will heal by granulation tissue from the depth.
This abscess is situated just deep to the mucous membrane of the anal canal above the dentate line. It occurs usually from spread of infection from anal gland or even after injection of haemorrhoids. This is treated by small incision either by stretching the anus or by a proctoscope and draining the pus.
This is situated above the pelvic floor and below the pelvic peritoneum. It is simple pelvic abscess which may occur from appendicitis, diverticulitis and salpingitis. This is due to over-enthusiastic attempts to drain ischio-rectum and push a probe or a curate through the attachment of the pelvic floor. If untreated, pelvi-rectal abscess may burst into the rectum or may pass through the hiatus of Schwalbe causing ischio-rectal abscess. Treatment is drainage of the pelvi-rectal abscess.