Complex Anal Fistula

Acute diverticulitis is inflammation of a colonic diverticulum and adjacent tissues, most commonly involving the sigmoid colon.

Uncomplicated disease is confined inflammation without abscess, fistula, obstruction or free perforation.

Complicated disease includes abscess, fistula, stricture, obstruction, perforation or diffuse peritonitis.

Typical presentation is progressive left lower quadrant pain with local tenderness and fever.

Constipation or diarrhoea may occur. Urinary frequency or dysuria can result from adjacent bladder irritation.

Diffuse guarding, haemodynamic deterioration, ileus or systemic toxicity suggests complicated disease.

CT abdomen and pelvis with IV contrast: preferred when diagnosis is uncertain, disease is moderate or severe, or a complication is suspected; determine whether inflammation is uncomplicated or associated with abscess or perforation.

Uncomplicated disease

Stable immunocompetent patients with mild uncomplicated disease do not all require antibiotics.

Use oral fluids or a light diet according to tolerance, analgesia and close follow up.

Antibiotics are appropriate when systemic inflammation is prominent, significant comorbidity or immunosuppression is present, symptoms are refractory, or disease is complicated.

A practical outpatient regimen is:

Amoxicillin clavulanate 875 mg/125 mg orally every 12 hours for approximately 4 to 7 days.

For hospitalised complicated infection:

Ceftriaxone 2 g IV every 24 hours plus metronidazole 500 mg IV every 12 hours.

Diverticular abscess

An abscess below approximately 3 cm can often be treated with antibiotics alone in a stable patient.

A collection above approximately 3 cm should generally be considered for image guided percutaneous drainage where a safe route exists.

Operate when drainage is impossible and infection remains uncontrolled, or when peritonitis or physiological deterioration develops.

Emergency surgery

Free perforation with generalised peritonitis requires urgent source control.

Resect the diseased sigmoid.

In a stable patient with viable bowel and manageable contamination, primary colorectal anastomosis, often with selective diverting ileostomy, is appropriate.

Septic shock, severe acidosis, gross faecal contamination or poor tissue perfusion may favour an end colostomy with rectal stump or staged reconstruction.

Elective colectomy after recovery is particularly appropriate after diverticulitis complicated by fistula, obstruction or stricture. After a large or drained abscess, future resection should be considered according to recurrence risk and patient factors.