Endoscopic retrograde appendicitis therapy (ERAT) is a new and minimally invasive method for the diagnosis and treatment of acute appendicitis.After a positive diagnosis of acute appendicitis is established by either colonoscopic direct-vision imaging or fluoroscopic endoscopic retrograde appendicography (ERA) imaging in patients with suspected acute appendicitis, the procedures to relieve the appendiceal lumen obstruction including appendiceal luminal irrigation, appendicolith removal, and stenting for drainage whenever necessary will be carried out. In this multicenter prospective randomized clinical trial, the patients with uncomplicated acute appendicitis will be divided into three groups randomly: ERAT group, antibiotic therapy group and appendectomy group. The primary outcome is duration of abdominal pain. The secondary outcomes include mean hospital stay, mean operative time, duration of fever, duration of leukocytosis, bed time, rate of complication, rate of recurrence and rate of appendectomy during follow-up period of 1 year.

Intervention

The patients with uncomplicated acute appendicitis will be divided into three groups randomly: ERAT group, antibiotic therapy group and appendectomy group.

1) ERAT group: In preparation for ERAT, low-pressure cleansing enemas (500 mL normal saline solution per enema) will be administered for three times before the procedures for bowel preparation. Antibiotic therapy (levofloxacin + metronidazole) will be intravenously administrated to the patients in the perioperative period.

The procedures of ERAT will be performed as below：

1. Cannulation of the appendiceal lumen: Colonoscopic examination under direct vision of the whole colon, ileocecal junction and terminal ileum will be performed to exclude other abnormalities first, and focus on the appendiceal orifice and the surrounding mucosa. Colonoscope attached by a transparent cap will be positioned close to the appendiceal orifice. Gerlach's valve will be pushed aside using the transparent cap, a standard catheter loaded with a 0.035-inch guidewire (loop-tip or hydrophilic-tip) will be placed in the appendiceal orifice. The guidewire will be probed gently to insert into the appendiceal lumen. The catheter will be then subsequently moved forward after the guidewire inserting deeply into the lumen under fluoroscopic guidance.
2. Endoscopic retrograde appendicography (ERA): After cannulation of the appendiceal lumen, decompression of lumen will be achieved by suction using a 5-mL syringe attached to the catheter. A soluble contrast agent (iobitridol) will be then used to fill the appendix while being monitored by fluoroscopy to check the radiographic features of the appendix (including position, length, contour, mobility, intraluminal content and inner diameter of appendiceal lumen).
3. Irrigation and appendicolith removal: The appendiceal lumen will be irrigated with normal saline solution to clear away the pus and the sand-like appendicoliths, while the large appendicoliths will be extracted using a balloon catheter or an extraction basket.
4. Stenting for drainage: If the pus is massive or the lumen is stenosis, a plastic straight stent (8.5F) will be placed into the lumen over the guidewire for luminal decompression with the plan to retrieve the stent after about one week.

2) Antibiotic therapy group: The patients will be treated with intravenous broad-spectrum antibiotics (Carbapenems) for 3 days and oral antibiotics (Levofloxacin and Metronidazole) for 7 days. If patients in the antibiotic group deteriorate during the hospital stay (suspicious perforation or any symptoms of peritonitis) patients will be operated.

3) Appendectomy group: The patients will undergo laparoscopic appendectomy according to standard routines.

Follow-up and outcome measures

Follow-up will be performed until the end of the study period. The primary outcome is duration of abdominal pain. The secondary outcomes include mean hospital stay, mean operative time, duration of fever, duration of leukocytosis, bed time, rate of complication, rate of recurrence and rate of appendectomy during follow-up period of 1 year.

Inclusion Criteria:

• patients with Alvarado scores ≥7 (with or without US/CT) diagnosed of uncomplicated acute appendicitis
• patients with Alvarado scores <7 but US/CT suggested uncomplicated acute appendicitis or could not exclude acute appendicitis.

Exclusion Criteria:

• perforated appendicitis
• periappendiceal abscess
• contraindications for colonoscopy
• allergy to contrast media or iodine
• pregnancy
• unable to cooperate or provide informed consent