The findings at operation included a 4 cm by 5 cm pericaecal abscess mass adjacent to the anterior tenia coli. Within the abscess mass was a perforated anterior caecal diverticulum with necrotic wall. There was a polypoid mass within the wall of the caecum. The appendix was macroscopically normal with no evidence of acute inflammation. There was a suspicion of a perforated caecal tumour. He then underwent a right hemicolectomy with an ileo-transverse anastomosis through a medial extension of the appendicectomy wound. The histology of the right hemicolectomy specimen macroscopically

showed an inflamed and perforated solitary caecal diverticulum with abscess formation and an isolated caecal pedunculated mTOR activity polyp. Microscopically no dysplasia or malignancy within the caecal diverticulum and the polyp was a tubulovillous adenoma with low grade dysplasia. The caecal diverticulum lacked mucularis propria and therefore was considered to be acquired [Figures 1 and 2]. Figure 1 Showing partially maintained diverticulum mucosal lining with erosion and loose granulation tissues with acutely inflamed serosa

and extramural fat (indicated with black arrow). Figure 2 The perforation of the diverticulum mucosal is extending into the extramural fat (indicated with black arrow). His postoperative course was uneventful and he was discharged home within a week of admission with an outpatient colonoscopy planned to evaluate the rest of his bowel. His follow up colonoscopy revealed further left sided colonic polyps with histology showing tubulovillous adenoma with moderate dysplasia. Discussion Tanespimycin Solitary caecal diverticulum is uncommon and the first description in literature was by Potier 3-mercaptopyruvate sulfurtransferase in 1912 [1, 3]. Several cases have been reported since its first description but its preoperative diagnosis continues to be very elusive. The reported frequency in literature has been estimated to be 1 in 300 appendicectomies

[4, 7]. It accounts for 3.6% of all colonic diverticula with median age incidence of 44 years and male to female ratio of 3:2 [8]. Caecal diverticulitis is a rare cause of right iliac fossa abdominal pain in Caucasian patients, but is rather more common amongst the Asian or Oriental populations [1, 2]. It usually presents in a manner similar to an acute appendicitis and the two are clearly indistinguishable except occasionally by imaging investigations but mostly at operation [3–5]. Lane et al [6] reported that more than 70% of patients with caecal diverticulitis were operated on with a presumptive preoperative diagnosis of acute appendicitis. Solitary caecal diverticulum has been classified into congenital (true) and acquired (false) groups. Congenital or true diverticulum contains all layers of the colonic wall and embryologically is thought to have arisen from a transient outpouching of the caecal wall at about 6 weeks of gestational age.