Discussion
A solitary caecal diverticulum (SCD) represents a rare benign lesion, found in 3.6% of cases of colonic diverticula [1]. In contrast to left-sided diverticula, SCD is considered a congenital lesion and it represents a true diverticulum, containing all layers of colonic wall [2]. In most cases, it is located 1-2cm from the ileocaecal valve, arising from the anterior caecal surface. The typical patient is an Asian male in his forties.
SCD is an asymptomatic lesion, unless complicated with inflammation, perforation, torsion or haemorrhage. The most common complication is diverticulitis, and in this case, the clinical presentation with right iliac fossa pain, low grade pyrexia and leucocytosis, is usually indistinguishable from acute appendicitis [3]. Only in about 9% of patients can be achieved correct preoperative diagnosis, despite all clinical, laboratory and radiological investigations, and most of them have already a history of appendicectomy. Therefore, correct diagnosis is usually made intraoperatively [4].
Preoperative imaging should be considered in patients with an atypical history for appendicitis (longer duration of pain, absence of nausea and vomiting, lack of toxicity) [2]. Ultrasound and computed tomography are useful in the preoperative diagnosis [1].
The demonstration of a round or ovoid, hypoechoic structure arising from a thickened colonic segment is the hallmark of US diagnosis of caecal diverticulitis, especially if a normal appendix can be recognised. Additional findings include stronger echoes inside the diverticulum (gas or faecolith), inflamed, echogenic pericolonic fat with increased flow on colour Doppler US and the presence of complications due to perforation i.e. abscesses (fluid collections with echogenic debris and air, producing dirty shadowing), fistulas (hypoechoic, linear structures extending to adjacent fat) and free air, locally and intraperitoneally. According to Chou et al, US has a sensitivity of 91, 3%, a specificity of 99, 8% and an overall accuracy of 99, 5% in diagnosing caecal diverticulitis. Despite its advantages (non-invasive, widely available, cost-effective, lacking ionising radiation), its accuracy can be limited by operator skills, especially in western people, where the disease is rare, and therefore, the experience limited [2, 5].
CT may be considered in complicated cases, older patients at risk of malignancy and those who have undergone previous appendicectomy. Findings are similar to those of left-sided diverticulitis.
Differential diagnosis is extensive and may include (other than appendicitis) caecal malignancy (especially in the case of a posteriorly located SCD, where perforation produces a localised mass), caecal ulcer, Crohn’s disease [6].
Treatment consists of conservative management, diverticulectomy, limited ileocaecal resection or right hemicolectomy [2].
