Acute diverticulitis of the appendix

Abstract

Acute diverticulitis of the appendix (ADA), though uncommon, often presents similarly to acute appendicitis but carries a higher risk of complications such as perforation and malignancy. We report the case of a male patient in his 50s with acute right iliac fossa abdominal pain, diagnosed via CT scan with ADA. Urgent laparoscopic appendicectomy was performed, and the patient was discharged without further issues. This case highlights the importance of promptly identifying and managing such conditions to minimise complications and improve outcomes. Despite the overlap in symptoms between appendiceal diverticulitis and acute appendicitis, accurate diagnosis is crucial for appropriate treatment. Healthcare providers should maintain a high index of suspicion, particularly in older patients presenting with an acute appendicitis, like clinical picture to ensure timely intervention and optimal patient care.

Background

Acute diverticulitis of the appendix (ADA) is an uncommon pathological condition that often presents with clinical manifestations resembling those of acute appendicitis. However, it tends to manifest in an older age group, typically diagnosed around the age of 43. Notably, patients with ADA may experience symptoms for a longer duration compared with classical acute appendicitis, warranting careful consideration during diagnosis. Using CT scan imaging offers a high sensitivity in preoperatively diagnosing ADA, providing clinicians with valuable insights for treatment planning. It is imperative for healthcare providers to recognise this condition promptly due to its heightened propensity for complications such as perforation leading to abscess formation and fistula and increased mortality risk compared with acute appendicitis. Furthermore, emerging evidence suggests a noteworthy association between ADA and underlying malignant lesions, including mucinous neoplasms and carcinoid tumours, underscoring the importance of thorough evaluation and management strategies. This underscores the significance of clinical awareness and vigilance, especially in older patient populations presenting with symptoms resembling acute appendicitis. Understanding the distinctive clinical features, diagnostic modalities and associated risks of ADA compared with acute appendicitis is paramount for optimal patient care and outcomes.

Case presentation

A male patient in his early 50s presented with a 4-day history of right lower quadrant pain and nausea. He denied experiencing any red flag symptoms like alterations in bowel habits or weight loss. His medical history was unremarkable aside from moderate smoking with no previous abdominal surgeries or colonoscopies. Furthermore, there were no indications of colorectal disease in his family history. On examination, he had signs of localised peritonism at the right lower quadrant.

Investigations

Blood results showed mild leucocytosis with relative neutrophilia and a high C reactive protein level at 134 mg/L. A CT scan was performed which showed evidence of multiple appendiceal diverticulae with surrounding fat stranding and associated small amount of free fluid in the pelvis. There was no evidence of a fecolith or underlying colonic lesions (figures 1 and 2).

Figure 1.

Sagittal CT image showing appendiceal diverticulitis.

Figure 2.

Coronal CT image showing appendiceal diverticulitis.

Differential diagnosis

Given the short history of abdominal pain at the right lower quadrant, the examination findings and the raised inflammatory markers, acute appendicitis was the main differential diagnosis. An urgent CT scan was arranged to exclude any underlying colonic lesions. This was also to rule out other possible differential diagnoses such as colitis, diverticulitis and obstructive uropathy leading to pyelonephritis.

Treatment

Diagnostic laparoscopy confirmed the CT findings (figure 3). Multiple diverticulae were identified on the mesenteric edge of the appendix accompanied by inflammatory changes of the appendix and mesoappendix. The appendicular base appeared healthy with a small amount of reactive fluid present in the pelvis. However, both the small and large bowel appeared normal with no significant evidence of colonic diverticulosis. Laparoscopic appendicectomy was performed. The mesoappendix was divided using a large polymer ligation clip and was retrieved along with the appendix in a retrieval bag (figure 4). Following the procedure, the patient received two additional doses of antibiotics.

Figure 3.

Intraoperative photo showing appendiceal diverticulitis.

Figure 4.

A photo of the surgical specimen.

Outcome and follow-up

The patient made a smooth recovery and was discharged on the first day after surgery, experiencing no complications during the healing process. Histological analysis of the surgical specimen revealed multiple pseudo-diverticula with focal diverticulitis, perforation, inflammation of the fat of the mesoappendix and overlying serositis. Notably, there was no evidence of dysplasia or malignant changes in the surgical specimen. Following discharge, the patient did not undergo any further follow-up investigations.

Discussion

ADA is a rare pathology of the appendix, initially described by Kelynack in 1893.¹ Its incidence ranges between 0.014% and 3.7%.² Typically, ADA diagnosis occurs postoperatively through histological examination of surgical specimens.³ Appendiceal diverticulosis can be classified into congenital and acquired. Congenital diverticulae, arising from the antimesenteric side, represent true herniations of the three layers of the appendicular wall. Conversely, acquired diverticulae, which are more common, are false diverticulae that are usually smaller in size and affect the mesenteric side of the wall. There are various theories to explain the pathophysiology of appendiceal diverticulitis. Acquired diverticulosis may result from wall weakening due to inflammation or increased luminal pressure, causing mucosal protrusion through the muscularis propria. Unlike sigmoid diverticulosis, appendiceal diverticulosis usually present at the mesenteric border of the appendix. Congenital appendiceal diverticulosis may be associated with chromosomal anomalies, such as trisomy 13 or trisomy 21.⁴

In the colon and cecum, diverticulae form due to increased pressure and weakness in the colonic wall, notably at sites where blood vessels penetrate the muscle layer. Taeniae coli, bands of muscle in the colon, cause it to pucker and create diverticula, typically false, involving only the mucosa and submucosa. Unlike the colon, the appendix lacks taeniae coli, possessing a continuous layer of longitudinal muscle. The orientation of muscle layers differs from that of the colon, possibly influencing diverticulitis development in the appendix compared with the colon.^5–7

Patients with acute appendicitis of the appendix typically present with symptoms resembling acute appendicitis. However, studies by Ito et al indicate that patients tend to be older and experience longer symptom duration prior to hospitalisation than patients with acute appendicitis. CT imaging can aid in visualisation of appendiceal diverticulitis. Preoperative ADA diagnosis is crucial due to its association with a higher risk of appendiceal neoplasms, such as carcinoid tumours and mucinous neoplasms. Patients with acute appendiceal diverticulitis face a fourfold higher risk of postoperative complications and increased mortality rates, necessitating early diagnosis and surgical intervention.⁶

Differentiating between appendicitis and appendicular diverticulitis through CT diagnosis is vital in clinical practice. CT imaging allows for precise assessment of the appendix, revealing signs of inflammation, such as wall thickening, peri-appendiceal fat stranding and the presence of appendicoliths, indicative of appendicitis. Conversely, in appendicular diverticulitis, CT scans can detect diverticula along the appendix, accompanied by associated inflammatory changes. Accurate CT diagnosis enables clinicians to tailor treatment strategies, whether conservative management, antibiotic therapy or surgical intervention, leading to improved patient outcomes. Therefore, emphasising the role of CT imaging in distinguishing between these conditions is essential for effective clinical management.⁸

Complications of acute appendiceal diverticulitis include perforation, leading to peritonitis or abscess formation. Fistula formation may occur, creating abnormal connections between the appendix and adjacent structures like the colon. Sepsis can develop, causing widespread organ dysfunction and potential mortality. Furthermore, there is an increased risk of appendiceal neoplasms, such as carcinoid tumours or mucinous neoplasms. Early recognition and intervention are crucial to prevent these complications and improve patient outcomes.⁶

Unlike colonic diverticulitis, conservative management holds no role in acute appendiceal diverticulitis. Philips et al classified ADA into four subtypes, ranging from an inflamed diverticulum within a normal appendix (Type 1) to acute appendicitis with associated inflamed diverticulae (Type 2). If appendiceal diverticulosis is incidentally detected radiologically or intraoperatively, appendicectomy is recommended to prevent diverticulitis-related complications and rule out underlying malignancies.^{9 10}

Learning points.

• Acute diverticulitis of the appendix (ADA) often presents with a slower onset compared with classical appendicitis, and typically affecting older individuals.

• ADA is associated with a significantly higher risk of complications and appendiceal neoplasms, emphasising the importance of early surgical treatment.

• Unlike classical appendicitis, conservative management is not appropriate for ADA.

• In cases where appendiceal diverticulosis is incidentally found on imaging or during surgery, appendicectomy is recommended to prevent future complications.

Ethics statements

Patient consent for publication

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