Perforation of appendiceal diverticulum causing local peritonitis: a case report and literature review

Introduction

Appendiceal diverticulosis is a rare pathological entity (1). Inflammation of appendiceal diverticula shares many clinical features with acute appendicitis, and fewer than 100 cases have been documented in the literature (1). Perforation of a diverticulum, as a result of inflammation of the appendix, is an even rarer medical condition (1-6). To the best of our knowledge, only a few cases have been described (Table 1) (1-6).

Diagnosing appendiceal diverticulosis is challenging. Ultrasound and abdominal computed tomography are important tools for verifying the diagnosis (5,7,8). Despite these efforts, most of the time, the diagnosis is made either during the operation or, more commonly, after pathologic examination of the surgical specimen (5,7,8).

Surgery is considered the cornerstone of treatment (8-10). Any delay in surgical approach may lead to prolonged length of hospital stay and increased risk of morbidity and mortality (1). Reports imply an association between the presence of appendiceal diverticula and neoplasms, especially carcinoid tumours and mucinous adenomas, and for this reason, right hemicolectomy is valid alternative in cases where concurrent pathology is suspected (11-16).

This case report highlights this rare clinical entity, which is frequently misdiagnosed as typical appendicitis. We present this article in accordance with the CARE reporting checklist (available at https://acr.amegroups.com/article/view/10.21037/acr-2025-176/rc).

Case presentation

A 53-year-old Caucasian male presented to Accident and Emergency Department experiencing lower abdominal pain associated with vomiting and fever for 2 days. He reported gradual deterioration and worsening of the abdominal pain which had become localized to the right iliac fossa by the time of presentation. On admission, the blood pressure was 145/89 mmHg, the heart rate was 95 beats/minute, the respiratory rate was 22 breaths/minute and the temperature was 38.5 ℃. His body mass index was 32.8 kg/m², and he was smoker with a history of 50 pack-years. His past medical history included hypertension and dyslipidemia, with no prior surgical history.

On clinical examination, there was localized tenderness in the right iliac fossa with positive McBurney’s sign. In addition, there was no blood or palpable mass on digital rectal examination. Furthermore, cardiopulmonary and urogenital examinations were unremarkable. The blood tests revealed elevated inflammatory markers, electrolyte disorders and raised urea and creatinine levels (Table 2). Blood and urine cultures were negative.

An ultrasound scan failed to identify any pathology. The diagnosis was made by the computed tomography of the abdomen which revealed acute perforated appendicitis (Figure 1). Furthermore, a small fluid collection and free air were detected in the right iliac fossa (Figure 1).

Figure 1 Computed tomography of the abdomen depicts the perforation of the appendix associated with local peritonitis. The green arrow is demonstrating the perforated appendix. The red arrow is demonstrating the fluid collection adjacent to the perforated appendiceal diverticulum.

Four hours after his admission, due to clinical deterioration associated with hemodynamic instability, the patient moved to theatre. A diagnostic laparoscopy was performed which identified localized peritonitis at the right iliac fossa due to perforated appendix. The perforation was noted at the distal third of the appendix. An appendicectomy was performed, and a substantial amount of pus was aspirated, located in the area between the appendix and the abdominal wall.

The pathology report of the surgical specimen revealed a perforated appendiceal diverticulum with abscess formation in the mesoappendix (Figure 2). Furthermore, two more diverticula without inflammation were detected (Figure 3).

Figure 2 Ruptured appendiceal diverticulum in the mesoappendix (hematoxylin and eosin stain, ×40).

Figure 3 Intact second appendiceal diverticulum (hematoxylin and eosin stain, ×20).

The patient had an uneventful recovery. Intraoperatively, he received a single dose of cefoxitin 1 g and metronidazole 500 mg. During his 4 day hospital stay, the patient received the same antibiotic regimen which he continued after his discharge for six more days. Moreover, a colonoscopy was scheduled three months after his procedure in the context of population-based screening. On follow-up clinical examination and laboratory tests were unremarkable and he was discharged from our care four months after his operation in good clinical condition. All procedures performed in this study were in accordance with the ethical standards of the ethics committee of the Scientific Board of Venizeleio General Hospital and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

This case illustrates a rare diagnosis of appendiceal diverticulitis complicated by perforation in a 53-year-old male presenting with right iliac fossa pain, fever, and vomiting. Clinical and imaging findings were consistent with localized peritonitis, and an urgent diagnostic laparoscopy revealed the presence of a perforated appendix. Histopathological analysis of the resected appendix confirmed the presence of a ruptured diverticulum with abscess formation, along with two additional non-inflamed diverticula.

There is no established association between colonic and appendiceal diverticulosis (9). The appendiceal diverticula can be categorized into two distinct types, congenital and acquired based on histopathological and anatomical features (2,9). The congenital form is commonly located on the antimesenteric edge of the appendix and is characterized by herniation of all three appendiceal layers through abnormal wall (2,9). It is considered a developmental abnormality (2,9). Embryonic deformities such as failure of recanalization of appendiceal lumen, duplication of appendix and failure of obliteration of vitelline duct have been proposed as possible mechanisms for the formation of this type of diverticula (2,9). Most of the time, these diverticula are single and large in size (more than 5 mm), and are mostly found in patients with Patau or Down syndrome (2,9). On the other hand, acquired diverticula tend to be multiple, small in size (less than 5 mm) and located on the mesenteric margin of the distal part of the appendix (2,7). They are characterized by protrusion of mucosa and submucosa through a defect of the appendiceal muscular layer (2,7). The weakness of appendiceal wall caused by either inflammatory process or high intraluminal pressure is considered the responsible mechanism for the formation of this type of diverticula (2,7).

Partial or complete obstruction of the appendiceal lumen may lead to inflammation of the diverticula (1-10). Appendiceal diverticulitis can mimic the clinical presentation of acute appendicitis (1-10). However, compared to acute appendicitis, the inflammation of diverticula presents more often in older patients (more than 30 years) and usually lacks other gastrointestinal symptoms such as anorexia, nausea and vomiting (5). Furthermore, patients suffering from appendiceal diverticulitis commonly experience repeated episodes of right iliac fossa pain of variable duration and severity (5). The clinical signs and symptoms change dramatically if diverticula rupture occurs (1-6). The pain in the right lower quadrant of the abdomen becomes constant and severe, and manifestations indicating peritonitis such as fever and hemodynamic instability, may appear (1-6).

Computed tomography of the abdomen is probably the most useful imaging modality for the diagnosis of appendiceal diverticulitis, but it is associated with a relatively high, up to 50%, false positive rate (5,7,8). The inflamed diverticula are depicted as round cystic pouches with wall enhancement, or as solid, enhanced masses protruding from the appendix (5,7,8). In most cases, there is an absence of appendicolith (5,7,8). In case of diverticula perforation, fluid collection containing gas adjacent to the appendix and excessive peri-appendiceal fat stranding can be observed (7,8).

The risk of perforation in cases of appendiceal acute diverticulitis is four times higher compared to that of appendicitis and ranges in literature between 27% to 66% (1-3). This may be due to the thin wall of diverticula and explains the 30-fold increase in mortality rate of appendiceal diverticulitis compared to appendicitis (1-3). However, in many cases, inflammatory process is limited within mesoappendix due to surrounding adhesions, and a diffuse peritonitis is avoided (1-3).

Once the diagnosis of appendiceal diverticulitis has been established, surgery is the treatment of choice (8-10). A delayed surgical approach may lead to perforation of diverticula, formation of abscess and peritonitis (1-6). Appendicectomy is the gold standard treatment, but in some cases, an extended resection may be needed (11-16). Recent studies imply an association between the presence of appendiceal diverticula and neoplasms, especially carcinoid tumours and mucinous adenomas (11-16). In literature, the rate of co-existence ranges between 7.1% to 60.5% and for this reason in case of clinical suspicion intraoperatively, presence of serosal or mesoappendiceal mucin, or imaging indications such as concurrent thickening of the caecum, right hemicolectomy is the preferred surgical procedure (11-16). Another reasonable option in highly suspicious cases is to perform an on-table endoscopy which may contribute to surgeon’s decision-making.

Conclusions

Appendiceal diverticulitis is an uncommon but clinically important medical condition that carries a higher risk of perforation compared to acute appendicitis. High level of suspicion, particularly in patients with atypical presentation of acute abdomen, appropriate imaging and early surgical treatment, are essential elements for accurate diagnosis and prevention of complications. Future studies should focus on defining risk factors, improving preoperative diagnostic accuracy, and exploring whether tailored management strategies could further improve outcomes in these rare but potentially serious cases.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://acr.amegroups.com/article/view/10.21037/acr-2025-176/rc

Peer Review File: Available at https://acr.amegroups.com/article/view/10.21037/acr-2025-176/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://acr.amegroups.com/article/view/10.21037/acr-2025-176/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the ethics committee of the Scientific Board of Venizeleio General Hospital and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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