Plastron appendicitis or appendiceal tumor?


          Rocío Pérez Domínguez MAAC, MASACP, Guillermina Candia,

          Hernán Alejandro Santilli MAAC, MASACP, Sergio Schlain MAAC, MASACP


              Hospital Interzonal General de Agudos San Roque, Gonnet




A palpable inflammatory appendiceal mass may contain the inflamed appendix, adjacent viscera, and the greater omentum, associated or not with the presence of pus.

The management of an inflammatory appendiceal mass is controversial. When there are associated signs of sepsis, the indication is emergency surgery, otherwise, you can opt for a conservative treatment. The use of percutaneous drainage has a high rate of effectiveness, although the rate of undetected neoplasia is not negligible, especially in patients older than 40 years.

We present the case of a 65-year-old female patient with a presumptive diagnosis of an appendiceal mass with abscess, who underwent exploratory laparotomy and right hemicolectomy after percutaneous drainage failure. The histopathological diagnosis was mucinous adenocarcinoma of the appendix.


Keywords: inflammatory appendiceal mass, appendiceal abscess, appendiceal neoplasm




Acute appendicitis is a common gastrointestinal disease that annually affects 5.7-50 per 100,000 individuals, with a higher incidence in children and adolescents. The clinical presentation can range from mild symptoms to signs of generalized peritonitis and sepsis.

The term appendiceal plastron is used to describe a palpable mass in which a phlegmon forms due to patient's own defense mechanisms. It is defined as an inflammatory tumor containing the inflamed appendix, adjacent viscera, and greater omentum, or as a pus-containing appendiceal mass.

The management of the appendiceal plastron will depend on the clinical condition of the patient; if there are associated sepsis criteria, the indication is emergency surgery; otherwise, conservative treatment can be chosen. One of the problems with non-surgical treatment of the appendiceal plastron is the rate of undetected neoplasms.

We present a 65-year-old woman with a presumed inflammatory appendiceal plastron with pus who underwent surgery due to failure of percutaneous treatment. After right colectomy, the histopathological diagnosis was mucinous adenocarcinoma of the appendix.






The authors declare no conflicts of interest.

Correspondence: Sergio Fernando Schlain. Calle 21 C Número 2152 e/454 y 455 City Bell, CP (1896). Ph: 0221 5030669


Rocío Pérez Domínguez: ORCID 0001-8347-0849, Guillermina Candia: ORCID 0000-0003-2515-8923, Hernán Alejandro Santilli: ORCID 0001-6749-0655, Sergio Schlain: ORCID 0002-5615-3503



A 65-year-old woman attended the emergency department due to a 4-week history of pain in the right iliac fossa, associated with a palpable mass, febrile equivalents, weight loss, and anorexia. On physical examination, she presented slight distension, predominantly in the lower abdomen with increased tympany.

Colonoscopy: progress to cecum, ileocecal valve preserved. Normal colorectal mucosa.

US: on the flank and right iliac fossa, a heterogeneous, partially delimited mass of approximately 80 x 70 mm was observed, with aperistaltic loops, scant hypoechoic fluid, and air bubbles inside. It is suggested to rule out appendiceal plastron.

CT scan: defined collections in the right psoas major muscle (10 x 1.2 cm),  iliopsoas muscle (6.2 x 1.4 cm) and iliacus muscle (10 x 1.2 cm) with extension to the ipsilateral rectus femoris muscle and sartorius. Infrarenal intra-abdominal collection (5.8 x 3.3 cm) in relation to the posterior parietal peritoneum.  In the right iliac fossa, in relation to the cecum and loops of the small intestine, there is another partially defined collection (5.2 x 3.7 cm) and two other small collections (1.5 cm) with densification and thickening of the adjacent mesentery and fascia, suggesting a probable diagnosis of appendiceal plastron. Scant  free fluid in the pouch of Douglas. Small hypointense liver images with a cystic appearance measuring 0.3 cm in segment VIII and 0.5 cm in segment VI (Fig. 1).

Given the clinical and imaging suspicion of appendiceal plastron, it was decided to place a multifenestrated percutaneous drain, with immediate output of 50 ml of purulent characteristics that was sent for culture, obtaining as a result the presence of leukocytes, without a specific germ (Fig. 2).


Figure 1. Computed tomography showing a multiloculated collection with air bubbles in the right iliac fossa, with involvement of the right iliopsoas muscle.


Figure 2. Characteristics of the fluid obtained in the initial percutaneous drainage of the right iliac fossa collection.


The initial output of 150 ml decreased, so the drain was removed on the 10th day, after tomographic control (Fig. 3).

The patient continues in an acceptable general condition, however in the following days a progressive increase in the leukocyte count is recorded, so on the 4th day after removing the drain a new tomographic control is performed where an increase in the size of the leukocytes is observed. the collections ( Fig. 4).

With the presumption of underlying neoplastic pathology responsible for the recurrence of the collections, laparotomy is indicated. Given the finding of an appendiceal mass firmly adhered to the posterior planes, a right colectomy with primary anastomosis was performed, using oncological criteria.

Anatomic pathology: a 3 cm atypical proliferation of the appendix which continue to the appendiceal ostium is

236  Fig 3.jpg

Figure 3. Computed tomography prior to the extraction of the percutaneous drain.


236  Fig 4.JPG

              Figure 4. Computed tomography on the 4th day after removal of the percutaneous

              drain. An increase in the size of the residual collections is observed.



Identifiied. It is a well-differentiated mucinous adenocarcinoma that involves the entire circumference and infiltrates up to the mesoappendix (Fig. 5).

Vascular invasion and presence of periappendiceal implant is identified.

Nineteen negative lymph nodes were isolated. pT3N0Mx. 


                Figure 5. Right colectomy specimen showing a 3 cm tumor of the appendix

                which reaches its cecal implantation and infiltrates the mesoappendix.





Appendicitis is classified as uncomplicated or complicated based on preoperative, intraoperative, and/or histopathological findings. In uncomplicated appendicitis the appendix is inflamed without perforation, whereas in complicated appendicitis the appendix is gangrenous with or without perforation, or there is a periappendiceal phlegmon/plastron, an intra-abdominal abscess, or purulent free fluid. The perforation rate varies from 16 to 40% and occurs more frequently in younger patients (40-57%) and in those older than 50 years (55-70%).1

The term appendiceal plastron is used to describe a palpable appendiceal mass, in which inflammation is circumscribed by the patient's own defense mechanisms. It can present as a phlegmon, defined as an inflammatory tumor containing the inflamed appendix, adjacent viscera, and greater omentum, or as an appendiceal abscess or mass containing pus.2 The incidence of appendiceal plastron varies between 2 and 10%, although it can reach up to 14% when imaging studies are used compared to 5.11% when the diagnosis is exclusively clinical. The classic presentation is with intense pain in the right iliac fossa for one or two days associated with fever, which subsequently self-limits or decreases in intensity, generally after the administration of antibiotics and/or anti-inflammatory drugs. After 7 to 10 days, the fever and mild to moderate pain return. The main finding on physical examination is a palpable mass in the right iliac fossa, which together with the increased erythrocyte sedimentation rate and C-reactive protein should lead to suspicion of the diagnosis.

The advent of imaging methods has made it possible to improve the identification of appendiceal plastrons, allowing not only the diagnosis but also the management of complications.

Ultrasonography, a noninvasive study that avoids radiation, has a sensitivity of 71-94% and a specificity of 81-98% for the detection of appendiceal inflammation. Abdominal CT scan has a sensitivity of 76-100% and a specificity of 83-100%, probably due to the use of oral contrast.3

The management of the appendiceal plastron will depend on the clinical condition of the patient. In the case of associated sepsis criteria, emergency surgery is indicated, otherwise conservative treatment can be chosen.

Immediate appendectomy can be technically demanding because the distorted anatomy resulting from tissue inflammation makes identification of the appendix and closure of the appendiceal stump difficult. Surgical exploration has morbidity three times higher than conservative management and in approximately 3% of patients it can result in unnecessary ileocecal resection or right colectomy for technical reasons or suspicion of malignancy.

Conservative treatment is associated with a significant decrease in overall complications, a lower rate of wound infection and ileus, and a shorter hospital stay. The failure rate of this treatment is estimated at 7.6%2 and may be due to incomplete drainage, the need for additional drains, and fistulas.

Abscesses larger than 5 cm generally do not resolve with percutaneous treatment and require surgical exploration. Immediate surgery has been associated with a morbidity of 35.6% compared to 13.5% for non-surgical treatment.4

One of the problems with non-surgical treatment is the rate of undetected appendiceal neoplasms, reported from 2%4 to 29%.5 One study found an even higher incidence of 33% in older patients undergoing interval appendectomy.6

Wright et al.7 investigated a cohort of 188 patients with acute appendicitis over a 12-year period. The rate of appendiceal neoplasia in interval appendectomy was 12% compared with 0.5% when appendectomy was performed on hospital admission. Neoplasm identification increased in patients older than 40 years, occurring in 16% of this population after interval appendectomy.

Concern about not diagnosing an appendiceal neoplasm if interval appendectomy is not indicated may persist even with investigation of the colon, although these patients are likely to have recurrent symptoms or unresolved conditions.




There are multiple imaging studies capable of describing various pathologies in the topography of the appendix, such as mucoceles or mucinous neoplasms, neuroendocrine tumors, colonic neoplasms, or inflammatory pathologies, all of which cause diffuse thickening of the appendiceal wall and dilation of its lumen. These conditions can result in "abscesses" that are indistinguishable from acute perforated appendicitis.

For this reason, it is extremely important to have an adequate medical history and a strict follow-up of percutaneous drainage. This will allow, in the face of a poor evolution, to opt for early surgical treatment instead of an interval appendectomy capable of delaying the diagnosis and timely treatment of possible oncologic conditions.




1.     Di Saverio S, Podda M, De Simone B, Ceresoli M, Augustin G, Gori A, Diagnosis and treatment of acute appendicitis: 2020 update of the WSES Jerusalem guidelines. World J Emerg Surg. 2020;15:27.

2.     Andersson RE, Petzold MG. Nonsurgical treatment of appendiceal abscess or phlegmon. Ann Surg. 2007; 246:741-48.

3.     Gorter RR, Eker HH, Gorter-Stam MA, Abis GS, Acharya A, Ankersmit M, et al. Diagnosis and management of acute appendicitis. EAES consensus development conference 2015. Surg Endosc. 2016; 30:4668-90.

4.     Tannoury J, Abboud B. Treatment options of inflammatory appendiceal masses in adults. World J Gastroenterol. 2013; 19:3942-50.

5.     Furman MJ, Cahan M, Cohen P, Lambert LA. Increased risk of mucinous neoplasm of the appendix in adults undergoing interval appendectomy. JAMA Surg. 2013; 148:703-6.

6.     Mohan SCh, Gummalla KM, Chin H’ng MW. Malignant tumours mimicking complicated appendicitis and discovered upon follow-up after percutaneous drainage: a case of two patients. Case Reports in Radiology. 2017; vol. 2017, Article ID 3253928,

7.     Wright GP, Mater ME, Carroll JT, Choy JS, Chung MH. Is there truly an oncologic indication for interval appendectomy? Am J Surg. 2015; 209:442-46.






In the face of advanced acute appendicitis, without major clinical repercussions and often self-medicated with antibiotics, it is common for the appendix to be digested and the only finding is a plastron with a blocked perforation. In these cases, medical treatment may be correct. The age of the patient is a factor to take into account to assess whether this plastron is secondary to an infectious process or a perforated and purulent appendiceal or colonic tumor. If the patient is young (<25 years), an advanced and blocked appendiceal inflammatory process can be suspected, but in older patients exploration and surgical resection are indicated for adequate pathological evaluation. In this particular case, a 65-year-old female patient with four collections of moderate size and an appendiceal mass on the CT scan, surgery could have been indicated in the first instance.

In any case, the patient was well controlled and assisted at all times, until the appropriate measures were taken. It is important to highlight the existence of appendiceal tumors, their different presentations and possible complications. I congratulate and thank the authors for presenting this case, which helps readers to take this diagnostic possibility into account and be attentive to a picture of these characteristics. 


                             Dr. Marcelo Pollastri