Idiopathic Encapsulating Peritoneal Sclerosis Mimicking Acute Appendicitis: A Case Report and Systematic Literature Review

Abstract

Patient: Male, 63-year-old

Final Diagnosis: Idiopathic encapsulating peritoneal sclerosis

Symptoms: Anorexia • nausea • right iliac fossa pain

Clinical Procedure: —

Specialty: Surgery

Objective: Rare disease

Background

Encapsulating peritoneal sclerosis (EPS), also known as abdominal cocoon syndrome (ACS), is a rare pathological entity that is difficult to diagnose. The syndrome can be idiopathic or secondary, and is mainly associated with peritoneal dialysis or abdominal tuberculosis. Patients with EPS can display symptoms of subacute intestinal obstruction or acute symptoms of ileus. We present a case of idiopathic EPS, misdiagnosed as acute appendicitis. Here, we report an unusual presentation of ACS and review the literature to delineate its diagnosis and treatment.

Case Report

A 63-year-old man presented to the emergency department with abdominal pain, mainly located in the right iliac fossa. Acute appendicitis was misdiagnosed by contrast-enhanced CT findings. The diagnosis of EPS was established intraoperatively. Secondary causes of EPS were ruled out and the diagnosis of idiopathic EPS was made. We identified 52 studies (82 patients) of idiopathic EPS in the most recently published literature and studied their features.

Conclusions

Idiopathic EPS is rare, but clinicians should be aware of this uncommon entity and the variability of its clinical symptoms upon manifestation. High suspicion should be raised preoperatively. The management should be tailored to each specific patient, according to cause, manifestation, and severity of clinical symptoms.

Introduction

Encapsulating peritoneal sclerosis (EPS) was first described in 1907 by Owtschinnikow as peritonitis chronica fibrosa incapsulata [1]. The term EPS refers to the presence of a dense fibrocollagenous membrane that encases the loops of the small intestine, creating a cocoon-like formation. The pathophysiology of the disease remains unknown. Peritoneal dialysis and abdominal tuberculosis are the main causes of secondary EPS. Idiopathic EPS, also known as abdominal cocoon syndrome (ACS) is a rare entity and involves all the cases where a probable cause cannot be found. Reports of patients with idiopathic EPS [2] come mostly from China, India, and Turkey, with only a few cases from Europe. Idiopathic EPS usually presents with symptoms of chronic or acute intestinal obstruction, but our patient presented with signs mimicking acute appendicitis. Radiologist and surgeons were misled to make an incorrect preoperative diagnosis.

Case Report

A 63-year-old white man presented to our emergency department with right iliac fossa pain lasting for 2 days, as well as anorexia and nausea, without constipation, diarrhea, or fever. His medical history included diabetes mellitus type II, coronary artery disease, dyslipidemia, and chronic atrial fibrillation, managed with a pacemaker-defibrillator implant. No previous history of abdominal operations or symptoms of gastrointestinal disease were reported. Clinical examination revealed diffuse tenderness and slight distension of the abdomen. Laboratory findings included a slightly elevated white blood cell count (11 300/μL, normal range 4300–10 300/μL) with a high neutrophil count (74.2%), but C-reactive protein was within the normal range (<0.5 mg/dL). Plain abdominal radiography showed no air-fluid levels. A contrast-enhanced computed tomography (CT) scan showed an enlarged appendix 1.2 cm in diameter with periappendiceal fat stranding (Figure 1). The patient initially underwent an exploratory laparoscopy, which was converted to a midline laparotomy due to the inability to access the right iliac fossa, as thick and dense adhesions affecting the small-bowel loops were observed. During laparotomy, the presence of a thick membrane covering all bowel loops, indicative of abdominal cocoon syndrome, was confirmed (Figure 2). A small amount of clear ascitic fluid was also identified and sent for cytologic examination. The cecum and the appendix were mobilized after careful and challenging local adhesiolysis. Although no macroscopic signs of inflammation were present, an appendectomy was performed. The decision was made due to the presence of palpable fecaliths, in order to prevent the need for future laparotomy due to appendicitis. Further adhesiolysis was not performed, since no further findings of mechanical intestinal obstruction were observed. Cytologic examination of the fluid was negative for malignancy and revealed mesothelial cells with chronic inflammation. Ziehl-Neelsen staining and molecular testing for Mycobacterium tuberculosis were also negative. Histopathological examination of the appendix showed no signs of acute inflammation. The postoperative course was uneventful and the patient was discharged on the ninth postoperative day. Due to rapid remission of clinical symptoms and the first diagnosis of the disease, we decided no further medical treatment (such as tamoxifen or cortisone) was needed. He was advised to consume a low-fiber diet. At 6-month follow-up, he remained asymptomatic.

Figure 1.

CT scan showing a possible enlarged appendix (1.2 cm diameter) with periappendiceal fat stranding (white arrow). A cluster of accumulated small-bowel loops in the lower abdomen is observed (inside the area marked by the yellow arrows), although initially (preoperatively) not considered pathognomonic.

Figure 2.

Intraoperative image depicting the entire small bowel covered by a transparent fibrous membrane. Dense adhesions between the loops can be seen. The image is consistent with the typical abdominal cocoon syndrome.

Literature Review

In 2015 Akbulut [2] reviewed the published literature on idiopathic EPS and accurately defined the terms abdominal cocoon and idiopathic and secondary EPS. Here, we provide a review of the most recent literature published from January 2015 to February 2025. The terms “abdominal cocoon,” “idiopathic sclerosing encapsulating peritonitis,” “abdominal cocoon syndrome,” and “idiopathic encapsulating peritoneal sclerosis” were searched using the PubMed, Google Scholar, and MEDLINE databases. The results were evaluated by 2 independent researchers, with any discrepancies resolved by a third researcher. We excluded non-human studies, studies with non-available full texts, studies with non-extractable data, and studies referring to secondary EPS, even if the term abdominal cocoon was used. The literature search yielded 402 articles, with 130 duplicates. After the initial screening, 197 articles were irrelevant or non-human studies. Seven studies could not be retrieved. When exclusion criteria were applied, 16 more articles were excluded. A total of 52 published studies, reporting 82 cases of ABS, were finally included in our study (Figure 3) [3]. Tables 1 and 2 summarize the included studies. Publication year and origin of study, patients’ demographic data and symptoms, diagnostic and treatment methods, and data for recurrent disease were recorded and analyzed.

Figure 3.

PRISMA 2020 flow diagram. Source: Page MJ, et al. BMJ 2021;372: n71; doi: 10.1136/bmj.n71. This work is licensed under CC BY 4.0. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/.

Table 1.

Number of published cases and articles of patients with idiopathic encapsulating peritoneal sclerosis according to the country of origin.

Countries	Published cases	Published articles
China	32	7
India	7	7
USA	4	5
Greece	4	3
Saudi Arabia	4	3
Tunisia	3	3
Turkey	3	3
Ethiopia	3	2
Morocco	3	3
Iran	2	2
Iraq	2	1
Pakistan	2	2
Korea	2	1
United Arab Emirates	1	1
Japan	1	1
Palestine	1	1
Somalia	1	1
Nepal	1	1
France	1	1
Australia	1	2
Singapore	1	1
Oman	1	1
Indonesia	1	-
Spain	1	-

Table 2.

Clinical data of the reviewed articles.

Clinical data	No. of cases	%
Sex
Male	58	71.0
Female	24	29.0
Symptoms
Acute intestinal obstruction	52	63.4
Subacute intestinal obstruction	26	31.7
Acute appendicitis	4	4.9
Establishment of diagnosis
Contrast-enhanced CT	24	29.3
During laparoscopy	19	23.2
During laparotomy	39	47.6
Treatment
Operative	78	95.1
Resection of fibrous membrane and adhesiolysis	63	80.8
Appendectomy	14	17.9
Bowel resection	11	14.1
Other	7	9.0
Non-operative	4	4.9
Recurrence
Yes	7	8.5
No	48	58.5
Not stated	26	31.7
Death in early postoperative period	1	1.2

CT – computed tomography.

Discussion

The term abdominal cocoon syndrome (ACS) was first described in 1978. Foo et al [4] noted the presence of a fibrocollagenous membrane partially or completely encasing the small intestine of 10 adolescent girls with small-bowel obstruction (SBO) of unknown etiology. The suggested treatment was membrane resection, adhesiolysis, with possible decompression of the small intestine and elective appendectomy. Akbulut [2] suggested that mesothelial injury with activation of inflammatory cells and fibroblasts, leading to a chronic inflammatory process and fibrosis, may play an important role in the development of the so-called cocoon membrane [2,5].

In our literature review, most of the cases included originated from China (39%, n=32), followed by India (8.5%, n=7). Patient age ranged from 13 to 90 years old (mean=44.8 years), with data being unavailable for 2 patients. Regarding sex, 71% of the patients were male (n=58) and 29% were female (n=24). Time of onset of symptoms was unavailable for 9 patients, and for the remaining cases it ranged from 5 h to 2 years. In 95% of the patients, symptoms of acute (n=52), or subacute (n=26) intestinal obstruction were present, while in 5% of the patients, symptoms mimicked the clinical image of acute appendicitis (n=4), as in our case. Of the 82 patients, diagnosis was made preoperatively in 29.3% (n=24) based on contrast-enhanced CT findings, while 67.1% (n=55) were diagnosed during laparoscopy/laparotomy. In 3 patients (3.7%), authors reported that idiopathic EPS was strongly suggested by contrast-enhanced CT, but laparotomy established the diagnosis. Surgery was performed in 95.1% (n=78) of the patients, including 4 patients in which the initial conservative treatment failed. Three patients received postoperative therapy with tamoxifen, prednisolone, or a combination of both. Of the others,

2 refused surgery, 1 was considered a poor candidate due to general status, and in 1 patient the treatment was not reported. Of the 78 patients who underwent surgery, laparotomy was chosen in 57 patients (75%), laparoscopy in 14 (18.4%), and initial laparoscopy converted to laparotomy in 5 patients (6.6%). Data on the type of surgery were unavailable for 2 patients. Additional data on surgery were reported in 74 patients, with resection of the fibrous membrane and adhesiolysis being performed in 63, appendectomy (prophylactic, enlarged size, or fecaliths) in 14, and bowel resection (ischemic bowel) in 11 patients. There was 1 reported case of primary bowel repair, 1 report of decompressive gastrotomy, and 1 report of loop ileostomy. Data on recurrence rates were unavailable in 26 cases and 1 patient died in the early postoperative period. From the remaining 55 patients, recurrence was reported in 7 cases, with a mean follow-up of 30 months (range: 7 days to 10 years).

The present case and the results of our literature review show that ACS is more prevalent in adults than in adolescents, with a male-to-female ratio of 2: 1 [2]. In addition, while the prevalence of ACS is higher in tropical and subtropical countries [2,4,6], in the last decade reports of patients from non-tropical countries have been increasing [7–10].

Clinical suspicion for idiopathic EPS is usually low. Patients typically present with symptoms of acute or subacute SBO, but can also present with a variety of other symptoms such as abdominal mass formation, chronic malnutrition, and pain in the right iliac fossa. Preoperative diagnosis is therefore challenging. Common misdiagnoses made based on contrast-enhanced CT scans include internal hernia, ileus of unknown origin [8,10–14], and (rarely) acute appendicitis [15]. In our case, the diameter of the appendix misled the radiologist to make a diagnosis of acute appendicitis, ruling out other possible diagnoses despite the existing cluster of accumulated bowel loops on the CT scan. This highlights the need for radiologists and clinicians to be aware of this entity and its radiographic signs. CT findings suggesting the presence of ACS include the cauliflower sign (a cluster of dilated bowel loops with narrow base enveloped in a thick membrane), fixation of intestinal loops, thickening and calcinosis of the peritoneal reflections, and bowel wall thickening. Sharma et al [16] even described the “bottle gourd” sign (extremely dilated duodenal loops abruptly transitioning to less dilated jejunal loops) on CT, in cases of ACS causing intestinal obstruction [5,17,18].

Concerning the management of idiopathic EPS, Solak et al [19] suggested conservative treatment in cases with mild subacute intestinal obstruction involving nasogastric tube placement, total parenteral nutrition, sufficient fluid administration, and peritoneal rest. Steroids, immunosuppressants, tamoxifen, and colchicine can be administered as a second-line treatment to block fibrogenesis through inhibition of growth factor beta, but the literature data regarding their effectiveness is insufficient to allow their use as standard therapy [6,19]. A conservative first approach is further supported by the fact that many ACS patients have significant weight loss and malnutrition, owing to episodes of nausea and vomiting, putting them at high risk for postoperative complications [20]. On the other hand, many authors [21–23] suggest that surgery should be the treatment of choice. According to the results of our review, conservative treatment was advised only in 4 cases and it proved unsuccessful, leading to surgery [10,12,13,24]. Our patient underwent a laparotomy due to the misleading diagnosis, so there was never a dilemma of which approach to choose.

Regarding the surgical approach, there is a debate of whether laparoscopy or laparotomy is more suitable. Akbulut [2] reported that laparoscopy should not be the standard procedure. Hu et al [25] described insertion of a laparoscopic trocar in the intestinal lumen due to extensive adhesions, pointing out the potential danger of the laparoscopic approach. On the contrary, approximately half of the 26 patients reported by Li et al [21] were successfully treated laparoscopically. Although it remains the individual surgeon’s choice, there is an increasing tendency towards the open approach, especially if the diagnosis of ACS is made preoperatively.

Regardless of the approach, the operation of choice is adhesiolysis and partial or complete membrane resection. The extent of the encasing membrane must be considered when proceeding to adhesiolysis. Three types of ABS have been described: Type I, in which only part of the intestine is encased by the membrane; type II, in which the entire intestine is encased; and type III, in which the membrane also encapsulates other organs (eg, appendix, ovary, cecum) [26]. During extensive adhesiolysis, especially in type II and III cases, the risk of bowel injury with serious postoperative complications (eg, need for bowel resection, anastomotic failure, enterocutaneous fistula, intra-abdominal infection) is significant and surgeons may choose not to proceed to an extensive adhesiolysis and membrane resection, especially if no signs of intestinal obstruction are present. Our literature review only found 1 report describing the need for bowel resection due to manipulations [27], while in approximately 15% of the patients, adhesiolysis and resection of the membrane was not performed. Bowel resection is mainly carried out in cases of non-viable (necrotic) intestine [2,6]. Appendectomy was performed in very few cases, usually to prevent the need for future emergency laparotomy due to appendicitis, if it is enlarged, or in the presence of fecaliths [11,15,28–31]. In our case, we opted only for local adhesiolysis to have access to the right iliac fossa. Further adhesiolysis and excision of the membrane was rendered dangerous and unnecessary, since the patient did not have malnutrition or a history of recurrent abdominal pain, and no signs of intestinal obstruction were present. An appendectomy was performed because of the presence of fecaliths and the enlarged appendix to prevent a challenging reoperation due to appendicitis or another misleading diagnosis because of the diameter of the appendix.

Data concerning recurrence rates after successful operative treatment are limited in the literature. In our study, the recurrence rate was low, but the range of follow-up length varied greatly among studies (7 days to 10 years).

Conclusions

Idiopathic EPS is rare and its pathophysiology is still obscure. It mainly presents with symptoms of chronic SBO, but also with symptoms of acute abdomen. Regardless of the timing of diagnosis (preoperatively by CT scan or intraoperatively during exploratory laparoscopy/laparotomy), the widely accepted treatment is the resection of the fibrocollagenous membrane and adhesiolysis. Although conservative management can be attempted in patients with mild symptoms, clinicians need to remain vigilant since failure rates are high and laparotomy may be required. Finally, a more structured follow-up of those patients may be valuable, since data on recurrence rates and disease progression in the literature are scarce.