Peritoneal Inclusion Cyst in an Unusual Location in a “Virgin” Abdomen: A Diagnostic Dilemma Expanding the Clinical Spectrum

Abstract

Peritoneal inclusion cysts (PICs) are benign, multilocular fluid-filled lesions that predominantly affect women of reproductive age, often arising after abdominal surgery or chronic inflammation. We report a case of a 28-year-old female presenting with chronic left upper-quadrant abdominal pain for 1 year. Radiological evaluation revealed a large cystic lesion closely abutting the left adrenal gland and adjacent organs, creating a diagnostic dilemma regarding its tissue of origin. The patient was planned for diagnostic laparoscopy, which revealed a large, thin-walled cyst containing clear serous fluid. The lesion was not arising from the suprarenal gland or the pancreatic tail. Complete excision of the cyst was performed, and histopathological examination confirmed the diagnosis of a PIC. Notably, the patient had no prior history of abdominal surgery, making this presentation particularly unusual. The postoperative course was uneventful, and at 6-month follow-up, the patient remained asymptomatic with no evidence of recurrence. This case highlights a rare suprarenal presentation of a PIC in a “virgin” abdomen, closely mimicking adrenal and pancreatic cystic pathology on imaging despite normal endocrine evaluation. It underscores the importance of imaging – particularly ultrasonography and contrast-enhanced computed tomography of the abdomen and pelvis – in evaluating cystic lesions and differentiating PICs from Paraovarian cysts, hydrosalpinx, or ovarian malignancy based on anatomical location. However, due to significant imaging overlap with adrenal and pancreatic cystic lesions, histopathological confirmation remains essential. Diagnostic laparoscopy with complete excision was crucial in establishing the diagnosis, avoiding unnecessary adrenal resection, and ensuring a favorable outcome without early recurrence.

INTRODUCTION

Peritoneal inclusion cysts (PICs) are benign and reactive lesions typically found in women of reproductive age, often following abdominal surgery or in cases of chronic inflammation. These cysts, which manifest as multilocular fluid-filled formations, are located within the abdominopelvic cavity and may sometimes be incidentally discovered in asymptomatic patients during imaging studies.[1] PICs are rare and typically affect females, with only limited cases reported in males. These cysts can be asymptomatic or present with nonspecific symptoms such as abdominal pain or distension, often requiring imaging and, occasionally, surgical exploration for diagnosis. The differential diagnosis includes other cystic abdominal lesions, emphasizing the need for thorough clinical and imaging assessment.[2] Treatment options range from conservative management to surgical intervention, depending on the patient’s symptoms and clinical presentation.[1]

CASE REPORT

A 28-year-old, Multiparous (Para2, Living2) female of reproductive age group, presented with nonspecific symptoms like left upper quadrant abdominal pain for 1 year, exacerbated by prolonged standing or walking and relieved by rest. She denied nausea, vomiting, bowel or bladder disturbances, and reported regular menstrual cycles without dysmenorrhea or menorrhagia. She had no previous abdominal surgical history; both her deliveries were vaginal. In addition, she was diagnosed with rheumatoid arthritis 8 months back and started on treatment in the form of oral (DMARDs) Disease-Modifying Anti-Rheumatic Drugs (Methotrexate, Leflunomide, and Methylprednisone). She had no other comorbidities. Clinical examination revealed mild tenderness in the left lumbar region on deep palpation without guarding, rebound tenderness, or palpable mass. Bowel sounds were normal.

Laboratory tests, including complete blood count (white blood cell 8700/µL), liver and renal function tests, and serum amylase/lipase, were normal. A pregnancy test was negative.

Abdominopelvic ultrasound revealed an anechoic cystic lesion in the left upper quadrant in close proximity to the pancreatic tail and superiorly to the upper pole of the left kidney raising suspicion of a left adrenal cyst. Contrast-enhanced computed tomography (CT) abdomen and pelvis [Figure 1] showed a well-defined thin-walled hypodense nonenhancing cystic lesion (82 mm × 65 mm × 72 mm) in the left suprarenal region. The lesion abutted the lateral aspect of the left adrenal gland with loss of fat plane, displaced the distal pancreas and splenic vessels, and abutted the spleen and upper pole of the left kidney with preserved intervening fat planes. Hence, giving no definitive diagnosis about the tissue of origin so as to plan the further management. No solid components or calcifications were noted.

Figure 1.

Contrast-enhanced computed tomography abdomen and pelvis-coronal (left) and transverse (right) section showing hypodense, nonenhancing cystic lesion in the left suprarenal region, abutting the spleen and displacing the distal pancreas, The arrow indicates the cystic lesion located in the left suprarenal region abutting the adrenal gland and adjacent structures

Based on the aforementioned imaging findings, a differential diagnosis of a left adrenal cyst was considered. However, the patient was normotensive throughout the evaluation period, with no recorded hypertensive episodes. To exclude a functional adrenal lesion, biochemical evaluation was performed, including an overnight dexamethasone suppression test, measurement of plasma free metanephrines, serum aldosterone with plasma renin activity, and serum dehydroepiandrosterone sulfate, which were all unremarkable. Further discussions with the radiologists could not ascertain the origin from the tail of the pancreas either, and radiological findings were not entirely conclusive.

Given the patient’s increasing discomfort, the lesion’s size, and the potential risk of complications such as torsion or rupture, surgical intervention was pursued. The patient underwent diagnostic laparoscopy followed by laparoscopic excision of the cyst. Intraoperatively, a large thin-walled cyst containing clear serous fluid was identified [Figure 2] and that the cyst had no signs of origin from the suprarenal gland or tail of Pancreas, hence dissected free from its surrounding peritoneal/omental adhesions, and complete in toto excision was performed. On aspiration of the contents without spillage, a large volume of clear, viscous fluid was obtained, which was sent for cytology evaluation, and the excised cyst specimen was delivered. No other signs of intra-abdominal or pelvic inflammation were noted. Histopathological examination [Figure 3] showed a fibrous wall lined by mesothelial cells without atypia or neoplastic changes, consistent with a PIC. Cytology of cyst fluid was negative for malignant cells.

Figure 2.

Intra-operative laparoscopic view demonstrating a well-defined cystic lesion in the left suprarenal region

Figure 3.

Individual cyst lined by flattened mesothelial cells with bland nuclei (H and E, ×100)

The patient recovered uneventfully and was discharged on postoperative day 2. At 6-month follow-up, she remained asymptomatic with no evidence of recurrence.

DISCUSSION

PICs occur predominantly in women of reproductive age, usually following disruption of the peritoneum due to surgery, trauma, inflammation, or endometriosis. Usually, impaired peritoneal absorption of ovarian fluid leads to its entrapment within adhesions, forming complex cystic masses containing serous, gelatinous, or hemorrhagic fluid without true cyst walls. Their ovarian origin is supported by higher ovarian hormone levels in peritoneal fluid compared to plasma. Although the exact pathogenesis remains unclear, the presence of functioning ovaries and peritoneal adhesions is essential, explaining their postpubertal occurrence.[3]

In contrast, the lack of prior surgery or inflammation in some cases, along with developmental behavior and high recurrence rates, has led some authors to theorize a neoplastic origin. Consequently, Peritoneal Mesothelial Cyst (PMC) has been suggested to lie on a spectrum between adenomatoid tumors and malignant mesothelioma.[3] Moreover, a possible genetic or familial predisposition for PIC has been proposed.[3]

They mostly occur in women of reproductive age, although rare cases involving men and children are documented. The average age at diagnosis is approximately 32 years.[4]

Patients with PICs most commonly present with lower abdominal or pelvic pain, ranging from acute to chronic. Associated symptoms may include abdominal distension, dyspareunia, constipation, or a palpable mass. Many patients have a history of pelvic surgery or intraperitoneal inflammation, such as endometriosis or pelvic inflammatory disease. Symptom duration varies from days to months, and the interval between prior surgery and PIC detection may range from 6 months to 20 years. Diagnosis is often challenging due to nonspecific symptoms, with PICs sometimes discovered incidentally during surgical procedures. Physical examination may be unremarkable, complicating the diagnosis further, as the clinical presentation can mimic other conditions like infected para-ovarian cysts or endometriomas.[1]

The pelvis is the most common site[5,6] with the ovarian surface, peritoneal cul de sac, and rectal serosa frequently involved; ~50% also involve the abdominal peritoneum; Minority (~20%) also involve the retroperitoneum,[4] and rare cases involve the splenic capsule or perinephric region.[7] The left suprarenal location of the PIC in this case makes it an exceptionally rare presentation.

Ultrasound is the first-line imaging modality for evaluating pelvic pain because of its availability, low cost, and absence of radiation. It is particularly useful for detecting PICs, which typically appear as a normal ovary surrounded by anechoic fluid with multiple septations. The fluid may become echogenic if hemorrhagic or proteinaceous, producing the characteristic “spider-in-a-web” appearance due to surrounding adhesions.[1]

Magnetic resonance imaging (MRI) is a valuable second-line imaging modality, particularly in complex cases, due to its superior soft-tissue contrast and multiplanar capability. PICs typically show low signal intensity on T1-weighted images and high signal intensity on T2-weighted images, consistent with serous fluid, with increased T1 signal when hemorrhage is present. Their irregular configuration reflects mass effect from adjacent structures, as they lack true walls. Contrast-enhanced images usually demonstrate minimal or no enhancement, and the characteristic “spider-in-a-web” appearance may be seen. MRI also helps confirm the extraovarian nature of fluid collections when the ovary is poorly visualized on ultrasound.[1]

CT imaging provides additional insights, showing PICs as cystic masses with regular or irregular borders. These masses demonstrate attenuation properties indicative of fluid and/or haemorrhage, which helps in differentiating benign from malignant processes.[1] Overall, the combination of ultrasound, CT, and MRI provides a comprehensive approach to diagnosing and managing PICs and other pelvic conditions.[1]

Definitive histologic diagnosis requires tissue sampling. Although negative fine-needle aspiration cytology may reduce suspicion of malignancy, results are often inconclusive due to nonspecific reactive mesothelial cells. Therefore, when malignancy is suspected, biopsy is recommended, with laparoscopy being the most reliable diagnostic modality.[3] On microscopic examination, PMC is typically lined by a single layer of flat to cuboidal mesothelial cells with generally bland nuclear features. The septa typically consist of a loose, fibrovascular connective tissue with a sparse inflammatory infiltrate accompanied by fibrin, granulation tissue, and recent and old haemorrhages in the cyst walls.[3]

The differential diagnosis of PICs includes para-ovarian cysts, hydrosalpinx or pyosalpinx, macrocytic lymphatic malformations, and ovarian epithelial malignancies. Other considerations are lymphoceles, mesenteric or omental cysts, pseudomyxoma peritonei, and malignant mesothelioma, which usually show distinct clinical and imaging features.[1]

Current literature is mostly based on case reports and small series, and a uniform treatment approach and long-term follow-up data are lacking. The treatment options for PMC range from observation to complete resection.[3] Although the treatment of choice has not been firmly established, conservative management is preferable to surgery in asymptomatic patients, which includes observation with serial imaging in asymptomatic patients, with more aggressive treatment if the disease develops. Hormonal treatment with oral contraceptives, gonadotropin-releasing hormone agonist, and the anti-estrogenic agent, tamoxifen, can be administered to suppress the formation of ovarian fluid.[3]

Image-guided interventions such as percutaneous or transvaginal aspiration, sclerotherapy, and potassium-titanyl-phosphate laser ablation are minimally invasive alternatives. Surgical options, including laparoscopic or open resection of cysts and adhesions, are considered for persistent symptoms, infertility, or severe cases. While surgery is often preferred for definitive management, it carries a recurrence rate of 30%–50%. Finally, given the rare reported case of malignant transformation, some authors have advocated aggressive surgery (extended peritonectomy) followed by hyperthermic intraperitoneal chemotherapy. They have been performed in cases of recurrence or even in first-line treatment, as the optimal treatment to prevent transition to a truly aggressive tumour. However, since PIC mainly affects women of reproductive age, these therapeutic strategies often result in very aggressive, with important repercussions on fertility.[3] Overall, treatment strategies are individualized based on cyst size, symptom severity, and patient circumstances.[1]

PIC in this patient posed a significant diagnostic challenge due to its atypical suprarenal location, absence of prior surgery or intra-abdominal inflammation, and close radiological relationship with the left adrenal gland and pancreatic tail that obscured the exact tissue of origin. This case expands the recognized clinical spectrum of PIC by demonstrating that it can present as a large retroperitoneal-appearing cyst in a so-called “virgin” abdomen, radiologically mimicking adrenal or pancreatic cystic lesions despite a completely normal endocrine work-up. The successful use of diagnostic laparoscopy with complete excision and histopathological confirmation underlines the pivotal role of minimally invasive surgery in resolving such diagnostic dilemmas, preventing overtreatment such as adrenalectomy, and achieving excellent short-term outcomes without recurrence.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initials will not be published and due efforts will be made to conceal her identity, but anonymity cannot be guaranteed.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.