Diagnostic and operative challenge of a giant non-pancreatic intra-abdominal pseudocyst: a rare case report

Introduction

Intra-abdominal pseudocysts are characterized by a fluid-filled sac, encapsulated in a fibrous capsule lacking an epithelial lining, generally composed of scar tissue. While they are typically associated with the pancreas, non-pancreatic pseudocysts are a rarer occurrence and may potentially arise secondary to chronic inflammation, trauma, or hemorrhage (1). These pseudocysts can rapidly expand to a substantial size and become symptomatic due to their mass effect. They are often a diagnostic challenge due to nonspecific imaging characteristics and nondiagnostic percutaneous biopsy findings.

Larger non-pancreatic pseudocysts can impersonate mesenteric cysts, duplication cysts, and even cystic neoplasms of the bowel (2). They may consist of blood products, debris, and/or organized hematoma, which exacerbates the level of difficulty in a preoperative evaluation. The rarity of intra-abdominal pseudocysts, especially those of larger size (e.g., >20 cm), allows them to provide valuable information to the literature regarding presentation, diagnosis, and surgical management (3). Here, we report a 21 cm hemorrhagic pseudocyst in the left lower abdominal wall intimately associated with the colon, with nondiagnostic imaging, biopsy, and eventual complete surgical excision. Prior abdominal surgery and chronic inflammatory reactions, including foreign body response to retained suture material, have been proposed as potential mechanisms for pseudocyst formation and chronic encapsulated hemorrhagic collections. We present this article in accordance with the CARE reporting checklist (available at https://acr.amegroups.com/article/view/10.21037/acr-2026-0095/rc).

Case presentation

A 73-year-old male with a body mass index of 43 and a past medical history of hypertension and type 2 diabetes presented to the emergency department at Mobile Infirmary with left-sided abdominal pain and was found to have a ureteral stone. Incidental computed tomography (CT) imaging demonstrated a large left lower quadrant abdominal mass (Figures 1,2). Follow-up magnetic resonance imaging (MRI) confirmed a large cystic-appearing collection in the left lower quadrant (Figure 3). Imaging suggested a large cystic lesion centered within the left lower abdominal wall with close adherence to adjacent intra-abdominal structures, including the colon. The patient did not report awareness of a progressively enlarging abdominal mass prior to presentation. The patient had a history of prior abdominal surgery for small bowel resection and hernia repair.

Figure 1 Axial computed tomography image with the red arrow demonstrating a large, well-circumscribed cystic mass within the left lower abdominal wall.

Figure 2 Sagittal computed tomography image showing the extensive cranio-caudal dimension of the lesion (arrow) with mass effect on adjacent bowel structures.

Figure 3 Axial magnetic resonance imaging demonstrating a large, homogeneous cystic lesion (arrow) with a well-defined capsule, consistent with a chronic pseudocyst. The dotted line represents the maximum diameter of the mass with a length of 215.5 mm.

Initial percutaneous biopsy, on day 8, of the mass was nondiagnostic. Review of imaging suggested the lesion had a prominent vascular supply arising from the rectus musculature. Aspiration performed by interventional radiology again, on day 15, yielded nondiagnostic material and showed no evidence of malignancy according to the pathology report. The lesion was suspicious for a potential cystic lesion, hematoma, seroma, or mucinous neoplasm.

Given the uncertain nature of the lesion and its large size, the patient elected to proceed with surgical excision 57 days later for complete resolution. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent for publication of this case report and accompanying images was not obtained from the patient or the relatives after all possible attempts were made.

Operative course

The patient was induced under general anesthesia. A midline incision was made through a previous scar. The subcutaneous tissue was dissected through, and a large, well-vascularized mass in the left lower quadrant was exposed. Suture material from an earlier surgery was identified at the superior margin of the fascia. The cyst was intimately associated with the fascia and colon intraoperatively, findings that differed somewhat from the initial radiographic appearance, suggesting a predominantly abdominal wall lesion. Multiple vessels that vascularized the cyst were encountered and individually cauterized. The cyst wall was thickened and fibrotic.

Due to the large volume of the cyst and to improve visualization in the operative field, the cyst was entered, and approximately 3 L of fluid were evacuated. The colon was not fully mobilized; it was carefully dissected to allow for safe retraction and then was returned to the abdominal cavity.

During the dissection, two large bowel enterotomies were incurred inadvertently. These injuries occurred secondary to dense inflammatory adhesions and obliteration of normal tissue planes between the cyst wall and adjacent colon. Both enterotomies were immediately repaired with a thoracoabdominal (TA) stapler and reinforced in standard fashion. The mass was entirely excised and sent to permanent pathology for further evaluation. After hemostasis was achieved with electrocautery, the space was irrigated and suctioned to remove any remaining blood. The incision was subsequently closed in layers. The patient was advised to follow up in a week post-discharge. Postoperatively, the patient recovered bowel function appropriately without evidence of leak, obstruction, or additional bowel-related complications. On follow-up, the staples were removed, the patient was satisfied with the procedure, and was instructed to follow up as needed.

Specimen findings

The excised specimen consisted of a cystic structure containing hemorrhagic fluid. Histopathologic images were unavailable for review. Final pathological evaluation of the specimen was reported as a benign fibrotic cystic lesion without evidence of malignancy, consistent with a chronic pseudocyst. Biochemical analysis and tumor marker evaluation of the cyst fluid were not performed.

Discussion

In comparison to existing literature, our patient’s cyst contained nearly 3 L of fluid and was adherent to the colon, which is among the most significant published examples of an intra-abdominal pseudocyst (4). Additionally, it provides a layer of considerable fibrosis and a degree of bowel involvement. It closely follows other cases of operative challenges and nondiagnostic cytology, which contribute to it as an additional critical perspective in managing extremely large pseudocysts (5).

Diagnostic difficulty with fine-needle aspiration (FNA)/biopsy

Percutaneous FNA is frequently used to characterize cystic lesions; however, in the case of a pseudocyst, its diagnostic utility is inherently limited. Due to the lack of an epithelial lining in a pseudocyst, cytology results in nonspecific components, including blood products, fibrin, hemosiderin-laden macrophages, and amorphous debris (1). Several of these findings matched our patient’s results. Two separate samples were completely nondiagnostic, and our patient demonstrated only cellular debris, blood, and fibrin with no indication of epithelial structures or malignant cells to clarify the cyst’s origin. Additionally, due to this, pseudocyst aspirates frequently resemble chronic hematomas rather than a distinct pathology (6). Therefore, FNA alone cannot be a reliable discriminator.

Mimicking other lesions

Non-pancreatic pseudocysts can also closely mimic a broad spectrum of different pathologies when presented intra-abdominally on imaging. They frequently appear unilocular and demonstrate a thickened capsule (7). These features often make it difficult to distinguish them from mesenteric cysts, duplication cysts, lymphangiomas, mucinous neoplasms, and postoperative fluid collections such as hematomas, seromas, and infectious abscess cavities (8).

In this unique case, the cyst’s proximity to the rectus musculature and its dense adhesions to the colon made it suspicious for either a bowel-associated process or a postoperative complication. Prior surgical material identified intraoperatively further complicated the differential diagnosis. Pseudocysts with thickened, hypervascular walls create diagnostic ambiguity as the vascularity can be misinterpreted as a sign of neoplasia or a more aggressive pathology and therefore need to be clarified by histologic evaluation to affirm their benign nature (9). This highlights the need for pseudocysts to be included in the differential diagnosis for abdominal masses, especially when biopsy results are nondiagnostic.

Operative challenges

The excision of a giant pseudocyst presents a substantial technical challenge due to the chronic inflammation, hemorrhage, and accumulation of debris and fibrosis over time. These factors often obliterate normal tissue planes and produce dense adhesions to the surrounding structures, similar to the ones in this case, necessitating meticulous dissection. The evacuation of fluid is well documented as a practical and sometimes essential maneuver to improve exposure (3). Decompression reduces the mass effect and tension on adjacent structures, also allowing for safer mobilization. Despite these efforts, enterotomies can occur where encasement or distortion of bowel makes injury difficult to avoid (3). This reinforces the notion that even benign cystic lesions may require complex surgical intervention.

Pathogenesis and pathology

Final pathology showing omental fibrosis, chronic organizing hemorrhage, scar tissue, and the absence of epithelial lining confirms the diagnosis of a chronic pseudocyst. Several mechanisms have been proposed for formation in non-pancreatic locations, including:

• Encapsulation of a chronic hematoma;
• Evolution of postoperative seroma;
• Lymphatic collection postoperatively;
• Foreign body inflammation;
• Repeated hemorrhage into a potential space;
• Blunt trauma and infection.

In this patient, due to the intraoperative findings, chronic hematoma formation is a likely mechanism. This is a potential complication even after surgery due to persistent low-grade inflammation or intermittent hemorrhage into a postoperative cavity (10). Cycles of hemorrhage, fibrosis, and capsule thickening can increase adherence to surrounding tissue, which would explain the distorted anatomy.

The patient’s prior abdominal surgeries, including small bowel resection and hernia repair, likely contributed to chronic inflammatory changes and foreign body reaction resulting in pseudocyst formation.

In this case, the intraoperative identification of retained suture material adjacent to the cyst with chronic low-grade inflammation related to foreign body reaction may have promoted fibrosis, recurrent hemorrhage, and gradual cyst enlargement over time. Given the absence of pancreatic disease or trauma history, prior abdominal surgery may be another plausible alternative.

Therapeutic role of excision

Complete excision fulfills both diagnostic and curative roles. It helps avoid potential large lesion complications such as rebleeding, superinfection, rupture, bowel obstruction, mass effect, visceral entrapment, and fistulization into bowel or abdominal wall. Therefore, excision of a large or symptomatic pseudocyst, even when malignancy is unlikely, is widely endorsed (11).

Conclusions

Giant non-pancreatic pseudocysts are rare entities that can pose significant diagnostic and operative challenges. This is seen particularly when imaging and biopsy fail to establish a definitive diagnosis. This case highlights the limited utility of FNA in hemorrhagic pseudocysts and the potential for these lesions to mimic bowel-related or neoplastic pathologies. Additionally, it highlights the technical complexity that is associated with resection of densely fibrotic lesions when vascularity has distorted the normal anatomy. For both diagnostic and curative therapy, surgical excision remains the best option, especially in cases where malignancy can’t be excluded, lesions are exceptionally large, or there is high risk for future complications. Surgeons should maintain a broad differential for large cystic abdominal masses and anticipate difficult dissection even in ultimately benign pathology.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://acr.amegroups.com/article/view/10.21037/acr-2026-0095/rc

Peer Review File: Available at https://acr.amegroups.com/article/view/10.21037/acr-2026-0095/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-2026-0095/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 institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent for publication of this case report and accompanying images was not obtained from the patient or the relatives after all possible attempts were made.

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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