The Role of Endoscopic Ultrasonography in the Diagnosis of Retroperitoneal Lymphatic Malformations

Summary

This article explores the value of endoscopic ultrasound (EUS) in diagnosing retroperitoneal lymphatic malformation and proposes its imaging criteria.

Abstract

Lymphatic malformation (LM), formerly known as lymphatic cyst, is an extremely rare condition with no specific symptoms, often incidentally detected during examinations for other diseases and confirmed by postoperative pathology. Endoscopic ultrasound (EUS), a non-invasive tool, plays a critical role in diagnosing LM and reducing unnecessary surgeries. We report the case of a young male with 4-day upper abdominal pain was admitted. Imaging (chest CT, enhanced upper abdominal CT, MRI+MRCP) revealed a cystic lesion in the pancreatic head connected to a tubular structure. EUS further showed the lesion was linked to an enlarged lymph node, leading to a diagnosis of retroperitoneal LM, later confirmed by pathology. EUS facilitates early diagnosis by visualizing ductal continuity, avoiding unnecessary interventions like biopsy or surgery.

Introduction

Lymphatic malformation (LM) is a congenital vascular anomaly characterized by dilated, aberrant lymphatic channels. Historically and inaccurately termed "lymphangioma," it is now recognized as a malformation of lymphatic development rather than a true neoplasm, a critical reclassification formalized within the International Society for the Study of Vascular Anomalies (ISSVA) framework¹. While LMs can occur throughout the body, retroperitoneal localization is exceptionally rare, accounting for less than 1% of all cases². The diagnosis of deep-seated lesions in this anatomically complex region is challenging, with patients often remaining asymptomatic until complications such as mass effect or cyst hemorrhage occur³.

CT and MRI have significant limitations in specifically diagnosing retroperitoneal LMs. The primary shortcoming is their low specificity. CT offers poor soft-tissue contrast, making it difficult to distinguish lymphatic fluid from the mucinous or necrotic content of more common cystic neoplasms like sarcomas. Although MRI is the superior modality for delineating anatomy and fluid characteristics, even its findings (e.g., T2 hyperintensity, septal enhancement) are non-specific and can be mimicked by other tumors such as cystic schwannomas or mucinous liposarcomas⁴. Consequently, the preoperative misdiagnosis rate for retroperitoneal LMs based on imaging alone is notably high², as they are often mistaken for other retroperitoneal malignancies. A key limitation shared by both CT and MRI is their inability to provide a histologic diagnosis, frequently necessitating image-guided aspiration or biopsy for definitive confirmation.

Endoscopic ultrasound (EUS) has emerged as a pivotal diagnostic tool for evaluating lesions in and around the gastrointestinal tract⁵. Its unique advantage lies in combining high-resolution ultrasound with an endoscopic perspective, allowing for unparalleled detailed assessment of the gut wall, pancreas, and retroperitoneal structures⁵. Compared to external imaging, EUS provides superior visualization of a cyst's internal features, such as septa, debris, and wall structure, and enables real-time, Doppler-guided assessment of vascularity without radiation exposure⁶. EUS is particularly informative in specific clinical contexts: for retroperitoneal lesions adjacent to the gastrointestinal lumen, for cystic lesions where fluid analysis (e.g., triglyceride levels) can confirm chylous origin⁶, and for small lesions or those with indeterminate features on cross-sectional imaging. However, EUS has limitations, including reduced sensitivity in the setting of severe underlying inflammation⁵ and diagnostic accuracy that may be lower for celiac and retroperitoneal lesions (78.2%) compared to mediastinal lesions (89.7%) due to anatomical challenges and vital interfering structures⁵.

Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA), a technique derived from endoscopic ultrasonography, has emerged as a critical tool for diagnosing indeterminate peripancreatic/retroperitoneal cysts and lymphadenopathy of unknown etiology⁷. Studies have demonstrated that EUS-FNA can significantly impact patient management, with one series showing that management was affected in 16 of 18 patients with retroperitoneal lesions⁵. For cystic lesions specifically, EUS-FNA enables fluid analysis, including triglyceride measurement, which can be essentially diagnostic of cystic lymphangioma when chylous fluid with elevated triglycerides is obtained⁶.

The goal of this report is to demonstrate the specific application and diagnostic value of EUS in the context of a rare retroperitoneal LM, confirmed by pathology, highlighting its role in optimizing preoperative diagnosis and clinical management.

Case presentation:
A young male was admitted with 4-day upper abdominal pain. He had no significant medical history, smoking/alcohol use, or relevant family history. Physical examination showed upper abdominal tenderness without rebound pain. Initial outpatient color Doppler ultrasound suggested acute cholecystitis and cholecystolithiasis, leading to a preliminary diagnosis of "cholecystolithiasis with acute cholecystitis."Admission chest CT revealed cholecystitis, gallbladder enlargement, and a cystic lesion in the pancreatic head (Figure 1A). Enhanced upper abdominal CT and MRI+MRCP confirmed multiple gallstones with cholecystitis (linked to abdominal pain) and a 47 mm × 52 mm marginal low-density shadow (CT value ~10 HU, no enhancement) in the pancreatic head, with multiple swollen lymph nodes in the hilar, peripancreatic, and retroperitoneal areas (Figure 1B). MRI+MRCP showed a 53 mm × 44 mm long T2 signal cystic lesion in the pancreatic head connected to a tube (Figure 1C,D).

Diagnosis, assessment, and plan:
Based on the MRI findings suggesting a pancreatic head connected to a tube, an intraductal papillary neoplasm of the bile duct was initially suspected. However, due to the inherent limitations of cross-sectional imaging modalities such as CT and MRI, which cannot definitively confirm the anatomical relationship between the lesion and the pancreaticobiliary ducts, nor fully characterize the nature of the cyst, EUS was subsequently performed for definitive diagnosis and further evaluation. Under EUS, a 45 mm × 47 mm circular anechoic cystic lesion (Figure 2A)with internal septations (no wall nodules) between the pancreatic head, liver lower edge, and right kidney. Tracking along the direction of the presumed ductal communication revealed that the cyst was connected to an enlarged lymph node measuring 2.7 × 1.4 cm (Figure 2B). Further scanning towards the common bile duct confirmed the absence of communication between the cystic lesion and the biliary system (Figure 2C,D). Retroperitoneal LM was suspected. EUS-FNA was prioritized for definitive characterization of the cyst. EUS confirmed no communication between the cyst and the biliary tree and identified multiple gallbladder stones. Consequently, cholecystectomy, along with cyst excision, was performed as decided by the family. A 6 cm × 5 cm round cystic lesion with a complete capsule was seen near the pancreatic head and duodenal descending part (Figure 3A). Rupturing it released milky fluid (Figure 3B). The lesion was separated from the inferior vena cava, with roots connected to the 12^th and 13^th lymph node groups and extending along lymph nodes (Figure 3C). The operative findings confirmed the EUS results. Abdominal pain was resolved postoperatively.

Protocol

This study was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee of the Yueyang Central Hospital. Written informed consent was obtained from the patient. The consumables and the equipment used are listed in the Table of Materials.

1. Equipment and patient preparation

1. Equipment
   1. Echoendoscope: A linear array echoendoscope was used for real-time ultrasound imaging.
      NOTE: FNA was not performed in this case.
   2. Ultrasound processor: A compatible ultrasound processing system was used.
   3. Imaging parameters: The ultrasound frequency was typically set between 5–10 MHz to balance penetration and resolution. B-mode gain and depth were adjusted dynamically to optimize image clarity. For Doppler assessment, the color Doppler velocity scale (pulse repetition frequency) was initially set to detect low-flow velocities (e.g., 1.5–3.0 kHz) and adjusted as needed, with the color gain increased just below the noise threshold.
2. Patient preparation
   1. The patient was required to fast for at least 6–8 h prior to the procedure to ensure an empty stomach.
   2. Conscious sedation or monitored anesthesia care was administered by an anesthesiologist. This typically involved intravenous propofol (titrated to effect) to ensure patient comfort and safety.
   3. Written informed consent for the diagnostic EUS procedure was obtained from the patient prior to the examination.

2. Procedural steps for EUS examination

1. Initial survey and lesion localization
   1. The echoendoscope was advanced into the duodenal bulb and, if necessary, the descending duodenum to visualize the pancreatic head and adjacent retroperitoneal regions.
   2. A systematic survey was performed to identify the cystic lesion. This was achieved by a combination of gentle scope torquing, tip flexion, and withdrawal. Both B-mode and color Doppler imaging were used to locate the lesion and assess its relationship to major blood vessels.
2. Characterization of the cystic lesion
   1. Measurement: Once the lesion was clearly visualized, the built-in electronic calipers were used to measure its maximum dimensions in two orthogonal planes.
   2. Internal architecture: The internal structure of the cyst was carefully examined at different frequencies and gain settings. The following features were documented:
      1. Septations: The presence of thin, hyperechoic linear structures dividing the cyst lumen was assessed.
         NOTE: Confirmation point - It was confirmed whether the septations were thin and regular or thick and irregular.
      2. Mural nodules: The cyst wall was meticulously scanned for any solid projections into the lumen. A mural nodule was defined as a discrete, hyperechoic, solid structure protruding from the wall.
      3. Echogenicity of content: The cyst contents were characterized as anechoic (clear fluid) or containing hyperechoic debris.
   3. Assessment of anatomical relationships
      1. The margins of the cyst were traced in its entirety by rotating the scope and adjusting the scanning plane to evaluate its relationship to the duodenal wall, pancreatic parenchyma, and peripancreatic vessels.
      2. Assessment for lymphatic connection: A meticulous scan of the peri-cystic soft tissue was performed. The key observation was to identify any anechoic, tubular structure connecting the cyst wall to an adjacent lymph node or coursing along lymphatic pathways.
         NOTE: Observation checkpoint - The critical finding to observe was a direct, fluid-filled communication between the cyst and an extra-pancreatic lymph node.
      3. Exclusion of ductal communication: The relationship of the cyst to the common bile duct and the main pancreatic duct was carefully examined.
         NOTE: Confirmation point - Multiple scanning angles confirmed that there was no visible communication between the cyst lumen and either the bile duct or the pancreatic duct. The absence of such communication was a key diagnostic confirmation.
      4. Assessment of gallbladder: The gallbladder was examined, and the presence of gallstones and signs of wall thickening (consistent with cholecystitis) were confirmed.
   4. Clinical decision point
      1. Based on the EUS findings, specifically, the presence of thin septations, the absence of mural nodules, the confirmation of no communication with the pancreaticobiliary ducts, and the presence of cholecystolithiasis, the decision was made not to perform fine-needle aspiration. The procedure was therefore concluded as a diagnostic examination only.

3. Post-procedural care and follow-up

1. The patient was transferred to the recovery area and monitored until full recovery from sedation.
2. Vital signs, including heart rate, blood pressure, respiratory rate, and oxygen saturation, were monitored at regular intervals.
3. The level of consciousness and airway patency were assessed continuously until the patient was fully awake and responsive.
4. The patient was observed for procedure-related complications, including abdominal pain, nausea, vomiting, bleeding, or signs of perforation.

Results

Pathological examination revealed a well-circumscribed cystic mass characterized by prominent smooth muscle hyperplasia within the cyst wall, along with areas of mucinous degeneration. Dense lymphoid hyperplasia with reactive follicle formation was also observed, supporting the lymphatic origin of the lesion (Figure 4A). No significant cytologic atypia or malignant features were identified in the examined sections.

Immunohistochemical analysis further confirmed th...

Discussion

Lymphatic malformations (LMs) are rare benign cystic lesions, with retroperitoneal cases constituting less than 1% of all occurrences¹. Conventional imaging modalities (ultrasound, CT, MRI) can characterize cystic properties but cannot definitively distinguish LM from other cystic masses, often necessitating pathological confirmation^8,9. This article details a focused endoscopic ultrasound (EUS) protocol for evaluating suspected retroperit...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Built-in imaging software	Fujifilm	https://www.fujifilm.com/in/en/healthcare/endoscopy/endoscopy-ultrasonography/endoscopic-ultrasonography-system
Linear array echoendoscope	Fujifilm	EG-5800UT	"For real-time ultrasound imaging of retroperitoneal lesions"
Ultrasound processing system	Fujifilm	9000	"Compatible processor for echoendoscope; provides B-mode