The present study evaluated the feasibility and safety of EUS-FNA for pelvic lesions with our reference method to decide the approach route either via the upper or lower GI approach. The study results showed a technical success rate of 91.8% (45/49) of all patients—89.3% (25/28) and 95.2% (20/21) with the upper and lower GI approaches, respectively. Among patients who achieved a technical success with EUS-FNA, the accuracy for malignancy in EUS-FNA was 97.8% (44/45; 95% CI 88.4–99.6%) in all patients—100% (25/25; 95% CI 86.7–100%) and 95.0% (19/20; 95% CI 76.4–99.1%) with the upper and lower GI approaches, respectively. Only one patient developed an AE sigmoid colon perforation (2.0%; 1/49) and required surgical management.
The reference method to decide an approach route, either with the upper GI or lower GI, during EUS-FNA for pelvic lesions was evaluated as the technical success in this study. The upper GI approach was selected for pelvic lesions located around the aortoiliac and internal–external iliac bifurcation levels and the lower GI approach was chosen for those located below the level of the internal–external iliac bifurcation. The technical success rates in this study were considered as relatively high and were 91.8% (45/49) in overall—89.3% (25/28) with the upper GI approach and 95.2% (20/21) with the lower GI approaches. The EUS-FNA failed in 2 of 4 patients because of interposing large vessels on the puncture line. Unnecessary procedures can be avoided if large vessel disruption during EUS-FNA can be estimated based on CT findings; however, the estimation could be difficult because the intestines are movable during the insertion of EUS, which change the positional relation between the lesion and the scope. Considering the high technical success rate with our approach method and the difficulty in estimating the interposing vessels during FNA, our determination method of the approach route in EUS-FNA for pelvic lesions can be considered appropriate.
The accuracy of EUS-FNA has been reported as 96% in pancreatic lesions [3, 6], 87.5–98% in upper abdominal lymph nodes [7, 8], and 70–90% in upper gastrointestinal submucosal lesions [11] in previous studies. Among patients who achieved a technical success with EUS-FNA in this study, the overall accuracy for malignancy with EUS-FNA for pelvic lesions was 97.8% (44/45), which was comparable to the these reported diagnostic capability. In addition, the 19-gauge needle was most frequently used for FNA in this study, which might contribute to the high histological specimen acquisition rate (97.8%) and high diagnostic capability since almost half of the final diagnosis in our present study was malignant lymphoma which requires a histological analysis including immune histochemical staining [20, 21]. Large-bore needles generally compromise maneuverability because of its rigidity and stiffness, making the puncture difficult during EUS-FNA, especially via the transduodenal approach. Our high feasibility might be not applicable for other centers, considering our extensive experience with EUS-FNA using a 19-gauge needle. Recently, new fine-needle biopsy (FNB) needles have been developed; they have been reported to have excellent tissue acquisition and histological diagnostic rates, even with a smaller gauge needle size[22, 23]. Therefore, the size and type of FNA needle should be chosen considering the location and shape of the EUS scope, lesion size, and operator’s experience.
Regarding the safety of EUS-FNA for the pelvic lesion via the upper GI, although no AEs were recognized in this study, the echoendoscope has to be pushed downward against the duodenal or gastric wall to visualize the pelvic lesion, which might increase the risk of perforation or bleeding. The operator should be cautious of not using too much pushing force to visualize the lesions. In a systematic review and meta-analysis of EUS-FNA via the lower GI approach for pelvic lesions conducted by Han et al. [15], which included 10 studies with a total of 236 cases, AEs occurred in 1.7% (4/236) of cases and were 2 cases of abscesses after EUS-FNA for cystic lesions, 1 case of gross hematuria and 1 case of hemorrhage. They concluded EUS-FNA via the lower GI for pelvic lesions is a safe procedure with low AE rate. In our study, only 1 patient developed an AE of sigmoid colon perforation during the EUS-FNA via the lower GI. Considering the limited angulation of a convex-type EUS with oblique viewing, deep insertion of the EUS scope into the sigmoid colon is challenging and requires careful maneuver of the scope to minimize the risk of preformation. Recently, forward-viewing EUS (FV-EUS) having forward optical view and wider scope angulation has been developed; they can be theoretically used as a regular colonoscope. In a study by Thinrungroj et al., EUS-FNA using FV-EUS and fluoroscopy via the lower GI approach, including the deep colon approach, was successfully performed in 13 patients without any AEs [24]. The authors concluded that FV-EUS under fluoroscopy guidance might be an easy, safe, and effective technique for transcolonic EUS-FNA. FV-EUS for pelvic lesions can expand the indication of EUS-FNA for pelvic lesions via the lower GI approach and improve the safety especially during the scope insertion.
This study has several limitations. A retrospective study design in a single center with a small sample size might cause biases in the patient selection and external validity of the procedure. The final diagnoses were determined according to both surgical and FNA results, which might cause misdiagnosis in indolent tumors, even with a minimal follow-up period of > 6 months.