Traditional Endoscopic Resection Techniques and Their LimitationsESD is performed by first injecting fluid like saline or epinephrine into the submucosa to lift the lesion off the muscularis propria. This creates a submucosal cushion that prevents perforation. The endoscopist then uses an electrosurgical knife to make circumferential mucosal incisions around the lesion and carefully dissects the submucosa to separate the lesion from the deeper layers. This enables en bloc resection of lesions regardless of size. ESD allows histologic assessment of 100% of the specimen margins to confirm complete resection.
EMR relies on resecting lesions in a piecemeal fashion after elevating them off the muscularis propria using submucosal injection. A wire snare is placed around the lifted lesion and electrocautery is applied to resect the tissue above the submucosal cushion. For larger lesions, piecemeal EMR divides the lesion into sections for serial snare resection.
While ESD and EMR have proven effective for many superficial GI neoplasms and subepithelial tumors, limitations exist. Laterally spreading colorectal lesions with flat, smooth surfaces can be challenging to fully resect with EMR snares. The slippery mucosa often causes the snare to slide right off the lesion, leaving lateral margins behind. piecemeal EMR of these lesions leads to a high local recurrence rate of up to 20%.
Small, flat serrated polyps in the colorectum also often evade polypectomy snares. To achieve proper en bloc resection, the entire lesion must be elevated on a submucosal cushion. But the subtle surface of these polyps makes this difficult. Incomplete resection can leave behind tissue with malignant potential.
The ESD-EMR Hybrid TechniqueTo overcome the challenges of removing slippery, flat lesions, experts developed a hybrid ESD-EMR technique. This combines aspects of both ESD and EMR to improve complete resection.
The procedure involves four main steps:
1. Submucosal injection - Saline, epinephrine, or specialized solutions are injected into the submucosa beneath the lesion to lift it off the muscularis propria. This creates a submucosal cushion to prevent perforation (Figures 1a and 1b).
2. Circumferential precutting - Using the tip of a snare, a shallow incision is made circumferentially around the lesion through the mucosal layer (Figures 1c and 1d). This exposes the lateral and deep margins of the lesion.
3. Submucosal dissection - The snare tip can further dissect the submucosa beneath the lesion to minimize the size of the resection base if needed (Figure 2).
4. Final snare resection - The opened snare is anchored in the pre-cut groove around the lesion and standard EMR technique is used to resect the lesion en bloc (Figures 1e and 1f).
Making a customized groove around the lesion enables complete snare capture and resection. The lateral and deep margins can be thoroughly evaluated histologically to confirm R0 resection.
Clinical Applications and Benefits
The ESD-EMR hybrid technique is useful for:
- Laterally spreading colorectal lesions - The pre-cut groove enables lateral margins to be resected en bloc rather than piecemeal. This decreases the high recurrent rate of 20% with standard EMR.
- Difficult to resect adenomas - Large, flat, fibrous adenomas often cannot be resected en bloc with conventional EMR. The hybrid technique allows complete resection.
- Serrated colorectal polyps - The pre-cut groove solves the problem of these flat, slippery polyps evading snares. Complete removal minimizes residual tissue with malignant potential.
- Non-lifting lesions - Injecting hyaluronic acid or fibrin glue rather than saline can create submucosal lift even in fibrotic tumors.
- Subepithelial lesions - The combined ESD-EMR approach allows resection of larger lesions like lipomas, granular cell tumors, heterotopic pancreas, and small GISTs.
Other benefits include decreased recurrence rates due to better lateral margins, as well as lower perforation risks compared to full ESD in inexperienced hands. The hybrid technique expands the range of lesions amenable to non-surgical, endoscopic resection.
Limitations and AlternativesThe ESD-EMR hybrid technique has a few limitations. Performing the pre-cut incision can be technically challenging in hard to reach locations or if visibility is suboptimal. Poor scope stability and maneuverability increase risks. The procedure also tends to be more time consuming than conventional piecemeal EMR.
In non-lifting lesions, devices like the IT-knife could be used instead of a snare to safely dissect the submucosa. The IT-knife's insulated ceramic tip prevents energy transmission beyond the tip, minimizing risks like perforation. This expands the hybrid technique's applicability.
For smaller lesions under 2cm, traditional EMR or ESD may provide sufficient resection. But for challenging lesions like laterally spreading tumors over 2cm, early data indicates the hybrid ESD-EMR approach improves en bloc and complete resection rates compared to EMR alone.