What is submucosal dissection?
Submucosal dissection is a partial-thickness resection of the bowel wall. The resection plane is in the deep submucosa at the junction to the muscularis propria. Submucosal dissection was originally developed for the purpose of obtaining a larger biopsy specimen then called “strip biopsy,” but evolved into a therapeutic procedure when it was discovered that this technique was capable of completely removing the mucosal layer. The technique is widely used in Japan for the curative treatment of superficial “early” cancers of the gastrointestinal tract. Unlike techniques that burn or destroy tissue, submucosal dissection provides a tissue specimen for surgical pathology. The procedure is curative when two criteria are met: 1) the cancer is superficial, ie, limited to the mucosal layer; and 2) the margins of resection are free of tumor.
How does submucosal dissection differ from polypectomy?
The resection plane of submucosal dissection is deeper than that of polypectomy and the surface area to be resected is more extensive. Whereas polyps are readily captured and removed by the single application of a standard snare, cancerous or flat neoplastic growths require special accessories and techniques to achieve a deeper resection plane and a sufficiently wide area of resection.
How is submucosal dissection performed?
Various accessories and techniques are used. Mucosectomy snares are made of stiffer wire and designed to grasp flat tissue. A deeper plane of resection is achieved by using endoscopic suction or saline injection to lift the lesion-bearing mucosa. Fitting a transparent cap on the tip of the endoscope can enhance the lifting power of suction. The cap has a rim to hold an open mucosectomy snare. Mucosectomy can also be assisted by band ligation of tissue (analogous to variceal ligation). Lesions that cannot be removed in one piece (en bloc) with EMR are removed by endoscopic submucosal dissection (ESD) This involves the use of electrocautery dissecting knife to resect the lesion.
Role of magnification endoscopy
Special magnification or “zoom” endoscopes enable the detection of subtle irregularities of the mucosa, such as aberrant pits, crypts, and vascular patterns that correlate with neoplastic transformation. The magnification effect is enhanced by spraying dyes or acetic acid onto the mucosal surface thus, “enhanced magnification.” Zoom endoscopy is performed prior to submucosal dissection to define the precise extent of neoplastic involvement. In patients with Barrett’s esophagus, zoom endoscopy facilitates the detection of high-grade dysplasia and carcinoma. The orderly villiform appearance, characteristic of Barrett’s esophagus, is replaced by featureless mucosa with aberrant crypts. These sites are then targeted for biopsy confirmation of cancerous transformation.
Role (EUS)of endoscopic ultrasonography (EUS)
EUS is performed prior to submucosal dissection to select those patients who are suitable candidates for endoscopic treatment. EUS defines the infiltration depth of neoplasia relative to the wall layers and interrogates surrounding tissue for metastatic spread. Both standard echoendoscopes and high-frequency ultrasonic catheter probes are used.
Mucosectomy for Barrett’s esophagus
Treatment of Barrett’s esophagus is indicated when biopsies show high-grade dysplasia or carcinoma-in-situ. Local endoscopic treatment by submucosal dissection may be curative when cancerous change is intramucosal. A raised or nodular area suggests a focal cancerous change (see Case Study 1). Widespread submucosal dissection of Barrett’s esophagus is performed when the cancerous transformation is diffused (see Case Study 2). When Barrett’s esophagus is circumferential, resection is performed piecemeal over two or more sessions to avoid post-resection structuring. The stripped Barrett’s mucosa re-epithelializes with normal squamous epithelium.
Mucosectomy for large sessile adenomas
Large sessile adenomas require submucosal dissection for removal. Chromoscopy, with indigocarmine or methylene blue, aids in defining the extent of such growths, which may be carpet-like. When very flat, fluid is injected into the submucosa to raise the lesion from the underlying muscularis propria to enable ensnarement and provide a safety “cushion” to prevent perforation. Before injection, the perimeter of the growth is marked with diathermy using the tip of a snare. After submucosal dissection, the resection site is tattooed with India ink to enable easy recognition on surveillance endoscopy.
Patient Referral to the IESMG for Mucosectomy
Patients need a referral from their primary care provider or physician specialist prior to scheduling endoscopic submucosal dissection evaluation and procedure. Medical records, pertinent laboratory reports, and imaging reports need to be forwarded to California Pacific’s Interventional Endoscopy Service to determine referral indication appropriateness.
Medicare, Medi-Cal, and most private insurance plans cover endoscopic submucosal dissection. In order to avoid unexpected medical expenses, it is always best for patients to contact their insurance company prior to treatment to confirm coverage for this service and obtain prior authorization.