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STER: Submucosal Tunneling and Endoscopic Resection is a technique used in the resection of the upper and lower gastrointestinal mucosal tumours.
Submucosal tumours (SMT’s) are protruding lesions covered with mucosa found in the gastrointestinal tract. The majority of them are small in size and found to be asymptomatic. SMT’s which have a diameter under 3 cms, are usually benign leiomyomas. However, SMT’s, like the gastrointestinal stromal tumours (GIST’s), are malignant in nature. These are lesions that grow from the muscular layer and possess a larger diameter or are connective tissue tumours. The SMT’s must be accurately diagnosed to continue further treatment. Inspite of the (EUS-FNA) and biopsy, it isn’t easy to accurately diagnose the SMT’s without resection.
Submucosal Tunnelling and Endoscopic Resection (STER) gives more accurate results and is less invasive.

STER Equipment
When your STER is conducted, you will be given general anaesthesia. The procedure will be done by an endoscopist who is well experienced. When the procedure is being performed, insufflation will be done with carbon dioxide insufflators. The majority of the procedures will be performed with dual knives, some using a hybrid knife and yet others with a knife having insulation-tip to dissect the SMTs. Besides the said equipment, they will also need the following:

  • Hemostatic clips
  • Hypodermic needle
  • Argon plasma coagulation unit
  • High-frequency generator

Endoscopic treatment using STER

  • A submucosal injection is given at the site where the maximum number of SMT’s are located. It is given about 3cm away from the nearest SMT.
  • The tunnel entry point is created: A 1.5 to 2.0 cm longitudinal mucosal opening is made by a knife.
  • A submucosal tunnel is formed between the Muscularispropialayers and the submucosal making sure that all the Submucosal tumours are exposed. In case of difficulty finding the submucosal tumours during this, the endoscope is brought out from the tunnel, and methylene blue is injected to locate the tumour and set the tunnel route.
  • The SMT’s are dissected if they are a hindrance in the tunnel creation or if they are too large.
  • After complete resection of all the SMT’s and careful hemostasis, the mucosal entry is closed.


  • If you are going in for a lower gastrointestinal tract procedure, take a liquid diet. It would be best if you took a laxative or an enema to cleanse the bowel.
  • In the case of an upper gastrointestinal tract procedure, you should observe fasting (no food or water) for 12 hours before the procedure. This is to make sure that your oesophagus is clear.
  • Inform your doctor about any allergies you have or any medication which do not suit you.

Postoperative management
After the procedure, for the following 48 hours, you will not be given any food that you can eat. This is referred to as nil per os (NPO) or ‘nothing by mouth’. After this, for the next 2 hours, you will be kept on a liquid diet. Post that period, you can eat normally. The doctor will put you on intravenous proton pump inhibitors in the three days following the STER procedure. On the second day after your procedure, your doctor will conduct thoracoabdominal radiography on you to ensure that there are no complications that have arisen due to the STER procedure. Some of the complications that your doctor will check for are pneumothorax, emphysema and pneumoperitoneum.

Pathological evaluation
The specimens that are resected during your procedure will be sent for pathological testing and evaluation after being fixed and embedded within paraffin. For evaluating the SMTs general characteristics, Hematoxylin and eosin (HE) staining will be used. Also, for deeper diagnosis of the pathology, immunohistochemical (IHC) staining (e.g., SMA, CD117, CD34, Ki67, Dog-1 and S-100) is conducted.

What will happen after the STER treatment?

After your STER is complete and some weeks have gone by, you will be required to go back for a regular endoscopy examination 2 or 3 times. These could be in the third, sixth and 12th-month post STER. The purpose of these endoscopies is to check if all is going well. After these, an annual endoscopy will be required for the same purpose. During these endoscopies, your doctor will check how the mucosal incision’s healing is holding up and observe for any residual tumour. Generally, first, an EGD will be performed, and if it shows up any abnormalities, then EUS and/or CT will be conducted.

STER: Submucosal Tunnelling and Endoscopic Resection is a novel technique for the treatment of gastrointestinal submucosal tumours. This technique is feasible and safe. It has a quick recovery and a shorter hospital stay. As compared to conventional endoscopic resection, the new technique is less invasive. Rates of postoperative GI tract leakage and secondary infection are also low. By maintaining the integrity of the mucosa, it prevents mediastinitis and peritonitis.