Transanal Endoscopic Microsurgery (TEM)

UCSF Medical Center is one of the few medical centers in the U.S. that offers an advanced, minimally invasive procedure called Transanal Endoscopic Microsurgery (TEM). TEM is performed by specially trained colorectal cancer surgeons to remove certain non-cancerous rectal tumors and early stage rectal cancers.

Previously, removing rectal tumors warranted a major surgery with a large abdominal incision, followed by a lengthy hospital stay and recovery. TEM does not require any surgical incisions; it is performed through the rectum with specially designed microsurgical instruments that can remove lesions high inside the rectum. Traditionally, these lesions were accessible only with major abdominal surgery.

Advantages of Transanal Endoscopic Microsurgery (TEM)

With TEM, colorectal surgeons have a longer reach and better visibility into the rectum. Benefits to the patient include:

  • No abdominal incision
  • Less bleeding
  • Less risk of infection and complications
  • Less risk of bowel obstructions post-surgery
  • Shorter hospital stay
  • Faster recovery and return to normal activities

It is important to note that not all rectal tumors can be removed by TEM. Your surgeon will evaluate your condition and determine the best treatment plan for you.


You will need to completely cleanse the bowel before you have TEM in the same way you would before undergoing a colonoscopy. Your doctor will give you instructions for doing this. This may include a combination of enemas, not eating solid foods for two or three days before the test and taking laxatives. You will usually be told to stop taking aspirin, ibuprofen, naproxen, or other blood-thinning medications for several days before the test.


You will have general anesthesia for the procedure. TEM is performed through your anus, eliminating any need for incisions. Your surgeon will use specially designed instruments to precisely remove the polyp or small cancer, while leaving surrounding healthy tissue intact. In most cases, the healthy edges of the rectal lining are stitched together using dissolvable sutures or metal clips. These are either absorbed or expelled from the body naturally, so there is no need for follow-up suture removal.


After surgery, you will need to stay in the hospital for one or two days. Most patients feel some discomfort, though rarely pain, in the back passage. Immediately after the procedure (within the first 24 hours), you will need:

  • Oxygen through a face mask
  • A drip into a vein in one of your arms to give you fluid
  • A catheter (tube) in your bladder to drain away urine
  • A tube is sometimes left in the back passage for the first day to drain away any excess fluid

Later the same day or following day, you will be able to eat again, starting with liquids and gradually introducing solid foods. It is important that you move around as soon as possible following surgery.

When you first start going to the bathroom again, your feces (bowel movements) will be liquid. Sometimes it takes several weeks to get back to normal; in some cases, patients may have to adjust their diets. Nutritionists are available to help you develop a suitable diet to meet your nutritional needs.


Reviewed by health care specialists at UCSF Medical Center.

Related Information

UCSF Clinics & Centers

Center for Colorectal Surgery
1825 Fourth St., Fourth Floor
San Francisco, CA 94158
Phone: (415) 885-3606
Fax: (415) 885-7678

Condition Information

Our Experts

Emily  Finlayson
Dr. Emily Finlayson,
colorectal surgeon
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Dr. Hueylan Chern,
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Dr. Madhulika Varma,
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