A Big Bite or a Little Bite?
Benefits and Limitations of Full Thickness GI Biopsies vs. Endoscopic GI Biopsies
By Fiona Park (Medicine Specialist)
One of the tests sometimes used to help investigate problems such as vomiting and diarrhoea in dogs and cats is biopsy of the gastrointestinal tract. This will often be recommended after simpler tests (such as blood tests, stool tests, xrays, ultrasound) have eliminated other causes of these symptoms.
For gastrointestinal biopsies, samples of tissue from the stomach, small intestine and/or large intestine are submitted to a laboratory for analysis by a pathologist (histopathology). There are 2 ways that a veterinarian can obtain these biopsies:
- Endoscopic biopsies – using an endoscope, which is a type of flexible tube attached to a video camera
- Surgery – this involves an incision into the abdomen (laparotomy) or sometimes keyhole surgery (laparoscopy)
Both of these methods have their own advantages and disadvantages which are outlined below.
Advantages of endoscopic biopsies:
- This is a relatively non-invasive procedure – although the patient will require a general anaesthetic, in most cases recovery from the procedure is rapid. As the endoscope is introduced to the body through the mouth and/or bottom (anus), there is no incision to heal.
- The inside lining (mucosa) of the oesophagus, stomach, parts of the small intestine and large intestine (colon) can be visually inspected at the time of the endoscopy.
- Endoscopic biopsies can safely be obtained from the colon (see below)
- Endoscopic biopsy sites heal very quickly and can be used to obtain biopsies in cats and dogs with low protein levels in their blood, without increased risk of complications.
Disadvantages of endoscopic biopsies:
- Only a limited portion of a dog or cat’s small intestine is actually able to be accessed using an endoscope. Most endoscopes are 1 metre long whereas the average dog’s small intestine length is 6 metres long! This may be an issue if the disease only affects a certain area of the small intestine that is out of reach of the endoscope.
- Endoscopic biopsies encompass the innermost layer of the wall of the stomach or intestine only (called the mucosal layer). This might be an issue if the disease has only caused changes in the outermost layers of these organs.
- The quality of endoscopic biopsies obtained can vary and is highly dependent on the expertise of the veterinarian performing the procedure.
Full thickness (surgical) biopsies:
Advantages of full thickness (surgical) biopsies:
- A sample that includes all the layers in the stomach or small intestine can be obtained. This means that diseases that only affect the deeper layers of the stomach or intestine can still be diagnosed.
- At surgery, all the parts of the small intestine can be accessed and biopsied as necessary. Furthermore, any areas of bowel that are seen to be abnormal from the outside layer (eg thicker than normal) can be specifically tested.
- Biopsies can also be taken from lymph nodes and other organs in the abdomen such as pancreas and liver at the time of surgery. This is not possible during endoscopy. This may be of importance in some cats and in dogs with cancer of the gastrointestinal tract.
Disadvantages of full thickness (surgical) biopsies:
- Although both methods of obtaining biopsies require a general anesthetic, recovery time is expected to be longer following surgery than following endoscopy. This means that a longer period of hospitalization is generally required after full thickness biopsies are taken, in comparison to endoscopic biopsies. Furthermore, your pet’s exercise will need to be restricted until the surgery site has healed completely. If laparoscopy is possible, then this may reduce the recovery time.
- Some dogs and cats with gastrointestinal problems may have decreased protein levels in their blood as part of their disease process. These patients have a higher risk of complications after full thickness biopsies, as the biopsy sites will not heal as efficiently as they should. Such complications can sometimes be life-threatening and/or require a second surgery to remedy.
- Full thickness biopsies of the large intestine (colon) are rarely performed as there is a high risk of complication.
The decision on whether your pet’s gastrointestinal biopsies will be full thickness or endoscopic should be discussed with the veterinarian treating your pet.