YOU MAY BE HESITANT to perform a full-thickness incisional biopsy to obtain an intestinal tissue sample, but in many cases, this technique is preferred. In this article, we review when incisional biopsy is best and provide a simple step-by-step guide to the procedure to increase your confidence. For general perioperative considerations when performing this procedure, including diagnostic testing, patient monitoring, and postoperative support, please see the symposium introduction.
INDICATIONS AND METHODS
Indications for intestinal biopsy include chronic diarrhea, vomiting, or weight loss; protein-losing enteropathy; or an intestinal mass.1 Biopsy samples can be obtained endoscopically, percutaneously by using ultrasound guidance, or surgically during laparotomy or laparoscopy.1-4
Many veterinarians prefer endoscopic biopsy because it is minimally invasive and permits direct visualization and sampling of the focal lesions. However, endoscopic biopsy samples can be routinely obtained only from the duodenum and colon, and lesions below the mucosa will be missed with this technique.4 For example, neoplastic and inflammatory lesions seen with lymphoma and feline infectious peritonitis, respectively, often do not extend into the mucosa.5,6 Dilated lymphatic vessels in dogs with intestinal lymphangiectasia may be limited to the mucosa-submucosa junction, making endoscopically obtained biopsy samples nondiagnostic.7 Lymphatic lesions can also be artifactually eliminated with iatrogenic collapse of the lacteals during sample retrieval with flexible biopsy forceps.7
Core biopsy samples of the intestines can be obtained percutaneously by using ultrasound guidance. An automated microcore biopsy (Biopty-Cut biopsy needle—C.R. Bard) requires a bowel wall thickness of at least 2 cm and is best used on infiltrative lesions.2 However, a diagnosis based on histologic examination of ultrasound-guided percutaneous biopsy samples is correct in only 69% of patients; accuracy varies with the lesion's location and underlying etiology.2
Surgical biopsy via celiotomy is performed in patients that require concurrent surgical procedures such as liver biopsy, mass resection, or feeding tube placement or in patients with intestinal lesions that cannot be reached endoscopically.1 It is also performed when samples from an endoscopic mucosal biopsy are not diagnostic.7 Obtaining a full-thickness, high-quality sample by surgical biopsy minimizes the difficulty of histologically interpreting samples from dogs with inflammatory bowel disease and other disorders.7,8
Surgical intestinal biopsy samples are usually obtained with scalpel blades or scissors but can also be taken with a Keyes biopsy punch. With this technique, the procedure duration, sample quality, and postoperative complication rate are similar to those of techniques in which scissors or scalpel blades are used.1