INTESTINAL BIOPSY

Indications for performing this procedure: The intestinal biopsy specimen is one of the most important pieces of diagnostic information a clinician can obtain in a horse with a chronic gastrointestinal disorder. While a tentative diagnosis of such conditions as chronic inflammatory bowel disease, Salmonella infection, and intestinal lymphosarcoma, can be reached through other means, the biopsy specimen may provide the critical missing piece of the puzzle. A biopsy should differentiate inflammation from neoplasia, allow detection and characterization of the severe inflammatory diseases, and can be useful when ruling out differential diagnoses by demonstrating mucosal histology that is considered "normal".

Laparoscopy is indicated in a variety of cases, including: when an abdominal mass is palpable, viscera are enlarged, abdominal adhesions are present, the horse has suffered acute or chronic colic, unexplained weight loss has occurred, or to obtain visceral biopsy specimens. Rectal mucosal biopsy is utilized when lesions are palpable in the rectum and distal colon, and also in cases of unexplained weight loss and diarrhea. Laparotomy is usually employed only when less-invasive methods have failed.

An intestinal biopsy showing Cryptosporidiosis (seen along the top of the columnar epithelium).

Surgical approaches: There are three main approaches to obtaining intestinal tissue for histopathologic analysis. See the table below for information about these approaches.

Biopsy Method	Cost Estimate	Pros	Cons
Laparotomy/Exploratory Surgery (performed under general anesthesia)	$1,250.00	Allows excellent visualization of the entire abdominal cavity. Full-thickness biopsy specimens, the most diagnostic available, can be obtained.	Expensive Carries with it all of the risks of anesthesia and surgery (injuries, infections, etc.).
Laparoscopic Intestinal Biopsy (standing, with sedation and local anesthesia)	$650.00	Allows fairly good visualization of most abdominal organs. Safer than laparotomy.	Cannot obtain full-thickness biopsy specimens with laparoscopy. Some risk of organ damage/perforation, or post-operative infection/subcutaneous emphysema.
Rectal Mucosal Biopsy	$35.00	Fairly inexpensive. The safest method for performing intestinal biopsy.	Specimens are only as thick as the mucosa, and so of limited diagnostic value. In an intestinal disease that has not yet progressed to the distal colon, the biopsy will not yield diagnostic results.

The Procedure: The procedure is dependent on which surgical approach is chosen, ranging from excision of a piece of bowel with the scalpel followed by suturing of the defect, to a simple pinching off of a piece of rectal mucosa with uterine biopsy forceps. Once obtained, the tissues are fixed, sectioned, stained, and examined. In some cases, special staining may be performed for the detection of certain microorganisms, as when looking for clusters of acid-fast Mycobacterium avium bacilli. If such an organism is suspected, biopsy specimens should be obtained from a number of intestinal locations and mesenteric lymph nodes, in case the organisms are not present in every inflammatory lesion. Another organism that is somewhat dangerous to culture and so is diagnosed by way of a biopsy specimen is Histoplasma capsulatum. Biopsy specimens can also be submitted for culture when fecal cultures are unrewarding.