Page 558 - Clinical Small Animal Internal Medicine

526 Section 6 Gastrointestinal Disease

insufflation can compromise attempts to traverse the types, and removal of the sample from the central needle
VetBooks.ir sphincter. As there is little in the way of colonic wall close can be difficult. The biopsies are inherently fragile and
repeated “scraping” to remove the sample from the cen-
to the sphincter, due to the disparity in ileal versus
colonic lumen diameters, full insufflation deprives the
Endoscopic biopsy samples obtained using flexible
endoscopist of support from the colon walls. tral needle can result in severe crush artifact distortion.
If the endoscope can be successfully maneuvered into instruments are unavoidably small. Even the largest of
contact with the sphincter, gentle forwards pressure will the flexible biopsy instruments that will fit in the endo-
usually result in entry to the ileum. If the ileum cannot be scopes used most commonly in companion animal prac-
3
entered in this manner due to ileocolic anatomy, a flexi- tice will typically only yield a 2.5–3 mm tissue sample
ble biopsy instrument can be threaded through the under most conditions. Most samples obtained endo-
working channel and ileocolic sphincter to act as a guide scopically will have relatively little submucosal tissue
wire. The instrument is advanced, cups closed, until it present, and in many cases small intestinal biopsies may
has penetrated the ileal lumen for 2–3 cm. The biopsy only yield villus tips. Correct technique is necessary to
instrument is then held in place and the endoscope avoid excessive crush artifacts or villus degloving.
advanced over it. It is not recommended to simply follow Because of the extreme wide‐angle view and deep
the biopsy instrument with the endoscope, as this may depth of focus of the endoscope lens, and lack of depth
result in significant trauma to the ileal mucosa (which cues due to monocular vision, the distance between the
has not been visualized). end of the endoscope, the biopsy instrument, and the
lesion to be biopsied can be difficult to judge. Once a site
Normal Findings for biopsy is identified, the biopsy instrument is carefully
The normal ileal mucosa is grossly similar in appearance deployed through the working channel until it is visible
to the duodenal and jejunal mucosa. The normal villus to the operator. Fine tip adjustments can then be made to
structure results in a “velvet” appearance. The mucosa is align the instrument with the area to be biopsied, and
more friable than the duodenum, even in normal indi- then the instrument is advanced to make contact with
viduals. Villus lymphatics are not readily appreciated. the tissue. The flexible shaft of the biopsy instrument will
start to bend slightly as the instrument is pushed up
Potential Abnormalities Observed during against the tissue. This bending is a good indicator that
Ileoscopy Procedures an appropriate amount of pressure is being applied to the
The ileal mucosa is assessed for changes in granularity, tissue to provide the best chance of an adequate biopsy.
friability, the existence of preexisting erosions or ulcera- The biopsy instrument emerges from the distal face of
tive lesions and mass effects, and these changes docu- the endoscope (Figure 49.18), which will usually result in
mented if seen. Mucosal biopsy specimens should always the instrument running parallel to the gastrointestinal
be obtained from the ileum. If the endoscopist is unable lumen. If the endoscope is maneuvered close to a natu-
to traverse the ileocolic sphincter, it is possible to obtain rally occurring fold or corner in the lumen, it is possible
mucosal biopsy samples blindly by advancing a biopsy to directly sample tissue perpendicular to the distal
instrument through the sphincter, although this should scope face. For biopsies from the wall in an area that does
be approached with caution as the risk of perforation is not have a naturally occurring fold or local corner (such
higher without the ability to visualize preexisting lesions. as in the descending duodenum), a number of strategies
are available. Gently suctioning some of the insufflating
gas may result in formation of rugal folds. After minor
Endoscopic Biopsy Technique suction is applied, the endoscope tip is diverted towards
the mural surface using the tip deflection controls, then
Endoscopic biopsies are an attractive option for more the biopsy instrument is advanced out until just in view
complete diagnostic assessment of the gastrointestinal and close to, but not touching, the mucosa. The biopsy
tract, but are not without significant potential pitfalls. jaws should be open at this point. Full suction is then
Correct biopsy technique, careful sample handling, and applied, which will cause the lumen to collapse and the
the collection of adequate sample numbers are all mucosa to “drape” over the end of the scope. The biopsy
important to obtain the best diagnostic yield from these instrument is advanced very slightly and then the jaws
samples. are closed. The biopsy is then collected.
Flexible endoscopic biopsy instruments are available The necessary action to collect an endoscopic biopsy is
in several different types, including serrated or smooth with a sharp “snapping” pull on the instrument at the
jaws, and with or without central needles. Theoretically control end of the scope. The aim is to avulse the mucosal
the central needle types are easier to lodge in the mucosa sample by breaking the submucosal tissue. If the tissue is
but in practice there seems to be little advantage to these collected with a slower “drag” motion, it is not