Tissue handling and processing
Most importantly, any sample should be protected from crushing, dehydration, and autolysis. Also, biopsy handling needs to be tailored to the investigations that are to be performed, such as histopathology, immunohistochemistry, or biochemistry.
For morphologic assessment, tissue samples should be collected very carefully and handled with great delicacy in order to preserve tissue structure and to avoid artefacts. It also requires optimal condition of the cutting instruments, such as the biopsy forceps, needles, or others as well as proper placing of the specimens into containers with 7% buffered formalin enabling immediate fixation. Larger samples should be incised or dissected. Needle biopsies and endoscopic samples should be lifted from the instruments by use of a needle or flushed off with sterile saline. Any excessive or rough handling of the tissueTable 1.16: Comparison of advantages and disadvantages of full- and partial-thickness gastrointestinal biopsies
Full-thickness biopsies collected by exploratory laparotomy or laparoscopy Partial-thickness biopsies collected by endoscopy
■ Visualization / palpation of the GI tract, liver, pancreas, and lymph nodes
■ Blind and potentially inappropriate sampling
(except of lesions that are apparent from the serosal surface)
■ Sufficient sample size and appropriate orientation
■ Limited number of samples
■ Representative sample
■ All layers of the gastrointestinal tube
■ Biopsies from associated organs
■ Increased risk
■ Requires experienced pathologist
■ No macroscopic orientation; associated organs not visible
■ Visualization of lesions of the GI tract mucosa
■ Small sample size and potentially insufficient orientation
■ Numerous samples
■ Sample may not be representative
■ Limited to mucosa and maybe submucosa
■ No biopsies from associated organs
■ Minimal invasiveness
■ Requires a very experienced pathologist
specimen will lead to artefacts and thus will limit their diagnostic value.
The biopsy sample should also be accompanied by a detailed description of any relevant clinical data and a diagram of the sample collection site. Some authors have recommended placing small samples on lens paper, foam, thin cards, or even slices of cucumber in order to prevent distortion and to allow better tissue localization and orientation. However, this should be done with extreme caution as those efforts may result in additional artefacts rather than in their prevention. Some investigators allow the samples to adhere to the support surface for a short period of time. However, this may cause additional stress and is not recommended. In the author’s experience it is sufficient to pool biopsies of the same region, but to keep different sites or specific lesions separate. It is not recommended to pool samples from different sites of the GI tract. Identification of the samples by included pencil-written labels and /or labeling the containers is of fundamental importance. Containers should be stable and adequate for storage and transport and should prevent accidental leakage. They should be shatter-proof with a twisted cap. Containers should be shipped in padded packaging materials.Samples for electron microscopy should be immersed in 2.5% glutaraldehyde as a fixing solution. Biopsies for biochemical, immunological, and molecular biological purposes should be snap-frozen at -135 °C in isopentane, kept on liquid nitrogen, and then handled, transported, and further processed on dry ice. Under these conditions, samples for histopathological evaluation can also be sent unfixed as long as the tissue samples are protected against dehydration (J Vet Intern Med 2003; 17: 291-297.
6. Jergens AE. Inflammatory bowel disease: Current perspectives. Vet Clin N Am (Small Anim Pract) 1999; 29: 501-521.
7. Willard MD. Feline inflammatory bowel disease: a review. J Feline Med Surg 1999; 1: 155-164.
8. Richter KP. Feline gastrointestinal lymphoma. Vet Clin North Am (Small Anim Pract) 2003; 33: 1083-1098.
9. Willard MD, Jergens AE, Duncan RB et al. Interobserver variation among histopathologic evaluations of intestinal tissues from dogs and cats. J Am Vet Med Assoc 2002; 220: 1177-1182.
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