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Avian
Biopsy technique
One of the great benefits of endoscopy is that when an abnormal structure or pathological lesion is observed, biopsies can be taken under direct visual control.
Biopsies can be harvested from the kidneys, gonads, liver, spleen, pancreas, lung, fat, air sac membranes and, in general, any abnormal soft tissue structure.
When confronted by a potentially cystic lesion or abscess, it is safer to perform a fine needle aspiration and avoid leakage of contents into the sair sacs or coelom.
In cases of diffuse liver pathology, the most accessible sampling site is the caudal edge of the liver, located on the ventral floor of the caudal (or sometimes cranial) thoracic air sac.
To access the liver it is necessary to break through the air sac membrane and hepatoperitoneal membrane. These membranes are generally thin and transparent, but it can be difficult to break through using the delicate biopsy forceps, and repeated bite attempts may have to be made before tissue is obtained.
The author prefers to use single action endoscopy scissors to incise these membranes covering the organ prior to using the biopsy forceps. The preferred scissors have one fixed blade and one moveable blade.
The scissors are opened and the fixed blade is gently and inserted through the membranes but not deep into the tissue parenchyma. Maintaining the jaws open, the scissors are elevated and the membranes are incised as the sheath-scope-scissors are advanced as a single device.
Once the incision is sufficiently large enough to permit the introduction of the biopsy forceps, the jaws of the scissors are closed and retracted.
The biopsy forceps can now be inserted through the membranous incision, and a clean tissue biopsy can be taken. Multiple biopsies can be taken from the same site.
There is often some minor post-sampling bleeding which, thanks to tissue-associated thromboplastin in birds, quickly stops and is generally inconsequential.
Renal biopsies in most birds are most easily collected from the cranial pole of the kidney, left or right side. Lung biopsies are most easily collected from the left or right caudal thoracic air sac.
Splenic biopsies are most easily collected from the left abdominal air sac. Pancreatic biopsies are most easily collected from the right abdominal air sac.
In any case of suspected organ disease it is important to examine as much of the organ's surface as possible in order to determine whether a disease process appears to be focal, multifocal or diffuse.
In cases of diffuse renal or hepatic disease (e.g. tubulonephrosis, nephrocalcinosis, hepatic lipidosis, hepatitis), two or three biopsies taken from the most convenient sites are generally diagnostic.
Ultrasound guided and blind, percutaneous biopsy techniques are equally effective in diagnosing diffuse organ disease. Most diagnostic failures occur because of poor tissue selection for biopsy, and this is especially true when dealing with focal (e.g. abscess, neoplasia, cyst) and multifocal diseases (e.g. pyogranulomata, mycobacteriosis).
In these cases, direct visualization offers the best chances of sampling the diseased area(s). In cases of focal or multifocal disease, single or multiple discrete lesions are visible and biopsies should ideally be harvested from the edge of the lesion taking normal and abnormal tissue in the same biopsy sample for both microbiology and histology.
Alternatively, and technically easier, small biopsies can be collected from the abnormal and normal areas and submitted together for comparison.
It is particularly important to correlate histopathological and microbiological biopsy results with clinicopathologic data when dealing with hepatic, renal and pancreatic disease.
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