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Exotic Animal Endoscopy Course
© Stephen Hernandez-Divers, The University of Georgia
Avian Endoscopy Endoscopy is the examination of internal structures and organs using a small endoscope or telescope. This technology allows us to examine and sample the internal
organs of birds down to 100g in size via a tiny surgical incision, generally 2-4mm in size. The benefits are obvious; a) minimally invasive internal examination b) ability to safely biopsy c) avoidance of
major, lengthy surgery.Avian veterinarians have been endoscopically sexing birds for many years, although blood-test sexing has greatly reduced the need for this procedure. However, those
involved with large collections (e.g. breeders, wholesalers, retailers) often require immediate confirmation of. Therefore endoscopic gender determination and reproductive tract evaluation retains its
importance in aviculture. More recently the use of diagnostic endoscopy has really accelerated in popularity. The ability to exploit the air sac system of birds enables the endoscopist to
visualize most, if not all, of the major organs of clinical interest including liver, lung, air sac, heart, kidney, adrenal, spleen, pancreas, ovary or testis, oviduct, shell gland, and intestinal tract. In
addition the oral approach permits examination of the mouth, esophagus, crop, proventriculus and ventriculus, glottis and trachea down to the level of the syrinx. The cloacal (vent) approach permits
examination of the cloaca, and openings to the shell gland and ureters. Coelioscopy
The most commonly employed endoscopic approach in birds involves a left sided approach. With the bird lying on its right side and
the wings secured over its back, the left limb is pulled forward and secured to the neck to expose the lower left flank. Very few feathers, if any, need to be plucked prior to aseptic prep of the area. A
small (2-4mm) skin incision is made just behind the last rib, and just ventral to the flexor cruris medialis muscle. The endoscope enters the caudal thoracic air sac first and from this point most of the
coelomic organs can be identified by moving through the air sac system of the bird. The scope is gently pushed through the delicate air sac membranes to gain access to the adjacent air sac – there is no need
to repair the air sac membranes as they heal quickly. Remember that the terminal end of the scope is angled – press the sharp (bottom) edge of the scope into the air sac membrane and use a sweeping motion to
enter into the adjacent air sac.
General operating room layout and positioning for avian coelioscopy
Macaw positioned in right lateral recumbency with the left flank exposed and aseptically prepared for a standard left lateral coelioscopic examination.Pic03 and 04: Diagramatic representation of bird positioning and close-up of the left flank illustrating the relationship between the flexor cruris medialis
muscle and the last rib. The endoscope is inserted behind the last rib, just below the ventral margin of the flexor cruris medialis muscle.
Caudal thoracic air sac (CaTAS): lung, air sac, liver, proventriculus. (pic05) Cranial thoracic air sac (CrTAS) entered cranially from the CaTAS: heart,
great vessels, air sac and cranial lung tissue, liver. Abdominal air sac (AAS) entered caudally from the CaTAS: kidney, gonad,
ureters, adrenal, spleen, ventriculus and intestines, cloaca, shell gland (left side, pic06), pancreas (right side, pic07)
Samples, including aspirates and biopsies, can be collected using the aspiration needle, scissors, and biopsy forceps.
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.Pic08 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. Tracheoscopy
Probably the second most common endoscopic procedure is the oral approach to examine the trachea and syrinx for disease, esp. syringeal infections. Parrots that suddenly lose their voice and present in acute
respiratory distress are first stabilized using an air sac tube (placed using the same approach as for left sided endoscopy described above) to provide an
alternative airway. The bird can then be anesthetized with isoflurane or sevoflurane via this air sac tube leaving the mouth clear for tracheoscopy,
biopsy and debridement. In larger birds the exam/protection sheath should be used (OD 3.5mm) and will enable tracheoscopy of birds over 400g (e.g.
Amazons, African grays, macaws and cockatoos). In smaller birds, either use a 1.0mm semi-rigid endoscope, 1.9mm telescope, or unsheathed
(unprotected) 2.7mm telescope. It is vital that when using any unsheathed (unprotected) telescope that the bird's head and neck are kept extended and
straight, and that the endoscopist does not exert any bend or torque on the scope, otherwise fracture of the glass rods will occur.
Pic09: Tracheoscopy in an African gray parrot in sternal recumbency using an unsheathed (unprotected) 2.7mm telescope. Note that the parrots' head
and neck are extended, and air sac intubation has been employed to maintain anesthesia. Pic10: Mycotic granuloma occluding the entire distal trachea of a cockatoo.
The biopsy forceps are being advanced to biopsy and debride the lesion while anesthesia is maintained via an air sac tube. Gastro-Intestinal & Cloacal Endoscopy
Examination of the mouth, esophagus, crop, proventriculus, and ventriculus are possible in most birds under 500g using the 2.7mm telescope and 14.5 Fr
operating sheath, via an oral approach. In birds over 500g, an ingluviotomy approach is required to be able to reach the proventriculus and ventriculus.
Gas insufflation can be used to dilate and examine the esophagus, crop and proventriculus for foreign bodies. However, warm (100oF, 38oC) saline
irrigation provides better visualization and vastly superior mucosal detail. It is important to dilate the tract when advancing the scope-sheath system to
avoid damage and laceration to the thin intestinal wall. All birds must be intubated to avoid aspiration of irrigation fluids. Excessive cloacal fluid administration can result in oral regurgitation. Pic11: Endoscopic view of the ventriculus or gizzard of a pigeon. Note the yellow-green pigmented kaolin covering of the gizzard and the presence of grit.
Pic12: Cloacoscopy in a pigeon using a sheathed telescope and utilizing saline irrigation to dilate the intestinal tract and improve visualization.
Pic13: Endoscopic view of the cloaca of a pigeon. Note the dorsal urodeal fold and the opening to the bursa of Fabricus. |
