Lorenzo Crosta, Dr. Med. Vet.
Avian, Zoo and Exotic Animal Consulting Clinica Veterinaria Valcurone, Missaglia (LC), Italy
Since when, in the early seventies, modern rigid arthroscopes were firstly used to determine the gender of monomorphic birds, it became clear that birds are ideal patients for endoscopy. In fact, the absence of a diaphragm and the presence of the airsacs system render useless the insufflation of air into the coelomic cavity. This makes laparoscopy (or better celioscopy), much more easy in birds, compared to other zoological classes.
So it was a natural process that brought endoscopy to be both a primary diagnostic and therapeutic tool in avian medicine and surgery. To date, we can assess that a modern approach to avian veterinary science cannot be made without the help of an endoscope.
Rigid endoscopy: The basic equipment for avian endoscopy includes a light source, a fiberoptic cable, a small diameter (1.9-2.7 mm) rigid endoscope, and a simple sheath into which the endoscope may be inserted, if needed.
Rigid endoscopes may have different lens angle offset. Generally speaking, when operating with birds a 30° offset is the standard offset. This angle will allow for a direct, but also slightly lateral vision and rotating the endoscope on its major axis will widen the field of vision. A more advanced equipment will include also an examination sheath, with a built-in working channel.
The most common tools to be used with the working sheath are the flexible biopsy forceps, the flexible grasping forceps and the semi-rigid endoscopy scissors. All the work, especially the advanced one, will be made easier and the operator's skill enhanced, by the use of a video-camera and monitor.
Rhino-choanoscopy: Patient is in dorsal recumbency, the beak will be opened and the endoscope introduced directly into the choanal slit.
Tracheo-syringoscopy: Is one of the commonest endoscopic maneuvers in avian medicine. Diseases of the upper respiratory tract are frequent in birds and a tracheoscopy often has a enlightening diagnostic value. The patient will be anesthetized and brought to a deep anesthetic level. The bird can be either be in sternal recumbency, or hold vertically by a helper. The endoscope is introduced into the trachea and the syrinx is rapidly reached. If a longer work is needed, such as for a biopsy, or retrieving a foreign body, or a granuloma, then the anesthesia will be delivered through the airsacs.
Esophago-ingluvioscopy: Is one of the few maneuvers that require air to dilate the anatomic tract to be inspected. Observation of the esophagus and ingluvies, or crop, is a common procedure. This because is common to suspect crop traumas, infections or neoplasm. Esophagoscopy is done either for a direct inspection of the crop, for taking biopsy samples and also for retrieving foreign bodies. Patient will preferably be fasted 2 or 3 hours before the procedure. The rigid endoscope, or a flexible fiberscope, has to be connected to an air pump, in order to dilate the esophagus and crop.
Gastroscopy (proventriculo- and ventriculoscopy): Is still a common procedure, even if less frequent than the previous one. Indications for a gastroscopy are a simple inspection, to confirm a diagnosis, but also for taking biopsy samples and retrieving foreign bodies. A good knowledge of the anatomic differences between the various bird species is a must. Proventriculus and ventriculus (gizzard) can have different shape, looking, structure and anatomic relationships. Gastroscopy is the natural consequence of an esophagoscopy: once in the crop, the cavity will be gently dilated with air and the ostium that connects the crop to the thoracic esophagus, located. Once entered into the distal part of the esophagus, proventriculus and ventriculus are easily reached and inspected.
Cloacoscopy: Cloaca, or the combined terminal opening of the alimentary, urinary and reproductive systems, is often involved in local and generalized disease processes. The endoscopic inspection of this organ can have great diagnostic value. Also this maneuver needs a dilatation of the organ, but this will be obtained with a sterile saline solution, and not with air. Normal saline, or RLS, will be warm and delivered through the sheath of the rigid endoscope. Also this procedure needs a perfect knowledge of the anatomic differences between the various bird species.
Since birds do not have two separated thoracic and abdominal cavities, but instead a single coelomic cavity, laparoscopy in birds should be named coeloscopy. There is no other zoological class in which laparoscopy is made so easy by the natural anatomical situation of the patient. Although several accesses to the avian coelom have been described, there are only two that are routinely used: the lateral approach (especially the left one) and the ventral midline one.
The patient is placed in right lateral recumbency, with the wings extended dorsally. The left leg is flexed cranially, while the right leg is maintained in its normal position. The flank area is prepared for surgery. A small incision is made in the skin where the caudal thigh muscle crosses the last rib. The abdominal muscles are then bluntly dissected, with an Adson, or small, curved mosquito forceps and the endoscope is inserted.
Through a right lateral approach there is a similar vision, but the female reproductive system can be inspected only in the few bird species that possess a right functional one. The only organ that needs to be accessed from the right side is the duodenal part of the pancreas.
Determine the gender in monomorphic species was the first practical application of avian endoscopy: in fact, although other techniques of sex determination are widely used by now, endoscopy still gives information of paramount importance, especially when selecting birds for breeding purposes. The surgical access is always left lateral, since in almost all the bird species, only the left part of the feminine reproductive system develops. Further, in the few species that have a developed right part, also the left one is developed.
Inspection of the air sacs and pulmonary base: Immediately after entering through the body wall of the patient, the endoscope is directed cranially, in the caudal thoracic air sac. In this way the walls of the airs sac can be inspected, as well as the air sac itself, the base of the lung, and the ostium that connects the lung to the air sac.
Inspection of the Liver
The liver can be accessed through two approaches. When the routine left lateral approach is used, the endoscope will be directed into the peritoneal cavity. Once the thoracic esophagus and proventriculus are located, the endoscope will be driven dorso-laterally to the latter, until the caudo-lateral border of the liver is encountered. If the liver has to be accessed through the ventral, midline approach, the patient has to be in dorsal recumbency. A small incision is made few mm. caudally from the distal end of the sternum. Then the muscles are bluntly dissected, with and the endoscope is inserted.
Inspection of the heart: Due to the lack of a diaphragm, the avian heart, like the liver, can be observed for two different surgical approaches. After a left lateral access, from the caudal thoracic air sac, the endoscope is passed into the cranial thoracic air sac, where the dorso-lateral portion of the heart can be easily spotted. If the distal part of the heart needs to be inspected, then the access will be similar to the ventral one described for the liver. After passing the ventral surface of the liver, the cardiac apex ca be observed in the groove formed by the two hepatic lobes.
Indications for the inspection of the kidneys and also for a renal biopsy, are linked to the suspect of a nephropathy that cannot be ascertained in a different way. So this procedure is indicated in case of PU/PD, chronic hyperuricemia, and swelling of the kidneys, when this is diagnosed by radiography, ultrasounds, or even during the same endoscopic examination. Access to the kidney follows exactly the same route described for the gonads.
Inspection and sampling of the spleen can be very important in avian diagnostics. Surgical approach is the same described for the gonads and kidneys. Once the cranial lobe of the left kidney is located, the endoscope is driven ventrally, in the groove formed by the kidney and mesentery on one side, and the proventriculus on the other.
This is possibly the most difficult organ to be accessed in the avian coelom, and has to be reached through a right lateral approach. The pancreas is hidden between several intestinal loops. Only the endocrine part of the avian pancreas can be observed endoscopically.
1. Crosta L, Gerlach H, Bürkle M, Timossi L. Endoscopic testicular biopsy technique in Psittaciformes. J. Avian Med. Surg. 16(2), 106-110, 2002.
2. Crosta L, Bürkle M, Timossi L. Endoscopy assisted resolution of egg binding in an emerald-collared parakeet. Exotic DVM, , vol. 6.1, pp 19-22, 2004.
3. Taylor M. Endoscopy in birds. In: Murray MJ, Schildger B, Taylor M. Endoscopy in Birds, Reptiles, Amphibians and Fish. Tuttlinge, Germany, Endo-Press, pp 7-28, 1998.