X-ray is an indispensable diagnostic tool when dealing with wild bird patients and enables a quick, reliable diagnosis in most cases. Sedation of the patient is usually not required (except for panoramic images). Experience of the veterinarian in X-raying birds and small animals is a prerequisite for producing a meaningful X-ray image!
In cases of fractures, dislocations and other severe injuries, it should be weighed whether the patient can be subjected to the pain of a radiological examination without anaesthesia. In any case, administer oral analgesics (Meloxicam) ! If surgical wound or fracture treatment under general anaesthesia is to follow, it makes sense to take the X-ray image already under anaesthesia. In all traumatised patients, careful consideration must be given to anaesthesia capability. Swifts with injuries that, upon clinical examination, clearly rule out restoration of fitness for release into the wild are only radiologically examined under anaesthesia or post-mortem, if an X-ray is needed for scientific interest.
If work is still done using the old method with X-ray cassettes rather than digitally, the cassettes should be placed directly on the X-ray table to keep the distance from object to film as small as possible. The film-focus distance should be 100 cm. X-ray cassettes of size 13 x 18 cm, for panoramic images 18 x 24 cm, can be used and divided into two halves by defocusing if needed. Depending on the X-ray equipment used, exposure values between 42 KV/10 mAS and 42 KV/12.6 mAS or between 45 KV/8 mAS and 50 KV/12 mAS have proven suitable. For X-ray images of patients at the Swift Clinic, in earlier years a film-screen system consisting of green-sensitive medical X-ray film from Agfa-Gevaert, "Perutz Radiolix G Plus" was used, and intensifying screens were employed to reduce radiation dose and achieve shorter exposure times. Digital X-ray is now used.
Indication
In the following cases, a radiological examination of the swift foundling is a necessary indication and must therefore be performed:
- in swifts with visibly asymmetrical wing posture and/or incongruent wing beat,
- in swifts with macroscopically and/or palpatorily recognisable defects of the wings or shoulder girdle (instability, crepitation, swelling, haematoma, open wounds),
- in swifts with lameness, paralysis, stiffness of the wings that cannot be classified during clinical examination.
In the following cases, a radiological examination of the foundling appears helpful and should be performed if possible:
- in swifts with flaccid paralysis of the legs,
- in fledged young swifts found on the ground,
- in young swifts with a history of severe and/or prolonged malnutrition.
Swifts in which the experienced veterinarian can already clearly, obviously and without the need for further examinations rule out restoration of fitness for release during the clinical examination should no longer be X-rayed intra vitam to spare them pointless suffering.
X-ray Technique
The following four types of images have proven effective for radiological examination of swifts:
1) The dorso-ventral overview image
This projection, tested at the Swift Clinic since 1999, specially suited for swifts and very well proven, is used to display obvious defects of the shoulder girdle without any fixation and without stress for the bird. The beam path runs dorso-ventrally.
The overview image, in its present form probably only usable for swifts, enables quick and stress-free assessment of the shoulder girdle without disturbing the bird through restraint measures. A cassette of format 13 x 18 cm, marked with side indicators, is fully collimated, covered with a piece of cellulose or kitchen paper and the swift is placed on it without restraint. Usually the moment of surprise, when the bird looks around curiously, is enough to create a dorso-ventral overview image whose perfect positioning results naturally from the posture of the swift sitting in prone position. Shoulder girdle fractures are usually very well visible in this way; limb defects are not always reliably assessable due to possible superimposition with the feet.
2) Limb representations in the two standard planes
When radiologically examining the wings, taking two images at a 90° angle to each other is mandatory and absolutely essential for diagnosis. If X-ray images of the legs appear necessary, the same procedure is followed. Wing images are always taken in medio-lateral and caudo-cranial beam paths, leg images analogously in ventro-dorsal and medio-lateral beam paths.
Limb representations in the two standard planes can be performed by the examiner alone on the non-sedated swift. For the medio-lateral image of the wing, the bird is held with one hand over the chest, the other hand maximally extends the affected limb. Then the caudo-cranial plane is projected on the second half of the plate. For this, the examiner holds the bird upside down and vertically over the plate, so that it lies with its throat on the plate, head bent back into the neck. The affected wing is extended with the second hand and held as close to the plate as possible.
The representation of the hind limb is analogous, however, manual extension of the affected limb is omitted here, as the swift's leg is too short to place the examiner's fingers outside the central beam. Fractures are usually well recognisable even without abducted limb. If extension is still necessary, it can be done using a rubber band looped around and tightened on the leg.
3) Images in ventro-dorsal and latero-lateral
This standard radiological examination for pet bird patients is rarely required for swifts. It serves to examine and assess the internal organs. The cassette is placed perpendicular to the examiner on the table. The ventro-dorsal image is taken on the lower half, the latero-lateral on the upper half. For assessing shoulder girdle defects, the latero-lateral image is superfluous. A ventro-dorsal projection of the shoulder girdle area with maximally spread wings is necessary. If required, the second half of the cassette is needed for a special positioning to clarify a dislocation of the articulatio sternocoracoidea.
For the ventro-dorsal image, the non-sedated bird is placed in supine position on the defocused lower half of the cassette. The left hand fixes the head, the right hand extends the feet. Then the animal is brought into left lateral position on the now defocused upper half of the cassette for the latero-lateral image. Both wings are placed on top of each other and extended dorsally. With the edge of the left hand, the examiner holds the wings on the cassette and simultaneously grasps the head with thumb and index finger. The right hand pulls the superimposed feet in the ventro-caudal direction.
For a ventro-dorsal image with maximally spread wings, a second person is needed. Again, the bird is fixed in supine position as described above. The second person, standing opposite the examiner on the other side of the X-ray table, simultaneously grasps both wings as far proximally as possible and extends them maximally.
A special positioning can be helpful to clarify a luxatio articulatio sternocoracoidea: After the first image with abducted wings, a second is taken on the upper part of the cassette, with the shoulder girdle area tightly focused. The examiner grasps the bird lying on its back at the carpal joints and pushes both wings medially and caudally simultaneously against the body. The leverage effect achieved thereby displaces a coracoid dislocated from the sternum, often not visible in a normal ventro-dorsal image, clearly over the median. Both imaging techniques can be performed quickly and safely on the non-sedated swift with some practice.
4) The Panoramic Image
This serves for an overall view of the internal organs and the locomotor system in ventro-dorsal positioning with spread wings and is only possible on the sedated or dead swift. A cassette in format 18 x 24 cm is required. This type of image is rarely required and of little relevance in daily handling of swift patients.