ISRAEL JOURNAL OF
VETERINARY MEDICINE
ULTRASOUND IN PET BIRDS
Hochleithner C.
Tierklinik Strebersdorf Mühlweg 5 1210 Vienna, Austria
Summary
This paper provides an overview of the possibilities and the
limiting factors when performing ultrasound as a diagnostic
tool in pet birds at the clinic.
Key words: Ultrasound, Pet Birds, Air Sacs, Anesthesia.
Introduction
In exotic animal medicine ultrasound is a very helpful and stress-free tool for
investigation and diagnosis, alongside more invasive techniques like blood
chemistry or endoscopy (1,2,3). Some problems may occur while performing an
ultrasound scan in pet birds due to the size of the bird and its anatomical and
physiological features. A clinician must therefore consider carefully whether or
not to use this procedure on a sick bird.
Material and Methods
In our clinic we use the AU3 Partner from Esaote Biomedica with a 5/7.5 MHz
convex transducer and a 7.5/10 MHz linear transducer using the B-mode. Images
are documented using a mini-DV recorder or by videoprinter (4). Most of our
birds, especially psittacines, are put under isofluran anesthesia provide a stressfree investigation. Birds are positioned either in lateral or ventral recumbency;
and if there are severe respiratory or cardiac problems the birds are either
positioned in an upright position or not scanned at all. The feathers in the contact
area are either parted or plucked. If acoustic stand-off is necessary we use either
commercially available pads or investigation gloves filled with acoustic coupling
gel (5). The acoustic windows are especially very small in small birds,. The
midline approach is situated caudal of the processus xiphoideus and cranial to the
pubic bones for the cranial abdominal cavity, and between the pubic bones for
the cloaca. The lateral acoustic window is located behind the last rib on the right
side. Some veterinarians perform transintestinal approaches with specific
transducers (6,7). For getting a better image it is helpful to fast the birds for at
least three hours (up to 48 hours in birds of prey!).
Ultrasound investigation is indicated in birds with: abdominal enlargement,
radiographical findings which show abdominal masses, suspected internal
disorders based on laboratory results, and any kind of tumor. Birds with egg
binding, with soft shelled or laminated eggs have also been diagnosed using
ultrasound.
Results
The air sac system is the main limiting factor for using ultrasound in birds.
Therefore we have only very small acoustic windows under normal conditions
(8,9).
The first organ which can be investigated from the midline is the liver with its
two lobes. Normally the pattern of the liver is homogenous, slightly granulated
with average echogenity. The gallbladder lies as an anechoic round or oval
structure on the dorsal side of the right lobe (except in Psittacines and
Columbiformes which do not have a gallbladder). The size of the liver is
individually variable, but if the liver reaches caudal to the xiphoid it is possible
that there is hepatomegaly. If the gastrointestinal tract is filled with food and gas
or the proventriculus is enlarged it is very difficult to get a clear image of the
liver. In birds with ascites the shape of the liver can be determined.
Parenchymal changes can be either focal or diffuse. The most common
parenchymal alteration is fatty liver degeneration with higher echogenity, and
hepatomegaly. Focal parenchymal changes can be found with tuberculosis,
neoplasia, cysts and hematomata (10).
Ascites in birds, especially Mynah birds, is commonly seen with hepatopathies
(hemosiderosis). The ascitic fluids are used as an acoustic window to the internal
organs but care should be taken in scanning time due to respiratory distress of the
bird (10).
The homogenous pattern of the spleen is more echoic than the liver. The spleen
lies dorsal to the right lobe of the liver. Normally the spleen is hidden by the
proventriculus and ventriculus, therefore only an enlarged spleen is
sonographically visible.
The kidneys are difficult to scan. On the ventral side they are hidden by the
intestine and laterally by the air sac wall. If nephromegaly is present the kidneys
are sonographically visible. In contrast to mammals there is no distinction
between the renal sinus, medulla and cortex. Pathological changes are seen as
changes from low to high echogenicity. Cysts are demonstrated as round,
anechoic structures with typical distal acoustic enhancement (1).
In order to demonstrate inactive gonads it is necessary to use special high
frequency transintestinal transducers. Well-developed follicles can be seen as
anechoic round structures. In the oviduct the eggs have a typical appearance with
the yolk as a high echoic round structure surrounded by the hypoechoic albumin.
The shell can be demonstrated as a hyperechoic wall with a typical acoustic
shadow depending on the calcification of the eggshell. Egg binding with soft
shelled eggs, laminated eggs, oval or round areas with different layers of
different echogenity (onion shaped), or egg-related peritonitis are clearly visible.
Other pathological changes such as tumors of the testicles, the ovary and cystic
changes of the ovary can be imaged (6).
To get a clear image of the gastrointestinal tract ideally it should be empty or
filled with liquid, which is normally not possible under clinical conditions.
Therefore radiographs are preferable in our clinic to investigate the GI-tract. In
cases where the bird has ascites and is in good condition it is possible to
diagnosed wall changes and enlargements of the proventriculus and ventriculus
(2).
The investigation of the heart is possible from the midline using the liver as an
acoustic window. Pathological changes as hypertrophy of the heart and
pericardial effusions can be distinguished using ultrasound (3,10).
Discussion
Ultrasound is a very helpful diagnostic tool in small animal medicine. There are
also indications for using it in birds. When the radiographical findings lead to
suspected abdominal enlargements, ascites or cardiac enlargement, it may be
possible to get a diagnosis using ultrasound. There are limitations on its use in
birds: air sacs, which give a very small acoustic window to get a good view of all
organs; cooling the bird by the use of coupling gel; duration of the examination;
and also circulatory and respiratory distress. Experience of the veterinarian is
very important in order to reduce examination time as much as possible.
References
1. Enders F, Krautwald-Junghanns M.E, Dühr D. (1993) Sonographic evaluation
of liver diseases in birds. Proceedings of the European Conf. on Avian Med.
Surg. pp 155-163, 1993.
2. Nyland T.G, Mattoon J.S, Veterinary diagnostic Ultrasound. WB Saunders Co.
Philadelphia, 1995.
3. Mcmillan M.C. Imaging techniques. In: Avian Medicine: Principles and
Applications: Ritchie BW, Harrison GJ, Harrison L (ed), Wingers Publishing Inc,
Lake Worth, Florida. pp 247-326, 1994.
4. Fritsch R, Gerwing, M. Sonografie bei Hund und Katze. Enke. Stuttgart, 1993.
5. Hochleithner C., Hochleithner M. and Artmann A. Avian Imaging. In:
BSAVA Manual of Exotic Pets: Meredith A, Redrobe S (ed), Fourth Edition. pp
149-156, 2002.
6. Hildebrand T.B, Göritz F., Schnorrenberg A., Thielebein J., Heidmann D.,
Schmitt R.M., Seidel B.and Pitra C. Transintestinal sonography (TSI) in common
quail. Proceedings of the 4th Conference of the EAAV. pp26-27 1997.
7. Thielebein J, Hildebrand T.H, Göritz F Ultrasonographische Verlaufskontrolle
der saisonalen Hodenveränderungen bei Gantern während einer
Reproductionsperiode. Abstracts zum Dreiländertreffen Ultraschall ¥96. p 88,
1996.
8. Krautwald-junghanns M.E, Enders F Ultrasonography. In: Avian Medicine
and Surgery: Altmann RB, Clubb SL, Dorrestein GM, Quesenberry K (ed), WB
Saunders, Philadelphia. pp 200-209, 1997.
9. Lumeij J.T and Ritchie B.W,Cadiology, In Ritchie B.W., Harrison G.J,
Harrison L.R Avian Medicine: Principles and Applications. Wingers Publishing
Inc. Lake Worth. Florida, 1994.
10. Krautwald-Junghanns M.E., Riedel U.and Neumann W. Diagnostic use of
ultrasonography in birds. Proceedings of the Assoc. of Avian Vet. pp269-275,
1991.