Diagnostic Imaging

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RATITES

DIAGNOSTIC IMAGING Jamie Williams, MS, DVM

In many respects, diagnostic imaging, including radiography and ultrasound of ratites, will have to develop to attain the diagnostic capability currently used in food animal species. Although the portable radiography units common to mobile mixed animal practices may provide diagnostic images of the wings or the legs distal to the femorotibial joint of emus and ostriches, this equipment is not sufficiently powerful to penetrate the muscular upper portions of the legs. Nor are they powerful enough to penetrate the cranial or caudal body cavity. These areas require a radiography unit capable of an output of 300 rnA or higher. Ultrasonography of ratites has been infrequently documented in the veterinary literature. RADIOGRAPHY

As with all radiographic investigations, two orthogonal views (views at 90° angles to each other) are necessary to fully evaluate a body part or cavity. In ratites, this is accomplished with a lateral and a dorsoventral view of the coelomic cavity. If an extremity (leg or wing) is evaluated, a lateral view and either a craniocaudal or caudocranial view, with appropriate diagnostic obliqued views, constitute a complete study. General anesthesia or sedation should be considered in order to obtain high-quality radiographs. Wing fractures may occur secondary to improper handling. l l Leg fractures are common in commercially raised ratites. l l As with all species, fractures of the long bones are easily diagnosed. Fractures of the

From the Department of Veterinary Radiology, Louisiana State University School of Veterinary Medicine, Baton Rouge, Louisiana

VETERINARY CLINICS OF NORTH AMERICA: FOOD ANIMAL PRACTICE VOLUME 14' NUMBER 3 • NOVEMBER 1998

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lower extremity are often open, communicating with the outside environment and leading to infection.ll Those of the upper extremity may result in significant hemorrhage, leading to exsanguination of the patient. ll The femur is the only pneumatic long bone in ratites. 4, 5, 13 This might suggest that fracture of the pneumatic portion of the femur could result in subcutaneous emphysema in an otherwise closed fracture. Osteomyelitis often affects the distal aspect of the pelvic limb in ratites, usually following injury to the lower legs caused by gates or fences. 9 Osteomyelitis and septic arthritis ll have been diagnosed radiographically in an ostrich (Fig. 1).2 Osteochondritis has been radiographically diag-

Figure 1. Dorsoplantar radiograph of the foot of a lame ostrich. Note the destruction of the distal interphalangeal joint space and the destruction of the distal one half of P2 in the main digit. (From Burba DJ, Tully TN, Pechman RD, et al: Phalangeal amputation for treatment of osteomyelitis and septic arthritis in an ostrich (Struthio came/us). J Avian Med & Surg 10(1):19-23, 1996; with permission.) Figure 2. Caudocranial radiograph of the distal tibiotarsal bone of a lame ostrich. The subchondral bone defect (arrow) is diagnostic of osteochondrosis. (Copyright: Jamie Williams, MS, DVM; with permission.)

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nosed in the stifle of a lame ostrich (Fig. 2). Radiography of the extremities is recommended in cases of suspected trauma. Radiography was used to diagnose exertional myopathy in an emu.13 Fracture was excluded in this case of accidental trauma in a confined bird, although soft tissue swelling and subcutaneous free air were noted on radiographic examination. Angular limb deformity may occur in immature ratites. 5 Radiography may be used to define the origin of the deformity and may contribute to appropriate therapy. Sequential radiographs can be used to monitor progress and guide decisions on removal of external coaptation. Proventricular and ventricular impaction is common in ratites, especially immature birds or those moved to a new pen, relocated, or provided with a different substrate. Impaction may result from ingested

Figure 3. Dorsoventral abdominal radiograph of an ostrich. Rocks and metallic buttons (arrows) are visible within the proventriculus, and the fibrous character of the rest of the ingesta suggests fibrous material impaction. (Copyright: Jamie Williams, MS, DVM; with permission. )

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sand, rocks, fibrous vegetation, or as a result of ingestion of metallic or other foreign bodies. 7, 11 Reports in the veterinary literature suggest that radiographic diagnosis of impaction is only possible when the impaction is owing to radiopaque material such as sand, rocks, or metal. 7 Reference to normal radiographic anatomy will reveal impaction caused by cloth, vegetation, or matted fibrous material (Fig. 3). Ratites have the tendency to ingest any novel or unusual object. This predilection, coupled with their keen eyesight, may explain the presence of unusual foreign bodies that may be diagnosed radiographically in the ventriculus (Fig. 4). Gastrointestinal foreign bodies may not be responsible for the clinical signs on presentation, but may lead to subsequent impaction. Bacterial and mycotic infections are relatively prevalent in ratites,11 especially in immature birds. Pneumonia or air sacculitis may result from bacterial or mycotic infection. Aspergillosis produces granulomatous

Figure 4. Dorsoventral abdominal radiograph of an ostrich. Notice the distinctive appearance of the cigarette lighter (arrow) within the proventriculus. (Copyright: Jamie Williams, MS, DVM; with permission.)

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plaques or nodules throughout the lungs11; radiography is suggested for the diagnostic evaluation of either mycotic 1o, 11 or bacterial pneumonia 11 and to assess the response to treatment. Reproductive dysfunction is documented in commercially reared ratites. Stewart estimated that 50% of the eggs produced by ratites in the United States during 1994 were infertile. Radiography has been used to diagnose diseases of the reproductive tract. 6,11 Hicks suggested that radiography is useful to determine the quantity of oviductal exudate in cases of salpingitis. 6 Radiography has been used to diagnose egg retention (Fig. 5)/6,8,11 especially when the egg is soft-shelled or cannot be palpated in the caudal coelomic cavity. Ovarian tumors have been reported in avian species other than ratites. Radiography could demonstrate a neoplastic ovary or kidney as a mass occurring in the left ventral synsacral region. Peritoneal hernias occur in the caudal coelomic cavity of ratites. 6 , 11 This may be attributed to the violent exertions of these birds during

Figure 5. Dorsoventral radiograph of the caudal abdomen of a ratite. Notice the mineralized shell of the retained egg. (Copyright: Jamie Williams, MS, DVM; with permission.)

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capture, handling, or fighting. There is a distinct lack of muscle tissue on either side of the linea alba in ratites. 13 Radiography may be a diagnostic aid, especially if the intestine prolapses into the pericloacal region. 4 ULTRASONOGRAPHY

Reports in the veterinary literature relate to the application of diagnostic ultrasonography for diseases of the reproductive tract,6,8 peritoneal hernia,6 egg binding,6,8 proventricular or ventricular impaction, and neoplasiaY In common with radiography, a thorough knowledge of anatomy is essential to localize and identify specific organs and possible abnormalities. There is little information in the literature concerning the normal sonographic characteristics of ostriches and emus. Ultrasonography of the internal organs and soft tissues may be accomplished with relative ease. The larger feathers may be parted and the smaller down feathers plucked to provide access to the skin surface for transducer (probe) placement. Acoustic coupling gel must be applied to the skin surface to provide a smooth transition of the mechanical (sound) energy from the transducer through the skin and into the underlying tissues. Application of acoustic coupling gel allows the sound to be transmitted with little or no loss of signal or strength of signal between the transducer and the skin surface. Normal emu sonographic anatomy has been documented and compared to magnetic resonance images in the same bird to confirm correspondence. 12 Depressed patients may remain in sternal recumbency or be positioned laterally for the sonographic examination. Anesthesia greatly facilitates examination of nondepressed birds, which resent handling or restraint and become agitated. Avian species overinflate their air sacs when stressed. This can prevent effective ultrasonographic examination, as sound does not penetrate air. Anesthesia is recommended if biopsy samples are to be obtained using ultrasonography to guide the operator. TOPOGRAPHICAL ANATOMY

The lungs and air sacs of ostriches and emus are similar to flighted avians/ although the capacity of the air sacs is diminished in ratitesY These structures may pose a barrier to sonographic imaging of certain anatomical structures (heart, kidneys, bowel, spleen, reproductive organs), especially if the patient is excited or agitated. The pubic bones of the ostrich are joined to form a solid ventral bony floor.4, 5, 11 This presents a focal barrier to ultrasound transmission, because sound waves do not penetrate bone. The pelvic structure of the emu allows greater access for ultrasound transmission compared to the ostrich. Ratites possess a four-chambered heart4 occupying the cranioventral portion of the coelomic cavity, adjacent to the sternum between the first

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three ribs. I Air sacs extend over the dorsal aspect of the heart, 1 which may hinder intercostal echocardiography. The liver is immediately caudal to the heart, separated by a thin transverse membrane.l, 4, s, 11 The liver occupies the caudoventral aspect of the cranial coelomic cavity (within the bony thorax). The proventriculus is located dorsal to the liver. It is large and thin-walled, forming a saclike structure in the ostrich.l, 3-S, 11 The proventriculus of the emu is also large but more spindle-shaped. 3-s,11 The ventriculus is a relatively thick-walled, muscular structure located caudal and somewhat ventral to the proventriculus in the emu3-S,11 but primarily ventral to the proventriculus in the ostrich.l, 3-S, 11 The small intestine occupies most of the caudal coelomic cavity immediately caudal to the ventriculus in the emu. s, 11 Ostriches have elongated and sacculated ceca characterized by spiral folds. 1 The ceca of the emu are vestigial with longitudinal striations.3-S,l1 In the ostrich, the base of the ceca is in close proximity to the cranial pole of the right kidney.1 The large intestine of the ostrich is long l but comparatively shorter in the emu. 3-S,11 The two kidneys are located just ventral to the synsacrum, as in other birds.l, 4 Bezuidenhout describes elongated kidneys in the ostrich, measuring approximately 30 cm in length. I The spleen is elongated and oval in the ostrich and located cranial to the right kidney between the sixth and eighth ribs,t dorsolateral to the proventriculus. 4 In the emu, the spleen is cylindrical.4 Paired testes are found in males ventral to the kidneys and dorsal to the caudal coelomic air sacs. 1, 4, 6, 11 The testes enlarge during the breeding season.4, 6, 11 Stewart noted a two- to threefold increase in size,l1 whereas Hicks suggested a fourfold increase in size in ostriches during the breeding season. 6 The single left ovary is located in a similar position in females to that of the left testis in males. I , 4, 6, 11 Once sexual maturity is reached, the ovary may demonstrate multiple ovules of various sizes.4, 6, 11 SONOGRAPHIC ANATOMY

There is no muscle tissue on either side of the linea alba in ratites, which provides an adequate sonographic window for imaging the internal organs. This area extends for 19 cm on either side of the linea alba in the ostrich and begins approximately 13 cm from the sternum in the emu. 4 Prominent callosities are located over the ventral aspect of the sternum in mature ratites. Additional callosities are present over the fused pubic bones in the ostrich. 4 These thickened dermal areas are found over areas of high wear or pressure and may inhibit ultrasound transmission, and should therefore be avoided. Liver

The liver should be imaged in sagittal and transverse planes (Fig. 6). A parasternal approach provides an acceptable window to image the

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Figure 6. Sagittal ultrasonographic view of the liver, showing the gallbladder (G8) and the

hyperechoic walls of the portal vasculature. (Copyright: Jamie Williams, MS, DVM; with , permission.)

liver. The liver is sonographically similar to that seen in dogs and cats. It is slightly inhomogeneous in echotexture and presents a "cobble-

stoned" appearance. The portal veins appear to have hyperechoic walls as in small animal species. The hepatic veins appear to have no walls, because the acoustic impedance of the venous wall is similar to that of the hepatic parenchyma. The ostrich does not possess a gallbladder. The gallbladder of the emu is located in the right liver as with other species. The gallbladder should be anechoic centrally within the lumen, representing bile. The caudal vena cava is dorsal or deep to the liver. In the sagittal plane, the caudal vena cava is a tubular anechoic or hypoechoic structure passing through the dorsal aspect of the liver to the heart.

Spleen

Anatomically, the spleen is situated dorsocaudal to the liver, proventriculus, and ventriculus. Radiographically, the spleen presents a rounded soft-tissue shadow. The spleen is a difficult organ to image with ultrasound, especially with gas present in the lumen of the gastrointestinal tract or if the patient becomes agitated with resulting inflation of the caudal coelomic air sacs.

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ProventriculusNentriculus

The proventriculus is seen immediately caudal to the liver on sagittal section. Wall thickness has been measured at 1.82 to 2.59 em in emus and at approximately 1.48 em in the ostrich. Gas within the lumen produces a "ring down" artifact, commonly seen with small accumulations of gas or with mixtures of mucous and microbubbles of air (Fig. 7). Bowel

The intestinal wall measures approximately 0.28 em in thickness in emus and ostriches. Ingesta may be seen moving within the lumen during real-time examination as echo genic material. If the bowel is fluid-filled, the anechoic to hypoechoic luminal contents allow better visualization of the mucosal border of the particular loop. A corrugated appearance has been documented in the colon (Fig. 8). Kidney

The kidney is located dorsal or deep to the corrugated colon in the caudal coelomic cavity, against the synsacrum (Fig. 8). The kidney is an

Figure 7. Sagittal ultrasonographic view of the liver, demonstrating the thick walled proventriculus caudal to the liver. (Copyright: Jamie Williams, MS, DVM; with permission.)

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Figure 8. Sagittal ultrasonographic view of the right dorsal abdomen. The corrugated appearance of the colon is seen in the near field, with the sagittal image of the kidney immediately below or dorsal to it. (Copyright: Jamie Williams, MS, DVM; with permission.)

oblong echogenic structure that measures 2.35 em (emu) in thickness in the sagittal plane. The renal cortex of the emu is hyperechoic to the renal medulla, and there is approximately twice as much cortical tissue as medullary tissue on sagittal imaging. Fat or fibrous tissue of the collecting system and renal pelvis may be responsible for their hyperechoic appearance.

Reproductive Tract

The ovary is a homogenous, rounded echogenic structure in the caudal coelomic cavity (Fig. 9), imaged with the ratite in lateral recumbency and an imaging plane of ventral-left to dorsal-right. The patient should be placed in right lateral recumbency and rolled slightly up on her back. The transducer is placed in such a way that the sound beam travels from the ventrum of the animal on the left side of midline toward the right dorsal aspect of the synsacral area. The echotexture of the ovary is rather uniform, although a slight "cobble-stoned" appearance has been noted. Ovules of various size may be visualized in mature females during the breeding season.

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Figure 9. Sonographic image of the ovary, demonstrating the rounded appearance. (Copyright: Jamie Williams, MS, DVM; with permission.)

Heart

The heart can be imaged through the liver, which serves as a sonographic window to avoid the distended air sacs (Fig. 10). The heart may also be imaged using an intercostal approach in cases where the air sacs have not been overly distended. The heart should be imaged in at least two planes, transverse and sagittal (or long-axis). The atria and ventricles are readily distinguished, and the valves are imaged with relative ease. The posthepatic caudal vena cava may be seen entering the right atrium in sagittal or long-axis view. The left ventricular free wall measured 2.4 to 2.84 cm in thickness, the right ventricular free wall measured 1.29 cm in thickness, and the interventricular septum measured 2.25 to 2.46 cm in thickness in an ostrich (Fig. 11). Ophthalmic Examination

The ostrich eye (Fig. 12) measures 41.1 mm in anterioposterior dimension. The lens measures approximately 8.1 mm in anterioposterior dimension, and the posterior lens capsule to posterior eyewall measurement is 25.7 mm. Corneal thickness in the ostrich has been measured at 3.1 mm. Cataracts, which are frequently diagnosed in ostriches, are of little clinical importance unless bilateral. l1 Removal of a cataract will not restore the vision of affected ratites if retinal detachment is concurrently

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Figure 10. Long-axis ultrasonographic view of the heart using the liver as a sonographic window (transhepatic image). The atrium and the ventricle are seen, with the A-V valve in between. (Copyright: Jamie Williams, MS, DVM; with permission.)

Figure 11. Long-axis transhepatic sonographic view of the heart, showing the right ventricle, the interventricular septum, and the left ventricle. (Copyright: Jamie Williams, MS, DVM; with permission.)

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Figure 12. Sonographic image of the ostrich eye. The posterior eyewall is designated by the arrows. (Copyright: Jamie Williams, MS, DVM; with permission.)

present. Sonographic examination is warranted prior to any attempt at surgical correction of cataracts. FNAlBiopsy

Diagnoses can be facilitated by ultrasound-guided fine needle aspiration (FNA) or biopsy of affected tissue or organs. This procedure can be completed with relative ease, once the practitioner becomes accustomed to sonographic visualization of needle placement. As with most procedures, success is improved with practice. Sonographic visualization of needle placement ensures more precise tissue sampling than that obtained with blind aspirates or biopsies. More representative samples may be obtained, and the practitioner can determine the occurrence of hemorrhage or other complications after sampling. FNA rarely precipitates complications. Ultrasound-guided liver biopsies have been obtained in ratites without complication. CONCLUSION

More research is required to document normal sonographic anatomy and measurements in ratites. The values and image appearances dis-

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cussed in this paper were obtained from a small number of patients and do not represent sampling of a large population of normal birds. These data provide a baseline from which to proceed. A portable ultrasound unit equipped with the appropriate transducer can provide on-site images of the structures in the coelomic cavity. A 300-mA or higher radiography unit located at a veterinary hospital requires the patient to be transported for radiographs. Ultrasonography is not meant to replace radiography, but rather to augment radiography in the diagnostic imaging of lesions. Portable ultrasonography may provide a preliminary on-site screening view of the structures of the coelomic cavity prior to radiography. Any disease resulting in a mass effect, especially within the caudal coelomic cavity, could be investigated by radiography and ultrasonography. Radiography can be used to narrow the list of possible organs of origin of the mass effect and would be the diagnostic procedure of choice if the coelomic air sacs are greatly distended with air. Ultrasonography would provide additional information concerning the organ of origin and the internal characteristics of the mass and would provide a means of obtaining fine-needle tissue aspirates or biopsies to further limit the differential diagnoses. In cases of neoplasia, multiorgan involvement may be demonstrated ultrasonographically. Radiography of ratite species requires equipment of adequate power to penetrate the body and upper legs and a thorough knowledge of ratite anatomy. Ultrasonography of ratite species requires an appropriate transducer, a thorough knowledge of ratite anatomy, and an understanding of basic ultrasound physics in order to interpret the changes in echogenicity and how they relate to possible disease.

References 1. Bezuidenhout AJ: The topography of the thoraco-abdominal viscera in the ostrich (Struthio camelus). Onderstepoort J Vet Res 53:111-117, 1986 2. Burba DJ, Tully TN, Pechman RD, et al: Phalangeal amputation for treatment of osteomyelitis and septic arthritis in an ostrich (Struthio camelus). J Avian Med & Surg 10(1):19-23, 1996 3. Cho P, Brown R, Anderson M: Comparative gross anatomy of ratites. Zoo Biology 3:133-144, 1984 4. Fowler ME: Comparative clinical anatomy of ratites. J Zoo & Wildlife Med 22(2):204227, 1991 5. Fowler ME: Clinical Anatomy of Ratites: In Fowler ME (ed): Zoo & Wild Animal Medicine. Philadelphia, WB Saunders, 1993, pp 194-198 6. Hicks KD: Ostrich Reproduction. In Fowler ME (ed): Zoo & Wild Animal Medicine. Philadelphia, WB Saunders, 1993, pp 203-206 7. Honnas CM, Blue-McLendon A, Zamos DT, et al: Proventriculotomy in ostriches: 18 cases (1990-1992). J Am Vet Med Assoc 202(12):1989-1992, 1993 8. Honnas CM, Jensen JM, Blue-McLendon A, et al: Surgical treatment of egg retention in emus. J Am Vet Med Assoc 203(10):1445-1447, 1993 9. Jensen JM: Infectious and Parasitic Diseases of Ratites. In Fowler ME (ed): Zoo & Wild Animal Medicine. Philadelphia, WB Saunders, 1993, pp 200-203

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10. Marks SL, Stauber EH, Emstrom SB: Aspergillosis in an ostrich. J Am Vet Med Assoc 204(5):784-785, 1994 11. Stewart J: Ratites. In Ritchie BW, Harrison GJ, Harrison LR (eds): Avian Medicine: Principles and Application. Lake Worth, Florida, Wingers Publishing, 1994, pp 12841326 12. Tully TN, Hillman D, Williams J: Anatomic examination of an emu (Dromauis novaehollandiae) using diagnostic imaging techniques and anatomic cross-sections. In Proceedings: Association of Avian Veterinarians, Philadelphia, 1995, pp 313-315 13. Tully TN, Hodgin C, Morris JM, et al: Exertional myopathy in an emu (Dromaius novaehollandiae). J Avian Med & Surg 10(2):96-100, 1996

Address reprint requests to Jamie Williams, MS, DVM Dept. Veterinary Clinical Sciences School of Veterinary Medicine Louisiana State University Baton Rouge, LA 70803