Diagnostic imaging and endoscopy

image of Diagnostic imaging and endoscopy
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Diagnostic imaging can be an important clinical tool in the investigation of disease in ornamental fish. Radiography and ultrasonography are commonly performed by veterinarians, and the same basic techniques used in small animal medicine can be used with fish. This chapter covers radiography, ultrasonography, advanced imaging techniques and endoscopy.

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Figure 14.1 Radiography of a fish, using a portable equine X-ray unit. This enables radiographs to be taken on site, close to the fish’s facility. The fish is in right lateral recumbency and the radiographic cassette is wrapped in a clear plastic bag to prevent damage from water and salt.
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Figure 14.2 The normal radiographic anatomy of koi fish. The skeletal features are readily visible, as are the two chambers of the swim-bladder (arrowed). The coelomic organs occupy the poorly defined area below the swim-bladder. (© W.H. Wildgoose.)
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Figure 14.3 Lateral skull radiograph of a koi. Koi and some other cyprinids have pharyngeal teeth (arrowed), which are clearly visible on the radiograph.
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Figure 14.4 Lateral radiograph of a surgeonfish. Barium sulphate was administered by gavage to help to delineate the gastrointestinal tract. A thin linear radio-opaque piece of metal wire (arrowed) is present in the mid-caudal coelomic area. Following ingestion, this perforated the intestines and caused a coelomitis.
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Figure 14.5 Ventrodorsal radiograph of a cownose ray. Barium sulphate was administered to outline the gastric mucosal folds. The air-filled spiral colon can also be visualized adjacent to the stomach.
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Figure 14.6 A goldfish with rupture of the posterior chamber of the swim-bladder. Free gas is present within the body cavity and caused significant buoyancy disturbance. The anterior chamber was full of fluid, which is visible as a homogeneous area, but the cause is unknown. (© W.H. Wildgoose.)
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Figure 14.7 A koi with extensive pathological change in the vertebrae that caused a progressive rigidity of the spine. The cause was not identified but was suspected to be of a metabolic origin. (© W.H. Wildgoose.)
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Figure 14.8 A koi with a large intracoelomic tumour. A large homogeneous tissue mass is visible in the caudal part of the body cavity and there is some displacement of the swim-bladder. (© W.H. Wildgoose.)
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Figure 14.9 Lateral radiograph of a French angelfish. There is good detail of the skeletal anatomy and swim-bladder but a distinct lack of contrast of the soft tissue organs.
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Figure 14.10 Lateral radiograph of a French angelfish that was exhibiting abnormal buoyancy. There is increased radio-opacity of the swim-bladder. A severe granulomatous disease of the swim-bladder and kidneys was found during the postmortem examination.
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Figure 14.11 Ultrasound scanning of an African cichlid. The patient has been sedated and is held in a bath with a maintenance dose of anaesthetic agent. Due to the small size of the fish, the probe is held at some distance to the animal, thus allowing the water to act as an echolucent stand-off.
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Figure 14.12 Cardiac ultrasound examination of a grouper. Percutaneous image acquired by placement of the probe on the ventral area, just between the base of the pectoral fin and the operculum.
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Figure 14.13 Cardiac ultrasound examination of a grouper. In species with very thick scales, a better cardiac image can be obtained by lifting the operculum and placing the probe just beneath the gill arches.
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Figure 14.14 Trans-oesophageal ultrasound imaging provides excellent detail of the heart, liver, gastrointestinal tract and occasionally the gonads. A 5.0 MHz linear equine rectal probe is being used in this grouper.
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Figure 14.15 Cardiac ultrasound image in a grouper using the trans-oesophageal method. In this long axis view, the thin-walled atrium (a), the thick-walled ventricle (v) and the fibroelastic sinus venosis (sv) are clearly visible. In real time, the AV valve can be seen closing with each ventricular contraction.
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Figure 14.16 Ultrasound image of the eye of a grouper. From the top of the image to the bottom, the following structures can be identified: cornea, anterior chamber, iris, lens, vitreous humour and retina. Ultrasonography can be an excellent diagnostic tool for evaluating the causes and extent of exophthalmos in fish.
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Figure 14.17 Ultrasound image of a koi with abdominal distension. A large amount of coelomic fluid with a polycystic mass attached to the body wall by a fibrin tag can be seen. Exploratory surgery revealed an undifferentiated carcinoma.
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Figure 14.18 Facilities for CT scanning of fish. The patient was anaesthetized and placed in lateral recumbency on foam blocks within the container, which was partially filled with a maintenance dose of anaesthetic.
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Figure 14.19 A mid-body cross-section CT image of a koi. The fish was scanned while part submerged in anaesthetic solution. This demonstrates the vertebral body, swim-bladder and a large coelomic mass. (Courtesy of Michele Miller and Don Neiffer.)
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Figure 14.20 A sagittal plane image of the fish in Figure 14.19, showing that the mass occupies much of the body cavity. (Courtesy of Michele Miller and Don Neiffer.)
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Figure 14.21 Endoscopic examination of an archerfish. In most cases, a midline ventral approach is used but here a lateral approach improves visualization of the swim-bladder and adjacent organs.
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