Page 307 - Veterinary diagnostic imaging birds exotic pets wildlife

CHAPTER 26 III Rabbits 303

immediate need to know, a chest drain may be used to Tumors
remove the fluid and the rabbit radiographed again.

Postural radiography can be used under such circum- Lung Tumors. In the advanced stages of development

stances; specifically, a lateral projection, using a hori- when individual tumors are coalescing with their neigh-

zontal x-ray beam, with the hind quarters elevated to bors, it can be difficult or impossible to differentiate

move the fluid to the cranial portion of the chest cavity any individual lesions. Instead, the lung appears con-
may result in better visualization of the diaphragm. solidated, much as it might with a severe pneumonia
Occasionally, one or more large cranial vessels are or abscess (Figure 26-23).
ruptured and spill their contents in the mediastinal

space. Confined by the interior pleura, the loculated Abdominal Tumors. As with many secondary lung
blood behaves like a mass, displacing the heart cau- tumors, abdominal tumors are often associated with
dally and potentially compressing the trachea (Figure large volume transudates, which swell the abdomen,
26-18). displace organs, and generally obscure the visceral
content as shown in Figure 26-23. In such situations,
ultrasound often reveals what is otherwise hidden in
III INFECTIONS radiographs (Figure 26-24).
Some abdominal tumors, for example, uterine car-
cinomas, may become mineralized, making their ra-
Middle Ear, Facial, and Jaw Infections
diographic detection quite straightforward (Figure
Rarely, chronic middle ear infections can lead to bone 26-25).

formation in the normally air-filled bullae, in some
instances completely opacifying the chamber. One or Common Abdominal Disorders
both ears may be affected (Figure 26-19). If both ears
are affected, the heightened density may be judged The Normal Rabbit Abdomen. The principal infl u-
normal because it is present on both sides. Thus the ences on the appearance of the normal rabbit abdomen
value of a normal comparison radiograph becomes are (1) the amount of peritoneal fat and (2) the volume
obvious. of air in the gastrointestinal tract. A large amount of
Occasionally, middle ear infections may spread from fat can substantially degrade abdominal detail, often
their point (or points) of origin to other parts of the leading to the misimpression of peritoneal fl uid. The
head, such as the face and jaw, and as in the previous visceral displacement caused by large abdominal fat
case, lead to large deposits of extensively mineralized accumulations (fat depots) can be particularly decep-
tissue (Figure 26-20). tive, creating the illusion of a mass, called a mass
Clearly, both of these cases are not just obviously effect.
abnormal, they are visually spectacular. Although the
viewer may not know the precise cause (or causes) Fat Depots. Abdominal fat depots are situated beneath
of these changes, it is blatantly clear that the bullae and behind the liver (sometimes referred to as falci-
are not normal. However, it is important to recognize form fat), around both kidneys, and about the urinary
that these are exceptional radiographic fi ndings. The bladder. In a female, substantial amounts of fat sur-
vast majority of rabbits with middle ear infections round the ovaries and uterus. The more fat there is in
appear entirely normal: no wall thickening, no these locations, the less room there is for the adjacent
increased chamber density, and no mineralization. The viscera. Thus crowding occurs, which in turn leads to
radiographic reality is that most infected bullae, even decreased abdominal detail, along with its attendant
those infected for months or even years, appear entirely diagnostic implications.
normal when radiographed.
Gastrointestinal Air Accumulations. Medium to
large volumes of air, especially within the stomach,
create a substantial mass effect that characteristically
Lung Abscesses
displaces the bowel mass caudally. As with large fat
Rabbits can develop some enormous lung abscesses, depots, this type of displacement crowds the intestine
often the result of a chronic Pasteurella pneumonia. (including the cecum) into a smaller area of the peri-
Some of these are solid, and others are cavitated, some- toneal cavity, with a resultant increase in superim-
times extensively. A typical lung abscess involves position, greater overall regional density, and a
most or all of a single lung lobe, usually increasing its commensurate reduction in visceral detail.
volume in the process. Those that involve the cranial
or middle lobes typically displace the heart and trachea Hairballs
to the opposite side of the chest (Figure 26-21). Caudal
lobe abscesses typically form silhouette signs (organ Hairballs are a fact of life where rabbits are concerned.
overlap) with the adjacent heart and diaphragm, as Large amounts of hair in the stomach may interfere
well as causing bronchial displacement (Figure 26-22). with emptying, leading to distention and discomfort.
Affected rabbits often do not appear that ill. Text continued on p. 310.

2/11/2008 11:12:56 AM
ch026-A02527.indd 303 2/11/2008 11:12:56 AM
ch026-A02527.indd 303