Page 400 - Atlas of Small Animal CT and MRI

390 Atlas of Small Animal CT and MRI

Primary malignant bone tumors commonly involve (Figure 4.1.11). Visceral enhancement occurs following
the ribs and rarely arise from the sternum. Osteosarcoma contrast medium administration unless strangulation
is the most common of the primary bone tumors to inhibits blood flow.
affect the ribs, followed by chondrosarcoma, and they
frequently arise at or near the costochondral junction. Peritoneopericardial diaphragmatic hernia
2–5
These masses have an expansile appearance on CT A description of peritoneopericardial diaphragmatic
images, with mixed destructive and productive compo- hernia can be found in Chapter 4.4.
nents (Figure 4.1.8). Depending on size, masses can
encroach on, displace, or envelop adjacent ribs. Masses Hiatal hernia
can enhance on CT images following contrast adminis- Hiatal hernias include simple sliding hernias as well as
tration, although enhancement may appear to be limited less common paraesophageal hernias. Both dogs and
6
if the mass margins do not extend beyond the bone cats are affected, and English Bulldogs and Chinese
proliferative response. Shar‐Pei dogs are predisposed. Although hiatal her-
7–9
Rib metastasis occurs frequently enough that close nias are routinely diagnosed using other imaging tech-
inspection of the ribs should be a part of every thoracic niques, such as fluoroscopy, they are occasionally seen in
(pulmonary) metastasis CT examination. Rib metastases patients undergoing thoracic or abdominal CT for other
usually have an aggressive mixed destructive and pro- reasons. The cranial displacement of the cardiac region
ductive appearance on CT images, with destruction often of the stomach through the esophageal hiatus leads to a
being the predominating component (Figure 4.1.9). characteristic stellate pattern produced by the gastric
rugal folds on transverse CT images (Figure 4.1.12).
Diaphragm On long‐axis images, the gastroesophageal junction is
displaced cranially.
The normal diaphragm is not well delineated from adja-
cent liver on unenhanced CT images, except for the dor- Gastroesophageal intussusception
sal diaphragmatic crura near their insertion on the
ventral aspect of the cranial lumbar vertebral bodies. Hiatal hernias must be distinguished from caudal esoph-
ageal masses and another rare disorder, gastroesopha-
Diaphragmatic hernia geal intussusception. In these patients, the stomach
Congenital diaphragmatic hernia is uncommon and is everts as it migrates through the gastroesophageal junc-
characterized by discontinuity of the diaphragm due to tion into the esophageal lumen (Figure 4.1.13).
incomplete fusion of its components, which can lead to
abdominal visceral migration into the thoracic cavity. A Inflammatory disorders
similar abnormality may occur with the loss of structural Phrenitis (diaphragmitis) can occur by extension of
integrity of the central tendon of the diaphragm, which pleuritis or peritonitis. Cross‐sectional imaging features
results in a thin distensible membrane within which of phrenitis and phrenic abscess have not been reported.
abdominal viscera can be displaced. Traumatic diaphrag- Rigid linear gastric foreign bodies occasionally penetrate
matic hernia results from muscle or tendinous tears. the stomach wall and diaphragm (see Figure 5.4.4).
The CT appearance of traumatic diaphragmatic her- Clinical signs in these patients are usually referable to
nia depends primarily on the size of the defect and the the thorax, liver, stomach, or peritoneal cavity.
specific abdominal viscera displaced into the pleural
space. Imaging features include the presence of solid and Neoplasia
hollow viscera in the thoracic cavity, pulmonary atelec- Primary neoplasms of the diaphragm are rare, and cross‐
tasis, and cardiac displacement. The liver is frequently sectional imaging features have not been reported.
herniated because of its position relative to the central Malignant neoplasms do metastasize to the diaphragm,
tendon (Figure 4.1.10). The omentum, stomach, small but in our review of CT imaging studies of patients with
bowel, and spleen may also herniate, resulting in a more confirmed diaphragmatic metastatic disease, imaging
complex pattern of attenuation of the herniated contents findings are ambiguous or unremarkable.

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