Contributors: Fraser McConnell
Species: Canine | Classification: Miscellaneous
- Radiography allows evaluation of liver size, position and shape. Severe liver dysfunction may be present with a normal appearing liver.
- Biopsy Biopsy: hepatic is usually required for definitive diagnosis of liver disease.
- See radiography: abdomen Radiography: abdomen for details of positioning technique.
- Lateral projections are usually the most informative but a ventrodorsal projection is useful if there is focal liver enlargement.
- A low kVp and high mAs should be used to maximize contrast in the abdomen.
- A grid is necessary if the depth of tissue is > 10 cm.
- Care should be taken to include the entire liver on the radiograph as the cranial portion is easily missed.
- Sedation is sufficient to restrain most dogs in lateral recumbency for standard procedures.
Care with the use of sedative drugs which are metabolized by the liver in dysfunction is suspected.
- Palpable hepatomegaly.
- Cranial abdominal pain.
- Raised liver enzymes.
- Hepatic encephalopathy Hepatic encephalopathy.
- Weight loss.
- Hypoproteinemia Hypoproteinemia.
Radiography is of little value in the presence of ascites.
- The liver is bounded by the diaphragm cranially and laterally by the body wall .
- The stomach lies adjacent to the liver caudally on both projections.Stomach axis is important in assessing liver size. The lesser curvature lies adjacent to the right medial, quadrate and left middle lobes. The fundus lies caudal to the left lateral lobe.
- Dorsally the cranial pole of the right kidney sits within the renal fossa of the caudate lobe.
- The caudoventral margin on the lateral projection is composed of the left lateral (caudally) and right middle lobes (cranially). On a VD projection the cranial duodenal flexure lies caudal to the right lateral and/or quadrate lobe.
- The gall bladder is not normally visible but lies just to the right of the mid-line at the level of 10th-12th thoracic vertebrae.
- The margins of the liver should be smooth and should form a relatively sharp angle (<30°).
- It is important to evaluate the entire radiograph as other features associated with conditions affecting the liver may be seen:
- An enlarged vena cava due to right-sided cardiac failure may cause hepatomegaly and ascites.
- A pendulous abdomen, soft tissue mineralization, enlarged liver and adrenal mass may be seen with hyperadrenocorticism.
- Enlarged kidneys and uroliths may be seen with congenital portosystemic shunts Congenital portosystemic shunt (CPSS).
- Radiological features of liver disease can be divided into three broad categories:
- Diffuse enlargement:
- Focal enlargement:
- Neoplasia Liver: neoplasia.
- Nodular hyperplasia.
- Reduced liver size:
Assessment of size
- Marked enlargement or reduction in liver size are reliable features of liver disease.
- There is considerable variation in the liver size amongst normal dogs. Deep chested dogs often appear to have small livers on a radiograph with a vertical or slightly cranially rotated gastric axis.
- The liver size is most easily assessed by evaluation of the gastric axis on a lateral projection. In normal dogs the gastric axis varies between perpendicular to the spine and parallel with the ribs.
- The liver is contained within the costal arch except for the caudal margin which often lies just caudal to the last rib.
- On the VD projection the gastric axis should be perpendicular to the spine.
The liver of young dogs appears larger than that of adults due to lack of mineralization of costal arches.
Signs of enlargement
- Generalized hepatic enlargement results in caudal displacement of the stomach.
- The pylorus and gastric axis are often displaced caudally and the caudoventral border of the liver loses its sharp, pointed appearance and becomes rounded .
- On a ventrodorsal projection the pylorus may be displaced caudomedially by the right liver lobe and fundus displaced caudomedially by the left lateral lobe .
- Focal enlargement:
- Enlargement of the right lateral and right medial lobes results in caudodorsal displacement of the pylorus on the lateral projection.
- On the VD projection the fundus is positioned normally but the pylorus is displaced caudally and towards the midline .
- Enlargement of the caudate lobe may result in caudal displacement of the right kidney and results in opacity within the craniodorsal abdomen.
- Enlargement of the left medial and lateral lobes results in indentation of the lesser curvature of the stomach or caudal displacement of the fundus. On a VD projection the fundus is displaced caudomedially.
Signs of microhepatica
It is easy to misdiagnose the liver as being reduced in size in deep chested dogs.
- With reduction in liver size there is reduction in mass of the liver between the stomach and diaphragm.
- The liver may appear as a narrow crescent of soft tissue .
- The stomach is displaced cranially and sits within the costal arch and the pylorus is displaced cranially resulting a cranially displaced gastric axis.
- The spleen and small intestines may sit within the costal arch in severe cases.
- The caudoventral margin often appears truncated.
- The liver position varies with the stage of respiration and moves caudally during inspiration.
Alterations in position
- Most commonly due to traumatic diaphragm rupture.
Only part of the liver may be herniated.
- Pleural effusion, lung masses or tension pneumothorax may displace the liver caudally.
- Liver lobe torsion is very rare but may displace the liver.
- Emphysema within a torsed liver has been reported.
- Due to accumulation of gas (a very rare and significant finding).
- Gas within the gall bladder is recognized as a gourd-shaped lucency between the right medial and quadrate lobes of the liver. This is approximately cranioventral to the pylorus on a lateral projection. Gas may extend into the biliary tract. Emphysematous cholecystitis has been associated with diabetes mellitus.
- Linear gas lucencies within the portal systems may occur secondary to gastric torsion Stomach: gastric dilatation / volvulus (GDV) syndrome or severe, ulcerative enteritis and has a poor prognosis.
- Focal gas accumulations may occur due to abscess formation and infection by gas producing organisms. This can occur due to trauma becoming necrotic, secondary to hematoma formation and acute cholecystitis.
- Mineralization of the liver is uncommon but may occur as an incidental finding (YT are reportedly predisposed).
- Dystrophic mineralization secondary to hematoma, cyst, abscess, neoplasia or chronic inflammation may occur.
- Biochemical testing Liver function assessment is required to assess signficance and biopsy may be required to find the cause.
- Choleliths are usually lucent are and often incidental findings rarely opaque.
- Usually in the gall bladder but are reported in bile ducts.
- The margins of the liver should be smooth.
- Knobbly margins may be associated with nodular hyperplasia, neoplasia, abscess, cysts or cirrhosis.
- Is extremely valuable in investigation of liver disease.
- See Ultrasonography: liver for further details Ultrasonography: liver.
- These are largely redundant due to advent of ultrasonography.
- Portal venography is of value in evaluating the portal system particularly during surgery in assessing the reperfusion of the liver following ligation of shunts.