Contributors: Fraser McConnell

 Species: Feline   |   Classification: Miscellaneous

Introduction

Overview
  • Radiography allows evaluation of liver size, position and shape. Severe liver dysfunction may be present with a normal appearing liver.
  • Biopsy is usually required for definitive diagnosis of liver disease.
  • See radiography: abdomen   Radiography: abdomen  for details of positioning technique.

Radiographic considerations

  • 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.
  • Care should be taken to include the entire liver on the radiograph as the cranial portion is easily missed.

Restraint

  • Sedation is sufficient to restrain most patients in lateral recumbency for standard procedures.

Care with the use of sedative drugs which are metabolized by the liver if dysfunction is suspected.

Indications

  • Palpable hepatomegaly   Hepatomegaly  .
  • Cranial abdominal pain.
  • Raised liver enzymes.
  • Jaundice.
  • Hepatic encephalopathy   Hepatic encephalopathy  .
  • Weight loss.
  • Hypoproteinemia   Hypoproteinemia  .

    Radiography is of little value in the presence of ascites.

    Radiographic anatomy

  • The liver is bounded by the diaphragm cranially   Abdomen: normal - radiograph lateral  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 and should be parallel to the intercostal spaces.
  • 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, located between the quadrate and right medial liver lobes. In fat cats the gall bladder is seen extending ventral to the liver as faint, ill-defined and soft tissue opacity.
  • The margins of the liver should be smooth and should form a relatively sharp angle (<30°).

Interpretation

  • It is important to evaluate the entire radiograph as other features associated with conditions affecting the liver may be seen:
    • Enlarged pericardial shadow could be associated with pericardioperitoneal diaphragmatic hernia.
    • An enlarged caudal vena cava due to right-sided cardiac failure may cause hepatomegaly and ascites.
    • The right kidney lies caudal to the caudate lobe and may be caudally displaced with hepatomegaly. In cats the right kidney is further caudal than in dogs and renal displacement is uncommon with hepatomegally.

Size

Assessment of size

  • Marked enlargement or reduction in liver size are reliable features of liver disease.
  • The liver size is most easily assessed by evaluation of the gastric axis on a lateral projection. In normal cats the gastric axis varies between perpendicular to the spine and parallel with the ribs   Abdomen: normal - radiograph lateral  .
  • 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 cats appears relatively larger than that of adults due to lack of mineralization of costal arches.

  • In cats the liver often appears to protrude well beyond the costal arch due to stretching of hepatic ligament.
  • A large falciform ligament may make the liver appear small.
  • A distended gallbladder may mimic a right-sided hepatic mass.

Signs of enlargement

  • Generalizedhepatic enlargement   Liver: portal hypertension - radiograph lateral  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

  • 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   Pelvis: malunion and obstipation - radiograph VD  .
  • The stomach is displaced cranially and sits within the costal arch and the pylorus is displaced cranially resulting a cranially displaced gastric axis.
  • The small intestines may sit within the costal arch in severe cases.
  • The caudoventral margin often appears truncated.

Position

  • The liver position varies with the stage of respiration and moves caudally during inspiration.
  • A fat-filled falciform ligament causes the liver to appear dorsally displaced on the lateral projection.

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.

Opacity

Decreased opacity

  • 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.
  • 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.

Increased opacity

  • Mineralization of the liver is uncommon but may occur as an incidental finding .
  • Dystrophic mineralization secondary to hematoma, cyst, abscess, neoplasia or chronic inflammation may occur.
  • Vascular and biliary mineralization are occasionally encountered.
  • Biochemical testing   Liver function assessment  is required to assess significance and biopsy may be required to find the cause.
  • Choleliths are usually non-radiodense are and often incidental findings rarely opaque. Usually in the gall bladder but are reported in bile ducts.

Appearance

  • The margins of the liver should be smooth.
  • Knobbly margins may be associated with nodular hyperplasia, neoplasia, abscess, cysts or cirrhosis.

Additional studies

Ultrasonography
  • Is extremely valuable in investigation of liver disease.
  • See Ultrasonography: liver for further details   Ultrasonography: liver  .

Contrast studies

  • 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.

Scintigraphy