Diagnostic Imaging

• Indications for thoracic radiography

  • Cardiac problems
  • Dyspnea
  • Abnormal lung sound
• Diaphragmatic hernia


  • Serious condition with a 50% mortality rate
  • The hernia may allow the liver, stomach and/or SI to enter the thoracic cavity
  • The herniated organs are often strangulated and may release a large volume of fluid (exudate)
• Common sites where oesophageal and pharyngeal foreign bodies lodge


  • Pharyngeal side of the esophageal hiatus
  • Cranial to the thoracic inlet
  • Cranial to the base pf the heart
  • Cardia of the stomach
• Persistent right aortic archCongenital defect in the development of the aortic archesthat results to oesophagus passes to the left of the aorta instead of to the right (dextraposition of the aorta)
• Megaoesophagus Acquired or congenital dilation of caudal cervical and thoracic oesophagus and it may lead to the ventral displacement of the heart and trachea
• Mediastinal lymph nodes


  • Found in the cranial mediastinum
  • Not visible unless enlarged (e.g. in lymphosarcoma, common in cats)
• Pneumomediastinum (Mediastinal emphysema)


  • Presence of air in the mediastinal space
  • Leads to an increased radiolucency of the region contrasting the soft tissue radiopacities (oesophagus and blood vessels), and making them visible
  • The air may dissect into the retroperitoneal space, or along the fascial planes of the neck
• Displaced Trachea

  Dorsal deviation of the trachea could be due to a cranial mediastinal mass, right heart enlargement, or excess fat
• "Cowboy legs"


  Enlargement of the left atria or the tracheobroncial lymph nodes may cause bowing of the primary bronchi in a DV/VD view
• Types of pleural effusions

  • Water (hydrothorax)
  • Air (pneumothorax)
  • Chyle (chylothorax)
  • Pus (pyothorax)
• Lobular pattern of lungs and the lung fissures


  • Not visible unless fluid or air are present in the pleural cavity, or there is pleural thickening or a collapsed lung
  • Radiographically, a fissure line is observed as a single white line due to the wicking of fluid between the two lung lobes
  • A lobar sign is represented by a white margin adjacent to an area of radiolucency, representing the edge of a lung lobe that is consolidated often due to the presence of exudates, edema and/or hemorrhage
• Scalloped appearance or leafing


  • Where there is pleural effusion the lungs are pushed away from the body wall and exudate fills the lung fissures, causing a serrated appearance
  • There is loss of detail, obscuring the heart and diaphragm
• Hyperlucent chest


  Increased radiolucency of the lung field; this may be due to emphysema, poor pulmonary circulation, hyperventilation or as an artefact resulting from overexposure
• Lung patterns with increased radio-opacities

  • Interstitial pattern: Vessels have fuzzy margins, giving the appearance of "trees in a fog"
  • Alveolar pattern: Vessels are completely obscured
• Bronchial patterns


  Radiographic signs are ring-like opacities ("donuts") and parallel lines ("tram lines"), caused by thickening of the larger, conducting airways
• Alveolar pattern

  • The vessels disappear because the soft tissue around them is filled with fluid
  • Causes include pneumonia, pulmonary oedema, haemorrhage (contusion)
• Vascular pattern changes

  • Hypervascular pattern: Vessels are larger than normal, may indicate heartworm disease
  • Veins larger than arteries: Indicates left heart failure
• Pulmonary oedema


  Fluid in the lungs resulting in increased radiographic opacity of alveolar patterns
• Loss of serosal detail


  • The presence of fluid in the abdomen has the same effect
  • A thin dog will be hollow-flanked and 'tucked up', while an accumulation of peritoneal fluid will make the abdomen look full or pendulous
• 'Ground glass' appearance


  • Classical description of an indistinct greyish abdominal radiograph due to loss of serosal detail
  • Use of contrast material in the abdomen will overcome this
• Focal loss of detail


  Small areas where serosal details is poor while the rest of the abdomen has good detail
• Hydroabdomen (ascites)


  Excess fluid in the abdomen; seen in heart failure, liver failure, renal failure, hypoproteinaemia and portal hypertension
• Sentinel loops


  Large distended loops of bowel that indicate trouble
• Intraluminal foreign bodies in the small intestine


  Appear as a gas-filled loop that ends abruptly
• Linear foreign bodies in the small intestine


  • Items such as string will cause the intestine to gather along the string due to peristalsis
  • Dangerous to pull on a string sticking out of the mouth or anus as this may seriously damage the puckered intestine; instead remove surgically
• Ileus


  • Multiple loops of gas-distended bowel indicating abnormal peristaltic function
  • The pancreas and right kidney may displace the right colic flexure, and an enlarged left kidney may displace the left colic flexure
• Enlarged liver


  • Indicated if the stomach extends back and exceeds the angle parallel to the ribs
  • A blunt and rounded caudal liver margin infers liver enlargement
• Hepatomegaly (liver enlargement)

  • Enlargement of the right liver lobe will extend past the costal arch in the lateral projection, which can be confused with splenic enlargement
  • Masses in the centre of the liver can distort the shape of the stomach
• Small liver


  • Indicated if the axis of the stomach inclines cranially in front of the line perpendicular to the spine
  • Small liver size can be due to chronic liver disease or a porto-caval shunt
• Paradoxical liver


  • When the stomach slants cranially, suggesting a small liver, but the caudal edge of the liver extends past the caudal arch suggesting a large liver
  • It has a crisp triangular caudal margin indicating a normal liver
  • This is a normal finding in older dogs, as gravity causes the liver to sag (splanchnoptosis)
• Cranial displacement of the duodenum or pylorus could indicate pancreatitis

  • The mass may not be visible if there is focal loss of serosal detail due to inflammation and the presence of fluid
• Splenic tumours can appear anywhere in the abdominal cavity because the spleen is so mobile