Loss of serosal detail: In neonatal or emaciated animals there may be little or no fat in the abdomen, causing lack of contrast. The presence of fluid in the abdomen has the same effect. The shape of the abdomen is assessed to differentiate between absence of fat and extra fluid. A thin dog will be hollow-flanked and ‘tucked up’. Where there is an accumulation of peritoneal fluid the abdomen will look full or pendulous. Young dogs under four months of age have poor serosal detail because their fat deposits are immature.
‘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 detail is poor while the rest of the abdomen has good detail. Seen for example in pancreatitis with focal peritonitis. This causes loss of detail in the right cranial quadrant of the abdomen where the pancreas is located.
The presence of gas within the a viscus allows differentiation and identification of hollow organs.
Hydroabdomen (ascites): Excess fluid in the abdomen; seen in heart failure, liver failure, renal failure, hypoproteinaemia and portal hypertension.
Kidneys can become invisible if there is surrounding fluid in the retroperitoneal space (ruptured ureter, abscesses).
Abnormal mass: May be caused by enlargement of any structure present in the area
Fluid in the stomach must not be confused
with a mass or foreign body. A foreign body can act as a ball valve within
the pylorus and cause projectile vomiting.
A thumb-print pattern is depressions in
the wall of the stomach indicating an infiltrative process.
Gastric distension can be extreme, causing
great pain and possibly a rupture of the stomach.
Sentinel loops: Large distended loops of bowel named because they 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. This is very apparent with a contrast study. It is 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. Indicates abnormal peristaltic function.
If the colon is focally displaced, try to determine what is displacing it. The pancreas and right kidney may displace the right colic flexure. An enlarged left kidney may displace the left colic flexure.
Liver
Enlarged liver:
Indicated if the stomach extends back and exceeds the angle parallel to
the ribs. A crisp, triangular caudal margin of the liver in a left projection
indicates normal liver. A blunt and rounded caudal liver margin infers
liver enlargement.
Liver enlargement
(hepatomegaly): Can be diffuse or focal. Enlargement of the right
liver lobe will extend past the costal arch in the lateral projection.
This 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). The liver is of normal size.
Pancreas
Cranial displacement of the duodenum or
pylorus could indicate pancreatitis. Pancreatic masses of the body and
right limb of the pancreas will be in the right cranial quadrant. The mass
may not be visible if there is focal loss of serosal detail due to inflammation
and the presence of fluid. Contrast studies may show displacement of the
pylorus and the descending duodenum by a pancreatic mass. Left limb pancreatic
disease if present will be seen on the left side of the abdomen.
Spleen
Disease processes can also cause the spleen
to be enlarged (splenomegaly). Splenic tumours can appear anywhere in the
abdominal cavity because the spleen is so mobile.
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