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Radiography of the Dog's Abdomen


Digital radiograph of the cat’s adbomen, lateral view, courtesy of Dr. K.L. How

Digital radiograph of the cat’s adbomen, VD view, courtesy of Dr. K.L. How

Caecum detail: VD view. This close up view of part of the ventrodorsal abdominal radiograph of the dog shows gas filling the caecum, which lies just right of the mid-line at the level of L3 to L5. This is a normal appearance.

The Stomach

Gastric Antrum: Right lateral view. This lateral radiograph of a large dog was made with the dog lying in right recumbency. Gas is visible in the gastric fundus, but the antrum and body of the stomach are predominantly fluid-filled and appear as a regular rounded structure in the cranioventral part of the abdomen. This appearance can be mistaken for a ball in the stomach.

Gastric Antrum: Left lateral view. By repositioning the dog into left recumbency, gas can be redistributed in the stomach and now fills the gastric antrum. The fluid that was in the antrum and body has now moved into the fundus, so the appearance of the stomach is now the opposite of what it was in right lateral recumbency. The presence of gas in the antrum makes gastric foreign body unlikely.

Gastric Rugae: Lateral view. This close-up view of part of the lateral abdominal radiograph of a dog shows the appearance of the gastric rugae, which in this instance are well outlined by gas. They have fairly uniform thickness and an undulating course. As the stomach distends, gastric rugae are stretched out and flattened and are less visible radiographically.

Pneumogastrogram: VD view. This ventrodorsal radiograph of a dog with an air filled stomach shows the relatively large rounded fundus of the stomach, which lies to the left of midline, and the more oblong gastric body extending across the mid-line to the right where the pyloric canal connects the gastric antrum with the duodenum. The duodenum is the most lateral of the gas-filled intestinal loops visible in this radiograph.

Pneumogastrogram: Lateral view. For this radiograph a large bore gastric tube has been passed and the stomach inflated to more clearly demonstrate its size, position and shape.

The Kidneys and Ureters

Intra-venous Ureterogram (IVU): VD view. This ventrodorsal radiograph was made several minutes after injection of contrast medium into a peripheral vein. Circulation of the contrast through the heart and lungs is followed by systemic distribution to all organs, including the kidneys. The kidneys filter contrast and excrete it into the renal pelvis and ureters which are visible clearly in this instance. This procedure is called an intravenous urogram (IVU). Opacification of the renal collecting system, pelvis and ureters is also known as a pyelogram. Note that the urinary bladder has been filled with air (pneumocystogram) to help identify it and to improve visualisation of the ureters as they pass over the urinary bladder in this view. Each ureter in this dog passes in a caudal direction and then makes an approximately 180º turn before draining into the bladder. This is a completely normal appearance.

Nephrogram: VD view, DSA. This radiograph was made in a similar way to the renal non-selective angiogram, but the technique of digital subtraction has enabled other abdominal structures not containing contrast medium to be removed from the image, leaving a particularly clear depiction of the contrast within the aorta and its various branches. Contrast medium arriving in the kidneys is quickly distributed evenly through the cortex where it is filtered by the glomerulus. Opacification of the renal parenchyma is known as a nephrogram.

Renal non-selective angiogram: VD view. This radiograph was made during injection of contrast medium into the mid-abdominal aorta via a catheter and shows contrast predominantly filling the renal arteries and the interlobar arteries of the kidneys. In many dogs, each kidney has two renal arteries.

The Bladder and Urethra

Male Urethrogram: Lateral view. This radiograph was made during injection of contrast medium into a urethral catheter and shows the contrast within the penile and pelvic urethra, the bladder and a small amount of contrast refluxing up one of the ureters. Note the uniform calibre of the urethra as it bends around the caudal aspect of the ischium before becoming wider within the pelvis. An elongated gas bubble is present in the caudal part of the pelvic urethra and could be confused with a lesion.

Bladder: Lateral view, Pelvic. This radiograph of a small breed female dog shows contrast medium (and a large air bubble) in the vagina and uterus. The oblique filling defect in the uterus dorsal to the bladder represents the site of the cervix. In this dog the urinary bladder has a very wide neck, which is located within the pelvis. Dogs (male or female) with this conformation often have urinary incontinence.

The Reproductive System

Vaginogram: Lateral view, Oestrus. This radiograph was made by injection of contrast medium into the vagina and urethra of an entire female dog. Contrast opacifies the urethra, bladder, vagina and the two horns of the uterus, which are visible as narrow coiled structures superimposed on the craniodorsal aspect of the bladder. The large diameter of the vagina and the open cervix are compatible with oestrus.

Uterus: Lateral view, Metoestrus. In this lateral abdominal radiograph the uterus can be faintly seen as a curved elongated, faintly lumpy-appearing structure superimposed over the bladder. This appearance is normal, although the uterus in many dogs is too small to be seen radiographically.

Prostate: Lateral view. In this radiograph of a male dog a rounded soft tissue structure is visible just caudal to the bladder and ventral to the faeces-filled colon at the pelvic inlet. This is the prostate. It is often difficult to see the prostate because it is usually within the pelvis, so is obscured by the surrounding bones. In entire male dogs the prostate gradually enlarges with increasing age and moves cranially so that it becomes visible cranial to the pelvic inlet, as in this instance. Note the triangular lucency that occupies the angle formed by the ventral abdominal wall, the ventral wall of the bladder and the cranioventral aspect of the prostate; this is abdominal fat and it is the fact that it is less opaque than soft tissues that enables visualisation of the prostate.

General Abdomen views

Abdominal Aortogram: Lateral view. This lateral radiograph was made immediately after injection of positive contrast medium into the left ventricle and shows opacification of the abdominal aorta and its major branches.

Abdomen: Lateral view. This is a typical lateral abdominal radiograph of a dog, in which the abdominal viscera are visible but are difficult to discern because of superimposition and because of the similar opacity of the organs and surrounding tissues. The liver is present on the cranioventral aspect of the abdomen between the stomach, which is gas-filled, and the diaphragm. In this instance the caudal port of the liver extends several centimetres caudal to the last ribs and some would interpret this as enlarged. Just caudal to the liver is an oblong soft tissue structure that corresponds to the tail of the spleen. Dorsal to this there are numerous loops of small intestine, some containing gas which makes them easier to see, and others containing a small amount of fluid. Dorsal to the small intestinal loops and bladder is the colon. This is recognisable because of its speckled content, which represents faeces. The kidneys are relatively difficult to see in many dogs and this is no exception. The left kidney is present in the mid-dorsal abdomen from the level of L2 to L4. The right kidney overlaps with the left and occupies the region from approximately T13 to L2.

Abdomen: VD view. This is the corresponding ventrodorsal view to the previous lateral. Again it is difficult to discern the individual abdominal organs in this typical dog. The left kidney is visible from approximately L1 to L3 with the elongated curvilinear spleen lateral to it and overlapping its caudal pole. The right kidney is virtually invisible. In this dog most of the small intestine appears to lie to the right of midline; this is not abnormal. The stomach is gas-filled, as it was in the lateral view, and has a rounded fundus to the left of midline and a narrower, more elongated body that crosses the midline towards the antrum, which lies on the right. The gas-filled piece of small intestine seen superimposed over the right 12th and 13th ribs is probably the duodenum, although its connection to the stomach is not visible. An incidental finding in this dog is the unusual left rib at T13, which is shorter and thicker than the other ribs. This represents transitional anatomy, having some of the features of a normal rib and some of the features of a normal lumbar transverse process. Transitional thoracolumbar vertebrae or lumbosacral vertebrae are commonly seen in dogs but are usually of no clinical significance.

Pup Abdomen: Lateral view. This lateral abdominal radiograph of a very young puppy shows open growth plates in the vertebrae, the pelvis and distal femurs. The abdomen has a virtually featureless, uniform opacity except for a few gas shadows in the stomach and parts of the intestine. Other abdominal organs are invisible. This is a normal appearance that occurs because in neonatal puppies and kittens there is very little abdominal fat, and in the absence of fat there is no contrast (difference) between the opacity of the different abdominal structures which therefore merge into one uniform grey.

Spleen: Lateral view. A lateral abdominal radiograph shows the spleen having a more elongated and shapely demarcated appearance than in the ‘Abdomen: Lateral View’ radiograph. The appearance of the spleen depends greatly on its position in the abdomen and as it is somewhat mobile it can vary from dog to dog and even from minute to minute. It is very easy to over-interpret the appearance of the spleen because of these variations. Dorsal to the spleen in the mid-abdomen there are a few small intestinal loops which are non-dilated and dorsal to that there is gas outlining the large intestine and caecum. The bladder occupies the caudoventral part of the abdomen and has the large intestine and rectum draped over its dorsal aspect.

Liver: Portogram. This ventrodorsal radiograph is made immediately following injection of contrast medium into a mesenteric vein at laparotomy. Contrast within the vein flows cranially into the hepatic portal vein and into the intrahepatic branches of the portal vein. This is a normal study.
In this image, the blood vessels appear as black structures, which is the opposite of what you might have been expecting based on experience of other angiograms. This is a digital subtraction angiogram in which the other parts of the body such as the bones and the other abdominal organs do not contribute to the image, and the contrast medium appears as black on a uniform grey background. This technique makes it possible to see clearly the tiny portal branches extending out into the periphery of the liver.

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