Abdomen Flashcards
Trauma
Trauma to the spine can cause hemorrhage to extend into the spinal musculature and retroperitoneal space.
On CT images, hemorrhage may be slightly hyperattenuating or isoattenuating and has ill‐defined margins as it dissects through the retroperitoneal space
On MR images, edema and hemorrhage appear as T2 hyperintensity in the spinal musculature and retroperitoneal space. Hemorrhage may also be seen in the pelvic retroperitoneal space
Foreign bodies
Foreign bodies that penetrate through the skin may cause multilobular, peripherally contrast‐enhancing masses with fluid‐attenuating centers in the subcutaneous tissues. They may also penetrate into the retroperitoneal space, causing an abscess in this region with a connecting draining tract to the skin. Other types of penetrating foreign bodies, such as projectiles, can introduce infection into the peritoneal or retroperitoneal space
Abscesses
Abscesses due to fungal disease occasionally occur in the retroperitoneal space.
On MR images, they appear as T2 hyperintense and T1 contrast‐enhancing masses that may surround the vasculature or cause vascular thrombosis
Lipomas
Lipomas are frequently encountered in the subcutaneous tissues and within the intermuscular fat depositions. These are rounded, fat‐attenuating masses that may have soft‐tissue septations present. Their often large size may displace neighboring organs or extend into the peritoneal or retroperitoneal space. Large lipomas may become hemorrhagic, with increased soft‐tissue attenuation interspersed with fat on CT images.
Infiltrative lipomas are characterized by dissection within surrounding musculature. Lipomas may also infiltrate fat planes within the pelvis, causing additional mass effects
Sarcomas
Feline injection‐site sarcomas occur in the abdominal wall or pelvic soft tissues because of extension of a distant tumor or misdirected injection meant for the distal extremity. Involvement of the musculature of the body wall appears as contrast enhancement of the tumor with extension to the musculature and surrounding tissues. Differentiating postsurgical inflammation from tumor extension in animals scanned for radiation therapy can be challenging and is not always possible.
Fibrosarcoma in dogs is an invasive neoplasm that may involve the peritoneal cavity or pelvic canal. Contrast‐enhanced imaging of the lesions is necessary to accurately define the tumor margins and evaluate for local lymph node enlargement. Fibrosarcomas and other sarcomas are moderately to intensely contrast enhancing with poorly defined margins, and tendrils of neoplastic tissue may extend to regional tissues.
Hemangiosarcoma
Hemangiosarcoma occasionally occurs as a mass in the pelvis or retroperitoneal space without apparent primary abdominal involvement. These masses are irregular and lobular in shape, with heterogeneous contents on both CT and MR images. Hemorrhagic components of the mass are hypoattenuating on CT and T1 hypointense and T2 hyperintense on MR images. In both modalities, the masses tend to be peripherally contrast enhancing.
Mesenteric Edema—Fluid Overload (Feline)
8y MC Bengal with ureteral obstruction. Aggressive intravenous fluid therapy had been initiated to treat acute chronic renal failure.
- The right kidney is enlarged with a dilated pelvis, and the left kidney is small.
- There is ground‐glass fluid attenuation within the fat surrounding the small intestine, as well as more linear fat stranding surrounding the right kidney (b: arrows).
- Subcutaneous edema is also present.
- On these contrast‐enhanced images, there is very little enhancement of the kidneys, indicating poor renal function.
Peritoneal Effusion (Canine)
6y FS Pit Bull Terrier with bicavitary modified transudative effusion.
- Fluid is widely dispersed within the peritoneal cavity with prominent collections surrounding the small intestine and spleen (a,b: arrowheads).
- Pleural effusion is also evident in the caudal pleural space (b: asterisks).
The effusion had both low cellularity and low protein and was thought to have resulted from abnormal hydrostatic or oncotic forces. A definitive diagnosis was not reached.
Migrating Foreign Body Abscess (Canine)
12y FS Labrador Retriever with acute onset of abdominal pain, recent history of coughing, and fever. Unenhanced (a–c) and comparable contrast‐enhanced (d–f) transverse images are ordered from cranial to caudal.
- There is a well‐circumscribed tract and abscess in the right retroperitoneal space lateral to the diaphragmatic muscle (d,g: black arrow) with peripheral contrast enhancement.
- There is additional nonenhancing fluid dorsal to the inflammatory tract, which contains gas bubbles (d: open arrow).
- The retroperitoneal fat surrounding the kidney has fat stranding in a linear pattern with central regions of ground‐glass opacity (f,g: arrowheads).
A migrating grass awn was retrieved from the retroperitoneal space.
Abdominal Wall Abscess (Canine)
8y FS Border Collie with a recurrent abscess on the left flank.
- There is a multilobulated mass in the subcutaneous tissues of the left dorsolateral body wall.
- The mass does not enter the deeper layers of fat adjacent to the spine.
- There is peripheral contrast enhancement with nonenhancing central regions.
Plant material from a migrating grass awn was discovered after surgical removal.
Abdominal Wall Infiltrative Lipoma (Canine)
3y FS Vizsla with recurrent lipoma after surgery. Images are ordered from cranial to caudal.
- There is a large, lobular fat‐attenuating mass in the left inguinal region. The mass separates and distorts the relationship of the internal and external oblique muscles and the rectus abdominis muscle (a: arrows).
- Widening and infiltration of the internal oblique muscle is visible in the center of the muscular discontinu ity (a: asterisk).
- The more dorsal arrow denotes a region of muscular irregularity.
- The abdominal musculature is more regular in the caudal aspect of the mass (b: arrows).
Encapsulated Lipoma with Organizing Hematoma (Canine)
12y MC Labrador Retriever cross with a suspected splenic mass based on abdominal palpation.
- There is a large mass with a thick, regular capsule in the right cranial abdomen.
- The inner portion of the mass is heterogeneous soft‐tissue attenuating material surrounded by fat.
- On contrast‐enhanced images, the capsule of the mass is moderately enhancing.
Histopathology showed a fibrous capsule with internal fat necrosis and hemorrhage.
Abdominal Wall Fibrosarcoma (Canine) CT
7y FS Golden Retriever with a previously diagnosed thoracic mass.
- On the unenhanced image, there is a large mass originating from the right ventral body wall and protruding both externally and internally in the cranial abdomen.
- The mass remains in a similar position in sternal (a) and dorsal (b) recumbency.
- The mass is soft‐tissue attenuating and deviates the stomach dorsally within the abdomen.
- On the contrast‐enhanced image, the mass is moderately and heterogeneously enhancing.
Histopathology revealed a grade I fibrosarcoma.
Pelvic Fibrosarcoma (Feline)
15y Domestic Shorthair with a history of straining to defecate. Images are ordered from cranial to caudal.
- There is an ill‐defined, contrast‐ enhancing mass in the right caudal abdomen (a,b: arrows) displacing the colon to the left (b: arrowhead).
- The mass infiltrates the muscles of the abdominal wall and lumbar spine, with fluid accumulation ventrally in the peritoneal space.
- Within the pelvic canal, the mass is peripherally contrast enhancing with a central, fluid‐attenuating region (c: arrows).
- The colon is completely compressed by the mass at this level (c: arrowhead).
Fine‐needle aspiration cytology was consistent with a fibrosarcoma.
Hepatic Blood Supply
- Arterial
- Venous
- Portal
The normal hepatic arterial vasculature:
- Consists of three to five arterial branches
- Course ventral to the portal vein and parallel the portal branches within the hepatic parenchyma.
The caudal vena cava receives:
- Short right veins from the right liver lobes
- Large left vein from the left liver lobes
- Slightly smaller vein from the right medial and quadrate lobes
- The phrenic vein courses parallel to the diaphragm and enters the left hepatic vein at its most cranial aspect.
The portal tributaries include the jejunal veins collecting into the:
- Cranial mesenteric vein
- Colic vein
- Splenic vein from the left side
- Gastroduodenal vein from the right and ventral aspect.
- The portal vein diameter increases with the addition of each tributary.
- The portal vein then branches to the:
- Right lateral liver lobe
- Two larger cranial branches supply the right medial lobe and left liver lobes
- The left gastric vein joins the splenic vein from the cranial direction and is often involved in anomalous vessels
Arterioportal fistula
Anomalous connections between the hepatic arterial and portal venous systems can occur congenitally. The presence of high‐pressure flow in the portal vasculature causes portal hypertension, resulting in extreme dilation of portal branches, ascites, and multiple acquired extrahepatic shunts.
With dual‐phase CT angiography, one or more anastomoses of the arterial system with the portal system can often be identified as a plexus of small vessels.
****The presence of contrast in the portal vasculature during the arterial phase is diagnostic.
The entire abdomen should be scanned to detect the multiple acquired shunts that are usually present between the abdominal portal vein and caudal vena cava.
Congenital Intrahepatic Shunts
Congenital intrahepatic shunts occur in large‐breed dogs (Irish Wolfhounds, Golden Retrievers, Labrador Retrievers, Australian Cattle Dogs, Old English Sheepdogs) and rarely in cats, resulting in a large‐diameter direct communication with the caudal vena cava.
These vessels may be classified as:
- Left divisional = as a remnant of the ductus venosus
- Central divisional = coursing relatively straight through the central liver
- Right divisional = coursing through the right liver lobes.
The majority of intrahepatic shunts in cats are left divisional.
CT or MR angiography demonstrates the anatomy of the abnormal vessel and helps with surgical planning for both open or minimally invasive procedures.
Key findings include:
- The anatomic path and termination of the shunt into the caudal vena cava
- Whether it intersects with large hepatic veins that might be occluded during surgery.
- The shape and size of the opening of the vessel into the caudal vena cava is also of importance when planning minimally invasive procedures.
- Caudal vena cava diameter is measured to determine the size of the stent required for shunt attenuation with coils.
Multiple intrahepatic shunts can also occur, either as a variant of the primary disorder or as an acquired consequence of attempted shunt attenuation. These are small‐diameter, irregular branches that connect to the hepatic veins and may mimic hepatic veins themselve).
Congenital extra-hepatic shunts
Congenital extrahepatic shunts occur in smaller‐breed dogs (Cairn Terriers, Yorkshire Terriers, Russell Terriers, Dachshunds, Miniature Schnauzers, Maltese) and cats. The majority of shunts are single; however, multiple congenital extrahepatic shunts are occasionally seen.
Extrahepatic shunts have been classified as:
- Splenocaval
- Splenophrenic
- Splenoazygos
- Right gastric–caval
- Right gastric–caval or azygos with a caudal shunt loop.
- Additional variations in shunt anatomy can be seen that do not conform to this general classification.
- A description of shunts involving the left gastric vein identified variants that entered the phrenic vein, the caudal vena cava, and the azygos vein
The diameter of the portal vein decreases after the exit of the shunt vessel, and the enlarged anomalous vessel should be followed to its termination. Multiplanar reformatting and 3D rendering can be helpful in defining the anatomy. The normal tributaries of the portal vein should also be identified and their junction with the portal vein or the shunt described. The entrance of tributaries to the shunt vessel (e.g. splenic vein, left gas tric veins) may affect surgical placement of occlusion devices to avoid residual shunting.
Multiple acquired extrahepatic shunts
Multiple acquired extrahepatic portosystemic shunts form because of portal hypertension, often due to primary hepatic parenchymal disease.
There are a variety of pathways arising from the portal vein and tributaries, including:
- Gastrophrenic
- Pancreaticoduodenal
- Splenorenal
- Mesenteric
- Hemorrhoidal collateral vessels
- The anomalous vessels are often large when arising from the splenic vein and small when arising from other veins, describing a tortuous route between the portal and systemic circulation.
- They are best detected by scanning the entire abdomen and by using thin collimation for maximal spatial resolution. Small collateral vessels may appear as a “blush” rather than individual vessels because of limitations of spatial resolution
Complex vascular anomalies
Interruption of the caudal vena cava occurs congeni tally and is often without clinical signs, as blood flows through the azygos vein to return to the heart. This may occur together with other anomalies, such as aplasia or interruption of the portal vein and situs inversus.
Complex anomalies, such as interrupted portal vein, result in a complete lack of intrahepatic portal vasculature, making these animals unsuitable for shunt attenuation.
When CT angiography is performed in some dogs, the intrahepatic portal vein branches may not fill with contrast, as pressures are low. This should not be mistaken for portal interruption, as these dogs can expe rience normal postsurgical vascular development with shunt attenuation
Hepatic Arteries
The regional hepatic arteries branch from the hepatic artery and are between three and five in number. These branches supply the left, central, and right regions of the liver.
- The left gastric artery branches from the celiac artery more proximally and caudally, and travels cranially along the gastric wall.
- The gastroduodenal artery continues after the hepatic arteries branch toward the right and caudal abdomen.
- The right gastric artery arises cranially from the gastroduodenal artery on the right side.
- On transverse images, the hepatic artery and branches (b: arrow) are positioned ventral to the portal vein (b: open arrow) and caudal vena cava (b: asterisk).
- Within the hepatic parenchyma, the hepatic arteries follow the portal veins (c: arrows).
Hepatic veins
- The largest vein draining the liver comes from the left liver lobes(a).
- The phrenic vein (a,b) is a small vein that enters the caudal vena cava parallel to the diaphragm.
- The right medial lobes are drained by a vein that spans the gallbladder(a).
- The portal vein branches (a: arrows) interdigitate with the hepatic veins.
- Small right veins enter the caudal vena cava from the dorsal right liver lobes (b: open arrows).
Portal veins (Canine)
- The jejunal veins travel from the intestine to the cranial mesenteric vein (a).
- The caudal mesenteric vein joins the portal vein from the left dorsal abdomen.
- The next most cranial tributary of the portal vein (b,c: arrow) is the splenic vein (c) from the left side and then, slightly more cranial, the gastroduodenal vein (d) from the right lobe of the pancreas.
- The portal vein gives off a right branch to the right lateral lobe (d) and then branches to the right medial (often called central division) and left liver lobes.
_Hepatic Arterioportal Fistula (felin_e)
5mo MC Domestic Shorthair with ascites. Transverse images (a–d) are ordered from cranial to caudal.
- During the arterial phase scan, the liver is markedly and irregularly contrast enhancing (b: asterisk).
- The hepatic artery is enlarged, and high‐attenuating blood is present in the dilated portal vasculature during this phase (a: arrows).
- There is a small plexus of vessels on the right lateral liver, representing a portion of the arterioportal anastomosis (a,b: arrowheads).
- Free fluid is present in the peritoneum (d: open arrow).
- A 3D image from the ventral perspective illustrates the multiple enlarged, intrahepatic vessels.
Congenital Intrahepatic Shunt—Left Divisional (Canine)
5mo FS Golden Retriever with poor growth. Transverse images (a–e) are ordered from caudal to cranial.
- There is a single intrahepatic shunt arising from the portal vein at the porta hepatis and traveling to the left side (b–d: arrows).
- The vessel forms a curve that returns to the caudal vena cava in the cranial liver near the diaphragm.
- The dorsal reformatted image demonstrates the typical shape of the patent ductus venosus (f: arrows).
Congenital Intrahepatic Shunt—Central Divisional (Canine)
1y Labrador Retriever with aggression after meals and polydipsia. Transverse images (a–c) are ordered from caudal to cranial.
- There is a short anomalous vessel (b,d: arrows) arising from the right side of the portal vein and traveling dorsally to join with the caudal vena cava.
- Cranial to the shunt, there is a blind‐ending portal branch that does not continue cranially (c: arrowhead).
- No other intrahepatic portal branches are present.
- The liver is small (b,d), and the parenchyma shows typical mottled enhancement in the early portal phase (a), which is a common finding in dogs with shunts, and is presumed to be due to increased arterial blood supply
Congenital Intrahepatic Shunt—Right Divisional (Canine)
1y FS Doberman Pinscher with suspected portosystemic shunt. Transverse images (a–d) are ordered from caudal to cranial.
- There is a large, tortuous anomalous vessel arising from the right side of the portal vein and traveling through the right liver lobes to the caudal vena cava (b,c: arrows).
- The vessel was visible on ultrasound images in the cranial liver (e: arrows).
- A 3D rendering from the ventral aspect demonstrates the shape of the shunt vessel (f: arrow).
Congenital Extrahepatic Shunt—Splenocaval (Canine)
2y MC Yorkshire Terrier with 2‐year history of episodic ataxia and seizures. Images a–c are ordered from caudal to cranial.
- The short extrahepatic shunt vessel arises from the portal vein at the junction of the splenic vein and curves dorsally and to the left to join the caudal vena cava (d: arrow).
- The portal vein decreases in diameter cranial to the shunt exit (c: arrow).
- The MIP image shows the relationship between the splenic vein and the shunt (d).
Congenital Extrahepatic Shunt—Splenophrenic (Canine)
7y FS Cocker Spaniel with poor recovery from anesthesia. Images are ordered from caudal to cranial.
- A shunt vessel arises from the splenic vein (a) and travels medial to the gastric fundus (b–d: arrow) toward the diaphragm.
- The vessel joins the phrenic vein and then travels to the caudal vena cava parallel to the diaphragm (e: arrows).
Congenital Extrahepatic Shunt—Splenoazygos (Canine)
6mo F Yorkshire Terrier failing to gain weight. Images are ordered from caudal to cranial.
- On portal phase angiographic images, a shunt vessel (a–e: arrows) exits the portal vein through the splenic vein, traveling along midline dorsal to the liver and then rising dorsally at the diaphragm through the caudal vena cava to the azygos vein.
Congenital Extrahepatic Shunt—Right Gastric–Caval (Canine)
1y FS Terrier with failure to gain weight. Images a–c are ordered caudal to cranial, and images d–f are ordered cranial to caudal. The white arrows denote the cranial course of the shunt and the black arrows denote the caudal course to the shunt termination.
- The large shunt vessel (a–c: white arrow) arises from the gastroduodenal vein at the level of the right gastric vein and travels cranially to the porta hepatis, where it gives off a right intra- hepatic branch (b: arrowhead).
- It crosses to the left side (a–c: black arrow) and travels caudally to join the caudal vena cava near the right kidney (d: black arrow).
- The dorsal plane MIP image shows the right (e: white arrows) and left (e: black arrows) arms of the shunt vessel.
A plastic ameroid constrictor was placed around the shunt vessel at its junction with the caudal vena cava (f: asterisk), occluding the blood flow.
Liver Lobe Torsion (Canine)
Unknown signalment and history. Images a–c are through the liver and ordered from cranial to caudal.
- The left liver lobes are enlarged, extending past the right kidney (a–c).
- The lobe is hypoattenuating on contrast‐enhanced images (a: arrowheads).
- No vascularity is noted in the lobe, in contrast to the normal enhancement of the right liver lobes (a: open arrow).
- There is fluid‐attenuating peritoneal effusion present (a: solid arrow).
At surgery, the affected lobe was enlarged, engorged, and friable
Myelolipoma (Feline)
9y FS Domestic Shorthair with a palpable abdominal mass. Images a–d are comparable unenhanced (a,b) and contrast‐enhanced (c,d) images of the liver ordered from cranial to caudal.
- A multilobular, fat‐attenuating (−67 HU) mass is present in the right lateral lobe and extends caudally (a,b).
- The mass is poorly demarcated within the cranial liver (c: arrowheads) and is well encapsulated caudally.
- There is very mild contrast enhancement of the mass (d).
- On ultrasonography, the mass was hyperechoic, suggesting fat as the tissue of origin.
Surgical excisional biopsy confirmed myelolipoma.
Hepatic Adenoma (Canine)
10y FS mixed‐breed dog with elevated liver enzymes.
- The liver mass is located in the left lateral lobe and is hypoattenuating on the unenhanced image (a: arrowheads).
- The gallbladder (a: asterisk) is displaced by the mass effect.
- There is contrast enhancement of the entire mass during the arterial phase (b), mild hyperattenuation on the portal phase (c), and isoattenuation on the delayed phase image (d).
Surgical excisional biopsy confirmed hepatocellular adenoma (e).
Biliary Cystadenoma (Feline)
13y FS Domestic Shorthair with lethargy and distended abdomen. Images a–d are comparable unenhanced (a,b) and contrast‐ enhanced (c,d) images of the liver ordered from cranial to caudal.
- There is a fluid‐attenuating, multicameral mass occupying the left liver lobes and extending into the right liver cranially with ill‐defined margins.
- On contrast‐enhanced images, there is no enhancement of the mass.
Surgical biopsy confirmed biliary cystadenoma (cholangiocellular adenoma).
Metastatic Hemangiosarcoma (Canine)
8y M Labrador Retriever. Hemangiosarcoma of the neck treated previously with radiation therapy.
- Arterial phase (a–c) and comparable portal phase (d–f) images are ordered from caudal to cranial.
- There are multiple variably sized, hypoattenuating nodules throughout the liver parenchyma (a: arrows).
- The largest nodule has a central region of more hyperattenuating tissue that contrast enhances (d: arrow), producing a target‐like lesion.
- The remainder of the nodules are hypoattenuating on late arterial phase images (a–c), and some become isoattenuating on portal phase images (d–f).
Spindle Cell Sarcoma (Canine)
14y FS Labrador Retriever with liver mass discovered on screening ultrasound. Images are comparable unenhanced (a–c) and contrast‐ enhanced (d–f) images through the liver and ordered from cranial to caudal.
- There is a large, irregularly margined mass in the right lateral liver lobe with a fluid‐attenuating center (a–c: arrows).
- The gallbladder is displaced to the left and contains mineral‐attenuating material (a: asterisk).
- On contrast-enhanced images, the mass is peripherally enhancing and is poorly defined from the normal liver on the medial border.
- The mass effect is causing compression of the caudal vena cava (e: open arrow).
Surgical biopsy confirmed spindle cell sarcoma.
Hepatic Cyst (Canine)
8y MC Pembroke Welsh Corgi with thymoma.
- A well‐circumscribed, fluid‐attenuating mass is present in the left lateral liver lobe (a: arrow) protruding from the capsular surface.
- The structure is opposite to the gall-bladder (a: asterisk).
- On contrast‐enhanced images, there is no enhancement of the structure (b).
The hepatic cyst was incidental and was discovered during evaluation of the cranial mediastinal mass. Surgical excisional biopsy confirmed the diagnosis.
Gallbladder Obstruction (Feline)
6y FS Domestic Shorthair with anorexia and lethargy. Images are ordered from cranial to caudal.
- There are multiple dilated bile ducts in the liver parallel to the portal branches (a: arrows).
- Additional cystic masses consist- ent with cholangiocellular adenoma are seen as multilobular, fluid‐attenuating nodules in the parenchyma (a: open arrow).
- The walls of the bile ducts are contrast enhancing, as is the gallbladder wall, as a result of cholangitis and cholecystitis (b,d: arrows).
- There is contrast‐enhancing soft tissue filling the lumen of the common bile duct at the junction of the cystic duct and hepatic ducts (c: arrowheads).
- The small gallbladder size in the face of obstruc- tion is a result of chronic fibrosis observed intraoperatively.
The position of the obstructive soft tissue precluded biopsy or surgical man- agement, and differential diagnoses included inflammatory disease and neoplasia.
Necrotizing Pancreatitis (Feline)
12y FS Domestic Shorthair with 1‐week history of intermittent vomiting and anorexia. Images a–e are ordered from caudal to cranial.
- There is a large, irregular soft‐tissue attenuating mass surrounding the left lobe of the pancreas.
- The pancreas is intensely contrast enhancing (b,f: arrows) and is enlarged.
- The central soft‐tissue material is nonenhancing, consistent with fluid, with peripheral contrast enhancement.
- The fat surrounding this region is hyperattenuating, consistent with peritonitis and steatitis.
Postmortem examination confirmed extensive suppurative and necrotizing pancreatitis with regional peritonitis, steatitis, and omental adhesions.
Pancreatic Pseudocyst (Canine)
10y FS Labrador Retriever cross with a nasal squamous cell carcinoma. The CT examination was performed for staging purposes after a fluid‐filled mass of uncertain origin was identified on a routine ultrasound examination (a: calipers).
- There is a well‐demarcated, thin‐walled fluid‐attenuating mass (b–d: arrowhead) within the left limb of the pancreas (b–d: arrows).
- The pancreas is otherwise unremarkable, as is the surrounding mesenteric fat.
The dog had no clinical signs associated with pancreatic disease, and the pseudocyst was considered an incidental finding.
Adrenal Carcinoma with Hemorrhage (Canine)
7y M Rottweiler with known adrenal mass and recent onset of abdominal discomfort. Image a–c are ordered from cranial to caudal.
- The right adrenal gland is enlarged (a,d: open arrowhead) with an eccentric, caudal cystic component of fluid attenuation (a,b: arrows).
- The remaining tissue of the mass and the adrenal capsule are peripherally contrast enhancing.
- The cystic component of the mass was hemorrhage, which extended caudally through the retroperitoneal space (d).
- The ureter is visible ventral to the hemorrhage (b: arrowhead).
The gross and histological diagnosis was confirmed by excisional biopsy (e: arrow). Compare the appearance of the mass on the CT image (d) to the gross excisional specimen (f).
Splenic Torsion (Canine)
3y F German Shepherd Dog with hematuria and mild anorexia.
- The spleen is markedly enlarged and hypoattenuating (a: arrows) with associated free peritoneal fluid (a: asterisk).
- The rotated splenic pedicle appears as a mass effect with a spiral shape (b: open arrows).
- On the contrast‐enhanced image (b), the spleen is non-enhancing.
Acute Splenic Infarction (Canine)
7y FS Labrador Retriever with left flank cellulitis. Images a and b are ordered from cranial to cau dal.
- On contrast‐enhanced images, the spleen is moderately enlarged with a nonenhancing region in the distal extremity (a,b: white arrow) and a more ill‐defined region in the body of the spleen (b: arrowhead).
- The capsule of the spleen enhances in this region, and there is geographic demarcation with normal splenic paren chyma.
- Wedge‐shaped, nonenhancing infarcts are also visible in both kidneys (a: open arrows).
Venous Thrombosis and Infarction (Canine)
2y MC Labrador Retriever with coagulopathy. Images b and c are ordered from cranial to caudal and image d is a magnified view of image c.
- The spleen is moderately enlarged on the unenhanced image (a).
- Following intravenous contrast administration, there is heterogeneous enhancement of the parenchyma in several regions (b,c: arrowheads).
- There are soft‐tissue attenuating filling defects in the splenic veins (c: black arrows), representing thrombosis.
- The thrombus was visualized as a hyperechoic filling defect on ultrasound (e: white arrow), as well as the hypoechoic infarcted regions of the parenchyma (e: open arrows).
Myelolipoma (Canine)
17y MC mixed breed with splenic mass. Images b and c are ordered from cranial to caudal.
- There is a complex, round mass arising from the midbody of the spleen (a: arrows).
- The mass is heterogeneous with a soft‐tissue attenuating rim and lobular regions of mixed attenuation approaching fat in the central region.
- On contrast‐enhanced images (b,c), the soft‐tissue regions are enhancing.
Surgical excisional biopsy confirmed the diagnosis of myelolipoma.
Splenic Metastasis (Canine)
9y MC Labrador Retriever with cutaneous hemangiosarcoma.
- There are ill‐defined, mildly hypoattenuating masses in the proximal extremity of the spleen, which are nonenhanc ing centrally with mild peripheral enhance ment (b: arrows).
Histology was performed after splenectomy, and a diagnosis of metastatic hemangiosarcoma was made.
Extramedullary Hematopoiesis (Canine)
12y FS Labrador Retriever with splenic nodules. Images b and c are ordered from cranial to caudal.
- There are moderately contrast‐enhancing, well‐defined nodules within the splenic parenchyma (b,c: arrows).
- The nodules are not well visualized on the unenhanced image (a).
The nodules were diagnosed as extramedullary hematopoiesis on histopathology.
Normal Renal Contrast Enhancement (Canine)
7y FS German Shepherd Dog imaged for a right adrenal mass (not shown). Dual‐phase CT angiography was performed with arterial, venous, and late‐phase series, as seen by the enhancement of the aorta and caudal vena cava (a–c).
- The arterial phase image (a) shows intense cortical enhancement, indicating the renal corticomedullary phase.
- The venous phase image has relatively isoattenuating cortex and medulla, indicating the nephrogram phase, with early renal pelvic enhancement.
- The late venous excretory phase image has mainly pelvic, ureteral, and medullary enhancement.
Retrocaval Ureter (Canine)
3y FS Bernese Mountain Dog with incidentally discovered hydroureter. Images c–g are ordered from cranial to caudal.
- The dilated ureter was visible on ultrasound examination ventral to the caudal vena cava (b: arrow).
- On both ultrasonographic and CT images, the caudal vena cava was located on the left side, forming a curved lateral deviation caudal to the kidneys (a,c–f: asterisk).
- The left renal pelvis and ureter are dilated (c–e: arrows), and the ureter takes a dorsal course relative to the caudal vena cava.
- The ureter is compressed between the caudal vena cava and aorta more caudally (f: arrow) before entering the bladder normally at the trigone (g: arrow).
Polypoid Cystitis (Canine)
9y MC German Shepherd Dog with hematuria for several years. Unenhanced (a–c) and corresponding contrast-enhanced (d–f) images of the urinary bladder are ordered from cranial to caudal.
- On unenhanced images, there is a hypoattenuating, rounded structure in the bladder lumen (a–c: arrow), which is surrounded by more hyperattenuating urine.
- On contrast‐enhanced images, the bladder wall is moderately thickened and enhancing (d: open arrow).
- There is a mass arising from the ventral bladder wall with a stalk and polypoid expansion.
- The mass has peripheral and heterogeneous contrast enhancement (d–f: arrow).
- Contrast‐enhanced urine is located in the dorsal aspect of the bladder as the dog was imaged in dorsal recumbency.
Polypoid cystitis was seen endoscopically (g)
Nephroblastoma (Canine)
2y MC Doberman Pinscher with hematuria. Images a–c are ordered from cranial to caudal.
- There is a large, heterogeneous, cavitary mass replacing the left kidney (a–c: arrows).
- The mass is heterogeneously contrast enhancing, and urine production is present in the most caudal cavitary region (c: arrowhead).
- The CT scan was performed in dorsal recumbency, hence the inverted fluid‐contrast interface.
- The left ureter is not identified.
- The right kidney has mild pelvic dilation with a thin lateral cortex (a: open arrow) and cortical infarct (not shown).
- The mass is vascular on Doppler ultrasound (d).
A nephrectomy was performed and nephroblastoma with disorganized renal tissue was diagnosed (e,f).
Ureteral Transitional Cell Carcinoma (Canine)
8y MC English Bulldog with respiratory distress and incidentally discovered left ureteral obstruction on ultrasound examination (a). A nephropyelogram was performed, demonstrating the dilated left renal pelvis and proximal ureter (b: arrowheads) without visualization of the distal ureter.
- Urine enters the bladder, suggesting a partial obstruction.
- On CT images, the dilated left renal pelvis and proximal ureter are again seen (c: arrowheads).
- There is a soft‐tissue mass enlarging the left ureter distal to the ureteral dilation (c,d: arrows), and the contrast‐enhanced urine traces a complex, tortuous path through this region. The distal ureter is a more normal diameter (c: open arrow).
- The bladder is visible (d: asterisk) ventral to the ureteral mass (d: arrow) on transverse images.
A nephrectomy was performed, and transitional carcinoma of the ureter was diagnosed.
Pelvic Bladder (Canine)
14y FS Chihuahua with stranguria and pollakiuria. A cystourethrogram was performed under fluoroscopy prior to CT. Images are displayed in a wide window to counteract artifact from high‐attenuation contrast medium in the bladder.
- The bladder is located entirely within the pelvis (a–c: arrows).
- The wall is thickened, most particularly in the cranioventral aspect.
- The caudal position of the bladder has caused lateral displacement of the urethra (c: open arrow), with partial outflow obstruction.
A cystopexy was performed that relieved the clinical signs of stranguria, and no bacteria were cultured from the urine.
Endometrial Hyperplasia (Feline)
5y F Persian imaged for ureteral obstruction. Images are ordered from cranial to caudal.
- The uterus is markedly enlarged and fluid filled with enhancing walls (a–c: arrows).
- Folds are visible in the wall of the uterus, causing an undulating pattern.
- The ovaries were unremark able (not shown).
An ovariohysterectomy was performed, and marked endometrial hyperplasia and endometritis were found on histopa thology, possibly related to recent pregnancy.
