Masses & Cranial Organomegaly

Question 1

What are the 3 diagnostic approaches to abdominal masses?

Answer 1

1. identify mass - recognize regions of increased opacity, changes in normal organ size, and abnormal organ location
2. describe organ displacement - fixed vs. mobile organs, recumbency
3. categorize focal vs. generalized enlargement

Question 2

What size is considered an abdominal mass?

Answer 2

> 2 bowel widths to be considered abnormal in size

Question 3

What is abdominal mass effect?

Answer 3

organ displacement is present, but discrete mass margins are not identified due to peritoneal fluid, superimposition of structures, or lack of intra-abdominal fat

Question 4

What organs have normal variations in size?

Answer 4

• urinary bladder
• stomach
• uterus

difficult to differentiate pathologic enlargement

Question 5

What organs are enlarged only if abnormal?

Answer 5

• liver
• spleen
• kidneys

Question 6

What organs are only seen when enlarged?

Answer 6

• lymph nodes
• adrenal glands
• pancreas

Question 7

What is the purpose of differentiating between focal and generalized organ enlargement?

Answer 7

decreases uncertainty to arrive at a succinct list of differential diagnoses

Question 8

What is focal organomegaly? What does it cause?

Answer 8

segmental or regional enlargement of an organ, involving only a portion of an organ while the remainder is normal

focal displacement of surrounding organs

Question 9

What is generalized organomegaly? What does it cause?

Answer 9

entire organ is enlarged, typically with rounded or abnormal margins

displacement of surrounding organs

Question 10

What do cranial abdominal masses cause?

Answer 10

caudal displacement of stomach and small intestine

Question 11

What is the most likely origin of cranial abdominal masses?

Answer 11

liver —> generalized or focal hepatomegaly

Question 12

What are the most common organ of origin of mid-abdominal masses?

Answer 12

• spleen
• pedunculated liver mass
• mesentery
• lymph nodes
• pancreas

Question 13

What is the normal anatomy of the liver like on radiographs? What 3 structures border efface it?

Answer 13

uniform soft tissue opacity with smooth and sharp margins

1. CRANIAL = diaphragm
2. CAUDAL = stomach
3. CAUDATE PROCESS = right kidney

Question 14

How is liver size extrapolated? What should its margins be like?

Answer 14

from gastric axis from fundus to pylorus - parallel to ribs and perpendicular to thoracic spine

sharp, not extending beyond the costal arch of the 13th ribs

Question 15

What changes in liver size is expected in deep-chested and shallow-chested breeds?

Answer 15

DEEP - relatively small appearance of liver with normal gastric axis

SHALLOW - extend caudal to the costal arch, remaining sharp margins

Question 16

Where should the gastric axis be seen on VD views?

Answer 16

perpendicular to the thoracic spine at T10-T11 intercostal space

Question 17

What is microhepatia? What does this cause?

Answer 17

reduced liver volume between the diaphragm and stomach seen on both views

cranial displacement of gastric axis

Question 18

What are the 2 major differential diagnoses for microhepatia?

Answer 18

very non-specific - correlate with blood work

1. portosystemic vascular anomaly - portosystemic shunt, microvascular dysplasia common in younger patients
2. chronic liver disease - cirrhosis, fibrosis common in older patients or those with known prior liver disease

Question 19

What are the 2 major imaging features of generalized hepatomegaly?

Answer 19

1. caudal displacement of the stomach gastric axis
2. liver extends past caudal margin of ribs, with blunted, rounder lobar margins

Question 20

What are the 4 major groups of differential diagnoses associated with generalized hepatomegaly?

Answer 20

1. smooth margins - neoplasia (lymphoma)
2. congestion - right-sided heart failure
3. fat accumulation - hepatopathy, hepatic lipidosis, DM, hyperadrenocorticism
4. inflammation/infection - acute hepatitis

Question 21

What does focal hepatomegaly most commonly cause?

Answer 21

• focal, caudal, dorsal, or lateral displacement of the stomach
• proximal duodenum and right kidney displacement

Question 22

What are the most common causes of focal hepatomegaly?

Answer 22

• nodular hyperplasia
• neoplasia - primary = hepatocellular carcinoma
• abscess
• cyst

Question 23

What are the most common causes of multifocal hepatomegaly?

Answer 23

irregular, lumpy margins due to nodules or masses within parenchyma

• nodular hyperplasia
• neoplasia - hepatocellular carcinoma, metastasis
• hepatitis
• cirrhosis

Question 24

What is the only attachment of the spleen?

Answer 24

gastrosplenic ligament attaches it to the fundus of the stomach

• body and tail are very mobile

Question 25

What 3 things cause size variation of spleens?

Answer 25

1. breed 2. activity 3. age

Question 26

What is the normal shape of the spleen? What does it look like end-on?

Answer 26

elongated and fusiform triangular

Question 27

Where is the splenic head seen on lateral radiographs?

Answer 27

ventral to the thoracolumbar junction

Question 28

Where is the splenic tail seen on lateral radiographs?

Answer 28

along the ventral abdominal wall with exact location dependent on size

Question 29

Where are splenic masses most commonly seen? What needs to be ruled out?

Answer 29

mid-ventral abdomen - pedunculated liver mass - mesenteric mass - LN enlargement - pancreatic mass

Question 30

Differential diagnoses for generalized and focal hepatomegaly:

Answer 30

Question 31

What is the gastric axis like in these radiographs?

Answer 31

caudally displaced and no longer perpendicular to the thoracic spine or parallel to the ribs - more obtuse angle secondary to hepatomegaly cranially displaced - more acute angle with the thoracic spine, suggesting reduction in hepatic size

Question 32

What tumors are likely to cause focal or generalized splenomegaly?

Answer 32

FOCAL - HSA, hematoma, hemangioma, mast cell tumor GENERALIZED - lymphoma, MCT