Masses & Cranial Organomegaly Flashcards
What are the 3 diagnostic approaches to abdominal masses?
- identify mass - recognize regions of increased opacity, changes in normal organ size, and abnormal organ location
- describe organ displacement - fixed vs. mobile organs, recumbency
- categorize focal vs. generalized enlargement
What size is considered an abdominal mass?
> 2 bowel widths to be considered abnormal in size
What is abdominal mass effect?
organ displacement is present, but discrete mass margins are not identified due to peritoneal fluid, superimposition of structures, or lack of intra-abdominal fat
What organs have normal variations in size?
- urinary bladder
- stomach
- uterus
difficult to differentiate pathologic enlargement
What organs are enlarged only if abnormal?
- liver
- spleen
- kidneys
What organs are only seen when enlarged?
- lymph nodes
- adrenal glands
- pancreas
What is the purpose of differentiating between focal and generalized organ enlargement?
decreases uncertainty to arrive at a succinct list of differential diagnoses
What is focal organomegaly? What does it cause?
segmental or regional enlargement of an organ, involving only a portion of an organ while the remainder is normal
focal displacement of surrounding organs
What is generalized organomegaly? What does it cause?
entire organ is enlarged, typically with rounded or abnormal margins
displacement of surrounding organs
What do cranial abdominal masses cause?
caudal displacement of stomach and small intestine
What is the most likely origin of cranial abdominal masses?
liver —> generalized or focal hepatomegaly
What are the most common organ of origin of mid-abdominal masses?
- spleen
- pedunculated liver mass
- mesentery
- lymph nodes
- pancreas
What is the normal anatomy of the liver like on radiographs? What 3 structures border efface it?
uniform soft tissue opacity with smooth and sharp margins
- CRANIAL = diaphragm
- CAUDAL = stomach
- CAUDATE PROCESS = right kidney
How is liver size extrapolated? What should its margins be like?
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
What changes in liver size is expected in deep-chested and shallow-chested breeds?
DEEP - relatively small appearance of liver with normal gastric axis
SHALLOW - extend caudal to the costal arch, remaining sharp margins
Where should the gastric axis be seen on VD views?
perpendicular to the thoracic spine at T10-T11 intercostal space
What is microhepatia? What does this cause?
reduced liver volume between the diaphragm and stomach seen on both views
cranial displacement of gastric axis
What are the 2 major differential diagnoses for microhepatia?
very non-specific - correlate with blood work
- portosystemic vascular anomaly - portosystemic shunt, microvascular dysplasia common in younger patients
- chronic liver disease - cirrhosis, fibrosis common in older patients or those with known prior liver disease
What are the 2 major imaging features of generalized hepatomegaly?
- caudal displacement of the stomach gastric axis
- liver extends past caudal margin of ribs, with blunted, rounder lobar margins
What are the 4 major groups of differential diagnoses associated with generalized hepatomegaly?
- smooth margins - neoplasia (lymphoma)
- congestion - right-sided heart failure
- fat accumulation - hepatopathy, hepatic lipidosis, DM, hyperadrenocorticism
- inflammation/infection - acute hepatitis
What does focal hepatomegaly most commonly cause?
- focal, caudal, dorsal, or lateral displacement of the stomach
- proximal duodenum and right kidney displacement
What are the most common causes of focal hepatomegaly?
- nodular hyperplasia
- neoplasia - primary = hepatocellular carcinoma
- abscess
- cyst
What are the most common causes of multifocal hepatomegaly?
irregular, lumpy margins due to nodules or masses within parenchyma
- nodular hyperplasia
- neoplasia - hepatocellular carcinoma, metastasis
- hepatitis
- cirrhosis
What is the only attachment of the spleen?
gastrosplenic ligament attaches it to the fundus of the stomach
- body and tail are very mobile
What 3 things cause size variation of spleens?
- breed
- activity
- age
What is the normal shape of the spleen? What does it look like end-on?
elongated and fusiform
triangular
Where is the splenic head seen on lateral radiographs?
ventral to the thoracolumbar junction
Where is the splenic tail seen on lateral radiographs?
along the ventral abdominal wall with exact location dependent on size
Where are splenic masses most commonly seen? What needs to be ruled out?
mid-ventral abdomen
- pedunculated liver mass
- mesenteric mass
- LN enlargement
- pancreatic mass
Differential diagnoses for generalized and focal hepatomegaly:
What is the gastric axis like in these radiographs?
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
What tumors are likely to cause focal or generalized splenomegaly?
FOCAL - HSA, hematoma, hemangioma, mast cell tumor
GENERALIZED - lymphoma, MCT
