Introduction to Abdominal Radiology

Dr. LeeAnn Pack

Dipl. ACVR

Abdominal Radiography

• Abdominal Preparation– Withhold food for 12-24 hours as needed– Give enema 2-3 hours before study

• Exceptions– Critically ill– Suspect obstruction (acute abdomen)

Indications

• Vomiting

• Abdominal pain

• Hematuria

• Pain on defecation

• Abdominal mass

• Pendulous fluid filled abdomen

• Many many more

Abdominal Imaging Technique

• VD and lateral views• Positioning

– Include from the diaphragm to the pelvic inlet

– Femurs are placed perpendicular to the spine

– Hind legs pulled forward for “butt shot”

• Exposure is made on expiration• Collimate to decrease scatter!

Normal Abdomen

Technical Factors - Abdomen

• The image should be made dark enough to penetrate the liver

• The abdomen has a low inherent contrast– Use lower kVp technique and higher mAs– A grid should be used to decrease scatter

Structures Normally Seen

• Liver • Spleen• Kidneys• Stomach• Duodenum• Small Intestine

• Cecum• Colon• Bladder• Prostate• Retroperitoneal fat

Structures Not Normally Seen

• Gall bladder• Pancreas• Adrenals• Ovaries• Uterus

• Ureters• Lymph nodes• Mesentery• Vasculature

Radiography of the Liver

• Liver size– Normal– Increased– Decreased

• Liver opacity– Increased– decreased

Normal Liver Lateral View

• Caudoventral margin extends to or slightly caudal to the costal arch

• Long axis of the stomach should be parallel to the ribs or perpendicular to the spine

Normal Liver VD View

• Long axis of the stomach is perpendicular to the spine

• Caudal margins of the liver are difficult to visualize on this view

Hepatomegaly

• Caudoventral margin projects caudal to costal arch

• Liver margins may be rounded

• Pylorus is displaced caudodorsally and to the left– Change in long axis

of stomach

Hepatomegaly

• Generalized with smooth margins– Cushing’s– Fatty infiltration

• Diabetes Mellitus

• Hepatic lipidosis

– Passive congestion• RHF

– Neoplasia• LSA

– Inflammation, cholestasis

Hepatomegaly

• General enlargement lumpy margins– Malignant neoplasia– Nodular hyperplasia

• Focal enlargement– Neoplasia– Nodular hyperplasia– Cysts, abscesses

Microhepatia

• Stomach shifted cranially – especially pylorus– May be functionally normal– Portosystemic shunt– Hepatic fibrosis

Changes in Liver Opacity

• Increased– Mineralization– Biliary – choleliths– Parenchymal

• Parasitic cysts• Granulomatous ds• neoplasia

• Decreased– Gas

Spleen

• On the VD view the head of the spleen is seen– caudolateral to the stomach fundus– craniolateral to the left kidney

• The position of the tail varies– More often seen on right lateral– In cats

• seen “laying along left side” sometimes on VD• Not seen routinely on lateral

Splenomegaly

• Normal shape, smooth margins– Drug induced

• Sedatives, anx

– Diffuse infiltrative process• LSA, HSA

– Vascular stasis– Splenic torsion

Splenomegaly• Focal enlargement

– Hematoma– Nodular hyperplasia– Neoplasia

• Hemangiosarcoma• Hemangioma

Splenic Masses

• May occur in the head, body or tail

• Located mid abdomen, left or right

• May be very large

• Can cause abdominal organ displacement– Can displace stomach cranially and small

intestines in various direction depending on location

Kidneys

• Right located more cranial than left

• Dogs = 2½-3½ * L2 on VD

• Cats = 2.4-3 * L2 on VD

• Size should only be evaluated on the VD view due to magnification on the lateral

• IV contrast can be used if necessary

Kidneys• Increase in size

– Acute inflammation– Infiltrative process

• LSA

• Decrease in size– Hypoplasia– Fibrosis– Renal failure

• Mineralization – look a kids on both views• Focal change in shape

– ACA

Stomach

• Caudal to liver

• Axis parallel to ribs

• Change in size, shape, mineralized, rugal fold abnormal

• Right vs. Left lateral (air/fluid)

• Foreign bodies, outflow obstruction

Stomach

• Dog – crosses from left to right

• Cat – from left to midline

Which one is Left? Right?

Small Intestine

• Duodenum – fixed along right side

• Jejunum and ileum – position varies

• Normal width = < 3* last rib width

• Contains both air and fluid

• Can not determine wall thickness

• Peyer’s patches, string of pearls

VD Abdomen

Small Intestine Obstruction

Cecum and Colon

• Cecum– mid right abdomen– Comma shaped –may contain air– Not often seen in cats

• Colon– Ascending, Transverse, Descending– Normal width = < 5 * last rib width

Colon

Urinary Bladder

• Dog – caudal abdomen or pelvic

• Cat – always intra-abdominal

• Vary in size (empty to very distended)

• Bladder wall changes can not be determined on radiographs

Urinary Bladder

• Change in Opacity• Mineral

– Cystic calculi

• Air– Emphysematous

cystitis– Iatrogenic

Prostate

• Usually well visualized in intact males

• Should be symmetrical with smooth margins

• Enlarged if – > 50% of pelvis inlet width (VD)– >70% of sacro-pubic distance (lateral)

Prostate

• Enlargement– Hypertrophy– Neoplasia– Prostatitis– Abscess

• Paraprostatic cysts• Mineralization

Prostatic Adenocarcinoma

Pancreatitis

• The pancreas is not normally seen• Increased density and decreased

serosal detail in the right cranial quadrant

• Duodenum may be persistently distended with gas (sentinel sign)

• Duodenum can be pushed to the right and pyloroduodenal angle is increased

Adrenal Glands

• Seen only when enlarged or mineralized• Enlargement

– Pheochromocytoma– Cortical carcinoma– Adenoma

• Adrenal mineralization– Dystrophic mineralization of tumors– Mineralization of non neoplastic adrenals

(cats)

Reproductive System

• Uterine enlargement– Metra’s– Gravid uterus

• Ovarian enlargement– Neoplasia

• Enlarged retained testicle– neoplasia

Enlarged Lymph Nodes

• Medial iliac (sublumbar)– Increased opacity (soft tissue) seen in

caudal abdomen ventral to caudal lumbar spine

– May displace colon ventrally

• Mesenteric LNN rarely large enough for radiographic detection

• US is best to evaluate for LAN

Enlarged Medial Iliac LN

• Lymphosarcoma – Most common

• Metastasis from neoplasia in the pelvis canal or further caudally– Prostate– Perineal tumors

Loss of Intra-abdominal Detail

• AKA – loss of serosal surface detail

• Causes:– Lack of Fat

• Young• Emaciated

– Peritoneal fluid– Pancreatitis, Peritonitis– Carcinomatosis

Thin and Young

Decreased Serosal Surface Detail

Free Intra-Peritoneal Gas

• Penetration of the abdominal wall– Surgery (common)– Penetrating wounds

• bullets

• Bowel perforation – Obstruction– GI ulcer rupture

• Large mounts may persist for days or weeks

Free Intra-Peritoneal Air

• Horizontal beam radiography – to detect small volumes of air– Lateral view with dog in dorsal

recumbency, cranial aspect elevated• Air collects under the diaphragm

– VD view with dog in left lateral recumbency• Air up against the liver instead of fundus

Free Peritoneal Air