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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