Abdominal Imaging 2024 PDF

Abdominal Imaging Georgina Catlow BVSc MRCVS 1 Learning outcomes Describe the positioning of common species encountered in small animal practice in relation to generating interpretable radiographic views of the abdomen Describe the number and type of views requi...

Abdominal Imaging Georgina Catlow BVSc MRCVS 1 Learning outcomes Describe the positioning of common species encountered in small animal practice in relation to generating interpretable radiographic views of the abdomen Describe the number and type of views required to achieve diagnostic quality films for a range of conditions and apply those to common examples Identify and recognise aspects of those views that my confound or prevent interpretation of films in relation to the abdomen Describe the various contrast media used in practice or radiography and, in general, how they may be employed 2 Indications – Abdominal radiography Abdominal distension Investigation of palpable masses Weight loss Abdominal pain Screening for neoplasia Screening following trauma Gastrointestinal signs Urinary signs Reproductive tract examination 3 General Considerations » Exposure Low kV and High mAs » End expiratory view Take during expiratory pause Less chance movement blur » Reduce scatter Consider use of a grid 4 Patient Preparation Withhold food for 12 hours Allow defecation and urination prior to study If urinary study, perform enema prior to study Coat should be dry and free from dirt Conscious, sedated, general anaesthesia Conscious animals must not be held, and positioning aids required Animals should not be sedated or under GA for gastrointestinal contrast studies General anaesthesia required for urological studies 5 Standard Radiographic Views Patient Positioning Ventrodorsal Right Lateral Left Lateral (Dorsoventral) (Decubitus lateral) Ideally three views should be taken of every vomiting animal! 6 Abdominal Imaging – approach to interpretation 7 Review of an abdominal radiograph Röntgen Signs Size o Enlargement liver, spleen, kidneys can all occur with pathology o Compare size to another structure or a fixed landmark Shape o Physiological enlargement o Pathological enlargement Number o Failure to see an organ is associated with displacement of the missing structure Opacity o Abnormal mineralisation or metallic opacity from foreign body o Mineralisation in urinary tract from calculi o Free abdominal gas in abdomen from gastrointestinal perforation 11 Review of an abdominal radiograph Röntgen Signs Margination o Free abdominal fluid results in loss of serosal detail o Young and emaciated animals have poor serosal detail o Position o Change in position can be due to change in size or shape o Small intestinal loops very mobile and easily displaced 12 Review of an abdominal radiograph 10 Gastrointestinal tract - Stomach Cranial abdomen, caudal to liver Opacity depends on content Gas distribution depends on position Ultrasound often better to determine wall layering o Serosa o Muscularis o Submucosa Thrall,D. Textbook of Veterinary Diagnostic o Mucosa Radiology o lumen 13 Gastrointestinal tract - Stomach Thrall,D. Textbook of Veterinary Diagnostic Radiology Gastric axis (from fundus to pylorus, P = pylorus, B = body, F = fundus, S= spleen, normally parallel to ribs) R= rib 14 Gastrointestinal tract – Small Intestine Ileus Failure of ingesta to pass through the GI tract An abnormal increase in diameter of the small intestine Greater than 1.6 x height lumbar vertebrae L5 Dilated loops contain fluid, gas, or mixture Assess number of dilated loops Obstructive (Mechanical) Functional (Paralytic) Types Foreign body Hypokalaemia Neoplasia Peritonitis Intussusception Inflammation (enteritis) 15 Gastrointestinal tract – Small Intestine 14  Gastrointestinal tract – Small Intestine Foreign Bodies Metallic or mineralised can be identified on plain radiograph Intestinal dilation and odd gas patterns increase suspicion ‘Gravel sign’ – partial obstruction Positional radiography – to redistribute gas and fluid Linear – intestinal plications Dilated loop small intestine Plication Thrall,D. Textbook of Veterinary Diagnostic Radiology 16 Gastrointestinal tract – Small Intestine Intussusception Younger animals (worms) Associated with neoplasia in older animals Ileocolic junction “sausage shape” mass in abdomen Diagnosis with ultrasound 17  Images: Textbook of veterinary anatomy. Dyce Gastrointestinal tract – Large Intestine Anatomy! 5, 6, 7: ascending, transverse and 9,10,11: ascending, transverse and descending colon descending colon 17 Gastrointestinal tract – Large Intestine Relatively consistent in appearance Filled various amounts heterogenous faecal material Constipation o Large intestinal dilation with opaque faecal material o Can see with megacolon o Caused by bone ingestion Displacement o Ventrally: enlargement of kidney, sub-lumbar LN, retroperitoneal space o Dorsally: enlarged prostate, uterus (pyometra), bladder 18 Displacement examples Enlarged sublumbar LN displace the colon Enlarge prostate causing narrowing of large bowel 19 Gastrointestinal tract Contrast Studies Positive contrast studies = more opaque than soft tissue o Barium sulphate for GIT studies o per os / per rectum o Relatively palatable o Good at coating mucosa o Contraindicated if perforation or swallowing disorder (aspiration risk) Perform AFTER plain radiography 19 Gastrointestinal tract – Contrast Studies Barium Swallow Starve 12-24 hours Given as liquid (stomach tube) Lateral and VD immediately Include thorax (oesophagus) Luminal filling defects Barium Meal Starve 24 hours Thrall,D. Textbook of Veterinary Diagnostic Radiology Mix food with barium and feed to animal Filling defect along greater curvature of stomach Serial images (10-30min) taken to evaluate gastric emptying and abdominal transit times Gastric emptying can be artificially prolonged in stress 20 Liver and spleen Generalised hepatomegaly Caudal displacement pylorus Extension beyond costal margin Non specific finding Ultrasound guided FNA required for diagnosis Neoplasia Liver: Generalised hepatomegaly or cranial abdominal mass Spleen: Variable sized mid abdominal mass Common cause of haemoabdomen = loss of serosal detail Portosystemic shunt Microhepatica Abdominal ultrasonography with Doppler required 21 Urinary Tract Kidneys size, shape, opacity No information on function Length: 2.5 -3.5 x L2 (dog) / 2.4 – 3.0 x L2 (cat) both assessed on VD view Ureters and Urethra Not seen (need contrast study) Bladder Location, size, shape No information on luminal surface bladder wall Ultrasound better diagnostic tool Prostate (dog) Size and location Height not more than 70% height pelvic brim Ultrasound better diagnostic tool 22 Urinary Tract Anatomy! Kidney shadow and bladder visible K Kidneys superimposed on the B lateral view 24 Urinary Tract This radiograph shows renal calculi as radio-opaque structures in the kidney The kidney is relatively fixed in the retroperitoneal space but if enlarged can ventrally displace the colon 25  Images: Textbook of veterinary anatomy. Dyce Urinary Tract Anatomy! 2 – kidneys 3 – ureters 4 - bladder 26 Urinary Tract 27 Urinary Tract - more examples of radiopacity in the bladder Remember only Struvite, Calcium Oxalate and Calcium Phosphate stones are radio-opaque Top tip: when looking for calculi in male dogs, always check the urethra! 28 Urinary Tract Contrast Studies Double contrast cystogram Retrograde Urethrogram Retrograde Vaginourethrogram Intravenous urography Contrast medium Positive contrast Water soluble iodinated contrast material “Conray” or “Omnipaque” Negative contrast Air or CO2 Preparation Enema essential Plain radiographs always taken first! 29 Urinary Tract – Contrast Studies Double contrast cystogram General anaesthesia Pass urinary catheter and empty bladder Fill bladder gas (air/CO2) Palpate bladder for fullness Then small volume positive contrast Withdraw catheter from lumen prior to exposure Indications Wall thickness Wall lesions Identification calculi Images courtesy of A.Denning 30 Urinary Tract – Contrast Studies Retrograde Urethrogram General anaesthesia Pass urinary catheter Tip of prefilled catheter into terminal urethra Urethra occluded around catheter (use foley catheter) Exposure during or at end-injection Hind limbs drawn cranially Indications Male Dysuria Anatomical abnormalities Images courtesy of carevetspecialists Filling defect in urethra 31 Urinary Tract – Contrast Studies Retrograde Vagino-urethrogram General anaesthesia Pass urinary catheter, empty bladder Catheter placed into vestibule and vulva clamped Urethra occluded around catheter (use foley catheter) Gentle infusion of contrast to avoid tearing vaginal wall. Expose before end of injection Indications Female Bladder wall rupture Urethral disease Images courtesy of A.Denning 32 Urinary Tract – Contrast Studies Intravenous Urethrography Check renal parameters Administer IVFT General anaesthesia, do not withhold water Contrast administered intravenously Views Plain lateral and VD Lateral and VD immediately post injection and at 5min, 10min Lateral at 15min post injection Indications Internal architecture kidneys Delineates ureters Ectopic ureter diagnosis 33 Radiography & Ultrasonography Why Use both? Foreign body – loops of gas filled intestine easier to recognise on radiography but non radio-opaque foreign bodies may require ultrasound Diarrhoea – ultrasound can assess intestinal wall thickening and motility which radiography cannot Abdominal mass – both can give an idea on location but ultrasound will give better information on structure and allow FNA Abdominal fluid – loss serosal detail will limit radiography but ultrasound can be used to investigate and sample Remember Endoscopy! 34 Loss of serosal detail due to ascites 35 Don’t forget to evaluate the whole radiograph, not just the abdomen……. 36 Summary Abdominal radiography and ultrasonography to be used together Use consistency in exposure and positioning Remember your radiographic anatomy Enlarged abdominal organs will change anatomy and indicate abnormalities Radiographic signs often no specific for diagnosis and sampling/further diagnostic may be required Contrast studies can be useful but are now largely superseded by other imaging modalities. 37 38