P. 566

An Urban Experience
 uid. The ileum is comparatively thick (up to 3.2mm) and characterized by a prominent hyperechoic submucosal layer. The colonic wall thickness depends on contents and ranges from less than 1mm when  lled with faeces to more than 2mm when empty. The body and left lobe of the pancreas are readily visualized caudal to the stomach, especially in older cats. The normal pancreas measures less than 1cm in thickness and contains a central duct. Some abdominal lymph nodes (gastric, medial iliac, ileocolic) are occasionally visualized in normal cats, are of similar echogenicity as the spleen, and measure less than 5mm in thickness. Female reproductive organs which may be visible include the ovaries and a pregnant uterus; internal male reproductive organs are not seen.
Contrast procedures:
An oesophagram is the imaging study of choice to
rule out disorders of the oesophagus, especially with
a presenting complaint of regurgitation rather than vomiting. Other gastrointestinal tract contrast procedures (barium series, colonogram) have largely been replaced by ultrasound and endoscopic procedures. Similarly, urinary tract contrast studies have largely
been replaced by ultrasound. However, an excretory urogram remains the technique of choice to evaluate ureteral integrity, and a cystourethrogram is helpful in identifying a bladder rupture or an intrapelvic urethral lesion inaccessible for ultrasonographic evaluation.
Imaging  ndings in cats with primary gastrointestinal disease:
Common gastrointestinal diseases in cats include
foreign bodies, in ammatory disorders, neoplasia and ileus. Foreign bodies may be radio-opaque and easily detectable on radiographs. Non-opaque foreign bodies are a diagnostic challenge, and a diagnosis is usually made based on secondary signs (obstruction or plication of intestine in case of a linear foreign body) or using ultrasound. In ammatory and neoplastic disorders are more commonly diagnosed using ultrasound, although advanced disease usually also results in radiographic changes. In ammatory disorders result in mild
to moderate generalized /multifocal intestinal wall thickening. Intestinal wall layers are usually maintained but are frequently altered (echogenicity changes of the mucosal layer, thickening of the muscularis layer). Mild
to moderate mesenteric lymphadenopathy is common. Lymphoma is by far the most common gastrointestinal neoplasm in cats; other neoplasms include mast cell tumour, adenocarcinoma and smooth muscle tumours. A focal mass (or masses) with loss of wall layers is most consistent with an intestinal neoplasm, and enlargement of local lymph nodes is common. Unfortunately, overlap exists between imaging  nding in cats with in ammatory and neoplastic disorders, and some intestinal neoplasms (lymphoma, mast cell tumours) behave the same way
as in ammatory disease. Ileus may be diagnosed either using radiographs or ultrasound. Obstructive ileus manifests as dilation of some intestinal segments while others retain their normal diameter; therefore, 2 different populations of intestinal segments are present. Paralytic ileus results in generalized intestinal dilation and decreased to absent intestinal motility noted on ultrasound.
Imaging  ndings in cats with non-gastrointestinal disease:
Radiographic and ultrasonographic abnormalities
may be detected in one or more organs of a vomiting cat. As imaging changes may or may not be clinically signi cant they have to be correlated with  ndings on clinical examination and laboratory analyses. Common liver diseases associated with vomitus in cats include cholangiohepatitis and lymphoma. Both result
in increased hepatic size with variable echogenicity changes observed on ultrasound. Sludge associated with the gall bladder is suggestive of cholecystitis
in cats. Renal disease is very common in cats and frequently results in vomiting. In ammatory (e.g.
FIP, acute nephritis) and neoplastic diseases (e.g. lymphoma) result in enlarged kidneys with variable echogenicity changes. Hydronephrosis also results in renomegaly on radiographs and is easily recognized by an enlarged renal pelvis on ultrasound. Visible ureters are concerning for obstruction and should be traced
to identify an obstructive lesion. Chronic degenerative renal disease results in small and irregularly shaped kidneys. Urolithiasis is readily diagnosed using either radiographs or ultrasound. Peritonitis and diffuse spread of abdominal neoplasia (carcinomatosis) result in lack of serosal margin detail (often with a granular appearance) on radiographs. Ultrasound  ndings
include abdominal effusion, hyperechoic mesenteric
fat and mesenteric/omental nodules. Pancreatitis is common in cats and may be dif cult to identify with imaging especially in chronic cases. A hypoechoic, irregular pancreas may be observed on ultrasound. Other possible  ndings include hyperechoic mesenteric fat, abdominal effusion and dilation of the pancreatic duct and common bile duct. Concurrent  ndings suggesting in ammatory bowel disease and/or cholangiohepatitis are common. Splenomegaly and enlarged abdominal lymph nodes may be noted on radiographs or ultrasound and suggest in ltrative in ammatory or neoplastic disease.
1. Thrall DE. Textbook of Veterinary Diagnostic Radiology. 6th ed. St. Louis: Elsevier Saunders; 2013.
2. Barr F, Gaschen L. BSAVA Manual of Canine and Feline Ultrasonography. Gloucester: BSAVA; 2011.
3. Pennick D, d’Anjou MA. Atlas of Small Animal Ultrasonography. Ames: Wiley Blackwell; 2015.

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