NORMAL CANINE PEDIATRIC GASTROINTESTINAL ULTRASONOGRAPHY

The normal sonographic appearance of the adult canine gastrointestinal tract has been described. Interpretation of abdominal ultrasonographic findings in puppies is difficult due to the lack of information on normal ultrasonographic findings. The gastrointestinal tract, jejunal lymph node size and the presence and appearance of abdominal fluid were investigated in 23 normal, 7–12-week-old Beagle puppies. The duodenal wall thickness was greater than in other parts of the gastrointestinal tract (mean 3.8 ± standard deviation [SD] 5 mm, range 3.2–4.8 mm). The mean stomach wall thickness was 2.7 ± SD 0.4 mm (range 2.2–3.7 mm), the mean jejunal wall thickness was 2.5 ± SD 0.5 mm (range 1.2–3.4 mm), and the mean colonic wall thickness was 1.3 ± SD 0.3 mm (range 0.7–2.0 mm). In addition, mean duodenal and jejunal mucosal layer thicknesses measured 2.7 ± SD 0.5 mm (range 2.0–3.8 mm) and 1.5 ± SD 0.4 mm (range 0.6–2.5 mm), respectively. Homogenous, hypoechoic jejunal lymph nodes were easily found and the mean thickness was 7.1 ± SD 2.2 mm (range 1.5–12.5 mm). A mild amount of anechoic free peritoneal fluid was present in all puppies.     

EVALUATION OF THE ABDOMEN USING ULTRASOUND FOLLOWING A VENTRAL MIDLINE CELIOTOMY

Over the last 20 years, ultrasound has become a useful diagnostic tool in veterinary medicine. The purpose of this study was to use ultrasonographic examinations to determine if intra-abdominal contents could be visualized. Nineteen dogs, ranging from 8 months to 18 years of age were included. Each animal was evaluated sonographically prior to surgery, 24 h after surgery, and then 2-6 weeks following the surgical procedure. The results of our study suggest that ultrasound is an effective means for evaluation of the abdomen and surgery site following surgery. Both the abdomen and surgery site were clearly visualized in all dogs. In addition, subjective evaluation of the intra-abdominal contents was performed. The limiting factor in this study was not the presence of air, as was expected. Rather the limiting factor for appropriate visualization was pain. The information obtained could prove to be useful to surgeons and radiologists in assessing a patient's status postoperatively.     

ULTRASONOGRAPHY OF PERIPHERAL NERVES IN THE NORMAL ADULT HORSE

A study of the ultrasonographic appearance and size of the sciatic, tibial, peroneal, suprascapular, radial, median, and ulnar nerves and a comparison with the anatomic size and location of these nerves in the normal adult horse is reported. Cadavers and live horses were studied. Landmarks for localization and techniques for nerve identification are described. The depth and diameter of each nerve at various locations and the success rate in imaging each nerve are reported. Statistically significant correlations were found between anatomically and ultrasonographically measured nerve depths and diameters. The success rate in identifying nerves was 70% in the live horses and 49% in cadavers, with the deep peroneal nerve being the easiest to identify. Some applications of this technique in horses are discussed.     

ULTRASONOGRAPHY OF THE NORMAL CANINE GASTROINTESTINAL TRACT

The normal sonographic appearance of stomach, small bowel, and colon was determined in normal dogs of small, medium, and large breeds. In all dogs studied, the stomach wall ranged from 3 mm to 5 mm in thickness, and the small and large bowel wall ranged from 2 mm to 3 mm in thickness. Peristalsis was routinely observed in the stomach and small bowel, but not in the colon. Ultrasonic identification of five gastrointestinal wall layers corresponding to the mucosal surface, mucosa, submucosa, muscularis propria, and subserosa/serosa was possible. Specific segments of the gastrointestinal (GI) tract were isolated and scanned in a water bath. In one dog, ultrasonic and histologic findings were compared and confirmed the anatomical identification found with ultrasound. Similarities and differences between the ultrasonic appearance of the GI tract of humans and small animals are discussed.     

DUODENAL ULTRASONOGRAPHY IN THE NORMAL ADULT HORSE

Ultrasonography was used to evaluate the duodenum of 6 clinically normal horses. Examinations were performed in horses which each, alternatively, received diets of; 1) concentrates and hay, 2) hay only, or 3) after 36 hours of starvation. The duodenum was constantly visualized just ventral to the right kidney at the 16th and 17th intercostal spaces on a line joining the olecranon and tuber sacrale. Cranial to the 16th intercostal space visibility depended on thickness of interposing liver and lung field interference. Duodenal distensions, contractions and content are described. Starved horses had fewer contractions and distensions than horses on hay, or hay and concentrate diets but the difference was not significant. Duodenal wall thickness ranged from 3–4 mm. Ultrasonographically five layers, corresponding to the mucosal surface, mucosa, submucosa, muscularis propria and serosa, could be identified. A necropsy specimen of the duodenum was evaluated histologically and Ultrasonographically in a water bath for comparison.     

SONOGRAPHY OF THE NORMAL FELINE GASTROINTESTINAL TRACT

The normal sonographic appearance of the stomach in various degrees of distension, the duodenum, the small intestine, and the large intestine was determined in awake and sedated cats. The mean stomach rugal fold thickness was 4.38 mm, and the interrugal thickness was 2.03 mm. No significant difference in stomach wall thickness was seen when the stomach was empty, half full, or full. The duodenal wall thickness was significantly greater than other parts of the small intestine, and this difference was accentuated by sedation (awake mean 2.4 mm; sedated mean 2.71 mm). The mean small intestinal wall thickness was 2.1 mm, and the mean colonic wall thickness was 1.67 mm. The five characteristic sonographic layers similar to that seen in the gastrointestinal tract of other species were routinely identified at all regions of the feline gastrointestinal tract.     

ULTRASONOGRAPHY OF ADRENAL GLANDS IN NORMAL FERRETS

The adrenal glands of 20 normal ferrets were imaged with ultrasound. Of the forty glands, only 4 (three right and one left) could not be clearly identified. Mean (±standard deviation) dimensions of the right (7.6 ± 1.8 mm length by 2.6 ± 0.4 mm width) and left (7.2 ± 1.8 mm length by 2.8 ± 0.5 mm width) glands were similar. Both adrenal glands were wider (p<0.05) sonographically in males than females. Measured length and width of the right gland positively correlated (p<0.05) with body weight. The glands had a hypoechoic outer zone and hyperechoic central region, were elongate to avoid in shape and located medial and, variably, at the level of the cranial pole of the ipsilateral kidney. This study demonstrates that normal adrenal glands can be imaged in ferrets.     

ULTRASONOGRAPHY OF GASTROINTESTINAL FOREIGN BODIES

The ultrasonographic findings of fourteen animals having gastrointestinal foreign bodies are presented. Ultrasonography confirmed the presence and location of foreign material within the gastrointestinal tract when radiographic findings were unclear. The acoustic patterns arising from each foreign body varied depending on its physical properties and interaction with the ultrasound beam. These patterns, some of which seemed characteristic for certain types of foreign bodies, and the associated findings of mechanical ileus, ascites, mesenteric lymph node enlargement and localized pancreatitis are discussed.     

EVALUATION OF IOHEXOL AS A GASTROINTESTINAL CONTRAST MEDIUM IN NORMAL CATS

The non-ionic, iodinated contrast medium, iohexol (240 mg I/ml) was evaluated as a gastrointestinal (GI) contrast medium in cats. Iohexol, both undiluted and diluted with tap water, was administered via a percutaneous endoscopically-placed gastrotomy (PEG) tube to 4 mature clinically normal cats. The dilution of contrast medium administered was 1:1, 1:2, and 1:3, and doses were 10 ml/kg and 5 ml/kg body weight. All combinations of dilution and dose of iohexol provided adequate visualization of the contrast medium column within the GI tract, and results were not significantly different than those observed using 30% w/v barium sulfate. Dehydration and diarrhea were not observed after contrast medium administration, but vomiting occurred within 15–30 minutes after administration of undiluted iohexol in all experimental cats. Renal opacification did not occur on exposures made through a 2 hour period, and dilution in transit was not apparent.     

THE NORMAL UPPER GASTROINTESTINAL EXAMINATION IN THE FERRET

Upper gastrointestinal examinations were performed in 11 unsedated ferrets and 4 ferrets sedated with ketamine and diazepam. Each animal received a 8-13 mL/kg body weight dosage of barium liquid (30% weight:volume). Radiographs were made immediately and at 5, 10, 20, 40, 60, 90, 120 and 150 min (mins) after the barium was administered. Gastric emptying began immediately. Mean total gastric emptying was longer in sedated ferrets (130 +/- 40 min versus 75 +/- 54 min); however, this difference was not statistically significant (p = 0.18). Small intestinal transit time was less than 2 h in all ferrets. The barium-filled small bowel was best visualized on the 20- and 40-min radiographs and did not exceed 5-7 mm in width. Flocculation of barium in the small intestine and adherence of barium to the stomach mucosa was seen in almost all animals. The longitudinal colonic mucosal folds in the colon were well visualized in the normal upper gastrointestinal study and aided in distinguishing small intestine from large intestine. The use of ketamine and diazepam sedation did not significantly affect the parameters evaluated in the upper gastrointestinal study series.     

INTRAOPERATIVE SPINAL ULTRASONOGRAPHY IN DOGS: NORMAL FINDINGS AND CASE-HISTORY REPORTS

Intraoperative spinal ultrasonography was performed in cervical and lumbar spine of 2 and 5 normal dogs, respectively, following ventral slot technique or dorsal or hemilamenectomy. The dura was hyperechoic, while the parenchyma was hypoechoic. The subarachnoid space was anechoic. An echogenic line was present in the center of the spinal cord, as seen in human. Pulsation of the spinal cord was noted during M-mode imaging. Clinical findings of one dog with thoracolumbar disk herniation and one with thoracic vertebral fracture/subluxation confirmed the usefulness of intraoperative spinal ultrasonography for real time evaluation of spinal canal spatial abnormalities (mass lesion and degree of spinal cord compression on scanning planes) and spinal cord motion. Follow-up ultrasound examinations were possible from 6 days postoperatively.     

ULTRASONOGRAPHY OF HISTOLOGICALLY NORMAL PARATHYROID GLANDS AND THYROID LOBULES IN NORMOCALCEMIC DOGS

The purpose of this study is to characterize the sonographic appearance of canine parathyroid glands using high‐resolution ultrasonography. Ten cadaver dogs were studied after euthanasia for reasons not relating to the parathyroid. The cervical region was examined using a 13–5 MHz linear transducer in right and left recumbency. Ultrasonographic features of the parathyroid and thyroid glands were compared with the gross and histopathologic findings. Thirty‐five structures were identified sonographically as parathyroid glands but only 26 of 35 glands (74% positive predictive value) were proven to be normal parathyroid glands histopathologically. Of the nine false positives, five (14%) were proven to be lobular thyroid tissue. The remaining four (11%) structures were visible grossly or found histopathologically. There were no statistical differences between ultrasonographic and gross measurements of the parathyroid glands. The average size as seen sonographically was 3.3 × 2.2 × 1.7 mm and the average gross size was 3.7 × 2.6 × 1.6 mm (length, width, height). The average size of the thyroid lobules assessed sonographically was 2.3 × 1.6 × 0.8 mm (length, width, height). Normal parathyroid glands can be identified using high‐resolution ultrasonography. But some thyroid lobules will be misinterpreted as parathyroid glands; this will result in false positives when identifying parathyroid glands with ultrasonography.     

TRANSESOPHAGEAL ULTRASONOGRAPHY OF THE NORMAL CANINE MEDIASTINUM

The mediastinum of eight normal research dogs was examined by transesophageal ultrasonography with a 5MHz frequency transducer to establish a baseline for future use of this new imaging modality as a diagnostic tool. Each examination consisted of 360 degree scans in both transverse and sagittal planes from the thoracic inlet to the esophageal hiatus. Dissections of four of these research dogs were then performed to confirm transesophageal ultrasonography findings. Transesophageal ultrasonography of the mediastinum was a good imaging modality for the evaluation of the heartbase, the major cranial mediastinal vessels, the descending aorta, and occasionally part of the azygos vein. Anatomic orientation was best obtained by beginning the examination at the heart base. Lymph nodes and smaller caliber vessels could not be distinguished from surrounding tissues; however, Doppler ultrasound was useful for identifying the smaller vessels. Although a 5 MHz frequency transducer is preferred for transesophageal echocardiography, a higher frequency transducer would improve the resolution of the images of small near-field structures and may be more appropriate for mediastinal imaging.     

CEREBRAL VENTRICULAR SIZE IN DEVELOPING NORMAL KITTENS MEASURED BY ULTRASONOGRAPHY

To evaluate the age of fontanelle closure of normal kittens and the size of their lateral ventricles, 50 ultrasonographic examinations using the bregmatic fontanelle as an acoustic window were made. Seven kittens, laboratory animals, were included in the study. To verify the location of the lateral ventricle, two of the kittens were sacrificed as neonates. In one of them ink was injected prior to autopsy into one lateral ventricle under sonographic guidance. In a longitudinal study of five of the kittens, the skull depth and the depth of the central part of the lateral ventricle reproduced in a longitudinal view could be measured up to the age of about 5 months. During that period, the skull depth increased from a median value of 1.95 cm (1.92-1.98) in a seven-day-old cat to 2.58 cm (2.52-2.59) in a 154-day-old cat, while the afore-mentioned ventricle values increased from 0.3 mm to 1.1 mm.     

ULTRASOUND EVALUATION OF SMALL BOWEL THICKNESS COMPARED TO WEIGHT IN NORMAL DOGS

The use of ultrasound to measure small bowel thickness is an important part of any ultrasound examination of the abdomen. Increased thickness of the intestinal wall is a hallmark for the detection of diseases ranging from inflammatory bowel disease to neoplasia. Our subjective impression has been that dogs with no clinical signs of gastrointestinal disease often have sonographic measurements greater than published norms. The purpose of this study was to prospectively reevaluate these norms. The clinical history on all dogs receiving an abdominal ultrasound examination was evaluated for signs of gastrointestinal disease. Those without clinical signs were entered into this study. The documentation of body weight, breed, jejunal thickness, and duodenal thickness was made in 231 dogs. Dogs were placed into five groups based on their weight. Sixty-nine breeds were represented with weight ranging from 2.1 to 64 kg. A statistically significant (P < or = 0.05) correlation between body weight and both jejunal and duodenal thickness was observed. We also found that the maximum thickness in both jejunum and duodenum in healthy dogs was larger than previously reported. These data indicate norms for the jejunum of < or = 4.1 mm for dogs up to 20 kg, < or = 4.4 mm for dogs between 20 and 39.9 kg, and < or = 4.7 mm for dogs over 40 kg. The data indicate norms for the duodenum < or = 5.1 mm for dogs up to 20 kg, < or = 5.3 kg for dogs between 20 and 29.9 kg, and < or = 6.0 mm for dogs over 30 kg.     

SURVEY OF THE USE OF RADIOGRAPHY VS. ULTRASONOGRAPHY IN THE INVESTIGATION OF GASTROINTESTINAL FOREIGN BODIES IN SMALL ANIMALS

A question frequently asked by clinicians who are treating small animals suspected of having gastrointestinal foreign bodies is whether one imaging test such as survey radiography or ultrasonography is sufficient to make the diagnosis. A study was undertaken to try and answer this question. Survey abdominal radiography and ultrasonography was performed on 16 small animals (11 dogs, five cats) with clinical signs of an obstruction because of a confirmed gastrointestinal foreign body. The majority of the foreign bodies (14/16) were confirmed by surgical removal and were located in the small intestine. A gastric foreign body was retrieved endoscopically and a colonic foreign body was passed in the feces. Radiographically identifiable foreign bodies were evident in nine animals. Small intestinal overdistension was present radiographically in seven animals. Ultrasonography detected a foreign body in all 16 animals. The foreign bodies were identified by their distal acoustic shadowing and variable degrees of surface reflection. An intestinal perforation was detected sonographically but not radiographically. The value of additional sonographic findings including thickening of the gastrointestinal wall and loss of layering, free peritoneal fluid, and lymphadenopathy in these animals is discussed. The findings in this series suggest that in a small animal with a gastrointestinal foreign body, ultrasonography alone could be used to make the diagnosis and may be a more appropriate choice than survey radiography.     

ULTRASONOGRAPHIC FEATURES OF CANINE GASTROINTESTINAL PYTHIOSIS

Pythiosis is a chronic pyogranulomatous infection of the gastrointestinal tract or skin caused by the water borne pathogen Pythium insidiosum. The ultrasonographic features of nine dogs with gastrointestinal pythiosis are reported. The stomach, duodenum, jejunum or colon were affected. All dogs had thickening of the gastrointestinal wall and areas with obliteration of the normal layered appearance. In one dog an eccentric mass was found arising from the serosal surface of the wall of the colon with mild diffuse wall thickening. Regional lymph node enlargement was seen in seven of the nine dogs. One dog had invasion of the pancreas and signs compatible with extrahepatic biliary obstruction. When compared to previous reports of gastrointestinal neoplasia, the features of wall thickening, loss of layering and regional lymphadenopathy are not considered specific for gastrointestinal pythiosis. Histological examination of tissue specimens is required for diagnosis.     

THE UPPER GASTROINTESTINAL EXAMINATION IN THE CAT: NORMAL RADIOGRAPHIC APPEARANCE USING POSITIVE CONTRAST MEDIUM

The normal radiographic appearance of the feline upper gastrointestinal (UGI) examination following oral administration of barium sulfate suspensions was described. Important findings included the minimal gastric air and small bowel gas present on survey abdominal radiographs. Gastric appearance was nearly constant. A normal duodenal pattern, referred to as a "string of pearls", was described. Small bowel lumen size was consistently less than 12 mm. Small bowel mucosal patterns varied widely. The most commonly identified normal radiographic UGI patterns in this study were found consistently in a group of 26 cats thought to be without gastrointestinal disease. Because of the consistency of observation of many radiographic patterns, rapid gastric emptying, and a short small bowel transit time, normal UGI examinations in the cat present a more constant appearance than in the dog, thus making them more valuable as well as easier to conduct.     

ULTRASONOGRAPHIC FEATURES OF CANINE GASTROINTESTINAL STROMAL TUMORS COMPARED TO OTHER GASTROINTESTINAL SPINDLE CELL TUMORS

Canine gastrointestinal stromal tumors (GISTs) are a recent subtype of gastrointestinal spindle cell tumor recognized with the increasing use of immunohistochemistry. To our knowledge, no imaging features have been described in immunistochemically confirmed canine GISTs. The objective of this retrospective, cross‐sectional study was to describe ultrasonographic features of canine GISTs compared with other spindle cell tumors. Thirty‐seven dogs with an ultrasonographically visible gastrointestinal mass and a histopathologic diagnosis of spindle cell neoplasia were examined. Immunohistochemistry staining was performed for retrieved tissue samples to further differentiate the tumor type and each sample was interpreted by a single veterinary pathologist. Ultrasonographic features recorded examined included mass echogenicity, homogeneity, presence of cavitation, layer of origin, bowel wall symmetry, and loss of wall layering, location, size, vascularity, and evidence of perforation or ulceration. Tumor types included 19 GISTs, eight leiomyosarcomas, six leiomyomas, and four nonspecified sarcomas. Gastrointestinal stromal tumors were significantly more likely to be associated (P < 0.03) with abdominal effusion than other tumor types. There was overlap between the anatomical locations of all tumors types with the exception of the cecum where all eight tumors identified were GISTs. Besides location, there were no unique ultrasound features of GISTs that would allow distinction from other gastrointestinal spindle cell tumors. Similar to previous studies, GISTs appeared to be the most common spindle cell tumor associated with the cecum in our sample of dogs. The high frequency of abdominal effusion with GIST's was of unknown etiology could possibly have been due to septic peritonitis.     

INTRAOPERATIVE CONTRAST‐ENHANCED ULTRASONOGRAPHY OF NORMAL CANINE JEJUNUM

Nine normal juvenile dogs were evaluated with direct jejunal contrast‐enhanced ultrasonography via midline celiotomy. Three different doses of ultrasound contrast medium (Definity^®) were injected through a peripheral venous catheter. Time‐intensity curves were used to calculate baseline, time to initial rise, inflow slope, time‐to‐peak, peak intensity (PI), and outflow slope for each administered dose. PI was directly proportional to dose. Outflow slope was similar for all patients, independent of dose. The most favorable images were acquired with a dose of 0.030 ml/kg given as a rapid intravenous manual bolus. The technique and normal jejunal perfusion pattern described herein may provide useful data for evaluation of intestinal vascular, inflammatory, and neoplastic disease in the dog.