COMPARISON OF TRANSPLENIC MULTIDETECTOR CT PORTOGRAPHY TO MULTIDETECTOR CT-ANGIOGRAPHY IN NORMAL DOGS

We evaluated transplenic injection of iodinated contrast medium for computed tomography (CT) assessment of the portal vasculature. Specific aims were to: (1) establish a protocol for transplenic transplenic CT portography using a 40-row multidetector scanner; (2) compare transplenic CT portography to dual-phase CT angiography in terms of image quality, opacification of the portal system, and contrast enhancement of the portal vasculature and liver; (3) compare personnel exposure during transplenic CT portography and transplenic portal scintigraphy. Seven juvenile dogs underwent transplenic portal scintigraphy, CT angiography, and transplenic CT portography. Transplenic portal scintigraphy and CT angiography were performed using previously established protocols. For transplenic CT portography, a 20- or 22 gauge needle attached to an extension set was placed into the splenic parenchyma using CT guidance. Iodinated contrast medium (175 mg I/ml) was administered, and CT acquisition was started at the time of the injection. Transplenic CT portography was simple, rapid and provided more intense enhancement of the splenic and portal veins, with a lower contrast medium dose (median dose: 525 mg I for transplenic CT portography, 7700 mg I for CT angiography), but caused inconsistent intrahepatic portal branches and parenchymal opacification due to streamlining and streak artifacts. Despite significantly lower attenuation values in the portal vein, CT angiography provided sufficient enhancement for vessel identification and more consistent parenchymal hepatic enhancement. Personnel radiation exposure rate was higher during transplenic CT portography (0.0725 mSv/min) compared with transplenic portal scintigraphy (0.000125 mSv/min). As transplenic CT portography requires an average injection time of 1 min per study; over 650 [corrected] studies must be performed before reaching the maximum permissible whole body dose of 0.05 [corrected] Sv.     

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.     

ULTRASONOGRAPHIC EVALUATION OF ADRENAL GLAND SIZE COMPARED TO BODY WEIGHT IN NORMAL DOGS

The accepted cut‐off value for adrenal gland maximum diameter of 0.74 cm to distinguish adrenal gland enlargement in dogs regardless of body weight may not be appropriate for small to medium breed dogs. The purpose of the current retrospective study was to examine adrenal gland dimensions as a function of body weight in healthy dogs in three weight categories (< 10 kg, 10–30 kg, and > 30 kg) representing small, medium, and large breeds, respectively, to establish greater confidence in determining if adrenal gland size is abnormal. The measurements of length (sagittal plane), cranial and caudal pole thickness (sagittal and transverse planes), and caudal pole width (transverse plane) of both adrenal glands were obtained ultrasonographically in clinically healthy dogs (n = 45) with 15 dogs in each weight group. Findings support our hypothesis that adrenal gland size correlates with body weight in normal dogs, and more precise reference intervals should be created for adrenal gland size by categorizing dogs as small, medium, or large breed. The caudal pole thickness of either adrenal gland in a sagittal plane was the best dimension for evaluating adrenal gland size based on low variability, ease, and reliability in measurement.     

COMPARISON OF THE RESISTIVE INDEX TO CLINICAL PARAMETERS IN DOGS WITH RENAL DISEASE

The resistive index (RI) is a measurement of arteriole vascular resistance and is obtained by pulsed-wave Doppler interrogation. The diagnostic potential of the renal resistive index (RI) was retrospectively investigated in 142 kidneys from 81 dogs. The resistive index of each kidney was compared to clinical laboratory parameters, clinical diagnoses, and sonographic findings. The mean renal resistive index (RI) for 22 normal kidneys was 0.61 (standard deviation = 0.06). An elevation in the mean renal RI (>0.70) was found for the clinical diagnoses of acute renal failure and congenital dysplasia. When a RI of greater than 0.70 was considered abnormal, the sensitivity and specificity of the RI in determining normal vs, abnormal kidneys were 38% and 96% respectively.     

PERCUTANEOUS CHOLECYSTOGRAPHY IN NORMAL DOGS

A technique for fluoroscopically guided percutaneous cholecystography, using a 23-gauge Chiba needle, is described. Successful percutaneous cholecystograms were obtained in 20 normal dogs, with minimal short-term and no long-term clinical side effects.     

DOPPLER ULTRASOUND OF THE PROSTATE IN NORMAL DOGS AND IN DOGS WITH CHRONIC LYMPHOCYTIC-LYMPHOPLASMOCYTIC PROSTATITIS

The prostate gland of 11 normal dogs and five dogs with histological confirmed chronic lymphocytic or lymphoplasmocytic prostatitis were imaged with grey-scale and Doppler ultrasound. Three vessel types (prostatic artery, capsular artery and parenchymal artery) were identified with color Doppler and the resistive index and maximum and minimum velocities were measured with pulsed wave Doppler. No differences between normal dogs and dogs with prostatitis was identified in either grey-scale ultrasound or in any Doppler parameters measured. Regardless of histologic diagnosis, acepromazine (0.05 mg/kg IV) caused a significant decrease in capsular artery maximum and minimum velocities and prostatic artery resistive index. This study establishes normal Doppler ultrasound parameters for the intact male canine prostate gland. Additional studies are necessary to further evaluate the clinical utility of Doppler ultrasound in canine prostatic diseases.     

COMPUTED TOMOGRAPHIC PNEUMOCOLONOGRAPHY IN NORMAL DOGS

Objectives of this prospective study were to describe effects of varying technical components that may contribute to an optimal protocol for computed tomographic pneumocolonography (CTP) in dogs, and to develop a standardized methodology for CTP as a future potential diagnostic tool in canine clinical patients with large bowel disease. Eight purpose‐bred intact male hound cross‐research dogs were enrolled and randomized to groups based on variables of pressure/body position (n = 4) and insufflation time (n = 4). For each segment of large bowel (rectum, colorectal junction, descending colon, transverse colon, ascending colon), the adequacy of bowel preparation, % of bowel lumen filled with fecal material, and bowel tortuosity or folding were assessed. Measurements of bowel wall thickness (cm), cross‐sectional bowel lumen diameter (cm), and cross‐sectional bowel luminal area (cm²) were obtained at standardized locations within the large bowel. False discovery rates (FDR) were calculated to adjust for multiple testing. Values of FDR < 0.05 were considered significant. Differences in mean cross‐sectional area and diameter and bowel wall thickness under increasing pressure were not significant after adjusting for multiple testing; some had raw p values <0.05. Ascending colon diameter and ascending colon area significantly increased with insufflation time (FDR < 0.05). No other response variables showed a significant change with insufflation time. The optimal insufflation pressure for maintaining pneumocolon in this study was determined to be 20 mmHg. CTP is a feasible technique to provide consistent distension for imaging of the large bowel and further study on application of CTP in clinical patients is warranted.     

TRANS-SPLENIC PORTAL SCINTIGRAPHY IN NORMAL DOGS

The purpose of this study was to (1) establish a technique for ultrasound-guided trans-splenic portal scintigraphy (TSPS) using 99mTcO4(-), (2) evaluate portal vein morphology, (3) compare the radiation exposures for TSPS vs. per-rectal portal scintigraphy (PRPS), and (4) compare the quality of numerical data from the TSPS vs. PRPS. Eight juvenile dogs underwent PRPS and TSPS (minimum of 48h between studies) after initial screening tests. PRPS was done according to established protocol using 425 +/- 36MBq (mean +/- SD) of 99mTcO4(-). TSPS was done with the dogs in right lateral recumbency over the gamma camera. 99mTcO4(-) (57 +/- 13.9 MBq) was injected into the spleen 1-2s following initiation of the dynamic acquisition. The frame rate was 4 frames/s for 5 min. There was significantly lower radioactivity of 99mTcO4(-) given and significantly higher total counts recorded in the liver and heart during the TSPS compared with PRPS. The total counts for the TSPS and PRPS were 7120 +/- 4386 and 830 +/- 523, respectively. Percent absorption from the spleen was 52.5 +/- 19.1% compared with 9.2 +/- 5.7% for the colon. Calculated transit time for the TSPS studies was 7 +/- 2.3s. In TSPS studies, the splenic and portal veins were clearly identified. Radiation exposure levels of the dogs were significantly lower following TSPS than after PRPS. TSPS appears superior to PRPS as a method to image the portal venous system representing a valid alternative diagnostic test for animals with suspected portosystemic shunts.     

DIURETIC RENAL SCINTIGRAPHY IN NORMAL DOGS

Diuretic renal scintigraphy is commonly used in human medicine to differentiate obstructive from nonobstructive pyelectasia. In order to determine normal parameters, 99mTc-DTPA renal scintigraphy was performed twice in 20 healthy adult Mongrel dogs. Each dog was injected with either 3.0 mg/kg furosemide or an equivalent volume of saline 4.5 min following injection of the radiopharmaceutical. The following parameters were evaluated: (1) global and individual glomerular filtration rate (GFR); (2) time of peak (TOP) of the time-activity curve (TAC); (3) shape of the TAC; (4) individual kidney excretion half-time (T1/2); (5) proportion of maximum activity measured at end of study (8 min); (6) time of onset; and (7) duration of the effect of the diuretic. Most TAC in the diuretic renography group showed a steep drop in the curve following administration of the diuretic compared with a gradual slope in the saline control group. There was a statistically significant difference in T1/2 between the control renograms (median 10.25 min, range 4.41-18.07 min) and the diuretic renograms (median 4.16 min, range 3.62-5.90 min). There was a statistically significant difference in percentage maximum activity between the control renograms (median 65.25%, range 48.27-93.68%) and the diuretic renograms (median 48.54%, range 35.64-58.76%). Median time of onset of the diuretic effect was 1.10 min (0.20-2.40 min), and median duration was 0.83 min (0.30-2.35 min).     

THE USE OF DIFFUSION TENSOR IMAGING TO EVALUATE THE SPINAL CORD IN NORMAL AND ABNORMAL DOGS

Diffusion tensor imaging (DTI) is a specialized magnetic resonance sequence to determine the direction of water molecule motion. Our hypothesis was that information derived from DTI will be significantly different in dogs with a spinal cord lesion compared with a normal dog. Eleven normal dogs and six dogs with a spinal cord lesions were imaged. DTI was performed along with standard T1‐ and T2‐weighted sequences in transverse and sagittal planes. Fractional anisotrophy and apparent diffusion coefficient (ADC) were obtained using regions of interests centered on the cranial aspect, middle cranial, middle caudal, and caudal aspects of the spinal cord. In normal dogs, the DTI sequence was characterized by normal fiber tracking with no statistical difference between the four sections of spinal cord (P>0.05). In the dogs with a spinal cord lesion, there was a significant difference in fractional anisotropy between the two groups (P=0.0003) and the ADC analysis statistical significance (P=0.048) at the caudal most site. Based on these findings, DTI is a potentially useful method to evaluate the spinal cord in dogs.     

MEASUREMENT OF NORMAL MIDDLE EAR CAVITY VOLUME IN MESATICEPHALIC DOGS

Water-filling and serial computed tomographic (CT) imaging techniques were used to measure normal middle ear cavity volume (MECV) in 18 dogs (10 live dogs, eight cadavers; 36 ears in total). The specific aims of this study were to (1) compare MECV measurements by water-filling and CT techniques and (2) define a model of MECV vs. body weight (BW) from CT values. There was a significant difference between the two techniques (P = 0.02). The volume obtained by water filling was consistently greater than that obtained by computed tomography. MECV (expressed in ml) increased with BW (expressed in kg) according to the following formula: MECV = -0.612 + 0.757 (In BW) (P<0.01, R2 = 0.74).     

SONOGRAPHIC EVALUATION OF URINARY BLADDER WALL THICKNESS IN NORMAL DOGS

Urinary bladder wall thickness was evaluated by ultrasonography in 16 normal dogs. Sterile saline solution was administered via urinary catheters to control the degree of bladder distention. Bladder wall thickness was measured on static ultrasound images in 4 locations and at 3 degrees of bladder distention (minimal, mild, and moderate). Four randomized distention sequences with 3 distentions per sequence were performed on each dog and the data were analyzed using Williams' balanced Latin square. Mean bladder wall thickness was 2.3 mm in minimally distended bladders (0.5 ml/kg saline), 1.6 mm in mildly distended bladders (2 ml/kg saline) and 1.4 mm in moderately distended bladders (4 ml/kg saline). Mean bladder wall thickness increased significantly with increasing body weight and with decreasing bladder distention. The caudoventral measurement location produced a statistically significant smaller measurement, with a difference of 0.3 mm. Sex did not affect bladder wall thickness. Distention sequence and repetition of distentions did not affect bladder wall thickness.     

QUANTITATIVE CONTRAST ULTRASOUND ANALYSIS OF RENAL PERFUSION IN NORMAL DOGS

Eight normal dogs with no evidence of renal disease, weighing between 8 and 25 kg were imaged using contrast harmonic ultrasound after injection of a microbubble contrast medium. All dogs received three separate bolus injections of 0.05 ml of commercial contrast medium (Definity). Time/mean pixel value (MPV) curves were generated for selected regions in the cortex and medulla of the left kidney in each dog. Upslope, downslope, baseline, peak intensity, and time to peak were calculated for each zone. For a bolus injection, within the renal cortex (averaging all subjects) the upslope was 7.4 +/- 1.5 MPV/s, downslope was -0.4 +/- .2 MPV/s, baseline was 66.8 +/- 9.3 MPV, peak was 103.6 +/- 8.2 MPV, time to peak (from injection) was 12.8 +/- 5.3 s and from time of contrast medium reaching the kidney was 5.1 +/- 2.0 s. Within the renal medulla (averaging all subjects), upslope was 2.8 +/- 1.7 MPV/s, downslope was -0.3 +/- .2 MPV/s, baseline was 39.3 +/- 6.0 MPV, peak was 65.2 +/- 14.3 MPV, time to peak from injection was 20.9 +/- 6.4 s and from time of contrast reaching the kidney was 11.6 +/- 4.1 s. These baseline data may prove useful in the evaluation of dogs with diffuse disease or vascular compromise.     

TIME-RESOLVED RENAL CONTRAST-ENHANCED MRA IN NORMAL DOGS

In humans, contrast-enhanced magnetic resonance angiography (CE-MRA) is a documented method to quantitatively and qualitatively evaluate renal vessels. It offers a safer alternative to computed tomography angiography. The aim of this study was to establish a renal MRA protocol in dogs using a 3D multiphase Fast Spoiled Gradient Recalled echo CE-MRA sequence (3D FSPGR CE-MRA). We used an elliptical centric ordering of k -space to acquire the contrast-sensitive data faster. Four to five consecutive 3D dorsal slabs, encompassing both kidneys, could be acquired in 40–65 s. The renal arterial and venous phases were obtained separately during phases 1 or 2, and 2 or 3, respectively without the need for any contrast medium bolus timing. The renal arteries and veins were clearly visualized. In conclusion, multiphase FSPGR 3D CE-MRA with an elliptical centric k -space ordering allows distinguishing renal arterial and venous phases in dogs, and can be used as a noninvasive diagnostic imaging alternative to map renal vessels in this species. Potential applications include the screening of renal donors in renal transplantation programs, and the pretreatment evaluation of animals with invasive renal neoplasia or renal vascular anomalies when surgery or embolization are contemplated.     

MAGNETIC RESONANCE IMAGING FEATURES OF THE TEMPOROMANDIBULAR JOINT IN NORMAL DOGS

Evaluation of the canine temporomandibular joint (TMJ) is important in the clinical diagnosis of animals presenting with dysphagia, malocclusion and jaw pain. In humans, magnetic resonance imaging (MRI) is the modality of choice for evaluation of the TMJ. The objectives of this study were to establish a technical protocol for performing MRI of the canine TMJ and describe the MRI anatomy and appearance of the normal canine TMJ. Ten dogs (one fresh cadaver and nine healthy live dogs) were imaged. MRIs were compared with cadaveric tissue sections. T1‐weighted (T1‐W) transverse closed‐mouth, T1‐W sagittal closed‐mouth, T1‐W sagittal open‐mouth, and T2‐W sagittal open‐mouth sequences were obtained. The condylar process of the mandible and the mandibular fossa of the temporal bone were hyperintense to muscle and isointense to hypointense to fat on T1‐W images, mildly hyperintense to muscle on T2‐W images, and were frequently heterogeneous. The articular disc was visible in 14/20 (70%) TMJs on T1‐W images and 13/20 (65%) TMJs on T2‐W images. The articular disc was isointense to hyperintense to muscle on T1‐W images and varied from hypointense to hyperintense to muscle on T2‐W images. The lateral collateral ligament was not identified in any joint. MRI allows evaluation of the osseous and certain soft tissue structures of the TMJ in dogs.     

PREVALENCE OF LATERAL VENTRICLE ASYMMETRY IN BRAIN MRI STUDIES OF NEUROLOGICALLY NORMAL DOGS AND DOGS WITH IDIOPATHIC EPILEPSY

Asymmetry of the cerebral lateral ventricles is a common finding in cross‐sectional imaging of otherwise normal canine brains and has been assumed to be incidental. The purpose of this retrospective study was to compare the prevalence of ventricular asymmetry in brain MRI studies of normal dogs and dogs with idiopathic epilepsy. Brain MRI archives were searched for 100 neurologically normal dogs (Group 1) and 100 dogs with idiopathic epilepsy (Group 2). For each dog, asymmetry of the lateral ventricles was subjectively classified as absent, mild, moderate, and severe based on a consensus of two observers who were unaware of group status. Ventricular areas were measured from transverse T1W images at the level of the interthalamic adhesion. An asymmetry ratio was calculated as the ratio of the larger to smaller ventricular transverse area. There was excellent agreement between subjective assessments of ventricular asymmetry and quantitative assessments using asymmetry ratios (k = 0.995). The prevalence of asymmetry was 38% in Group 1 dogs and 44% in Group 2 dogs. Assymmetry was scored as mild in the majority of Group 2 dogs. There was no significant association between presence/absence and degree of ventricular asymmetry vs. dog group, age, gender, or skull conformation. Findings from the current study supported previously published assumptions that asymmetry of the lateral cerebral ventricles is an incidental finding in MRI studies of the canine brain.     

ULTRASONOGRAPHIC PARAMETERS OF NORMAL CANINE ADRENAL GLANDS: COMPARISON TO NECROPSY FINDINGS

Ultrasonographic evaluation of the adrenal glands was performed in 14 fasted healthy adult dogs. Frequency of visualization was 100% for both the left and right adrenal glands. Moderate correlation was present between Ultrasonographic and gross measurements of thickness for both left (r_s= 0.727; p < .005) and right (r_s= 0.537; p < .05) adrenal glands. However, no correlation was found between Ultrasonographic and gross measurements for length or width of either adrenal gland. Differentiation of adrenal cortex and medulla was possible in 79% of left adrenal glands and 64% of right adrenal glands. The echogenicity of the adrenal glands was less than that of the renal cortex in all dogs. Factors which made evaluation of the adrenal glands more difficult included pyloric gas, intestinal gas, and deep-chested body conformation.     

MULTIPHASE TIME-RESOLVED CONTRAST-ENHANCED PORTAL MRA IN NORMAL DOGS

Portal vein anomalies are common in dogs and cats. Diagnostic imaging is central in their diagnosis and fundamental with regard to choosing the best therapeutic option. Various imaging techniques are used in veterinary medicine to assess the portal vein. Each has individual advantages and disadvantages. Contrast-enhanced magnetic resonance angiography (CE-MRA) is used routinely in humans to image the portal system and has excellent spatial and temporal resolution and three-dimensional (3D) acquisition. Herein, we report the development of a CE-MRA protocol that resulted in fast 3D imaging of the arterial splanchnic and portal venous system in normal dogs. Multiphase acquisition strategy allowed acquiring the same volume several times during one single breath-hold, thereby capturing the portal venous phase with excellent signal. Excellent depiction of the vascular anatomy, especially the portal afferent vessels and branches, was observed. Elliptical centric view ordering of k-space was used to acquire the contrast-sensitive data faster. Parallel imaging was used to increase coverage in the dorsal to ventral direction while keeping imaging time short. It is anticipated that 3D CE-MRA is a fast and noninvasive imaging method that could be used to diagnose various portal vascular anomalies in small animals.     

ULTRASOUND-GUIDED TISSUE-CORE BIOPSY OF LIVER, SPLEEN AND KIDNEY IN NORMAL DOGS

Six normal dogs were subjected to ultrasound-guided biopsy of the liver, spleen and kidney to examine the accuracy of the technique (i.e. the presence of targeted tissue) and the histologic quality of the biopsies. Five consecutive tissue-core biopsies of each organ were taken on one or more occasions. The accuracy of the technique was 77% for hepatic, 90% for splenic, 53.5% for left kidney and 40% for right kidney biopsies. The histologic quality of the liver and kidney samples was sufficient, although for some samples the diagnostic value was limited by their size and in renal samples either cortical or medullary tissue was sometimes lacking. In contrast, the quality of the splenic sections was not good. The effect of reused and resterilized needles on the quality of the specimens was evaluated by histologic inspection of the samples and by the amount of biopsies lacking tissue. All tissue samples, including those taken with reused or resterilized needles had sharp-cut edges. Twenty-two of the total number of 120 biopsies (18%) contained no tissue. Absence of tissue in the samples was observed in biopsies taken with all needle types. The animals were observed for possible complications of the repeated needle biopsy. Apart from one case of hematuria, no complications were encountered.