USE OF IOHEXOL AS A GASTROINTESTINAL CONTRAST MEDIUM IN THE DOG

Iohexol was administered orally in five dogs. The dose, gastrointestinal (GI) transit time, appearance of mucosal patterns and side effects were studied. Three different doses (525, 700, 875 mgI/kg) were used in each dog at 1-week intervals. GI transit time was rapid. In each dose, gastric emptying commenced immediately after administration of the contrast medium, and was completed within 30–60 min with doses of 525–700 mgI/kg and 90–120 min with 875 mgI/kg. Large intestinal filling was observed within 60-90 min. In the majority of studies, the mucosal border appeared as a thin homogeneous halo of lucency surrounding the more opaque bowel lumen contents. The contrast intensity was not adequate with the lowest dose. The image quality did not deteriorate along the GI tract. No adverse reactions were found. Iohexol is an alternative GI contrast medium in the dog when contrast media are contraindicated.     

Comparison of nonionic contrast agents iohexol and iotrolan for cisternal myelography in dogs

During this investigation, the use of iohexol was compared with iotrolan for canine cisternal myelography. Iohexol and iotrolan myelography was done in 6 dogs by cisternal puncture with a 6-week interval between both procedures; each dog served as its own control. Cerebrospinal fluid (CSF) was collected for baseline analysis from each dog immediately before the contrast agent was injected. Cerebrospinal fluid samples were obtained at 1, 3, 7, and 14 days after injection of each contrast medium for cytologic and chemical analysis. Total CSF leucocyte count and glucose concentration did not change significantly in comparison with baseline data in any of the samples. After the injection of iohexol, protein concentration increased significantly in the 24-hour sample, and lactate dehydrogenase activity increased significantly in the 3-day sample. Significant difference was not found between the different samples collected at 1, 3, 7, and 14 days, compared with both contrast media. None of the dogs had seizure activity during a 5-hour postmyelographic observation period. Pathologic changes were not found by gross or microscopic examination of the spinal cord. Although a degradation in time of radiographic quality of all myelograms took place, the average radiographic score decreased more rapidly with iohexol. The average score at 90 minutes with iotrolan was comparable with the score at 45 minutes with iohexol, and the average score at 150 minutes with iotrolan was better than the score at 90 minutes with iohexol. At 5 and 10 minutes after cisternal injection, no significant difference was observable between the myelograms, but from 45 minutes onward, myelograms with iotrolan were superior.     

Acute renal failure associated with contrast medium administration in a dog.

Intravenous administration of an ionic radiographic contrast medium was believed to have caused acute oliguric renal failure in a young dog. Intravenous pyelography was done on a healthy 14-month-old female Lhasa Apso prior to reconstructive surgery for pseudohermaphroditism. Within 24 hours of the radiographic procedure, acute oliguric renal failure developed. Cause for the renal failure was not found other than the recent IV administration of radiographic contrast medium. Treatment with fluids, furosemide, and dopamine was successful in returning renal function to normal. Various adverse reactions to IV administration of contrast media in human beings and animals have been reported; however, to our knowledge, acute renal dysfunction induced by IV administration of contrast material has not been reported in dogs.     

Effect of dopamine on excretory urographic image quality and the prevention of contrast-induced nephropathy in dogs

The effect of low dose dopamine on the excretory urographic image quality and contrast media-induced nephropathy in normal dogs (experiment 1) and the dogs with decreased renal function (experiment 2) were assessed. In experiment 2, decreased renal function was induced by gentamicin overdose. In each experiment, animals were divided into 3 groups. In group 1, only contrast medium (iohexol) was administered. In group 2, contrast medium plus intravenous fluid (0.9% saline) were administered. And in group 3, contrast medium plus intravenous fluid and low dose dopamine were administered. Investigated parameters included intrarenal resistive index (RI), serum BUN and creatinine concentrations, contrast medium elimination time and radiographic image quality. In experiment 1, RI of group I increased at 80 min after contrast medium administration (p<0.05), but RI of group 3 decreased at 48 and 72 hr (p<0.05). Serum BUN concentration of group 1 was higher than that of group 2 and 3 (p<0.05); in radiographic examination, contrast medium elimination time decreased in group 2 and 3, but image quality of group 2 was inferior to that of group 3. In experiment 2, image quality of group 3 only provided adequate visualization of renal structures. The formula of contrast medium plus low dose dopamine was found to provide good nephrogram and pyelogram image quality without supplemental contrast medium, and to protect renal tubules from prolonged exposure to concentrated contrast medium.     

IOHEXOL AS A GASTROINTESTINAL CONTRAST MEDIUM IN THE CAT

Iohexol was evaluated as a radiologic contrast medium in the gastrointestinal (GI) tract in cats. Three different doses (525, 700, 875 mg iodine/kg with an iodine concentration of 300 mg iodine/mL) diluted with tap water until a total volume of 10 ml/kg, were administered via an orogastric tube, to 5 cats at weekly intervals. The GI transit time was rapid and variable. Gastric emptying commenced immediately after administration of the contrast medium and was complete within 10–30 min. In each dose, iohexol reached the large intestine within 10–20 min. In 73% (11/15) of studies, the mucosal border appeared as a thin homogeneous "halo" of lucency surrounding the more opaque contents of the small intestine. Radiographic image quality of the GI tract was inadequate with the lowest dose (525 mg iodine/kg). Image quality did not deteriorate along the GI tract. Absorption of iohexol from the GI tract was observed in 40% (6/15) of examinations, where opacification of the urinary bladder was seen. No side effects were observed. lohexol should be considered as an alternative GI contrast medium in the cat when the use of other radiologic contrast media is contraindicated.     

Pressure-volume index-based volume calculation of contrast medium for atlanto-occipital myelography in dogs

Subarachnoid pressure recordings were made during atlanto-occipital myelography in 45 dogs with clinical signs of spinal disease. Iohexol was injected at a dosage of 0.3 ml/kg body weight and simultaneous pressure values were recorded in the cerebellomedullary cistern. The mean subarachnoid pressure was 9 ± 3 mmHg before and 70 ± 32 mmHg at the end of administration. From the pressure change induced by the volume load, the pressure-volume index (PVI) of the subarachnoid space was calculated and found to be in close correlation with body weight and the crown-rump length (r = 0.94 and 0.87). Using the estimated PVI values, the appropriate volume of contrast medium can be calculated for an animal according to body weight. Dogs of a large body size require relatively less contrast medium than small-sized dogs (range 0.17-0.35 ml/kg). This calculated volume is unlikely to increase the subarachnoid pressure above 40 mmHg as a specific pressure limit. Using these data, simplified recommendations for the choice of contrast medium volumes have been generated.     

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.     

Myelographic localization of spinal cord compression in dogs. A comparison between cisternal and lumbar injections of metrizamide "Amipaque" in diagnosing and locating spinal cord compression.

Metrizamide is a new water-soluble contrast medium possessing unique properties, one of which is that even in an isotonic solution it has a radiographic density sufficient for a diagnostic myelogram. Whereas in the past myelography with water-soluble preparations invariably entailed lumbar injections, which are technically difficult in dogs, the fact that isotonic metrizamide causes so little tissue irritation has made it possible to inject the contrast solution into the cisterna magna. The author has compared metrizamide myelograms obtained with both cisternal and lumbar injections. Myelography with a cisternal injection is preferable for demonstrating cervical cord compressions and also in cases in which it is desirable to obtain myelographic information on both the cervical and the thoraco-lumbar areas. If, on the other hand, it is necessary to determine exactly the extent of a thoraco-lumbar compression before decompressive laminectomy, the contrast should be injected in the lumbar region in such an amount and at a pressure high enough to ensure that the contrast is forced past the site of the compression. The safety of metrizamide will probably enable a better prognosis following surgery than was previously possible.     

Comparison of 51chromium-labeled ethylenediamine tetra-acetic acid and iohexol as blood markers for intestinal permeability testing in Beagle dogs

(51)Chromium-labeled ethylenediamine tetra-acetic acid ((51)Cr-EDTA) is the gold standard probe for assessing intestinal permeability (IP) in dogs, but exposure to radioactivity is a disadvantage. Iohexol is a safe contrast medium commonly used for medical imaging purposes and has been successfully applied more recently for the assessment of IP in animal models and humans. This study aimed at comparing (51)Cr-EDTA and iohexol as IP blood markers in dogs. A test solution containing (51)Cr-EDTA and iohexol was administered intragastrically to seven healthy laboratory Beagle dogs, and percentage recoveries in serum were calculated. The strong linear association (correlation, r=0.76 and linear regression, y=0.03+5.04x) between (51)Cr-EDTA and iohexol supports the potential usefulness of iohexol as an IP blood marker in dogs.     

CONTRAST MEDIUM-RELATED ARTIFACTS OBSERVED DURING IN VITRORADIOGRAPHIC CHARACTERIZATION OF UROCYSTOLITH MINERAL COMPOSITION

Nine pure mineral types of canine uroliths (bladder or urethral origin only) were exposed to sequential increasing concentrations of iodinated, radiographic contrast medium in petri dishes. The uroliths studied were those composed of 100% magnesium ammonium phosphate, calcium oxalate monohydrate, calcium oxalate dihydrate, calcium phosphate appatite, and calcium hydrogen phosphate dihydrate (Brushite), ammonium acid urate, sodium acid urate, cystine, and silica. Two phenomena were observed. First, there was a tendency for selected urocystoliths to undergo radiopacity augmentation beyond that expected for just contrast medium superimposition. This was termed, contrast medium adhesion, which persisted despite repeated washing of the urocystoliths. Second, there was a tendency for bubbles to form on or near selected urocystolith chemical types. These observations prompted careful scrutiny for their occurrence in subsequent clinical simulation of radiographic procedures using these same urocystoliths in a urinary bladder phantom. Imaging techniques simulated were survey radiography, pneumocystography, double contrast cystography (two iodine concentrations). The contrast medium adhesion occurrence found in the petri dish studies was compared to urocystolith mineral type. Similar comparisons were made for contrast medium adhesion occurrence in the bladder phantom. The detection of contrast medium adhesion in the bladder phantom differed from that observed in the petri dish experiments. While contrast adhesion occurred across a fairly broad range of the urocystolith mineral types in the petri dish studies, it was observed primarily for sodium acid urate and cystine urocystoliths in the bladder phantom. Prompted by the observation of bubbles in association with a limited number of urocystolith types in the petri dish studies, bubble occurrence in the bladder phantom was compared to the urocystolith type. Bubble formation on or near the urocystoliths, although uncommonly observed, was seen only with either cystine or silica urocystoliths. The potential clinical utility and clinical caveat aspects of these phenomena are discussed.     

POSITIVE-CONTRAST RHINOGRAPHY

Contrast rhinography is a simple noninvasive procedure that may be a useful diagnostic method for positive-contrast radiographic evaluation of the nasal cavity, nasopharynx, and paranasal sinuses in the dog. A standardized and reliable technique was developed using healthy adult Greyhounds. The radiographic appearance of the regional anatomy after intranasal administration of positive-contrast medium was established. Four contrast media: 60% propyl iodine, 37% organically bound iodine, a 60% barium sulfate suspension, and a 30% barium sulfate suspension were evaluated on the basis of their radiographic contrast and detail, distribution, and degree of evoked tissue reaction as defined by clinical assessment. A 30% barium sulfate suspension was selected using these criteria. Contrast medium enhanced the radiographic appearance of the regional anatomy when compared with noncontrast techniques. A procedure for positive-contrast radiographic evaluation of the nasal cavity, nasopharynx, and paranasal sinuses is described in detail. Recommendations are made regarding methods of contrast medium administration and positioning to ensure uniform distribution within the area of interest.     

Comparison of mesenteric lymphadenography performed via surgical and laparoscopic approaches in dogs

OBJECTIVE: To determine whether injection of a mesenteric lymph node with iodinated aqueous contrast medium results in radiographic delineation of the thoracic duct and its branches, ascertain the ideal interval between injection and radiographic imaging, and evaluate mesenteric lymphadenography performed via laparoscopic and surgical approaches in dogs. ANIMALS: 10 adult dogs. PROCEDURE: In each dog, a right paracostal laparotomy or a right laparoscopic approach was performed to identify a mesenteric lymph node for injection of an iodinated aqueous contrast agent (0.22 mL/kg [81.4 mg of iodine/kg]). Lateral radiographic views were obtained at 60, 120, 180, 240, and 300 seconds after injection. RESULTS: A mesenteric lymph node was identified and injected with contrast medium in each dog. Via paracostal laparotomy, lymph node injection resulted in successful lymphangiographic evaluation in 4 of 5 dogs, whereas via the laparoscopic approach, lymph node injection resulted in successful lymphangio-graphic evaluation in 2 of 5 dogs. In successful radiographic evaluations, injected lymph nodes, mesenteric lymphatics, and the thoracic duct and its branches were delineated. Radiographs obtained at 60 and 120 seconds after injection of contrast medium provided the most detail. CONCLUSIONS AND CLINICAL RELEVANCE: Injection of a mesenteric lymph node directly with contrast medium appears to be a feasible technique for delineation of the thoracic duct and its branches in dogs and might be useful in small animals in which mesenteric lymphatic catheterization can be difficult and lymphangiography is more likely to fail. Refinement of the laparoscopic technique may provide a minimally invasive approach to lymphadenography.     

A simple test phantom in the form of a staircase for running control of the image in veterinary roentgenology

Quality control in veterinary radiology seems to be neglected. For the correct estimation of the radiographic quality, there is no adequate phantom available. Although measurements have shown that the exposure to radiation is far under the admissible limits, the quantity of repeated examination has to be reduced. So it was necessary to create a phantom, which allows the objective judgement of the x-ray photograph taken immediately from the patient. The phantom shows the following characteristics: 1) It is small-sized, so that it can be represented on the radiograph together with the object, but without remarkable enlargement of the beam and additional exposure to radiation. 2) It consists of tissue-similar material, which absorbs and scatters x-rays similar to the body region. According to the fact that the indications for radiographs in veterinary medicine are mostly problems in skeleton regions, this region is represented first of all. 3) Therefore the phantom shows variable thickness, so that it can simulate different skeleton parts. 4) The represented parameters are: 4.1 the different radiographic densities; 4.2 the latitude; 4.3 the radiographic contrast; 4.4 the radiographic detail visibility (film-far, film-close) in the relevant parts of the x-ray picture 5) The phantom is universally applicable. By a way of "calibration" it is multipurpose for certain kinds and sizes of animals.     

Dacryocystography in a cat with orbital pneumatosis

A 2‐year‐old neutered male European short‐haired cat was presented for a persistent discharge from the scar of previous left eye enucleation, performed 6 months prior by the referring veterinarian. A surgical exploration of the orbit was performed and retained nictitating membrane glandular and conjunctival tissues were removed. Eleven days later, the cat developed an orbital pneumatosis caused by retrograde movement of air through a patent nasolacrimal system and diagnosed by survey radiographic examination of the skull. Nasolacrimal system patency was assessed by dacryocystography performed by injection of iodinated contrast medium under pressure into the orbital cavity. Computed tomography dacryocystography confirmed the radiographic findings. The condition resolved following dacryocystography, possibly as an inflammatory response to the contrast medium. To our knowledge, this is the first case of orbital pneumatosis reported in a cat.     

USE OF ULTRASONOGRAPHY AND CONTRAST RADIOGRAPHY FOR SNAKE GENDER DETERMINATION

The purpose of this paper is to characterize the sonographic and radiographic features of hemipenes in male snakes and to use these features for gender determination. The sonographic and radiographic examination of 17 male and 10 female snakes, whose gender was determined previously by probing, were evaluated by one examiner who was unaware of the gender. Sonographically, hemipenes appeared funnel shaped with an echogenic thin wall and hypo to anechoic contents. Radiographically, hemipenes filled by positive contrast medium appeared as funnel-shaped radiopacities pointing caudally. Snake gender was correctly determined in all snakes using sonography (accuracy=100%). Radiographic accuracy was 81.4%. Interpretation of radiographic examinations was limited by poor distribution of the contrast medium within the hemipenes.     

CONTRAST RADIOGRAPHY OF THE GASTROINTESTINAL TRACT IN SEA TURTLES

Intestinal obstruction by radiolucent foreign bodies is common in sea turtles. The absence of clinical signs and the extended fasting periods in these animals means that intestinal obstructions may not be diagnosed early. Digestive tract radiographic contrast procedures were performed to evaluate the gastrointestinal transit time and intestinal obstructions in loggerhead sea turtles. Barium sulfate and nonionic iodinate contrast medium were used for radiographic contrast procedures. Contrast medium was administered via a gastric tube or into the colon. These procedures are often necessary and are useful to document intestinal obstruction and foreign objects. The diagnostic procedures were not easily performed in some turtles, but often they were adequate for the diagnosis.     

The application of a scintigraphic grading system to equine tibial stress fractures: 42 cases

REASONS FOR PERFORMING STUDY: Tibial stress fractures are an important cause of lameness in the Thoroughbred racehorse. While it is recognised that these injuries can vary in clinical presentation and radiographic or scintigraphic appearance, little has been done to quantify lesion severity. By contrast the scintigraphic grading of tibial stress fractures in human athletes is widely reported and assists in the selection of appropriate management regimes. OBJECTIVES: To determine the relationship between scintigraphic grade, clinical severity and radiographic appearance of tibial stress fractures. METHODS: The current study involved the retrospective analysis of records from 42 Thoroughbreds with abnormal tibial scintigraphic activity. RESULTS: There was a significant association between lesion site and scintigraphic grade and good correlation of scintigraphic scoring between investigators. No significant association was found between scintigraphic grade and either radiographic grade or degree of lameness. CONCLUSIONS: The study confirmed that radiographic appearance is an unreliable measure of clinical severity or stage of progression of lesions. The scintigraphic grading system used in the study was not of use in defining stress fracture severity in the equine tibia. POTENTIAL RELEVANCE: Despite this finding, there is clearly a need for prospective investigations to explore the potential for targeted management regimes for tibial injuries based on lesion site or clinical criteria.     

Ultrasound-guided biopsy

Ultrasound-guided biopsy is a good and feasible technique in dogs. Although we have only used it for biopsy of liver and kidney, it can have further uses. In our use of ultrasound-guided biopsy of kidney and liver, we have found that we can achieve adequate biopsy samples using the Franklin modified Vim-Silverman and Tru Cut biopsy of kidney and liver. The fine-needle biopsies of the liver were adequate for examination of hepatocytes but inadequate to evaluate structure owing to small size of the sample. In contrast, the renal fine-needle samples were both poor in quality and quantity. This technique has the advantages of being noninvasive, quick, and easy, and it can be performed with the patient under local anesthesia. It has an advantage over blind percutaneous biopsy because the needle can be visualized in the organ and the organ scanned after biopsy for possible complications. Another advantage is that, unlike other radiographic biopsy procedures, ionizing radiation is not used for imaging.     

Ultrasound-guided biopsy

Ultrasound-guided biopsy is a good and feasible technique in dogs. Although we have only used it for biopsy of liver and kidney, it can have further uses. In our use of ultrasound-guided biopsy of kidney and liver, we have found that we can achieve adequate biopsy samples using the Franklin modified Vim-Silverman and Tru Cut biopsy of kidney and liver. The fine-needle biopsies of the liver were adequate for examination of hepatocytes but inadequate to evaluate structure owing to small size of the sample. In contrast, the renal fine-needle samples were both poor in quality and quantity. This technique has the advantages of being noninvasive, quick, and easy, and it can be performed with the patient under local anesthesia. It has an advantage over blind percutaneous biopsy because the needle can be visualized in the organ and the organ scanned after biopsy for possible complications. Another advantage is that, unlike other radiographic biopsy procedures, ionizing radiation is not used for imaging.     

EPIDUROGRAPHY IN THE NORMAL DOG: TECHNIC AND RADIOGRAPHIC FINDINGS

Ten clinically normal adult mongrel dogs were examined using lumbosacral epidurography in an effort to determine a reproducible technic and a normal radiographic appearance. The site of contrast medium injection was the ventral epidural space at the sacrococcygeal junction or the cranial coccygeal region. An initial dose of 0.15 ml/kg of metrizamide for the right lateral recumbent radiograph with 0.10 ml/kg additional metrizamide for additional right lateral or the subsequent dorsoventral radiographs was considered adequate. Two numerical values were observed for each normal epidurogram: the sacrovertebral angle; the ratio of the contrast medium column width to L6 body length. A statistically significant relationship between hindlimb positioning and the numerical value of the sacrovertebral angle was identified. Some advantages of epidurography for delineating the lumbosacral area are obvious: (1) it overcomes the limited value of lumbosacral area myelography; (2) it is technically easier than intraosseous vertebral venography; (3) there is minimal patient trauma; (4) there was no apparent adverse sequela to repeated contrast medium injections.