Intravenous Injection Of Contrast Medium Research Articles

Hepatoma feeding arteriogram created by CT during aortography using IVR 64-multidetector-row CT for catheterization in transcatheter arterial chemoembolization for hepatocellular carcinoma

CT during aortography (CTAo) using IVR 64-multidetector-row CT (IVR-64MDCT) enables the rapid and simultaneous depiction of both the hepatic and extrahepatic feeding arteries in hepatocellular carcinoma (HCC), and can be achieved using a reasonable volume of contrast medium. The scan time is approximately 6 s from the diaphragm to the kidney using CTAo with 64MDCT with a slice thickness and slice interval of 0.5 mm. The hepatoma feeding arteriogram appears in the angiographic monitor after CTAo, and can then be used to guide catheterization. We introduce the process for creating a hepatoma feeding arteriogram, synthesized from the following three volume-rendered images: background bone, aorta to hepatic-branch artery, and hepatoma to feeding artery. Uniquely, the hepatoma feeding arteriogram enables investigation of the feeding artery from the tumor side, rather than from the aorta side, and appears superior to selective arteriography in terms of detecting small HCC and its accompanying fine feeding arteries. Identification of these arteries by CT angiography with intravenous contrast medium injection is difficult because of the similarity in CT values between the feeding artery and the surrounding liver, thereby preventing the creation of a hepatoma feeding arteriogram. CTAo accelerates the process of deciding upon the catheter treatment strategy, shifting the decision to the point at which the feeding artery is investigated, because the hepatoma feeding arteriogram enables instant identification of the feeding artery and its connection to the hepatic branch artery. CTAo with IVR-64MDCT can potentially contribute to remarkable advances in IVR, especially transcatheter arterial chemoembolization for HCC.

Semiautomatic Volumetric Tumor Segmentation for Hepatocellular Carcinoma: Comparison between C-arm Cone Beam Computed Tomography and MRI

To evaluate the precision and reproducibility of a semiautomatic tumor segmentation software in measuring tumor volume of hepatocellular carcinoma (HCC) before the first transarterial chemo-embolization (TACE) on contrast-enhancement magnetic resonance imaging (CE-MRI) and intraprocedural dual-phase C-arm cone beam computed tomography (DP-CBCT) images. Nineteen HCCs were targeted in 19 patients (one per patient) who underwent baseline diagnostic CE-MRI and an intraprocedural DP-CBCT. The images were obtained from CE-MRI (arterial phase of an intravenous contrast medium injection) and DP-CBCT (delayed phase of an intra-arterial contrast medium injection) before the actual embolization. Three readers measured tumor volumes using a semiautomatic three-dimensional volumetric segmentation software that used a region-growing method employing non-Euclidean radial basis functions. Segmentation time and spatial position were recorded. The tumor volume measurements between image sets were compared using linear regression and Student's t-test, and evaluated with intraclass-correlation analysis (ICC). The inter-rater Dice similarity coefficient (DSC) assessed the segmentation spatial localization. All 19 HCCs were analyzed. On CE-MRI and DP-CBCT examinations, respectively, 1) the mean segmented tumor volumes were 87 ± 8 cm(3) (2-873) and 92 ± 10 cm(3) (1-954), with no statistical difference of segmented volumes by readers of each tumor between the two imaging modalities and the mean time required for segmentation was 66 ± 45 seconds (21-173) and 85 ± 34 seconds (17-214) (P = .19); 2) the ICCs were 0.99 and 0.974, showing a strong correlation among readers; and 3) the inter-rater DSCs showed a good to excellent inter-user agreement on the spatial localization of the tumor segmentation (0.70 ± 0.07 and 0.74 ± 0.05, P = .07). This study shows a strong correlation, a high precision, and excellent reproducibility of semiautomatic tumor segmentation software in measuring tumor volume on CE-MRI and DP-CBCT images. The use of the segmentation software on DP-CBCT and CE-MRI can be a valuable and highly accurate tool to measure the volume of hepatic tumors.

Distinguishing adrenal adenomas from non-adenomas on dynamic enhanced CT: A comparison of 5 and 10 min delays after intravenous contrast medium injection

To evaluate the usefulness of several parameters of 5 min compared to 10 min delayed contrast-enhanced CT in distinguishing adenomas from non-adenomas. The study population consisted of 94 patients (52 men and 42 women; mean age 62 years) with 103 adrenal lesions (75 adenomas and 28 non-adenomas). In each patient, unenhanced CT was followed by early, 5 and 10 min enhanced CT. Diagnostic parameters included delayed enhanced attenuation at 5 and 10 min, washout attenuation (WO) at 5 and 10 min, absolute percentage washout (APW) at 5 and 10 min, and relative percentage washout (RPW) at 5 and 10 min. The accuracy of each parameter for diagnosing adenomas from non-adenomas was calculated using receiver operating characteristic (ROC) analysis. Upon comparison between 5 and 10 min delayed contrast-enhanced CT for differentiating total adenomas or lipid-poor adenomas from non-adenomas, there was no significant difference in the area under the binomial ROC curve (Az) values of delayed enhanced attenuation (total adenomas versus non-adenomas, p = 0.164; lipid-poor adenomas versus non-adenomas, p = 0.178), WO (total adenomas versus non-adenomas, p = 0.216; lipid-poor adenomas versus non-adenomas, p = 0.230), APW (total adenomas versus non-adenomas, p = 0.401; lipid-poor adenomas versus non-adenomas, p = 0.870), or RPW (total adenomas versus non-adenomas, p = 0.160; lipid-poor adenomas versus non-adenomas, p = 0.780). Five minute contrast-enhanced CT was as useful as 10 min contrast-enhanced CT for differentiation of adrenal adenomas from non-adenomas.

Reply to letter to the editor re: Are intravenous injections of contrast media really less nephrotoxic than intra-arterial injections?

Reply to letter to the editor re: Are intravenous injections of contrast media really less nephrotoxic than intra-arterial injections?

Letter to the Editor re: Are intravenous injections of contrast media really less nephrotoxic than intra-arterial injections?

In a recent paper, the authors oppose the opinion that " intra-arterial administration of iodinated-based contrast media (CM) appears to pose a greater risk of contrast-induced nephropathy (CIN) than intravenous administration" . As nephrologists, we are happy to have the opportunity to offer our expertise in the setting of renal disease aimed at optimizing diagnostic algorithm and preventive strategies. Our comment relies on the fact that, from a nephrologist's point of view, there is no doubt that renal damage following CM intra-venous administration in patients not in intensive care or emergency department and treated with conventional preventive strategies not only occurs with low frequency, but also appears of negligible clinical impact; it is confined to an asymptomatic increase of serum creatinine of 25% or 0.5 mg/dL lacking any prognostic negative impact, and in some case not significantly different from controls.True CIN, just related to intravenous CM injection for diagnostic purpose, has to be differentiated from all the other cause of renal involvement in people stricken with sudden and acute illness also receiving intra-arterial CM injection, in order to avoid patients being denied necessary radiological examinations due to an inappropriate fear of risk. • Contrast induced nephropathy (CIN) is not any nephropathy following contrast medium(CM). • CIN should only refer to renal damage strictly due to CM infusion. • True CIN following CM intravenous infusion is a clinically insignificant event. • Renal damage following intra-arterial CM infusion in compromised patients is not CIN. • Patients should not forego necessary radiological examinations for inappropriate understanding about risk.

Rectal gastrointestinal stromal tumors: Imaging features with clinical and pathological correlation

To investigate computed tomography (CT) and magnetic resonance imaging (MRI) manifestations of rectal gastrointestinal stromal tumors (GISTs) in order to enhance the recognition of these rare tumors. Fourteen patients with pathologically proven rectal GISTs were retrospectively reviewed. Patient histories were retrospectively reviewed for patient age, gender, presenting symptoms, endoscopic investigations, operation notes and pathologic slides. All tumors were evaluated for CD117, CD34 expression, and the tumors were stratified according to current criteria of the National Institutes of Health (NIH). In all cases the first pre-operation imaging findings (CT and MRI, n = 3; MRI only, n = 8; CT only, n = 3) were analyzed by two experienced radiologists by consensus, which include: tumor size, shape, CT density (hypodense, isodense and hyperdense), MRI signal intensity (hypointense, isointense and hyperintense), epicenter (intraluminal or extraluminal), margin (well-defined or ill-defined), internal component (presence of calcifications, necrosis, hemorrhage or ulceration), pattern and degree of enhancement, invasion into adjacent structures. After review of the radiologic studies, clinical and pathological findings were correlated with radiological findings. The patients, 13 men and 1 woman, were aged 31-62 years (mean = 51.5 ± 10.7 years). The most common initial presentation was hematochezia (n = 6). The mean tumor diameter was 5.68 ± 2.64 cm (range 1.5-11.2 cm). Eight lesions were round or oval, and 6 lesions were irregular. Eleven lesions were well-defined and 3 had ill-defined margins. Ten tumors were extraluminal and 4 were intraluminal. The density and MR signal intensity of the solid component of the lesions were similar to that of muscle on unenhanced CT (n = 6) and T1-weighted images (n = 11), and hyperintense on T2-weighted MR images. Calcification was detected in 2 tumors. Following intravenous injection of contrast media, 3 lesions had mild enhancement and 11 lesions had moderate enhancement. Enhancement was homogenous in 3 lesions and heterogeneous in 11. In 1 of 11 patients who underwent both CT and MRI, the tumor was homogenous on CT scan and heterogeneous on MRI. Eight patients were classified as high risk according to the modified recurrent risk classification system of NIH. Rectal GISTs usually manifest as large, well-circumscribed, exophytic masses with moderate and heterogeneous enhancement on CT and MRI. The invasion of adjacent organs, bowel obstruction and local adenopathy are uncommon.

Kinetics of intravenous radiographic contrast medium injections as used on CT: simulation with time delay differential equations in a basic human cardiovascular multicompartment model

To develop a multicompartment model of only essential human body components that predicts the contrast medium concentration vs time curve in a chosen compartment after an intravenous injection. Also to show that the model can be used to time adequately contrast-enhanced CT series. A system of linked time delay instead of ordinary differential equations described the model and was solved with a Matlab program (Matlab v. 6.5; The Mathworks, Inc., Natick, MA). All the injection and physiological parameters were modified to cope with normal or pathological situations. In vivo time-concentration curves from the literature were recalculated to validate the model. The recalculated contrast medium time-concentration curves and parameters are given. The results of the statistical analysis of the study findings are expressed as the median prediction error and the median absolute prediction error values for both the time delay and ordinary differential equation systems; these are situated well below the generally accepted maximum 20% limit. The presented program correctly predicts the time-concentration curve of an intravenous contrast medium injection and, consequently, allows an individually tailored approach of CT examinations with optimised use of the injected contrast medium volume, as long as time delay instead of ordinary differential equations are used. The presented program offers good preliminary knowledge of the time-contrast medium concentration curve after any intravenous injection, allowing adequate timing of a CT examination, required by the short scan time of present-day scanners. The injected volume of contrast medium can be tailored to the individual patient with no more contrast medium than is strictly needed.

Intranodular signal intensity analysis of hypovascular high-risk borderline lesions of HCC that illustrate multi-step hepatocarcinogenesis within the nodule on Gd–EOB–DTPA-enhanced MRI

ObjectivesTo analyze intranodular signal intensity pattern of hypovascular high-risk borderline lesions of HCC that illustrate multi-step hepatocarcinogenesis within the nodule on Gd–EOB–DTPA-enhanced MRI. MethodsA total of 73 nodules showing hypervascular foci in hypovascular high-risk borderline lesions identified by angiography-assisted CT were included in this study. The intranodular signal intensities of both the hypervascular foci and the hypovascular high-risk borderline lesions were evaluated on hepatobiliary-phase EOB-enhanced MRI obtained 20min after intravenous injection of contrast media. ResultsAmong 59 hypervascular foci within hypointense hypovascular high-risk borderline lesions, 6 showed more hypointensity, 32 isointensity, and 21 hyperintensity compared to the surrounding hypointense, hypovascular portion of the nodules. Among 14 hypervascular foci within isointense hypovascular high-risk borderline lesions, 5 showed isointensity, and 9 hypointensity compared to the surrounding isointense hypovascular high-risk borderline lesions. No hypervascular foci showed hyperintensity compared to the surrounding isointense hypovascular high-risk borderline lesions. ConclusionsIn most of the hypovascular high-risk borderline lesions containing hypervascular foci within the nodule, the signal intensity was decreased in hypervascular foci as compared with hypovascular high-risk borderline lesions and the surrounding background liver parenchyma. This supports the concept of signal intensity decrease during the dedifferentiation process in multistep hepatocarcinogenesis. However, around 30% of the nodules did not follow this rule, and hypervascular foci showed hyperintensity relative to the hypovascular high-risk borderline lesions.

The serial effect of iodinated contrast media on renal hemodynamics and oxygenation as evaluated by ASL and BOLD MRI

Contrast-induced nephropathy is a prevalent cause of renal failure, and the mechanisms underlying this injury are not fully understood. We utilized noninvasive functional MRI in order to determine the serial effect of a single administration of iodinated contrast media (CM) on renal hemodynamics and oxygenation. Fifteen rabbits were randomized to receive an intravenous injection of CM (i.e. iopamidol-370; 6 ml kg(-1) body weight) or an equivalent amount of 0.9% saline. Both arterial spin-labeling and blood oxygen level-dependent imaging sequences were performed at 24 h before and at intervals of 1, 24, 48 and 72 h after injection to obtain serial renal blood flow (RBF) and relative spin-spin relaxation rate (R(2)*). Results showed that, in the iopamidol group, the mean cortical RBF decreased at 1 h (p = 0.04 vs baseline), reached its minimum at 24 h (p = 0.01) and gradually returned to baseline by 48 h (p = nonsignificant, NS). The outer medullary RBF decreased to its minimum by 24 h (p = 0.00) and remained less than baseline until 72 h. R(2)* in inner stripes was dramatically increased at 1 h (p = 0.00), remained elevated at 24 h (p = 0.05), but returned to baseline by 48 h (p = NS). R(2)* values within the cortex and outer stripes and inner medulla were slightly increased, but the changes did not reach a statistical significance (p = NS). Saline did not produce positive change in either RBF or R(2)* within different compartments of the kidney. We conclude that iopamidol is associated with a relatively longer-term hypoperfusion in whole kidney and decreased oxygen level in the inner stripes of the outer medulla.

C-Arm CT Measurement of Cerebral Blood Volume Using Intra-Arterial Injection of Contrast Medium: An Experimental Study in Canines

Measurement of perfusion parameters is typically done using an intravenous injection of contrast medium. This purpose of this study was to evaluate the feasibility of measuring regional and global CBV using C-arm CT with IA injections of contrast medium. Twelve canines were studied. CBV measurement was performed using standard PCT, and then using C-arm CT with IV and IA contrast. Values obtained using C-arm CT were compared with those using PCT. C-arm CT CBV maps using IA injections required less contrast than ones with IV injections. PCT and C-arm CT using IV and AA injections provided comparable maps. In controls, C-arm CT with a CCA or VA injection provided comparable maps to PCT. In animals with a stroke, a CCA or VA injection did not provide maps comparable to ones made with PCT. IV and AA C-arm CT showed excellent quantitative agreement with PCT, while CCA and VA C-arm CT studies did not. Measurement of global CBV using C-arm CT in conjunction with either an IV or an AA injection was feasible in controls and dogs with a stroke. Measurement of regional CBV with C-arm CT using either CCA or VA injection, in normal canines, provided CBV maps qualitatively comparable with those obtained with PCT; the absolute CBV values from these maps were in poor agreement with PCT measurements. Valid measurement of CBV using C-arm CT requires all tissue in a target region to be fully and equally opacified during any acquisition. Using CCA or VA injections, it was impossible to document if and when this had been achieved. CBV measurements using these routes of injection were therefore not reliable.

Imaging in infections of the left iliac fossa

The main organs in the left iliac fossa are the descending colon, sigmoid colon and, in women, internal reproductive organs. An infection of the left iliac fossa must lead the clinician firstly to suspect diverticulitis of the sigmoid colon in older patients and salpingitis in women of childbearing age. Other less common aetiologies are possible (inflammatory or infectious colitis, epiploic appendagitis, abscess of the psoas, pyelonephritis, renal abscess, etc.). Sonography as a first-line investigation may lead to diagnosis (especially in gynaecological disease), but a CT scan with intravenous injection of an iodine-containing contrast medium will allow for a full assessment of disease spread, and complications of sigmoid colitis or its differential diagnoses (abscess, fistula, perforation) to be investigated. It can also be used to guide percutaneous drainage or fine-needle aspiration for microbiology investigations.

Are intravenous injections of contrast media really less nephrotoxic than intra-arterial injections?

We oppose the opinion that the intra-arterial administration of iodine-based contrast media (CM) appears to pose a greater risk of contrast medium-induced nephropathy (CIN) than intravenous administration since 1) in intra-arterial coronary procedures and most other intra-arterial angiographic examinations, CM injections are also intravenous relative to the kidneys, 2) there is a lack of comparative trials studying the risk of CIN between intra-arterial and intravenous procedures with matched risk factors and CM doses, 3) a bias selection of patients with fewer risk factors may explain the seemingly lower rate of CIN after CT in comparison with coronary interventions, 4) the rate of CIN following intra-arterial coronary procedures may also be exaggerated owing to other causes of acute kidney failure, such as haemodynamic instability and microembolisation, 5) roughly the same gram-iodine/GFR ratio (≈1:1) as a limit of relatively safe CM doses has preliminarily been found for both intravenous CT and intra-arterial coronary procedures and 6) the substantially higher injected intravenous CM dose rate during CT relative to an intra-arterial coronary procedure might actually pose a higher risk of CIN following CT. • Most intra-arterial injections of contrast media are intravenous relative to the kidneys. • No evidence that intravenous CM injections should be less nephrotoxic than intra-arterial. • Considerably higher dose rates of CM are used for CT relative to intra-arterial procedures. • Higher dose rates may pose higher nephrotoxic risk for intravenous based CT studies.

CT in children – dose protection and general considerations when planning a CT in a child

Today CT represents about 10% of all ionizing radiation based imaging modalities, but delivers more than 50% of the total collective dose for diagnostic imaging. Compared to adults the radiation sensitivity of children is considerable higher than in adults. Additionally children differ from adults – factors like body size, mass, density, proportions as well as metabolism have to be mentioned. Children grow and maturate – all this components have to be mapped in examination protocols by Pediatric Radiology. The total dose of a CT examination depends on the settings of several factors such as the scout view, the scan length, exposure settings including automated exposure control, type of scanning (single slice, helical, volume mode), slice thickness, pitch values as well as on image reconstruction parameters. If intravenous contrast media injection is needed bolus tracking or timing represents another source of radiation.The aim of the paper is to present and discuss all aspects of defining a pediatric age and query adapted CT protocol particularly concerning all dose relevant factors in pediatric CT and their adjustment in children. Moreover hints are given concerning optimization of intravenous contrast media injection as well as special (low dose) imaging protocols.

Metformin and its clinical use: new insights for an old drug in clinical practice.

Metformin is generally recommended as first-line treatment in type 2 diabetes, especially in overweight patients, but in recent years new indications for its use have emerged. Metformin has been found to be safe and efficacious both as monotherapy and in combination with all oral antidiabetic agents and insulins. If metformin use during pregnancy and the lactation period is supported by few data, it could be indicated for women with polycystic ovary syndrome, since it could diminish circulating androgens and insulin resistance, thus ameliorating the ovulation rate. Metformin seems to reduce cancer risk, which appears to be increased in diabetics, and is a promising agent for oncoprevention and chemotherapy combinations. Moreover, metformin could find a place in the treatment of non-alcoholic fatty liver disease. Lactic acidosis could be decreased by avoiding metformin use in patients with hypovolemia, sepsis, renal impairment, hypoxic respiratory diseases and heart failure, in the preoperative period and before intravenous injection of contrast media.

Perfusion CT in Colorectal Cancer: Comparison of Perfusion Parameters with Tumor Grade and Microvessel Density

ObjectiveThe purpose of this study was to prospectively compare pre-operative computed tomography (CT) perfusion parameters with tumor grade from colorectal adenocarcinoma (CRC) and to correlate pre-operative CT perfusion parameters with microvessel density (MVD) to evaluate angiogenesis in CRC.Materials and MethodsPre-operative perfusion CTs were performed with a 64-channel multidetector row CT in 27 patients (17 women and 10 men; age range 32-82 years) who were diagnosed with CRC involving the sigmoid and rectum between August 2006 and November 2007. All patients underwent surgery without pre-operative chemotherapy or radiation therapy. Dynamic perfusion CTs were performed for 65 seconds after intravenous injection of contrast medium (100 mL, 300 mg of iodine per mL, 5 mL/sec). Before surgery, blood flow (BF), blood volume, mean transit time (MTT), and permeability-surface area product were measured in the tumor. After surgery, one gastrointestinal pathologist evaluated tumor grade and performed immunohistochemical staining using CD 34 to determine MVD in each tumor. The Kruskal-Wallis test was used to compare CT perfusion parameters with tumor grade, and Pearson's correlation analysis was used to correlate CT perfusion parameters with MVD.ResultsIn 27 patients with CRC, tumor grading was as follows: well differentiated (n = 8); moderately differentiated (n = 15); and poorly differentiated (n = 4). BF was higher in moderately differentiated CRC than well differentiated and poorly differentiated CRCs (p = 0.14). MTT was shorter in moderately differentiated than well differentiated and poorly differentiated CRCs (p = 0.039). The MVD was greater in poorly differentiated than well differentiated and moderately differentiated CRCs (p = 0.034). There was no significant correlation between other perfusion parameters and tumor grade. There was no significant correlation between CT perfusion parameters and MVD.ConclusionBF and MTT measurement by perfusion CT is effective in predicting moderately differentiated CRCs. However, perfusion CT is limited in distinguishing well differentiated and poorly differentiated CRCs. Pre-operative perfusion CT does not reflect the MVD of CRCs.

CT and MRI Imaging Diagnosis of Epidural Idiopathic Sterile Pyogranulomatous Inflammation in a Dog Spinal Canal

A 12-year-old neutered male shih tzu developed progressive pelvic limb paraparesis. Computed tomography showed a radiolucent mass lesion in the spinal canal at the left side of the 11th thoracic vertebra. The mass was not enhanced by intravenous contrast medium injection. It was hyperintense on both T1- and T2-weighted magnetic resonance images. The signal intensity of the mass was decreased with a fat suppression technique, indicating a fatty origin. After removal of the mass via T11-T12 hemilaminectomy, chronic panniculitis was confirmed by histopathological examination. This case demonstrates the utility of computed tomography and magnetic resonance imaging for the diagnosis of spinal canal pyogranulomatous inflammation.

Computed Tomography Perfusion Analysis of Pancreatic Carcinoma

The purpose of this study was to evaluate CT perfusion of pancreatic carcinomas using the Patlak model for assessing perfusion, permeability, and blood volume. A total of 25 patients with pancreatic carcinoma were examined prospectively with a 64-slice computed tomography (CT) using a dynamic sequence after intravenous injection of 80-mL contrast material (370 mg/mL; flow rate, 5 mL/s). Eighty-kilovolt (peak) perfusion acquisitions were evaluated for estimating perfusion parameters for carcinoma and healthy tissue using a 2-compartment model (Patlak model). Twenty patients had hypodense tumors; in 5 patients, the tumor could not be delineated in contrast-enhanced CT. All carcinomas could be identified clearly in the color-coded perfusion maps. Perfusion, permeability, and blood volume values were significant lower in pancreatic carcinomas compared to healthy pancreatic tissue (0.27 ± 0.20 vs 0.89 ± 0.19 min, P < 0.0001; 0.43 ± 0.20 vs 0.75 ± 0.16 × 0.5 min, P < 0.0001; and 38.9 ± 20.7 vs 117.8 ± 46.9 mL/100 mL, P < 0.0001). Computed tomographic perfusion of the pancreas using a 2-compartment perfusion model is feasible. Color-coded perfusion maps could be a helpful tool to delineate pancreatic carcinomas even if they are not visible in contrast-enhanced CT.

Acute Severe Thrombocytopenia Following Non-Ionic Low-Osmolarity Intravenous Contrast Medium Injection

Intravenous contrast medium (ICM) rarely induces anaphylactic reactions, including urticaria, hypotension and respiratory failure. Even the most modern ICM may cause such adverse events. Thrombocytopenia has been reported as an extreme rare consequence of ICM. Here we report on a case of a 72-year-old male patient with a self-limiting severe acute thrombocytopenia following administration of intravenous non-ionic low-osmolarity contrast medium. No such low platelet count has ever been reported. We also present a review of the literature.

CT colonography: Why? When? How?

Although optical colonoscopy is still the gold standard for diseases of the colon, radiologic examination of the colon is now being performed by CT scan. Evaluation of the colon is enhanced by distension, which "de-folds" the intestinal wall, thus facilitating its examination for abnormalities of the mucosa, the wall as a whole, and the diameter of the bowel lumen. Water or gas (CO(2)) may be used for the distension, depending on the suspected lesions. The water enema method of colonography combines filling the bowel lumen with water and intravenous injection of a contrast medium. It is indicated when there is a clinical suspicion of colon cancer, or for initial discovery of liver metastases, and for staging of colon tumors. This technique, which requires little or no colon cleansing preparation, can be performed with no special equipment and has a short learning curve. The gas enema method of colonography, or virtual colonoscopy, is performed by distending the colon with CO(2), without any intravenous injection of contrast medium. Its purpose is to detect polyps as part of a screening for precancerous growths. This technique, which does require bowel cleansing preparation, uses a dedicated console for reading and requires specific training.

Anatomical Study of the Gastrointestinal Tract of a Pudu (Pudu puda) Using Contrast-Enhanced Abdominal Computed Tomography

The pudu (Pudu puda), which is the smallest deer in the world and inhabits central and southern Chile and Argentina, is a ruminant and a browsing herbivore. The aim of this study was to provide a reference for interpretation of the normal anatomy of the pudu's gastrointestinal tract as imaged by abdominal computed tomography (CT). For the study, one adult female pudu was used. After a 24-h fast, the pudu was anaesthetized and positioned in sternal recumbency at the CT table. Image acquisition began immediately after intravenous injection of contrast media (MD-76(®); 370 mgI/ml) into the cephalic vein. Injection of contrast material was administered as a biphasic protocol. First, a manual bolus of contrast material was injected at a rate of 4 ml/s. Then, an additional continuous infusion injection (0.1 ml/min) was performed for adequate opacification of vascular structures. Transverse images of 5 mm thickness and 5 mm interval were obtained with a fourth-generation CT scanner, from the ninth thoracic vertebra (T9) until the first sacral (S1) vertebrae. CT images were labelled and compared with anatomical reference images for ruminants. Structures that were identified in the abdominal cavity included the stomach with its four compartments (rumen, reticulum, omasum and abomasum), the small and large intestines, liver, spleen, kidneys and some major blood vessels (aorta, caudal vena cava). The distal loop of the ascending colon, the transverse colon, the pancreas and lymph nodes could not be identified. The resulting CT images provide a reference for normal cross-sectional abdominal anatomy of the adult pudu.