Iodinated Contrast Allergy Research Articles

Midterm Outcomes of Endovascular Aortic Aneurysm Repair with Carbon Dioxide–Guided Angiography

Although iodinated contrast (IC) agents are commonly used in endovascular aneurysm repair (EVAR), perioperative use in patients with renal dysfunction or IC allergies is avoided. Carbon dioxide (CO2)-guided angiography is a promising alternative. We aimed to evaluate short-term and midterm outcomes of EVAR using CO2-guided angiography. Three hundred eighty-one patients who underwent EVAR from January 2012 to September 2016 were retrospectively reviewed and divided into an IC-EVAR group (n=351) and CO2-EVAR group (n=30). Subjects in the CO2-EVAR group had severe renal dysfunction (n=27) and IC allergy (n=4). Intraoperative, postoperative, and follow-up variables were compared. Compared with the IC-EVAR group, preoperative serum creatinine level was significantly higher (2.0 vs. 0.92mg/dL, P<0.0001) and mean IC dose was significantly lower (18 vs. 55mL,P<0.0001) in the CO2-EVAR group. The fluoroscopy time, operative time, number of stent grafts placed, and technical success rates of the groups were similar; no type I and/or type III endoleaks were detected on completion angiography. There was no acute kidney injury and one case of intestinal necrosis in the CO2-EVAR group, potentially due to cholesterol embolism. Postoperative endoleak, enlargement of aneurysms, survival, freedom from secondary intervention, and renal function change up to 3months, postoperatively, were similar between the groups. CO2-EVAR is technically feasible and exhibits prominent renal protection. However, consideration of the aortic lumen status remains an important challenge.

Endovascular Aortic Repair Follow up Protocol Based on Contrast Enhanced Ultrasound Is Safe and Effective

The aim of this study was to define the safety and effectiveness of a contrast enhanced ultrasound (CEUS) based follow up for endovascular aortic repair (EVAR) surveillance at a mid-term period (4 years). At the tertiary referral centre EVAR surveillance was based on plain abdominal radiograph and duplex ultrasound (CDU), with computed tomography angiography (CTA) reserved for any non-diagnostic imaging during the period 1999-2011 (Group A). From 2012, CEUS was performed when (a) any endoleak was detected at CDU, (b) sac growth>5mm within 6 months, and routinely for (c) patients with renal insufficiency (above Stage 3 chronic kidney disease), or (d) iodine contrast allergy (Group B). A total of 880 patients (mean age 75.6±8.4 years; 824 male) who underwent EVAR between 1999 and 2015 and with a minimum of 1 year follow up were included. Six hundred and nineteen patients were in Group A (70%) and the remaining 261 in Group B (30%). Median follow up was 48 months (interquartile range 24-84). During the study period 318 CEUS scans were performed with no related complications. Indications for CEUS were the following: (a) 160 (50%) endoleak presence, (b) 34 (11%) significant sac expansions, (c) 91 (29%) renal insufficiency (Stage 3 or above CKD), and 33 (10%) iodine contrast allergies. CEUS was compared with CTA, with additional confirmation by angiographic and operative findings in the case of repair in the first 100 patients. CEUS had 100% sensitivity and 100% specificity in classifying endoleaks. No differences in endoleak, re-interventions and sac shrinkage percentage were seen between the two groups at 4 years. A 4 year analysis of CTA use found a 90% reduction with the introduction of CEUS. The introduction of a CEUS based protocol for EVAR follow up was safe and effective and it was similar to the previous CTA based follow up protocol with regard to identification of endoleaks in a mid-term period. Moreover, CEUS allowed for 90% reduction of CTA, thereby decreasing radiation exposure for patients.

Alcohol septal ablation using myocardial contrast echocardiography on a patient with iodine contrast allergy.

Alcohol septal ablation using myocardial contrast echocardiography on a patient with iodine contrast allergy.

Use of carbon dioxide as an intravascular contrast agent: A review of current literature.

Use of X-ray contrast allows us to differentiate between two or more adjacent structures on radiographic studies. The X-ray contrast agent can be the one with increase X-ray absorption, like iodine and a barium X-ray contrast agent or the one with decrease X-ray absorption like air and carbon dioxide contrast agent. Each contrast agent possesses different risks and benefits in various ways. Carbon dioxide as an intravascular contrast agent can be used as an alternative intravascular contrast agent and has superior results in some cases. In patients with renal dysfunction or iodinated contrast allergy, the use of Iodinated Contrast Agent poses the risk of considerable morbidity. Similarly, use of Gadolinium is discouraged in subject with severe renal dysfunction. Use of carbon dioxide (CO2) as an intravascular contrast, offers an alternative in such patients for certain procedures, as it is not nephrotoxic and it does not incite allergic reactions. It is inexpensive, readily available and due to its unique physical properties, it can be used to image a wide variety of vascular beds and chambers. The aim of this paper is to systemically review the current literature to describe the indications, contraindications, adverse effects, instruments, precautions, latest methodologies and data supporting for the use of CO2 as a contrast agent.

Use of Clinical Decision Support to Increase Premedication Regimen Homogeneity

PurposePatients with prior allergic reactions to iodinated contrast require premedication. This study aimed to increase the homogeneity of premedication orders in such patients. MethodsA point-of-care (POC) clinical decision support (CDS) alert accompanied by an order set was implemented in the electronic health record (EHR) to notify providers of a prior allergic reaction upon ordering an examination involving iodinated contrast. Premedication regimens were retrospectively compared 11 months pre– and 11 months post–alert implementation, with the different regimens being classified as follows: (1) “preferred” (per ACR recommendations), (2) “nonpreferred” (corticosteroid administered <24 hours before examination, but not per ACR recommendations), or (3) “no premedication.” ResultsOver 22 months, 22,023 iodinated contrast examinations were performed, 200 (186 intravascular, 12 gastrointestinal/genitourinary, 1 intraarticular, 1 intrathecal) being in patients with a documented iodinated contrast allergy (106 pre–, 94 post–alert deployment). Prealert, 41 of 106 patients (38.7%) received a preferred regimen, 47 (44.3%) received nonpreferred regimens, and 18 (17.0%) received no premedication. Postalert, 58 of 94 patients (61.7%) received a preferred regimen, 21 (22.3%) nonpreferred regimens, and 15 (16.0%) no premedication. After alert initiation, the patients prescribed a preferred regimen significantly increased (Z-score = 3.25, P = .001), but there was no significant difference in the proportion of patients with no premedication (Z-score = -0.02, P = .85). In 2 of 200 patients (1.0%), an allergic reaction occurred, both after POC-CDS alert implementation with a preferred regimen administered. ConclusionsThe homogeneity of premedication regimens significantly increased after the alert’s launch. However, the proportion of patients with no premedication did not significantly change.

Feasibility of three-dimensional magnetic resonance angiography-fluoroscopy image fusion technique in guiding complex endovascular aortic procedures in patients with renal insufficiency

ObjectiveThree-dimensional image fusion of preoperative computed tomography (CT) angiography with fluoroscopy using intraoperative noncontrast cone-beam CT (CBCT) has been shown to improve endovascular procedures by reducing procedure length, radiation dose, and contrast media volume. However, patients with a contraindication to CT angiography (renal insufficiency, iodinated contrast allergy) may not benefit from this image fusion technique. The primary objective of this study was to evaluate the feasibility of magnetic resonance angiography (MRA) and fluoroscopy image fusion using noncontrast CBCT as a guidance tool during complex endovascular aortic procedures, especially in patients with renal insufficiency. MethodsAll endovascular aortic procedures done under MRA image fusion guidance at a single-center were retrospectively reviewed. The patients had moderate to severe renal insufficiency and underwent diagnostic contrast-enhanced magnetic resonance imaging after gadolinium or ferumoxytol injection. Relevant vascular landmarks electronically marked in MRA images were overlaid on real-time two-dimensional fluoroscopy for image guidance, after image fusion with noncontrast intraoperative CBCT. Technical success, time for image registration, procedure time, fluoroscopy time, number of digital subtraction angiography (DSA) acquisitions before stent deployment or vessel catheterization, and renal function before and after the procedure were recorded. The image fusion accuracy was qualitatively evaluated on a binary scale by three physicians after review of image data showing virtual landmarks from MRA on fluoroscopy. ResultsBetween November 2012 and March 2016, 10 patients underwent endovascular procedures for aortoiliac aneurysmal disease or aortic dissection using MRA image fusion guidance. All procedures were technically successful. A paired t-test analysis showed no difference between preimaging and postoperative renal function (P = .6). The mean time required for MRA-CBCT image fusion was 4:09 ± 01:31 min:sec. Total fluoroscopy time was 20.1 ± 6.9 minutes. Five of 10 patients (50%) underwent stent graft deployment without any predeployment DSA acquisition. Three of six vessels (50%) were cannulated under image fusion guidance without any precannulation DSA runs, and the remaining vessels were cannulated after one planning DSA acquisition. Qualitative evaluation showed 14 of 22 virtual landmarks (63.6%) from MRA overlaid on fluoroscopy were completely accurate, without the need for adjustment. Five of eight incorrect virtual landmarks (iliac and visceral arteries) resulted from vessel deformation caused by endovascular devices. ConclusionsFerumoxytol or gadolinium-enhanced MRA imaging and image fusion with fluoroscopy using noncontrast CBCT is feasible and allows patients with renal insufficiency to benefit from optimal guidance during complex endovascular aortic procedures, while preserving their residual renal function.

MR angiography can guide ED management of suspected acute aortic dissection

BackgroundAortic dissection is typically evaluated with computed tomography angiography (CTA). However, the feasibility of using magnetic resonance angiography (MRA) in the ED is unclear. This study examined the indications and outcomes of MRA in suspected aortic dissection evaluation in the ED. MethodsAn IRB approved review identified patients who underwent MRA in the ED for acute thoracic aortic dissection from January 2010 to June 2016. Demographics, clinical assessment, CTA contraindications, outcomes, and ED disposition were analyzed. Results50 MRAs were ordered for suspected thoracic aortic dissection. 21 (42%) for iodinated contrast allergy, 21 (42%) for renal insufficiency, 2 (4%) due to both, 2 (4%) to spare ionizing radiation, 2 (4%) for further work-up after CTA, and 2 (4%) due to prior contrast enhanced CT within 24h. Median ED arrival to MRA completion time was 311min. 42 studies were fully diagnostic; 7 were limited. One patient could not tolerate the examination. 49 MRAs were completed: 2 (4%) patients had acute dissection on MRA and 47 (96%) had negative exams. 17 (35%) received gadolinium. 18 (37%) patients were discharged home from the ED with a median length of stay of 643min. 2 (4%) were admitted for acute dissection seen on MRA and 29 (59%) for further evaluation. ConclusionMRA has a clear role in the evaluation for acute thoracic aortic dissection in the ED in patients with contraindications to CTA, and can guide management and facilitate safe discharge to home.

The use of carbon dioxide angiography for renal sympathetic denervation: a technical report.

Hypertension is the leading attributable cause of cardiovascular mortality worldwide. Patients with hypertension have multiple comorbidities including high rates of concomitant renal disease. Current pharmacological approaches are inadequate in the treatment of resistant hypertension. Renal sympathetic denervation (RDN) has been shown to effectively treat resistant hypertension. The traditional use of iodinated contrast in RDN is contraindicated in patients with significant renal insufficiency. In patients with renal impairment, carbon dioxide (CO2) can be used as an alternative contrast material for RDN. This article describes the technical aspects of RDN using CO2 angiography. Our centre is experienced in the innovative RDN procedure using CO2 angiography. We describe the protocol for CO2 angiography for RDN using a home-made CO2 delivery system and the Symplicity™ (Minneapolis MN 55432 USA) catheter (Medtronic) device. CO2 angiography is an excellent alternative to iodinated contrast for RDN procedures. CO2 angiography for RDN is a safe and effective alternative to iodinated contrast. RDN using CO2 angiography is an easy and feasible procedure that can be used in patients with renal insufficiency or iodinated contrast allergies. Advances in knowledge: There is a paucity of descriptive reports for CO2 angiography for RDN and we provide details of the optimal protocol for the procedure. In particular, we describe the use of a Symplicity Spyral™ catheter (Medtronic), which has not been reported to date for use in this procedure.

Premedication of pregnant patients with history of iodinated contrast allergy.

Pregnant patients can receive allergy premedication prior to a contrast-enhanced computed tomography exam if the exam is indicated. The risks and benefits of allergy premedication for pregnant patients will be discussed, as well as imaging strategies for the pregnant patient with a contrast allergy. Alternative imaging including ultrasound, noncontrast magnetic resonance imaging, or noncontrast computed tomography can be diagnostic depending on the clinical scenario and is usually preferred, allowing physicians to avoid giving allergy premedication in pregnancy, a 13h delay, and risking a breakthrough reaction.

Contrast ultrasound in hepatocellular carcinoma at a tertiary liver center: First Indian experience

To assess the role of contrast enhanced ultrasonography in evaluation of hepatocellular carcinoma (HCC) at the first Indian tertiary liver center. Retrospective analysis of contrast enhanced ultrasound (CEUS) examinations over 24 mo for diagnosis, surveillance, characterization and follow up of 50 patients in the context of HCC was performed. The source and indication of referrals, change in referral rate, accuracy and usefulness of CEUS in a tertiary liver center equipped with a 64 slice dual energy computer tomography (CT) and 3 tesla magnetic resonance imaging (MRI) were studied. Sonovue (BR1, Bracco, Italy, a second generation contrast agent) was used for contrast US studies. Contrast enhanced CT/MRI or both were performed in all patients. The findings were taken as a baseline reference and correlation was done with respect to contrast US. Contrast enhanced MRI was performed using hepatocyte specific gadobenate dimeglumine (Gd-BOPTA). Iomeron (400 mg; w/v) was used for dynamic CT examinations. About 20 (40%) of the examinations were referred from clinicians for characterization of a mass from previous imaging. About 15 (30%) were performed for surveillance in chronic liver disease; 5 (10%) examinations were performed for monitoring lesions after radiofrequency ablation (RFA); 3 (6%) were post trans-arterial chemo-embolization (TACE) assessments and 3 (6%) were patients with h/o iodinated contrast allergy. About 2 (4%) were performed on hemodynamically unstable patients in the intensive care with raised alpha fetoprotein and 2 (4%) patients were claustrophobic. The number of patients referred from clinicians steadily increased from 12 in the first 12 mo of the study to 38 in the last 12 mo. CEUS was able to diagnose 88% of positive cases of HCC as per reference standards. In the surveillance group, specificity was 53.3% vs 100% by CT/MRI. Post RFA and TACE specificity of lesion characterization by CEUS was 100% in single/large mass assessment, similar to CT/MRI. For non HCC lesions such as regenerative and dysplastic nodules, the specificity was 50% vs 90% by CT/MRI. The positive role of CEUS in imaging spectrum of HCC included a provisional urgent diagnosis of an incidentally detected mass. It further led to a decrease in time for further management. A confident diagnosis on CEUS was possible in cases of characterization of an indeterminate mass, in situations where the patient was unfit for CT/MRI, was allergic to iodinated contrast or had claustrophobia, etc. CEUS was also cost effective, radiation free and an easy modality for monitoring post RFA or TACE lesions. CEUS is a valuable augmentation to the practice of ultrasonography, and an irreplaceable modality for confounding cases and interpretation of indeterminate lesions in imaging of HCC.

Contrast alternatives for iodinated contrast allergy and renal dysfunction: Options and limitations

Diagnostic angiography and vascular interventions make routine use of iodinated contrast material (ICM). Patients with renal disease or contrast allergy pose limitations on the use of ICM. In such cases, alternative contrast media may be used to carry out the procedure. Current alternatives include carbon dioxide, gadolinium, and dilute ICM. Each of these alternatives has its own unique features and limitations. In the present review article, the current alternatives to ICM are explored, with a focus on the applications and restrictions of each.

Transient paralysis from carbon dioxide angiography in a patient after four-vessel endovascular thoracoabdominal aortic aneurysm repair

Contrast angiography with carbon dioxide (CO2) is frequently used in patients with renal dysfunction or iodinated contrast allergies, as CO2 is nonallergenic, nontoxic, and rapidly absorbed in the blood. However, when delivered intra-arterially, there is a possibility that CO2 may create a vapor lock with resultant transient ischemia. We describe a case of suspected CO2 embolus to the iliolumbar artery after iliac artery stenting resulting in immediate loss of bilateral lower extremity motor and sensory function. After placement of a spinal drain and elevation of mean arterial blood pressure, the patient had complete return of sensation with improvement in motor function.

Preoperative Staging of Patients with Liver Metastases of Colorectal Carcinoma. Does PET/CT Really Add Something to Multidetector CT?

This study was designed to determine prospectively whether the systematic use of PET/CT associated with conventional techniques could improve the accuracy of staging in patients with liver metastases of colorectal carcinoma. We also assessed the impact on the therapeutic strategy. Between 2006 and 2008, 97 patients who were evaluated for resection of LMCRC were prospectively enrolled. Preoperative workup included multidetector-CT (MDCT) and PET/CT. In 11 patients with liver steatosis or iodinated contrast allergy, MR also was performed. Sixty-eight patients underwent laparotomy. Sensitivity, specificity, positive predictive value (PPV), and negative predictive values for hepatic and extrahepatic staging of MDCT and PET-CT were calculated. In a lesion-by-lesion analysis of the hepatic staging, the sensitivity of MDCT/RM was superior to PET/CT (89.2 vs. 55%, p<0.001). On the extrahepatic staging, PET/CT was superior to MDCT/MR only for the detection of locoregional recurrence (p=0.03) and recurrence in uncommon sites (p=0.016). New findings in PET/CT resulted in a change in therapeutic strategy in 17 patients. However, additional information was correct only in eight cases and wrong in nine patients. PET/CT has a limited role in hepatic staging of LMCRC. Although PET-CT has higher sensitivity for the detection of extrahepatic disease in some anatomic locations, its results are hampered by its low PPV. PET/CT provided additional useful information in 8% of the cases but also incorrect and potentially harmful data in 9% of the staging. Our findings support a more selective use of PET/CT, basically in patients with high risk of local recurrence.

Catheter versus non-catheter angiography in isolated third nerve palsy

PURPOSE: To discuss the controversies surrounding the indications for catheter angiography versus non-catheter and less invasive angiography techniques (e.g. magnetic resonance angiography (MRA) and computerized tomography angiography (CTA)) in the evaluation of patients with a third nerve palsy. METHODS: Clinical opinion-perspective and literature review. RESULTS: The patient with an isolated third nerve palsy might have a vasculopathic (and typically benign, self limited course) etiology or a life threatening intracranial posterior communicating artery aneurysm. Although it is clear that non-isolated third nerve palsies require imaging directed at the topographical localization of the clinical findings, the evaluation of the neurologically isolated third nerve palsy remains controversial. The completeness of the external (i.e. somatic) motor dysfunction and the presence or absence of internal (i.e. pupillary) dysfunction are generally used to guide the choice of initial neuroimaging. Advances in MRA and CTA technology have reduced but not eliminated our dependence upon catheter angiography in this setting. A properly performed and interpreted MRA or CTA probably will be able to detect greater than 95% of aneurysms producing a third nerve palsy. The issues surrounding the use of catheter angiography in third nerve palsy are reviewed. CONCLUSIONS: If the clinician is highly confident in the capability, availability, and reliability of the neuroradiologist and of their institutional experience and quality of less invasive non-catheter MRA and CTA and if the risk of aneurysm is low or if the risk of angiography is high (e.g. elderly, renal failure, iodinated contrast allergy, risk of stroke) then MRI and MRA (or CTA) may be a reasonable alternative to catheter angiography. Patients with a moderate or uncertain risk of aneurysm and a lower risk for catheter angiography or if there is a low confidence in the quality or the interpretation of the institutional MRA (or CTA) may still require catheter angiography in select circumstances. The lowest risk categories for aneurysm are the isolated dilated pupil without ptosis or motility deficit (generally not a third nerve palsy but more commonly the tonic pupil, pharmacologic dilation, or iris damage) and the isolated, pupil-spared but otherwise complete external dysfunction third nerve palsy in a vasculopathic patient. In these patients, the risks of catheter angiography is probably higher than the risks for aneurysm and CTA or MRA is probably sufficient to exclude aneurysm. Patients with high risk for aneurysm (e.g. acute painful pupil involved third nerve palsy) however probably still require strong consideration for catheter angiography but this decision must be individualized.

Feasibility of gadolinium-diethylene triamine pentaacetic acid enhanced multidetector computed tomography for the evaluation of coronary artery disease

Multidetector computed tomography (MDCT) has been proposed as a noninvasive method for the diagnosis of obstructive coronary artery disease (CAD). In patients with high risk of iodinated contrast adverse effects such as acute allergic-type reactions, the use of gadolinium could be an alternative. We sought to evaluate the feasibility of gadolinium-enhanced MDCT for the diagnosis of obstructive CAD. Twenty patients (mean age, 61 years; range, 50-73 years) referred for X-ray coronary angiography were studied by both gadolinium and iodine-enhanced 16-row MDCT coronary angiography. The degree of enhancement and the accuracy for detection of obstructive CAD (>50% diameter reduction) were evaluated with X-ray coronary angiography as the standard. Renal nephrotoxicity was strictly monitored. Gadolinium- and iodine-enhanced MDCT showed adequate visualization of the coronary arteries in 310 of the 312 coronary artery segments that were available by X-ray angiography, respectively. The average density of the coronary arteries in both iodine and gadolinium CT scans was 253.65 Hounsfield unit (HU) and 135.20 HU, respectively. In a per-coronary segment analysis, gadolinium- and iodine-enhanced MDCT showed sensitivities of 89% vs 84%, specificities of 96% vs 95%, and negative predictive values of 97% vs 96%, respectively. In a per-patient analysis, both gadolinium- and iodine-enhanced MDCT showed sensitivities of 92.85% vs specificities of 83.33%. Intermethod agreement between gadolinium- and iodine-enhanced MDCT (kappa) was 0.95 (P < 0.0001). Our preliminary results indicate lower attenuation with gadolinium but similar diagnostic accuracy for the detection of obstructive CAD when compared with iodine-enhanced MDCT. Therefore, gadolinium is a feasible alternative contrast agent for patients with iodine contrast allergy referred for MDCT coronary angiography.

Imaging of liver metastases: MRI

Metastases are the most common malignant liver lesions and the most common indication for hepatic imaging. Specific characterization of liver metastases in patients with primary non-hepatic tumors is crucial to avoid unnecessary diagnostic work-up for incidental benign liver lesions. Magnetic resonance (MR) is rapidly emerging as the imaging modality of choice for detection and characterization of liver lesions due to the high specificity resulting from optimal lesion-to-liver contrast and no radiation exposure. Improvements in breath-hold T1-weighted fast spoiled gradient echo and rapid T2-weighted single shot echo-train acquisition enable imaging of the liver in a single breath-hold with high spatial resolution. Most metastases are hypo- to isointense on T1 and iso- to hyperintense on T2-weighted images. MR contrast agents provide critical tumor characterization and can be safely used in patients with iodine contrast allergy and renal failure. Other agents, including newly developing gadolinium-chelates or iron oxide agents may provide additional benefits in selected applications. The degree and nature of tumor vascularity form the basis for liver lesion characterization based on enhancement properties. Liver metastases may be hypovascular or hypervascular. Colon, lung, breast and gastric carcinomas are the most common tumors causing hypovascular liver metastases, and typically show perilesional enhancement. Neuroendocrine tumors including carcinoid and islet cell tumors, renal cell carcinoma, breast, melanoma, and thyroid carcinoma are tumors most commonly causing hypervascular hepatic metastases, which may develop early enhancement with variable degrees of washout and peripheral rim enhancement.

Use of gadolinium chelate to confirm epidural needle placement in patients with an iodinated contrast reaction

When performing epidural steroid injections for the management of chronic back pain, imaging guidance and a limited epidurogram improve accuracy of needle placement and ensure appropriate delivery of the injectate into the epidural space. We describe our experience using a gadolinium chelate as an alternative contrast agent for limited epidurography in patients with a history of an iodinated contrast reaction. Thirty-eight of 2,067 (1.8%) epidural steroid injections performed in our department over a 25-month period (December 2003-January 2006) employed gadolinium. All injections were performed in the lumbar spine employing a paramedian interlaminar approach. Procedural notes and patient charts were reviewed to evaluate for immediate or delayed complications related to incorrect intrathecal or intravascular needle placement. A retrospective analysis of selected fluoroscopic spot images was performed to evaluate confidence of epidural needle placement; this analysis compared these spot images against those obtained from age- and gender-matched control patients in whom iodinated contrast was used to confirm needle placement. Real-time fluoroscopic guidance permitted confident visualization of an epidurogram at the time of procedure in all 38 cases as documented in the procedural report, and no procedure resulted in a complication due to incorrect needle placement. Retrospective review of fluoroscopic spot images revealed at least moderate confidence of epidural needle placement by both readers in 29/38 cases (76.3%). Fluoroscopic spot images obtained using gadolinium yielded significantly less confidence than images obtained in control patients whose procedures were performed using iodinated contrast (P < 0.01). However, operators were sufficiently confident in needle placement based on real-time fluoroscopic images (not available in our subsequent review) to inject anesthestic in all 38 cases, despite the immediate consequences that could result from intrathecal administration. During the same time period, there were 11/2,067 (0.5%) instances of intrathecal needle placement discovered during attempted epidurography despite the use of fluoroscopy for needle guidance and reliance on loss-of-resistance technique. Gadolinium chelate represents a safe and useful alternative contrast agent for confirmation of epidural needle placement in patients with an iodinated contrast allergy.

Imaging of urinary tract infection in the adult.

The diagnosis of urinary tract infection (UTI) in the adult is primarily based on typical patient symptomatology and urinary evaluation for the presence of bacteria and white blood cells. Uncomplicated UTI usually does not require radiological evaluation unless it is recurrent. Imaging should, in general, be reserved for those patients in whom conventional treatment has failed or those who have recurrent or unusually severe symptoms. Patients with conditions predisposing to infection, or complications thereof, such as diabetes mellitus or immunocompromised states, may also benefit from early imaging. If pyonephrosis is suspected, early imaging and possible urgent drainage is also warranted. Intravenous urogram and ultrasound have traditionally been used in the assessment of these patients, allowing detection of calculi, obstruction and incomplete bladder emptying. These imaging techniques, while useful, have limitations in the evaluation of renal inflammation and infection in the adult. Computerised tomography has now become accepted as a more sensitive modality for diagnosis and follow-up of complicated renal tract infection. Contrast-enhanced CT allows different phases of excretion to be studied and can define extent of disease and identify significant complications or obstruction. Nuclear medicine has a limited role in the evaluation of urinary tract infection in adults. Its main role is in the assessment of renal function, often prior to surgery. Magnetic resonance imaging has a limited but increasing role. It is particularly useful in those with iodinated contrast allergies, offering an ionising radiation free alternative in the diagnosis of both medical and surgical diseases of the kidney.