Long-term performance and complications of the Tesio twin catheter system for hemodialysis access.

The Tesio twin catheter system (Medcomp, Harleysville, PA) was developed to overcome the problems with the existing central venous catheters in providing high-efficiency dialysis, such as inadequate blood flows, high recirculation rates, and need for surgical insertion. The relatively large internal lumens and multiple side holes in a spiral pattern allow for high blood flow rates and lower tendency to thrombosis. In this series, 82 catheter pairs were placed in 75 patients and monitored for a period encompassing 231 patient-months. We achieved mean nominal blood pump flow rates of 400 +/- 6 mL/min and an average recirculation of 4.6% +/- 0.5%. In 20 sets of catheters, a nominal blood flow rate of 388 +/- 6 mL/min was measured ultrasonically at 352 +/- 8 mL/min, representing an error of 36 +/- 5 mL/min. Thrombosis of the catheter occurred at a rate of one episode per 21 patient-months, and on all occasions responded to local instillation of urokinase. Despite having two exit sites, the infection rates were comparable to other catheters: exit site infections occurred at a rate of one per 21 patient-months and bacteremic episodes occurred at one per 11.5 patient-months, necessitating catheter removal once per 46 patient-months. Based on these data, we believe that the Tesio twin catheter system is an excellent long- and short-term vascular access for providing high-efficiency dialysis.

Comparison of ultrasound, CT, and MR imaging in the evaluation of candidates for TIPS.

To compare ultrasound (US), CT, and MRI in the evaluation of hepatic vascular anatomy, portal and splenic venous flow, and collateral pathways (varices and spontaneous shunts) in candidates for transjugular intrahepatic portosystemic shunting (TIPS), 17 patients with history of refractory variceal bleeding or intractable ascites underwent duplex US, contrast-enhanced CT, and MRI before TIPS. The appearance of portal and hepatic anatomy was graded from 1 (not visible) to 4 (excellent visualization) independently by four radiologists. Presence and direction of portal and splenic venous flow, and presence and location of varices and spontaneous portosystemic shunts were also assessed. Results and effects of interobserver variation were assessed for significance using Friedman's ANOVA and Wilcoxon's signed-rank test. MRI yielded higher scores than CT or US for hepatic veins (P < .0001) and inferior vena cava (P < .0001). MRI and CT scored better than US for portal vein branches (P = .012) and splenic vein (P = .0038). All tests demonstrated the main portal vein well, with no statistically significant difference. US and MRI were more sensitive than CT for detecting portal vein flow and direction (US 76%, CT 0%, MRI 82%). MRI was most sensitive for splenic vein flow and direction (US 41%, CT 0%, MRI 76%). CT and MRI were more sensitive than US in detecting varices (US 5%, CT 50%, MRI 58%) and spontaneous shunts (US 13%, CT 75%, MRI 75%). Interobserver variation did not influence results significantly P = .3691). MRI provides the most useful information and may be the preferred single imaging test prior to TIPS.

Carbon dioxide digital subtraction angiography: expanding applications and technical evolution.

Although several noninvasive techniques now exist for vascular imaging, including MR imaging, three-dimensional CT, and color-flow and duplex sonography, the gold standard to which these techniques are compared remains catheter angiography. Cut-film and digital subtraction angiography (DSA) using iodinated contrast material are the standard methods by which vascular imaging is performed. However, despite the development of low-osmolar contrast agents, premedication regimens, and careful patient selection, adverse reactions to contrast material, including idiosyncratic reactions and contrast-induced nephropathy, continue to occur in a small number of patients [1-3]. Carbon dioxide (CO2) was developed as an alternative to iodinated contrast material to avoid these problems [4]. Once the behavior of intravascular gas, the methods of safe delivery, and the principles of successful imaging are understood, the use of CO2 as an intravascular contrast agent during DSA allows accurate imaging with little risk. Recent advances in delivery systems, postprocessing capabilities, and its extension to new vascular interventional procedures have greatly expanded the usefulness of CO2 angiography in both diagnostic and interventional vascular radiology.

Current status of carbon dioxide angiography.

The current status of carbon dioxide as an angiographic contrast agent is reviewed in this article. The physical characteristics of intravascular carbon dioxide, pertinent physiology, and principles of imaging are discussed. In addition, the advantages and limitations of carbon dioxide are compared with those of iodinated contrast. Examples of diagnostic and therapeutic procedures in both the arterial and venous systems show the utility of carbon dioxide angiography.

CO2 digital angiography: a safer contrast agent for renal vascular imaging?

Although the new nonionic contrast agents are safer than ionic agents, renal insufficiency and even death still occur occasionally. Therefore, we have explored the use of carbon dioxide (CO2) as an alternative angiographic contrast agent used in combination with digital subtraction angiography. Clinical observations have been made in over 800 patients. The images obtained are of equivalent diagnostic quality compared with those using conventional iodinated contrast agents. Recent advances in imaging, including "stacking," provide images comparable with iodinated contrast. Very small vessels, equivalent to third-order branches of the renal artery, can be imaged satisfactorily with CO2. Occasional studies with CO2 yield information not apparent with iodinated contrast agents, including excellent visualization of arteriovenous shunts, collateral circulations, malignant tumors, and minute amounts of arterial bleeding. Many of the advantages and disadvantages of CO2 derive from its special physical and chemical properties. The advantages include no allergic potentiation and no renal metabolism of CO2, because CO2 is cleared by the lungs and does not recirculate. Other advantages include delivery by very small catheters because of the low viscosity of CO2, minimal discomfort on injection, and very low cost. However, the low-density and compressibility of CO2 poses some special problems. Imaging requires digital subtraction angiography with electronic enhancement and injections require an experienced investigator and, ideally, a dedicated CO2 injector. The dedicated CO2 injector provides calculated, controlled dosing and rates for injection, while excluding the possibility of air contamination. The buoyancy of CO2 inhibits good filling of dependent vessels. Accordingly, CO2 does not normally produce good nephrographic images, although proximal renal arteries are normally shown clearly. Experimental studies in dogs, whose renal arteries have been injected repeatedly with very large doses of CO2, demonstrate only transient changes in renal blood flow and no endothelial cell damage. However, these studies also showed clearly that renal ischemia can occur due to a "vapor lock" phenomenon if the kidney is positioned vertically above the injection site, and recurrent injections are given without time for absorption of the arterially delivered CO2 boluses. Uncontrolled studies in over 800 patients have confirmed that CO2 likely has a very low renal toxicity. At the University of Florida, CO2 is the radiologic contrast agent of choice in patients with renal insufficiency, especially those with diabetes mellitus, and in those with pre-existing allergy to iodinated contrast agents. Further controlled clinical studies are required to define the true clinical utility and safety of CO2 compared with conventional radiologic contrast agents.

Permanent indwelling peritoneal access device for the management of malignant ascites.

The case presented demonstrates an alternative management approach for malignant ascites. A permanent indwelling peritoneal port for at-home, small-volume paracentesis, provided palliative therapy for a patient who had malignant ascites secondary to breast cancer. The device allowed paracentesis without the risk of repetitive peritoneal puncture or diuretic therapy.

Mediastinal mass and tracheal compression due to an aneurysm of a systemic-to-pulmonary collateral artery in a patient with pseudotruncus arteriosus.

A patient with pseudotruncus arteriosus who presented with a large mediastinal mass due to a systemic-to-pulmonary collateral artery aneurysm is reported. This aneurysm caused tracheal compression with resulting dyspnea and postobstructive pneumonitis, which are unusual presenting features in these patients. The differential diagnosis for a mediastinal mass arising in a patient with pseudotruncus arteriosus, or any other patient with possible systemic-to-pulmonary collateral arteries, should include aneurysm.

Prediction of surgical resectability in patients with hepatic colorectal metastases.

OBJECTIVE: To evaluate the efficacy of two distinct imaging techniques to predict, before operation, unresectability compared with standard computed tomographic scan (CT). SUMMARY BACKGROUND: Accurate preoperative identification of the number, size, and location of hepatic lesions is crucial in planning hepatic resection for colorectal hepatic metastases. Although infusion-enhanced CT is the standard, its limitations are the imaging of relatively isodense and/or small (< 1 cm) lesions. The increased sensitivity of CT arterial portography (CTAP) may be offset by false-positive results caused by benign lesions and flow artifacts. METHODS: Fifty-eight selected patients considered to be eligible for resection by standard CT had laparotomy. Before operation and in addition to CT, all patients had CT arterial portography and hepatic artery perfusion scintigraphy (HAPS) using radiolabeled macroaggregated albumin. Early studies showed an increased sensitivity for detecting small lesions using the invasive CTAP. Similarly, the HAPS study has detected malignant lesions not observed by standard CT. RESULTS: Of 58 patients having laparotomy, 40 were resectable by either lobectomy (22) or trisegmentectomy (1) and the rest by single or multiple wedge resections. Eighteen patients could not be resected because of combined intra- and extrahepatic disease or the number and location of metastases. Standard CT detected 64% of all lesions (12% of lesions less than 1 cm). Unresectability was accurately predicted by CTAP and HAPS in 16 (88%) and 15 (83%), respectively, of the 18 patients considered ineligible for resection at laparotomy. Of the 40 patients who had resection for possible cure, CTAP and HAPS falsely predicted unresectability in 6 of 40 patients (15%) and in 10 of 40 patients (25%), respectively. The positive predictive value for unresectability of CTAP and HAPS was 73% and 60%, respectively. False-positive lesions after CTAP included hemangiomas, cysts, granulomas, and flow artifacts. False-positive HAPS lesions included patients in whom no tumor was found at surgery but with some identified by intraoperative ultrasound, blind biopsy, and blind resection. CONCLUSIONS: False-positive results by HAPS and CTAP may limit the ability of these tests to accurately predict unresectability before operation and may deny patients the chance for surgical resection. The HAPS study does, however, detect small lesions not seen by CT or CTAP. Standard CT, although less sensitive, followed by surgery and intraoperative ultrasound, does not necessarily preclude patients who could be resected.

Septic sacroiliitis due to Proteus mirabilis.

This case demonstrates the difficulty frequently encountered in making an early diagnosis of septic sacroiliitis. The proper use of appropriate laboratory tests and radiologic examinations can narrow the differential diagnosis significantly, with confirmation resting on culture results. Appropriate antibiotic therapy will depend on the organism isolated. When confronted by the typical clinical findings and supporting ancillary data of septic sacroiliitis, the physician should consider the possibility of an unusual organism such as Proteus mirabilis and should direct antibiotic therapy accordingly.