Characterization of radial forces in Z stents.

RATIONAL AND OBJECTIVES: The purpose of this study was to evaluate the effects of variation in design parameters on the resultant radial force. We evaluated the influence of wire gauge, leg length, and number of bends on the radial force produced by z stents and compared these with radial forces produced by commercial stents. A second goal was to develop an engineering model for predicting radial forces generated by z stents. METHODS: Z stents were fashioned by hand using stainless steel wire and solder that connected the ends. The radial force was measured as a function of wire gauge, vessel diameter, leg length, and number of bends and compared with the theoretical values of radial force calculated by combining Castigliano's theorem and the law of Laplace. RESULTS: Theoretically predicted radial forces were within 8% of each observed value of radial force up to 70% spring compression. CONCLUSIONS: These results suggest that the z-stent model can be used to build custom stents with preselected values of radial force for clinical use. In addition, they can be used to design model investigational stents made of similar materials and surface areas to test the effects of radial force on biological response.

Radiologic placement of a low profile implantable venous access port in a pediatric population.

PURPOSE: To evaluate the feasibility and complications of placement of a low-profile venous access port in the chest in children requiring long-term venous access. METHOD: A low-profile peripheral arm port (PAS port; Sims Deltec, St. Paul, MN, USA) was implanted in the chest in 22 children over a 4-year period. The mean age of the study group was 6 years (range: 9 months to 20 years). Ports were placed for the administration of chemotherapy, hyperalimentation and frequent blood sampling. Sonographic guidance was used to access the internal jugular or subclavian vein in each case. A review of all inpatient and outpatient charts was undertaken to assess catheter performance and complications. RESULTS: Access to the central venous circulation was successfully achieved in each case without complication. Ports remained implanted for 6579 catheter-days (mean: 299 days). Ten ports have been removed. Of three patients (13%) experiencing device-related infections (0.45 infections/1000 catheter days), two (9.1%) were unresponsive to antibiotics and removed (0.3 infections/1000 catheter days). One port was removed because of pain in the shoulder adjacent to the port implantation site. One port was removed because of difficult access. The final port was removed in order to place a dual-lumen catheter prior to bone marrow transplant. Twelve ports remain implanted. Aspiration occlusion occurred in four patients (18%). Deep venous thrombosis did not occur in any patient. CONCLUSION: Low-profile chest ports placed by interventional radiologists in the interventional radiology suite can be placed in children as safely as traditional chest ports placed in the operating room. The incidence of infection, venous thrombosis and aspiration occlusion is comparable to that of ports placed operatively.

Peripheral venous access ports: outcomes analysis in 109 patients.

PURPOSE: To perform a retrospective outcomes analysis of central venous catheters with peripheral venous access ports, with comparison to published data. METHODS: One hundred and twelve central venous catheters with peripherally placed access ports were placed under sonographic guidance in 109 patients over a 4-year period. Ports were placed for the administration of chemotherapy, hyperalimentation, long-term antibiotic therapy, gamma-globulin therapy, and frequent blood sampling. A vein in the upper arm was accessed in each case and the catheter was passed to the superior vena cava or right atrium. Povidone iodine skin preparation was used in the first 65 port insertions. A combination of Iodophor solution and povidone iodine solution was used in the last 47 port insertions. Forty patients received low-dose (1 mg) warfarin sodium beginning the day after port insertion. Three patients received higher doses of warfarin sodium for preexistent venous thrombosis. Catheter performance and complications were assessed and compared with published data. RESULTS: Access into the basilic or brachial veins was obtained in all cases. Ports remained functional for a total of 28,936 patient days. The port functioned in 50% of patients until completion of therapy, or the patient's expiration. Ports were removed prior to completion of therapy in 18% of patients. Eleven patients (9.9% of ports placed) suffered an infectious complication (0.38 per thousand catheter-days)-in nine, at the port implantation site, in two along the catheter. In all 11 instances the port was removed. Port pocket infection in the early postoperative period occurred in three patients (4.7%) receiving a Betadine prep vs two patients (4.2%) receiving a standard O.R. prep. This difference was not statistically significant (p = 0.9). Venous thrombosis occurred in three patients (6.8%) receiving warfarin sodium and in two patients (3%) not receiving warfarin sodium. This difference was not statistically significant (p = 0.6). Aspiration occlusion occurred in 13 patients (11.7%). Intracatheter urokinase was infused in eight of these patients and successfully restored catheter function in all but two instances. These complication rates are comparable to or better than those reported with chest ports. CONCLUSION: Peripheral ports for long-term central venous access placed by interventional radiologists in the interventional radiology suite are as safe and as effective as chest ports.

Translumbar placement of paired hemodialysis catheters (Tesio catheters) and follow-up in 10 patients.

For lack of other suitable access, 10 consecutive patients received paired hemodialysis catheters for long-term hemodialysis using a translumbar approach to the inferior vena cava (IVC). All attempts were successful. Five paired catheters were placed using the single-puncture technique, and five using the dual-puncture technique. Catheters were in place for a total of 2252 catheter days. The average duration of catheter placement was 250 days (range 30-580 days). All catheters were functioning up to the time the study was completed or the patient died. The most common complication was partial dislodgment of the catheter in 3 of 23 catheters (13%), all occurring in obese patients. One episode of retroperitoneal hemorrhage was noted in a patient having the single-access technique. There were no episodes of infection or IVC thrombosis.

Endovascular stent graft for management of ureteroarterial fistula after orthotopic bladder substitution.

We describe the first case of an ureteroarterial fistula developing after orthotopic neobladder substitution and its minimally invasive management using endovascular stent grafting. We outline the risk factors for the development of ureteroarterial fistulae and trace the evolution of diagnostic and therapeutic modalities used in the management of these life-threatening complications. Minimally invasive management with endovascular stent grafting and exclusion of two pseudoaneurysms in the iliac artery system was performed successfully. After successful endovascular exclusion of two pseudoaneurysms, the patient's hematuria resolved and he recovered fully. Three-dimensional computed tomography performed 3 months later documented a patent aortoiliac arterial system without evidence of pseudoaneurysm or endovascular leak. Ureteroarterial fistula after orthotopic bladder substitution was managed with an endovascular stent graft without the need for extra-anatomical vascular bypass. Early recognition, stabilization, and angiographic evaluation followed by this minimally invasive technique may avoid open operative repair and attendant morbidity.

Access to occluded infrainguinal bypass grafts with a loopsnare.

Thrombolysis for the treatment of occluded bypass grafts is used in selected clinical circumstances. Unfortunately, a minority of these procedures are technical failures because of the inability to access the occluded graft. We describe a technique that greatly increases the chances of technical success.

The role of interventional radiology in the management of intra- and extra-peritoneal leakage in patients who have undergone continent urinary diversion.

PURPOSE: To assess how radiologic intervention altered the hospital course of patients undergoing continent urinary diversion. METHODS: Thirty-seven consecutive patients with bladder cancer invading the muscular layer were treated with total cystectomy and construction of a continent urinary reservoir. Eleven of 37 patients suffered early and late anastomotic leakage; six had prolonged extraperitoneal leakage at the urethroenteric anastomosis, three had prolonged intraperitoneal pouch leaks, and two had delayed ureteroenteric leaks. Seven of these patients required radiologic intervention. RESULTS: Intervention in the form of drainage catheter manipulation (n = 4), percutaneous nephrostomy (n = 4), or ureteral stent placement (n = 2) resulted in cessation of leakage without surgical intervention in all seven patients. Intraperitoneal pouch leaks were more difficult to control than extraperitoneal leakage and required longer drainage intervals. CONCLUSION: Interventional radiologic procedures played a key role in the management of continent urinary diversion complications, obviating the need for repeat surgical intervention in all instances.

Ultrasound characteristics of subdermally implanted Implanon contraceptive rods.

This study was designed to define sonographic characteristics and the optimal sonographic technique for localization of the single rod Implanon system. Diagnostic ultrasonography was performed in eight women who had the Implanon rod implanted in the medial aspect of the upper arm. All implants were scanned in the longitudinal and transverse direction using 3.5 MHz, 5 MHz, and 7.5 MHz linear array transducers. Scanning was performed both directly against the skin and with 2 and 4 cm Kiteco ultrasound stand-off pads. Each image obtained was evaluated for detectability of the Implanon rod and the grade of acoustic shadowing produced by the Implanon rod by two independent observers. Discrepancies in evaluation were adjudicated by a third observer. The Implanon rod implant was not directly identified using the transducer and standoff pad combinations. Implanon rods were indirectly identified as a result of the posterior acoustic shadow cast by the Implanon. Best demonstration was achieved with the 5 or 7.5 MHz transducer and a 2 cm stand-off pad in the transverse direction. Appropriate ultrasonographic technique and familiarity with posterior acoustic shadowing patterns generated by the implant provide a noninvasive method for localization of nonpalpable, single rod implants prior to removal.

PIP: Although the single-rod Implanon subdermal implant system is easier to insert and remove than the six-rod Norplant system, localization of one rod can be difficult in cases where external palpation is not possible. The sonographic characteristics and optimal sonographic technique for localization of the single rod Implanon contraceptive system were investigated in a study of eight US women who had a rod implanted in the medial aspect of the upper arm. All implants were scanned in the longitudinal and transverse direction through use of 3.5 MHz, 5 MHz, and 7.5 MHz linear array transducers. Scanning was performed both directly against the skin and with 2 cm and 4 cm Kiteco ultrasound stand-off pads. Each image was evaluated for detectability of the contraceptive rod and the grade of acoustic shadowing. In no instance was the Implanon rod identified through the transducer and stand-off pad combination. Rods were indirectly identified by their posterior acoustic shadow. The best demonstration of the rod was achieved with the 5 or 7 MHz transducer and a 2 cm stand-off pad placed between the transducer and the skin surface, with scanning in the transverse direction. These findings suggest that ultrasonography provides a noninvasive method for localization of implants prior to removal. However, since all eight rods in this series were readily palpable and in ideal subdermal location without associated scar tissue, these results cannot be extrapolated to patients with nonpalpable devices, excessive subcutaneous fat, or excessive scar tissue.

Use of a snare wire to perform nephrostomy access in the presence of obstructive staghorn calculi.

We describe a technique for gaining access to the central collecting system via a chosen calyx, utilizing an alternative entry point to that calyx. An Amplatz nitinol loop snare is then used to convert this access to a traditional approach.

Radiology/pathology conference at Robert Wood Johnson Medical School.

A healthy female was noted to have an enlarging mass in the suprasternal fossa. The clinical diagnosis of post-traumatic arteriovenous fistula led to diagnostic arteriography and radiologic evaluation.

Radiology-pathology conference: Robert Wood Johnson Medical School. Eosinophilic granuloma of the lung.

Eosinophilic granuloma of the lung is a nodular infiltration of the interstitium of the lung by histiocytes, plasma cells, lymphocytes, and eosinophils. While radiologic findings of nodules and small cystic spaces of the upper lung zones are present, surgical biopsy is required for diagnosis.

Radiology-pathology conference at Robert Wood Johnson Medical School. Benign renal angiomyolipoma.

Angiomyolipoma is a benign tumor of the kidney. Conservative management of this tumor requires its differentiation from hypernephroma. This can be accomplished by identification of the fat within the tumor with CT scanning. The authors present a case report.

Radiology/pathology conference at Robert Wood Johnson Medical School. Benign mediastinal teratoma.

The authors review the findings for a 15-month-old female after a left thoracotomy was performed. Radiographs demonstrated a large mass involving the majority of the left hemithorax. Pathologic findings yielded a well-encapsulated, red and white, soft tissue mass.

Radiologic diagnosis of cystic fibrosis in adults and children.

RATIONALE AND OBJECTIVES: Most radiologists are familiar with the classic chest radiographic findings of cystic fibrosis (CF) when these occur in children. We hypothesized that given the same findings, a diagnosis of CF would be less likely to be considered in an adult than in a child. METHODS: We compiled 30 pediatric and 28 adult CF chest radiographs and obtained two independent readings on each by different general radiologists among the eight who volunteered to participate as they performed their daily clinical work. The cases were presented to the readers so that they did not know which radiographs were part of the study. The association between the correct diagnosis of CF and whether the patient was an adult or a child was assessed using odds ratios and logistic regression, so that Brasfield score, Schwachman-Kulczycki score, and the patient's sex could also be considered as predictive of correct diagnosis. RESULTS: In 67% of the pediatric cases, at least one of the radiologists considered CF as a possible diagnosis, whereas they considered CF a possibility in only 50% of the adults. Both radiologists suggested the correct diagnosis in 40% of pediatric cases and only 14% of adult cases (p < .05). CONCLUSION: Because the radiographic findings were similar in the two groups of patients according to severity groupings, we believe CF was less commonly considered in the adult patient because of the traditional belief that CF is a childhood disease.

Tunneled central venous access catheter placement in the pediatric population: comparison of radiologic and surgical results.

PURPOSE: To compare the success and infection rates of radiologic placement with those of surgical placement of tunneled central venous access catheters (TCVACs) in infants and small children. MATERIALS AND METHODS: In 17 pediatric patients, TCVACs were placed with vascular access under ultrasound or fluoroscopic guidance in the radiology department. In 29 other patients, TCVACs were placed with percutaneous puncture or surgical cutdown in the surgery department. RESULTS: Two (11%) of 18 attempts at radiologic placement were unsuccessful; six (38%) of the 16 radiologically placed catheters necessitated removal because of dislodgment, malfunction, or infection; six (38%) were electively removed; and four (25%) still function. Eight (23%) of 35 attempts at surgical placement were unsuccessful; 17 (63%) of the 27 surgically placed catheters required removal because of dislodgment, malfunction, or infection; nine (33%) were electively removed; and one (4%) still functions. CONCLUSION: The success and infection rates of radiologic placement of TCVACs were similar to those of surgical placement. Radiologic placement required fewer attempts and was slightly less expensive.