Maintenance of adequate hemodialysis access. Prevention of neointimal hyperplasia.

The maintenance of adequate hemodialysis vascular access is frequently complicated in the patient with polytetrafluoroethylene (PTFE) A-V hemodialysis grafts by venous anastomotic stenosis. This stenosis is caused by neointimal hyperplasia (NIH), a response to vascular injury. In this study, the authors prospectively analyzed the effect of a short-term regimen consisting of administration of two medications, heparin and low molecular weight dextran, on the development of NIH at the venous anastomosis in 79 patients with PTFE A-V hemodialysis grafts. In addition, they evaluated other parameters' effects on the development of NIH. In comparison with control subjects, heparin had some effect in minimizing the development of NIH in the PTFE grafts when evaluated radiologically at 3 months, although this effect was not statistically significant. Low molecular weight dextran, however, had no trend or statistically significant effect on this venous anastomotic narrowing. Interestingly, patient age, use of calcium channel blockers, and presence of diabetes mellitus (DM) all appeared to affect the development of NIH. Increasing age and use of calcium channel blockers was associated with decreased development of NIH; conversely, DM was associated with worsened NIH. In evaluation of access survival (time to first access failure), degree of venous anastomosis stenosis at 3 months was not predictive. Patient time on dialysis pre graft placement was the only measured parameter related to access failure. The method of dialysis pre graft placement (hemodialysis versus peritoneal dialysis) was not a significant factor in early access failure. Pharmacologic treatment of venous anastomotic narrowing in PTFE hemodialysis grafts due to NIH continues to be difficult. Short-term treatment with the tested medication failed to statistically affect NIH. Patient age, use of calcium channel blockers, and presence of DM were all factors in the development of NIH. Of measured parameters, time on dialysis pre graft placement was the only factor correlated with early access failure. In future treatment regimens, one should consider more prolonged treatment. In addition, noted risk factors should be considered when determining type of renal replacement therapy.

Split 24-F Amplatz dilator for percutaneous extraction of an intravascular bullet: case report and technical note.

An intravascular bullet was retrieved percutaneously in a 17-year-old boy with the use of a modified 24-F Amplatz dilator. The dilator was modified by means of a longitudinal incision with removal of a wedge at the distal tip of the tapered portion of the dilator. The bullet, which was located in the left pulmonary artery, was removed via the right femoral vein. No complications occurred.

Transrenal ureteral occlusion with Gianturco coils and gelatin sponge.

The authors report the use of Gianturco coils and gelatin sponge plugs to achieve complete occlusion of nine ureters in five patients with advanced pelvic malignancies and lower urinary tract fistulas. The method is simple to apply, is readily available, and to date has been associated with no significant complications. These results suggest that, before more elaborate methods of ureteral occlusion are applied, the use of coils and gelatin sponge should be considered as the primary method of ureteral occlusion. Further work is needed to elaborate the exact mechanism by which these materials cause occlusion.

Azotemia caused by renal artery stenosis: treatment by percutaneous angioplasty.

Percutaneous angioplasty of the renal artery was performed in 79 patients who had stable or climbing serum creatinine levels greater than 1.7 mg/dl and hemodynamically significant stenosis of the renal artery. Patients who had nonrenal causes of azotemia, nephropathy caused by iodinated contrast material, or serum creatinine levels that were declining while the patients were receiving medical therapy before angioplasty were excluded from the study. Angioplasty resulted in a significant (greater than 20%) decline in the level of serum creatinine (average, 2.7 mg/dl before to 1.7 mg/dl after) in 43% of these patients during an average follow-up period of 16 months. A significant decrease in the level of serum creatinine was seen in 61% of patients with bilateral stenosis, 38% of patients with unilateral stenosis with absent contralateral renal blood flow, and 38% of patients with unilateral stenosis and normal contralateral renal blood flow. Recapture of lost nephron function was least successful in patients whose levels of serum creatinine were greater than 4.0 mg/dl (14%); this included one (11%) of nine patients who were already on hemodialysis. We conclude that angioplasty of the renal artery can play a major role in the treatment of patients who have mild azotemia and bilateral stenosis of the renal artery. It is less successful in treatment of patients who have severe azotemia and those who have unilateral disease.

Retinal vascular permeability determined by dual-tracer fluorescence angiography.

Diabetic retinopathy is the leading cause of blindness in working age individuals in the United States. Breakdown of the blood-retinal barrier is one of the earliest events in the progression of diabetic retinopathy. Ideally, therapeutic measures would be directed at this early stage, but there are few sensitive, quantitative methods to assess the retinal vascular barrier in vivo. We present here a method that combines fluorescence microangiography and the simultaneous use of two fluorescent tracers to quantitatively assess the retinal vascular barrier. PS/F (permeability x surface area/flow) describing the retinal vasculature of Long Evans rats was found to be 0.086+/-0.031 (n=13, avg.+/-s.d.). Based on estimates of flow and surface area, we estimate the permeability of sodium fluorescein to be approximately 1.2 x 10(-5) cm/s. Infusion of a hyperosmolar solution of 1.6 M mannitol for 5 min significantly increased PS/F in individual veins and significantly increased a flow weighted PS/F from 0.073+/-0.028 to 0.16+/-0.034 (n=3). In conclusion, we have adapted indicator dilution techniques to quantitatively assess the retinal vasculature in vivo. We have found dual-tracer fluorescence angiography to be a sensitive indicator of increases in the blood-retinal barrier produced by hyperosmolar mannitol. This methodology is a promising new minimally invasive strategy which may be adapted to quantitatively track retinal vascular permeability.

The geometry of triple-balloon dilation.

Triple-balloon dilation (TBD) of a variety of luminal structures has been successfully, though infrequently, used. A mathematical model is presented for the selection of balloon sizes, and equations and tables are derived that allow the user to estimate more accurately the size of balloons needed for TBD of structures with large lumina. With TBD, an approximately circular lumen can be formed. Also, TBD allows smaller, higher-pressure balloons to be used instead of single, low-pressure, large balloons. However, multiple puncture sites may be required for TBD.

The correlation between MR and angiography in portal hypertension.

Forty-two MR examinations and hepatic panangiograms in 38 patients with portal hypertension were correlated with MR images to determine the ability of MR to detect portal vein hemodynamics. These studies were prospectively analyzed for degree of portal perfusion and direction of flow, portal vein thrombosis, and presence and type of shunt surgery. Thirty-three MR examinations were determined to have grade I (good) or II (fair) portal blood flow. Twenty-nine of these were grade I or II by angiography; the other four were grade IV. Of the eight cases documented as grade IV (hepatofugal portal blood flow) by angiography, none were considered grade IV by MR, suggesting that MR was unable to detect retrograde flow. The other case was not graded because of cavernous transformation of the portal vein. MR correlated well with angiography for the detection or absence of portal vein thrombus, agreeing with angiography in 41 of 42 cases. Two angiographically proven cases of portal vein thrombosis were correctly identified on MR. MR correctly identified the absence of portal vein clot in 39 of 40 angiographically negative cases. MR and angiography also agreed in 41 of 42 cases that a shunt was either present/absent or patent/occluded. The single error was due to inadequate MR scanning in the region of interest. The results show that MR cannot be used to grade blood flow in the portal vein. However, MR accurately detects portal vein thrombosis and the patency of surgical shunts.

Emergency skull radiography: the effect of restrictive criteria on skull radiography and CT use.

A prospective study was performed to determine the effect of restrictive criteria on the use of emergency skull radiography and computed tomography (CT) of the head. Emergency skull radiography required the completion of a special requisition form. Emergency CT of the head was done at the request of senior consultants and was available on a full-time basis. Over 1 year, 2,758 skull studies were performed, a decrease of 39.1% when compared with the year before restrictive criteria were instituted, during which 4,587 skull examinations were done. In the same period, the number of emergency CT scans of the head increased by 45.7%, from 471 in the control year to 686 in the experimental year. With the use of restrictive criteria, a net savings of +164,000 was achieved. Our results suggest that the use of restrictive criteria is a cost-effective means of limiting skull radiography when CT of the head is readily available.

Comparison of diagnostic accuracy with carbon dioxide versus iodinated contrast material in the imaging of hemodialysis access fistulas.

PURPOSE: Imaging of dialysis fistulas was performed with use of carbon dioxide and iodinated contrast material. Images were then compared to assess the quality and accuracy of CO2 as a contrast agent. PATIENTS AND METHODS: Thirty-two patients underwent digital subtraction imaging of the fistulas performed with both iodinated contrast material and CO2 to evaluate the venous anastomosis. The images were blinded and the degree of stenosis was graded in 10% increments by two physicians. Statistical analysis including sensitivity, specificity, and accuracy of CO2 images was performed. RESULTS: There was no significant difference in physician ratings of the degree of venous stenosis (P > .30). Estimation of the degree of stenosis was significantly higher with CO2 than with ionic contrast material (P = .0001). When iodinated contrast material is used as the gold standard, the sensitivity, specificity, and accuracy of CO2 were 94%, 58%, and 75%, respectively. CONCLUSIONS: CO2 has a role as a contrast agent in the imaging of dialysis access grafts when the use of iodinated contrast material is of concern. CO2 is safe for venous injections; however, it should not be used to evaluate the arterial anastomosis with the "reflux technique."

Percutaneous vascular intervention after surgical shunting for portal hypertension.

Twenty percutaneous transluminal angioplasty (PTA) procedures and 13 percutaneous venous embolization (PVE) procedures were performed in 23 patients who either had or were at risk for the development of recurrent bleeding, hepatic encephalopathy, or both after surgical shunt placement for portal hypertension. PTA, performed in 12 patients with significant shunt stenoses, resulted in reduction or elimination of gradients in all patients; rebleeding has occurred in only one patient. Complications consisted of one fatal rupture of a mesocaval interposition vein graft and one balloon rupture requiring surgical removal. PVE, performed in 11 patients, resulted in measurable improvement in four of seven encephalopathic patients and temporary control in the two patients with intractable bleeding. Three patients underwent PVE prophylactically. PTA of graft strictures is a valuable treatment modality. Embolization may be helpful in selected cases of hepatic encephalopathy.