Critical analysis of supracostal access for percutaneous renal surgery.

PURPOSE: Percutaneous renal surgery is currently performed for complex renal calculi as well as for various other endourological indications. In many patients an upper pole nephrostomy tract allows direct access to most of the intrarenal collecting system. Upper pole percutaneous access may be obtained via the supracostal or subcostal approach. The preferred route depends on the location and size of the specific stone or lesion. Previously others have cautioned against the supracostal approach above the 12th rib and many have discouraged an approach above the 11th rib due to concern about the increased risk of intrathoracic complications. We retrospectively assessed the morbidity associated with supracostal percutaneous renal surgery and compared and analyzed the morbidity of the supracostal and subcostal approaches. MATERIALS AND METHODS: The records of all patients who underwent upper pole percutaneous renal surgery between November 1993 and July 1999 were retrospectively reviewed. A total of 240 patients underwent percutaneous renal procedures, including 225 for managing symptomatic renal or ureteral stones, that is nonstaghorn calculi in 157, staghorn calculi in 41, proximal ureteral calculi in 12, calculi within a caliceal diverticulum in 6, calculi associated with primary ureteropelvic junction obstruction in 5 and calculi associated with a retained ureteral stent in 4. An additional 15 procedures were done for ureteropelvic junction obstruction (7), intrarenal collecting system tumors (5), a caliceal diverticulum without stones (1), a retained ureteral stent (1) and a ureteral stricture (1). RESULTS: A total of 300 nephrostomy tracts were placed to obtain access to the intrarenal collecting system via the supracostal approach in 98 (32.7%) cases and the subcostal approach in 202 (67.3%). Of the supracostal approaches 72 (73.5%) tracts were above the 12th and 26 (26.5%) were above the 11th rib. The overall complication rate irrespective of percutaneous approach was 8.3% (16.3% for supracostal and 4.5% for subcostal access). Complications included blood transfusion in 7 patients, intraoperative hemothorax/hydrothorax in 5, sepsis/bacteremia in 3, atrial fibrillation in 2, delayed nephropleural fistula in 2, renal artery pseudoaneurysm in 2, deep venous thrombosis/pulmonary embolus in 2, pneumothorax in 1 and subcapsular hematoma in 1. Seven of 8 intrathoracic complications (87.5%) developed in supracostal cases. CONCLUSIONS: Percutaneous renal surgery remains an important option for managing complex renal calculi and other upper urinary tract lesions. In our experience it is generally associated with low morbidity. The supracostal approach is often preferred for obtaining intrarenal access to complex renal and proximal ureteral pathology. Because supracostal access tracts are associated with significantly higher intrathoracic and overall complication rates compared to subcostal access tracts, this approach must be used with caution when no other alternatives are available.

Conversion of indwelling chest port catheters to tunneled central venous catheters.

PURPOSE: To determine the safety and efficacy of the conversion of subcutaneous chest wall infusion ports to tunneled central venous catheters. MATERIALS AND METHODS: During a period of 34 months, 67 patients were referred for conversion of indwelling subcutaneous chest wall ports to tunneled central venous catheters as part of a bone marrow transplant protocol. Six patients were deemed unacceptable for conversion and the remaining 61 underwent successful conversion. All patients had functioning surgically placed single-lumen (n = 50) or double-lumen (n = 11) chest ports, which were removed to maintain the original venous access sites for placement of a tunneled central venous catheter, incorporating the chest wall pocket for tunneling, in 46 patients (75%). A new tunnel was created in the other 15 patients. There were no immediate complications and all patients were followed until catheter removal or patient demise with the catheter in place. RESULTS: 57 of 61 (93%) catheters were used without evidence of infection for 23-164 days (mean, 57 d) after placement. Two (3%) were removed (both at 26 days) because of persistent neutropenic fever without physical signs or laboratory evidence of catheter infection, and two (3%) were removed (at 11 and 77 days) because of proven catheter infection, yielding an overall infection rate of 1.2 per 1,000 catheter days. Two catheters required exchange and two required stripping because of decreased function, resulting in an overall catheter-related complication rate of 2.4 per 1,000 catheter days. CONCLUSIONS: Indwelling subcutaneous chest wall infusion ports can be safely converted to tunneled central venous catheters, even in an immunocompromised patient population, with a low risk of complications such as infection.

Percutaneous cholecystostomy: who responds?

OBJECTIVE: Our purpose was to identify clinical or radiologic features predictive of response to percutaneous cholecystostomy performed for the treatment of acute cholecystitis. MATERIALS AND METHODS: The clinical records and radiologic images of patients who underwent percutaneous cholecystostomy for suspected acute cholecystitis between January 1987 and July 1994 were retrospectively reviewed. A response to percutaneous cholecystostomy was defined as an improvement in clinical symptoms and signs or reduction in fever and WBC to normal within 72 hr of percutaneous cholecystostomy. The number and type of radiologic investigations were reviewed by two radiologists. The presence of gallstones, gallbladder wall thickening, distention, and pericholecystic fluid was recorded. The clinical and radiologic findings were analyzed for their relationship to response to percutaneous cholecystostomy. RESULTS: Sixty-one percutaneous cholecystostomies were performed in 37 male and 24 female patients and were technically successful in 59. Thirty-one patients had gallstones, 28 did not. Thirty-one patients were in the intensive care unit, and 15 were ventilated. Complications occurred in six (10%): misplacement of the percutaneous cholecystostomy catheter in the colon (one), exacerbation of sepsis (three), and bile leakage (two). The mortality rate was 2%--one of the patients with septic shock succumbed to a cardiac arrest 3 days after the procedure. Forty-three patients (73%) responded to percutaneous cholecystostomy. Patients with gallstones and symptoms and signs localized to the right upper quadrant of the abdomen were more likely to respond (p = .006). The only individual radiologic feature predictive of a positive response was the presence of pericholecystic fluid in patients with gallstones (p = .03). The presence of all four radiologic findings was also associated with a positive response (p = .039). The results of bile cultures were not predictive of response. Of the 16 nonresponders, six had documented biliary sepsis and cholecystitis. CONCLUSION: Clinical symptoms and signs referable to the gallbladder, the presence of pericholecystic fluid in patients with gallstones, and the presence of an increasing number of radiologic findings in any one patient are predictive of a positive response to percutaneous cholecystostomy.

Prospective evaluation of pulmonary artery pressures during pulmonary angiography performed with low-osmolar nonionic contrast media.

PURPOSE: To determine the effects of pulmonary angiography performed with low-osmolar, nonionic contrast media on pulmonary artery pressures. PATIENTS AND METHODS: In a prospective, uncontrolled clinical trial, pulmonary artery pressures (systolic, diastolic, mean) of 116 patients referred for pulmonary angiography were recorded before and 1 and 5 minutes after injection of contrast material. RESULTS: There was a statistically significant rise in systolic, diastolic, and mean pulmonary artery pressure at 1 minute (4.6, 3.4, 4.1 mm Hg, respectively) and 5 minutes (3.8, 2.7, 3.4 mm Hg, respectively) after the initial contrast material injection (P < .05). Increases were smaller with additional injections. Systolic pressure changes at 1 and 5 minutes after the first injection were linearly dependent on the volume of contrast material injected (P < .05). There was no statistically significant difference in the increase in pulmonary artery pressure between patients with pulmonary embolus or pulmonary arterial hypertension and those without. CONCLUSION: There is a small but statistically significant rise in pulmonary artery pressure after injection of low-osmolar, nonionic contrast material for pulmonary angiography; it is unlikely to be of clinical significance.

Pulmonary angiography performed with iopamidol: complications in 1,434 patients.

PURPOSE: To evaluate the safety of pulmonary angiography performed with iopamidol compared with pulmonary angiography performed with ionic contrast media. MATERIALS AND METHODS: The data in 1,434 patients who underwent pulmonary angiography with iopamidol 76% were retrospectively reviewed. Complications that occurred within 48 hours were identified with review of hospital charts and/or computer records. RESULTS: Pulmonary arterial hypertension was present in 402 patients and was severe in 99. Pulmonary embolus was diagnosed in 357 patients (24.9%). Major complications occurred in four patients (0.3%). Respiratory insufficiency occurred in two of these patients. Catheterization was not completed in two patients due to catheter-induced cardiac arrhythmia that was refractory to treatment. No procedure-related deaths occurred. During the periprocedural period, eight patients required intubation and 10 patients died; all patients previously were critically ill. CONCLUSION: Pulmonary angiography is a safe procedure, and the margin of safety is enhanced by the use of iopamidol.

Case report: bleeding gastric varices secondary to splenic vein thrombosis successfully treated by splenic artery embolization.

Splenic vein thrombosis is a complication of pancreatic carcinoma or pancreatitis. It may lead to gastric varices which are difficult to treat and splenectomy may be required to stop variceal bleeding. A case of bleeding gastric varices secondary to splenic vein thrombosis and successfully treated by splenic artery embolization is reported. Embolization was performed by transcatheter deposition of four Gianturco coils into the splenic artery. This resulted in reduced blood flow through the spleen with partial splenic infarction and cessation of variceal bleeding. There has been no recurrence of bleeding in the 6 months since the procedure. Literature review confirms that experience of using this treatment is very limited and it should therefore be restricted to patients at high risk from surgery.

Evaluation of revised criteria for ventilation-perfusion scintigraphy in patients with suspected pulmonary embolism.

PURPOSE: To evaluate the accuracy of the revised PIOPED (Prospective Investigation of Pulmonary Embolism Diagnosis) criteria for categorization of ventilation-perfusion lung scans and to compare the diagnostic accuracy of the revised criteria with that of the original PIOPED criteria and subjective probability estimates. MATERIALS AND METHODS: The ventilation-perfusion scans of 104 consecutive patients with suspected pulmonary embolism were reviewed. All patients had also undergone pulmonary angiography. The scans were categorized according to the original and revised PIOPED criteria, and a "gestalt" percent probability estimate was made. In addition, the official clinical interpretation (made with the original PIOPED criteria) was recorded. RESULTS: The gestalt percent probability estimate was the most accurate for assessing the likelihood of pulmonary embolism (area under the receiver operating characteristic [ROC] curve = 0.836). The revised PIOPED criteria (area under the ROC curve = 0.753) were more accurate than the original PIOPED criteria. CONCLUSION: The revised PIOPED criteria are more accurate than the original PIOPED criteria. Experienced readers of lung scans can achieve higher accuracy after applying formal criteria by using their experience and subjective judgment.

Correction of central venous stenoses: use of angioplasty and vascular Wallstents.

Central venous stenoses are a frequent complication in hemodialysis patients. These lesions lead to fistula thromboses, arm swelling, and limit future vascular access. Stenoses are characterized by excellent initial response to transluminal angioplasty but rapid recurrence. Response to angioplasty allows classification of stenoses as elastic or nonelastic. The success of angioplasty alone in 30 patients with central venous stenoses was compared to angioplasty and Wallstent placement in 11 patients with recurrent stenoses. In those who had angioplasty alone, 7%+ failed angioplasty, 70% had > or = 50% improvement in the luminal diameter while 23% showed no improvement due to elastic lesions. Subsequently, 81% of those with a successful result restenosed at an average of 7.6 months while 100% of elastic lesions occluded in an average of 2.9 months. In the 10 patients who underwent angioplasty and Wallstent placement, 5 were due to elastic lesions with four recurrences at a mean of 8.6 months. Four of five patients (80%) stented with nonelastic lesions had reappearance of symptoms at a mean of 4.2 months. We conclude that vascular stents should be reserved for those lesions that show elastic recoil after standard angioplasty.

Pulmonary angiography with MR imaging: preliminary clinical experience.

PURPOSE: To study the accuracy of magnetic resonance (MR) pulmonary angiography in 20 patients in whom pulmonary embolism (PE) was clinically suspected. MATERIALS AND METHODS: Fourteen patients (group 1) were recruited for the MR pulmonary angiography study before they underwent conventional pulmonary angiography (CPA) based on clinical findings. Six patients (group 2) did not undergo CPA but were considered to have PE on the basis of findings in other studies. MR venography was performed at the time of MR pulmonary angiography in 13 patients. RESULTS: MR pulmonary angiography had a sensitivity of 92%-100% and specificity of 62% for detection of PE. Performance of MR pulmonary arteriography and MR venography in a single examination to demonstrate thrombus in both the arterial and deep venous systems was proved feasible. CONCLUSION: This report describes an early clinical implementation of new MR pulmonary angiographic techniques. Further advances to improve specificity by enhancing sensitivity to slow flow and increasing spatial resolution are necessary before routine clinical use of MR pulmonary angiography is justified.

1992 ARRS Executive Council Award. Detection of deep venous thrombosis: prospective comparison of MR imaging with contrast venography.

OBJECTIVE: Preliminary reports have described the use of MR imaging for the detection of deep venous thrombosis. However, no prospective study comparing MR imaging with contrast venography (the gold standard) has been reported. Accordingly, we performed a prospective, blinded study of the efficacy of MR imaging in 61 consecutive patients with clinically suspected deep venous thrombosis. In cases of disagreement, additional testing was performed to determine the diagnosis. SUBJECTS AND METHODS: From June 1991 to February 1992, 61 patients with clinically suspected deep venous thrombosis were examined with venography and MR imaging. The average time between studies was 3 hr. In 21 of the 61 patients, the final diagnosis was deep venous thrombosis. RESULTS: For detection of deep venous thrombosis in the pelvis, the sensitivity of MR imaging was 100% (9/9) with a 95% confidence interval of 72-100% and the specificity was 95% (52/55) with a 95% confidence interval of 85-99%. In the thigh, the sensitivity (16/16) and specificity (43/43) were both 100% with 95% confidence intervals of 83-100% and 93-100%, respectively. In the calf, the sensitivity was 87% (13/15) with a 95% confidence interval of 60-98% and the specificity was 97% (36/37) with a 95% confidence interval of 86-100%. CONCLUSION: We found no statistically significant difference between MR imaging and contrast venography in the detection of deep venous thrombosis. This result suggests that MR imaging is at least as sensitive and specific as contrast venography in the detection of deep venous thrombosis.

Utilization by human amniocytes for prostaglandin synthesis of [1-14C]arachidonate derived from 2-[1-14C]arachidonylphosphatidylcholine associated with human fetal pulmonary surfactant.

The phospholipids of human fetal pulmonary surfactant prepared from term amniotic fluid contained arachidonic acid and its utilization for prostaglandin synthesis by amnion cells has been investigated. Cells were incubated with surfactant labelled with L-alpha-1-palmitoyl-2-[1-14C]arachidonylphosphatidylcholine. The uptake of radioactivity into amniocyte phospholipids increased with time and with the concentration of surfactant and after 2 h of incubation at 37 degrees C, 63% of the incorporated radioactivity was recovered in phosphatidylethanolamine (PE) and phosphatidylinositol (PI). Similar results were obtained when amniocytes were incubated with liposomes prepared from lipid extracts of surfactant, but when cells were incubated with liposomes prepared from synthetic lipids the transfer of radioactivity to PE and PI was only 27%. Fetal surfactant contained platelet activating factor (PAF) but the addition of the antagonist hexanolamino-PAF did not affect either the uptake or intracellular redistribution of surfactant arachidonate by amniocytes, nor did the addition of PAF affect the results obtained with liposomes prepared with synthetic lipids. Cells preincubated with surfactant labelled with 2-[1-14]arachidonylPC released radioactive arachidonate and prostaglandin E2 when stimulated with calcium ionophore A23187 or with phorbol ester. These data demonstrate that surfactant provides a source of arachidonate that can be utilized by amnion cells for prostaglandin synthesis.

Retroperitoneal arteriovenous malformation, a rare cause of heart failure in infancy: consideration of therapeutic approaches.

We report an infant presenting with congestive heart failure secondary to a large retroperitoneal arteriovenous (AV) malformation. The heart failure was treated by catheter embolization of the feeding arterial vessels with Ivalon particles. Following resolution of the heart failure, a residual avascular mass remained. A biopsy revealed the diagnosis of an undifferentiated sarcoma that was successfully treated with chemotherapy and surgery.

Platelet-activating factor levels in human follicular and amniotic fluids.

Platelet-activating factor (PAF) was estimated in extracts of human follicular and amniotic fluids using a commercially available 125I-radioimmunoassay. Levels obtained before and after purification of the extracts by thin-layer chromatography were similar and PAF could be estimated with high accuracy and reproducibility over a wide dilution range. PAF levels in fluid aspirated from mature (17 mm average diameter) follicles from in vitro fertilization patients were 1005 +/- 129 fmol/ml in successful (clinical pregnancy) cycles and 949 +/- 75 fmol/ml in unsuccessful (failure of implantation) cycles. PAF levels were also similar in follicles containing eggs and those where no egg was found, and in fluid from follicular cysts characterised by low oestradiol and progesterone levels. PAF was detected in midtrimester amniotic fluid (60 +/- 20 fmol/ml). At term, PAF was low or undetectable in amniotic fluid obtained at elective caesarean section before the onset of labour, but increased to 102 +/- 28 fmol/ml in samples obtained following spontaneous labour and vaginal delivery. The data suggest that PAF may be involved in ovulation and parturition but further studies into the mechanism of action of PAF are necessary. The good performance of the radioimmunoassay and the convenience of gamma-counting are strong advantages of this method over the available bioassays, but its expense remains a drawback.

Fistula dysfunction: effect on rapid hemodialysis.

Rapid hemodialysis (Qb 400 to 500 ml/min) places considerable demands on hemodialysis vascular access. This six-month prospective study enrolled 52 patients and evaluated urea recirculation as a means of detecting fistula dysfunction. It evaluated the effects of fistula location and dialysis blood flow on urea recirculation during rapid hemodialysis and assessed the effect of rapid dialysis on fistula thrombosis. Urea recirculation increased as Qb increased from 300 to 400 ml/min (8 +/- 3% to 16 +/- 3%, P less than 0.05). The extent of urea recirculation was also fistula site dependent (radial fistulas 18 +/- 4%, upper arm fistulas 11 +/- 3%, Qb 400 ml/min, P less than 0.05). Site and blood flow dependent urea recirculations were an indicator of venous stenoses. When venous stenoses were corrected, urea recirculation rates improved (36 +/- 3% to 21 +/- 3%, P less than 0.05). There were no differences between methods of determining urea recirculation early in dialysis (contralateral arm venepuncture vs. stop flow technique; 30 to 60 min). However, at 120 minutes urea recirculation was significantly greater with the contralateral arm venepuncture technique. Venous dialysis pressure at Qb 400 ml/min had limited use as a predictor of venous stenoses unlike its value at lower Qb. Fistula thrombosis (0.26/patient year of dialysis) and fistula replacement (0.09/patient year of dialysis) were similar to our observations in a conventional hemodialysis facility where prospective correction of fistula dysfunction was also used.

Mechanisms of major biliary injury during laparoscopic cholecystectomy.

Laparoscopic cholecystectomy has become the procedure of choice for surgical removal of the gallbladder. The most significant complication of this new technique is injury to the bile duct. Twelve cases of bile duct injury during laparoscopic cholecystectomy were reviewed. Eight injuries were of a classic type: misidentification of the common duct for the cystic duct, resection of part of the common and hepatic ducts, and associated right hepatic arterial injury. Another injury was similar: clip ligation of the distal common duct with proximal ligation and division of the cystic duct, resulting in biliary obstruction and leakage. Three complications arose from excessive use of cautery or laser in the region of the common duct, resulting in biliary strictures. Evaluation of persistent diffuse abdominal pain led to the recognition of ductal injury in most patients. Ultimately, 10 patients required a Roux-en-Y hepaticojejunostomy to provide adequate biliary drainage. One patient had a successful direct common duct repair, and the remaining patient underwent endoscopic dilatation.

Human placental phospholipase A2 activity in term and preterm labour.

Phospholipase A2 activity (EC 3.1.1.4) was estimated in low-speed supernatants of human placenta by measuring the release of arachidonic acid from phosphatidylcholine, 1-stearoyl-2-[3H]arachidonyl and other phospholipids under alkaline conditions (pH 8). Activity was calcium dependent and followed Michaelis-Menten kinetics with an apparent Km of 0.19 (SD 0.04) mM and a Vmax of 486 (SD 52) pmol/mg protein per h. Placental phospholipase A2 activity was relatively high in early pregnancy (8-11 weeks gestation) and following spontaneous preterm labour (31-34 weeks), but decreased significantly towards term with no changes in relation to parturition. By contrast, activity in the fetal membranes (amnion and chorio-decidua) was low after preterm labour and increased significantly towards term. The placenta and fetal membranes have the capacity to contribute to the increased intra-uterine release of arachidonic acid and eicosanoids that occurs during term and preterm labour, but at present there is no evidence that this increase involves direct changes in phospholipase A2 activity.

Imaging of the renal arteries: value of MR angiography.

We compared the efficacy of MR angiography with that of conventional angiography for visualizing the renal arteries and detecting renovascular disease. Thirty-three MR angiographic studies, consisting of axial two-dimensional (2-D) phase-contrast, coronal 2-D phase-contrast, and coronal 2-D time-of-flight acquisitions, were performed within 48 hr of conventional arteriography. The studies were done to evaluate possible renovascular hypertension (n = 25) or potential donor nephrectomy (n = 8). The three MR image sets were interpreted independently, in random order by three observers, with regard to the number of renal arteries, degree of vessel visualization, arteriovenous overlap, and presence of renovascular disease. A fourth interpretation was based on the combined axial and coronal phase-contrast image sets. Evaluation was limited to the proximal 35 mm of each renal artery. Renal artery visualization and detection of renovascular disease were more complete with coronal phase-contrast (80% sensitivity, 91% specificity) than with time-of-flight (53% sensitivity, 97% specificity) images. Combined axial and coronal phase-contrast images permitted visualization of the proximal 35 mm of all dominant renal arteries and detection of 13 of 15 stenoses (87% sensitivity, 97% specificity). Our data suggest that biplanar MR angiography has considerable potential as a noninvasive screening technique for the evaluation of renovascular disease.

Intravascular ultrasound assessment of the renal artery.

OBJECTIVE: To determine the feasibility and diagnostic value of catheter-based intravascular ultrasound imaging compared with angiography for visualizing renal artery structure. DESIGN: Renal artery images were obtained in patients with renal artery stenosis having percutaneous balloon angioplasty and in normal subjects by digital angiography and by a 20-MHz, mechanically driven, catheter-based, intravascular ultrasound imaging system. SETTING: A referral-based university hospital. PATIENTS: Four randomly selected normal subjects without known renal disease and four consecutive patients with known renal artery stenosis referred for percutaneous balloon angioplasty. INTERVENTIONS: Digital angiograms and intravascular ultrasound images of nine renal artery segments were obtained. In patients with renal artery stenosis, imaging was done before and after balloon angioplasty. MAIN RESULTS: Digital angiography and ultrasonography correlated closely in the determination of arterial lumen diameter (r = 0.81) and cross-sectional area (r = 0.83). However, ultrasonography provided structural information not shown by angiography. All normal arteries showed discrete intimal, medial, and adventitial wall layers by ultrasonography. In the five stenotic segments, angiography identified the cause of stenosis to be atherosclerosis in four patients and fibromuscular dysplasia in one patient. Ultrasound imaging, however, identified the disease process as atherosclerosis in three patients and as fibromuscular dysplasia in two patients. After renal angioplasty, ultrasonography identified three arterial dissections, only one of which was shown by angiography. CONCLUSIONS: These preliminary data indicate that catheter-based intravascular ultrasound imaging of the renal artery is feasible and correlates well with angiography in assessing renal artery size and also provides potentially important additional structural information that permits a better characterization of arterial pathology.

Mechanisms of angioplasty in hemodialysis fistula stenoses evaluated by intravascular ultrasound.

Quantification of luminal dimensions and the mechanisms by which angioplasty (PTA) corrects non-atheroma venous fistula stenoses have been poorly studied. In 38 consecutive percutaneous balloon angioplasties of hemodialysis fistula stenoses, catheter-based, mechanically-rotated intravascular ultrasound (IVUS) images were obtained along with cineangiography. Images from 24 brachial vein, 11 central vein, 2 graft anastomoses, and 1 brachial artery were quantitatively and qualitatively evaluated. Semiautomated quantitative angiographic stenosis was 64 +/- 13% pre-PTA and reduced to 36 +/- 19% post-PTA (P less than 0.001). Post-PTA IVUS minimal lesion diameter and cross sectional area were 5.7 +/- 1.5 mm and 2.9 +/- 1.5 mm2, respectively. With IVUS, mechanisms observed were: vessel dissection in 16 (42%), arterial stretch (defined as vessel diameter: balloon diameter ratio = 0.75 to 1.0) in 19 (50%), and elastic recoil (defined as vessel diameter: balloon diameter ratio less than 0.75) in 19 (50%). Compared to angiography, morphologic information provided by IVUS were plaque composition (hard 11%, soft 89%), plaque topography (eccentric 94%, concentric 6%), thrombus (IVUS: N = 6 vs. angio: N = 1), dissection (IVUS: N = 16 vs. angio: N = 1). Thus, IVUS can evaluate lesion morphology and define luminal dimensions after angioplasty. Mechanisms of successful angioplasty of hemodialysis fistula stenosis occur primarily by vessel stretching and dissection, and significant post-PTA narrowing is due to elastic recoil.