| Abstract|| |
Interventional radiology is one of the fastest growing branches of medicine. Successful interventional radiology started in Egypt in 1982 by dilating narrow arterial segments using balloon catheters. There are three domains in nephrology in which the interventional radiologist can help: a) The renal fossa, b) The renal graft complications, and c) The malfunctioning hemodialysis blood access. In this report, there will be a review of the clinical application of the different radiological procedures that include our own experience. The interventional radiology in the renal fossa includes the following procedures: renal artery dilatation and renal artery embolization. The interventional radiology in the management of renal transplant complications includes: graft artery stenosis, arterio-venous fistulas, drainage of lymphocele and ablation of native kidneys. The interventional radiology can be very helpful in the correction of the malfunctioning hemodialysis shunts besides the insertion of temporary hemodialysis catheter.
|How to cite this article:|
Saeed AS. Interventional Radiology in Nephrology and Urology. Saudi J Kidney Dis Transpl 2004;15:346-61
| Introduction|| |
Interventional radiology is one of the fastest growing branches of medicine. It is the field of medicine in which radiologists are needed not only to diagnose, but also to treat; thanks to the accurate and sharp images provided by the new generations of MRI, CT scan, US and digital subtraction angiography. In addition, there have been many technologically advanced mini accessories that tremendously helped in assuring maximum possible safety when we intend to intervene.
Successful interventional radiology started in Egypt in 1982 by dilating narrow arterial segments using balloon catheters. It was followed by greater successes in embolization to stop bleeding at different levels of the body. This paved the way to apply the endovascular treatment to many critical conditions in surgery, oncology and other branches in medicine including intra cerebral embolization.
In the nephrological and urological fields, interventional radiology modify the way to treat certain disease or provide the least invasive methods in dealing with surgical complications.
There are three domains in nephrology in which the interventional radiologist can help: a) The renal fossa, b) The renal graft complications, and c) The malfunctioning hemodialysis blood access.
In this report, there will be a review of the clinical application of the different radiological procedures that include our own experience.
| Interventional Radiology in the Renal Fossa|| |
The intervention radiology in the renal fossa includes the following procedures:
- Renal artery dilatation.
- Renal artery embolization.
Renal Artery Dilatation in Renovascular Hypertension
Whether renovascular hypertension is induced by single or bilateral renal artery stenosis, the method of choice to correct the high blood pressure is to revascularize the ischemic kidney. 
The traditional surgical treatment has been renal artery bypass grafting.  Although surgical technique and results have improved dramatically over the past decades, especially in the management of the fibromuscular disease, significant morbidity such as loss of renal function and mortality (6%) discourage its frequent application. 
The importance of revascularization is not only the control of the blood pressure. It resulted in better nine year survival (84%) for a group of hypertensive patients controlled surgically versus 43% in another group controlled medically. 
Balloon angioplasty, as an alternative to surgery, was a natural extension of successful application of the same principle in lower limb ischemia. The first report on percutaneous transluminal renal angioplasty (PTRA) came from Andreas Gruntzig in 1978. 
We did our first case twenty years ago for a young woman suffering from severe persistent renovascular hypertension due to fibromuscular hyperplasia (FMH). The patient has had normal blood pressure without medications ever since [Figure - 1].
Since then a series of 115 patients were treated with PTRA that resulted in a primary success rate of 94%. The five years clinical success rate for the FMH group was 75%; the intimal type of FMH showed 96% success rate. This may be attributed to the fact that an intimal web like membrane can be easily ruptured and dilated by the balloon with less chance to recur, since it is devoid of muscular coat.
Among the atherosclerotic group, the clinical success rate over the subsequent three years were much inferior being 62%,52% and 33% in the first, second and third year, respectively. The clinical efficacy of PTRA at a 3-12 months follow-up was confirmed through a randomized controlled trial by Nordmann and co-workers who analyzed the results in 210 patients suffering from moderate to severe stenosis (more than 50% luminal reduction) and found that PTRA had modest but significant effect on blood pressure without major cardiovascular complications. 
Since the introduction of balloon expandable stents, the results for the atherosclerotic and/or the hard stenosis group have improved; it has become possible to overcome the hard lesions and allow for a long lasting hemodynamic and clinical stabilization [Figure - 2].
The efficacy of stenting was confirmed by the randomized controlled study conducted by the Utrecht group in the Netherlands comparing the results of PTRA with and without stent in 89 patients. They found a primary success rate of 57% and 86%, respectively, while the restenosis rate was 48% and 14% respectively.  Rees et al revised the results of 1128 renal stenting procedures and reported 95% technical success rate and patency of 77% at 8 months including 71% benefited patients and 6% cured. 
Meanwhile, de fraisiniette et al studied the results of the PTRA in dysplastic stenosis in 70 patients and concluded that PTRA should be considered the first line of treatment in these cases. They experienced 95% technical success and 87.9% clinical success rates and their worst results were among the group of patients above the age of 57 and in those whose hypertension was of more than nine years duration. 
Encouraged by the results of the endovascular treatment of renal artery stenosis, our protocol offers this treatment to all the FMH patients and to the renovascular hypertension patients who have persistently resistant hypertension and a more than 50% luminal reduction and whose creatinine has exceeded 2 mg/dl (200µmol/l). On the other hand, the patients are continued on medical treatment if they have luminal reduction less than 50% and their creatinine level is less than 2 mg/dl. Regarding the complications, our thirty days' mortality has been within 0.5%, deterioration in renal function within 3% and trauma to the renal artery requiring surgery within 2%.
Another uncommon interesting reason for renal ischemia is intrarenal highly dynamic arterio-venous fistula (AVF). Blood flow steal phenomenon may result from the AVF that may result in reduction of the blood flow to the juxtaglomeular apparatus and increased renin secretion. A major shunt may be difficult to correct by conservative surgery and the only way to avert a life threatening hypertension is nephrectomy. Transcatheter embolization of the fistula can be a better choice to correct the hypertension and preserve the kidney function [Figure - 3].
Trans-Catheter Embolization in Hematuria of Renal Origin
Occlusion of the renal artery using catheters and various occluding materials (embolization) has a definite and least invasive role in controlling the hematuria of renal origin. Various occlusive materials can be deployed to the bleeding arteries of all sizes. Moreover, there are microcatheters available now that can be navigated down the stream to the corticomedullary junction.
In our practice, the major indication for renal artery embolization is to control the post nephrolithotripsy bleeding. Our technical success rate since 1987 has been 98%.  It is almost the same success rate as that of controlling the intractable hematuria [Figure - 4]. The percentage of renal tissue infarction or ablation after this ultra selective embolization is minimal and adds no compromise to the active renal parenchyma.
Bleeding hypernephroma is another indication for embolization in order to control or totally ablate the tumor in patients not candidates for surgery. In these cases, the occlusion can be achieved by coils or alcohol perfusion.
| Interventional Radiology in the Management of Renal Transplant Complications|| |
Renal transplant graft survival is directly related to recipient and donor selection, the use of optimal immunosupressors, the strict surgical technique and the proper management of complications.
Complications are usually managed by open surgical correction. On many occasions, this is greatly hindered by previous operative scar tissue and dense peritransplant adhesions, which render surgery rather risky for grafts and patients.
As an alternative, minimally invasive procedures whether endourogical, laparoscopic or radiologically interventional are adopted in many centers.
In our practice we dedicated radiologically interventional procedures since the late eighties for the following conditions:
- Graft artery stenosis
- Arterio-venous fistulas
- Drainage of lymphocele
- Ablation of native kidneys
Graft Artery Stenosis
Transplant renal artery stenosis complicates up to 5% of renal transplants.  The cause is usually atherosclerosis, torsion, angulation, intimal damage or technical error. It is suspected whenever sudden severe hypertension occurs or when there is unexplained deterioration of renal function.
Non invasive diagnostic methods are mostly unreliable including captropril renography and duplex studies. The latter gives high false positive results up to 30% in our practice. Angiography remains the gold standard that can simultaneously confirm the diagnosis and allow corrective intervention.
PTRA has been steadily practiced in our institute for the last 20 years. The growing experience allowed the privilege of applying the technique to the renal grafts successfully. Our primary success rate is 88%, although the restenosis rate remained unavoidable within the range of 30% in two years. Recent reports continue to support the efficacy of PTRA as an appropriate initial management for the artery stenosis of the transplanted kidney. Technically successful procedures are reported to be from 85% to 93%, while the rate of restenosis to be from 23.1% to 30% of cases. , Redilatation is always possible allowing revascularization of 74% of the recurrences  and 70% in our experience.
Recently, balloon expandable stents are utilized to achieve better hemodynamic results and decrease the recurrence rate [Figure - 5]. Sierre et al and Nicita et al have reported 83% and 71% successful results. ,
Renal Transplant Arteriovenous Fistula
Renal biopsies are performed to evaluate renal graft dysfunctions that might be complicated by arteriovenous fistulas. The fistulas are usually small and tend to heal spontaneously with conservative therapy. However, sometimes they may progress to have serious hemodynamic and cardiogenic effects, which may endanger the graft or the life of the reciepient.
Super selective embolizaton of the segmental vessel plays a definite key role in avoiding the serious complications and in saving the graft. High flow fistula, even if small, can seriously affect the graft survival through the steal effect and the consequent graft ischemia [Figure - 6]. The technique is done under local anesthesia using microcatheters in order to pin point embolization of the target vessel. Technically successful procedures will result in the occlusion of the fistula that will allow better re-perfusion and reversal of the hemodynamic complications. The procedure, in the expert hands, has no serious complications. We treated 19 fistulas successfully along the past 15 years without nephrologic or systemic complications.
Persistent Hypertension after Transplantation
Persistence of the high blood pressure even after transplantation is sometimes a medical challenge. Harvesting of the native kidneys during transplantation is controversial among the different practicing teams.
In our practice, we offered (native kidney embolization) to a small group of 6 patients in order to achieve bilateral transcatheter renal tissue ablation. The procedure is preceded by selective serum renin estimation from the renal veins, the iliac vein, the proximal and distal Inferior vena cava (IVC) as well as the antecubital vein. High values at the renal veins and proximal IVC were indicative for ablation.
Preliminary results are encouraging with a mean decrease in blood pressure of 20% systolic and 10% diastolic in the first 6 months. Our results need further substantiation through a larger number of patients and longer followup period.
Drainage of Lymphocele
Pelvic lymphocele after renal transplantation occur in up to 18% of recipients. They may be asymptomatic, but when they grow in size they may present with graft dysfunction, hydronephrosis or lower limb edema.  The diagnosis is confirmed by ultrasound or CT scan.
Percutaneous drainage has been advocated as an alternative being less invasive than open or laparoscopic marcipulization and can be performed on outpatient basis.  The procedure is done under CT scan guidance and may entail either simple aspiration or indwelling tube drainage. One of the criticisms to this maneuver is the liability for recurrence. Although repeated drainage can always be advocated on the same simple basis, yet the idea of repeated puncture can carry risk for infection or compromise the graft. Therefore, the use of local sclerosant such as tetracycline,  iodine  or ethanol  was suggested to achieve long-term stabilization. We found that sclerosing the lymphocele may still entail repeated sessions, which will give extra burdens on the recipient both psychologically and financially.
In the last four cases, we started to use the tissue glue, which we used to use preferentially in many other interventional procedures including gluing the brain arterio-venous malformations, as a sclerosant agent in one step procedure. The results were very satisfactory with no reaccumulation up to one year without infection or graft compromise [Figure - 7].
| Intervention Radiology in Malfunctioning Hemodialysis Shunt|| |
Malfunctions of the hemodialysis access are frequent. The long-term survival of the shunts is not more than 15%.  For example, Keller et al found that the patency rate for the distal radio-cephalic fistula was 65%, 60% and 45% at 1, 2 and 4 years, respectively. The figures for graft shunts were even more disappointing being 50%, 43% and 10% for the same followup periods.  Surgical correction can be performed but exposes the treated shunt to the risk of infection and stenosis or occlusion of the anastomosis.  For the past 20 years, radiologically guided interventional procedures have been offering the same benefits of surgical correction, while avoiding the potential hazards. ,
The diagnosis of a failing fistula is a clinical entity in the first place. Diminished thrill noticed by an intelligent patient or his treating physician is a good indicator for a reduction in the flow. Flow measurements obtained during dialysis usually can substantiate the diagnosis. Color coded duplex scan although useful, yet it has offensive limitations in complex fistulas surrounded by collaterals. ,, Angiography is still the gold standard for evaluation of shunt anatomy and function. It gives excellent anatomical description not only for the veins of the elbow and forearm but also for the central ones. 
Most stenoses occur at the anastomotic or post-anastomotic areas. This was found in 66% of 59 stenoses in Turmel-Rodrigues et al series.  Beathard found that 58% of all graft -vein stenoses was anastomotic, while stenoses at the puncture areas were only 11% and 28% in fistulas and grafts respectively.  They also reported 12-22% central stenoses whereas 33% of all lesions were combined.
Stenoses at the venous side are commonly attributed to intimal hyperplasia and perivascular fibrosis.  Arterial stenoses are much less frequent and are usually the result of technical fault during surgery accompanied by intimal injury. Therefore, they present few days or weeks following the creation of the shunt. Such injury seldom complicates angiography. 
The radiologically guided interventions can be one of three procedures: 1) percutaneous transluminal angioplasty (PTA) with or without stenting 2) mechanical thrombectomy 3) creation of a temporary hemodialysis catheter access.
Percutaneous Transluminal Angioplasty (PTA)
a. Dysfunction of hemodialysis shunt with angiographically detected stenosis of more than 70% luminal reduction.
b. 50% Luminal reduction associated with high venous pressure
c. Residual stenosis after mechanical thrombectomy or surgery.
a. Early anastomotic stenosis of less than one month duration.
b. Anastomotic stenosis with a concomitant ulnar artery occlusion.
c. Early thrombosis (3 weeks) following surgery.
d. Associated adjacent pseudo-aneurysm.
e. Local infection.
The procedure is mostly performed through an antegrade brachial artery puncture rather than from the venous side since crossing the stenosis from the venous side is almost always difficult and sometimes impossible. The balloon size is chosen according to the site being 3-4 mm for the arterial stenoses, 4-7 mm for venous and 14-16 mm for the central subclavian stenoses. Venous (shunt) lesions are usually rigid and need high pressure balloons to be used with a longer inflation time.
The early technical success rate is high ranging between 70%  to 99%  depending on the length of the occlusion. The long-term patency according to Beathard  was 61%, 38% and 22% at 6 months, one and two years, respectively. The subclavian lesions showed the worst results being only 29% at 6 months; therefore a stent might be necessary to apply after repeated failures of PTA.
The results of PTA denote that the procedure can achieve limited long-term success. However, re-do procdures can be done in a way that a cumulative over all patency rate can be improved. A second or third PTA can achieve the same results like the first procedure.
Some lesions are technically difficult than others or resilient to dilatation so that restenosis or early recurrence is expected. Examples of these difficult lesions are the concentric stenoses frequently seen adjacent to venous valves, or collapsing lesions that recoil after dilatation as well as stenoses close to kinks. Furthermore, central venous stenoses are notorious for restenosis. In such situations, a stent is preferable trying to achieve a long lasting solution.
Percutaneous Mechanical Thrombectomy in Shunt Thrombosis
Shunt thrombosis is not uncommon especially in grafts.  The method of recanalization depends on how long and how fresh the thrombous is. A short fresh easily compressible thrombus may be treated by balloon angioplasty alone, where the balloon can smash and macerate the thrombous against the wall. A long fresh compressible thrombous may benefit from angioplasty alone or combined with fibrinolysis.
A long incompressible thrombous may deserve a true decloting procedure done through a special mechanical thrombectomy catheter. Hydrodynamic mechanical throm bectomy is a rather recent technique. , It aims at "pulverization" of the fresh part of the thrombous into small microscopic particles of less than an RBC size and fragmentation/ suction of its harder sub-acute part to an exhaust drainage port of the catheter. This is achieved through a double lumen catheter with a retrograde saline injection from a very small supply lumen that is drained into a larger efferent lumen. Due to the resulting pressure gradient, known as the venturi effect, between the jet flow and the larger exhaust lumen, the injected fluid instantaneously leaves the vessel via the exhaust lumen after creating a turbulent flow zone close to the catheter tip. The thrombus is fragmented by the flow and sucked into the exhaust lumen.
The technical success depends primarily on the time of discovery of the thrombosis. In our experience we do not accept patients who claim occlusion for more than 48 hours, unless there is inaccessibility to surgery. Failure rates increase significantly from the second day onward being 4% in the first day, 15% after the second day, 33% after the third day and 70% afterwards. 
In our 15 patients' series, a balloon angioplasty was necessary in 13 patients to remodel an underlying residual stenosis. Recanalization was achieved in 12 patients most of them had residual luminal irregularities in spite of effective patency [Figure - 8]. The technique was almost safe with local hematomas as the only encountered complication.
Interventional Radiology in Inserting Temporary Hemodialysis Catheter Access
There are clinical situations in which catheter dialysis is appropriate and indicated. Examples include patients with acute renal failure or chronic renal disease in whom the renal function is declining faster than expected, thus not permitting the necessary time for maturation of the permanent access. Other common reasons for catheter dialysis are to provide temporary access during infectious episodes in patients with established vascular or peritoneal access as well as revision of these accesses.
Access sites are many; the choice depends on the special clinical situation. The right internal jugular vein (IJV) is the recommended access. The puncture can be performed guided by surface landmarks, or better still, using ultrasound (US) guidance it allows easy and safe approach and a low posterior puncture of the vein most suitable for tunneled catheter without the risk of kink and later dysfunction. Doing this procedure in the interventional radiology suite avoids repeated punctures and ensures sterile conditions with least possible complications. The subclavian vein is less accepted in patients prepared for permanent AV shunts because of the high incidence of catheter induced stenosis (19 to 53%), a condition which will compromise shunt life span. , In bed ridden and acutely ill patients, a femoral vein approach is a favorable site for catheterization because mobility is not a concern and nursing care is easy. The IVC is easily accessed in the infrarenal segment by radiologists who had been trained on translumbar approaches to aorta and IVC. The IVC is a possible central root for high flow demands. Another approach to the IVC is via a direct transhepatic root usually under US/fluoroscopic guidance. The technique is preserved to patients who have IVC thrombosis.
The placement of central venous access devices by radiologists has been proven to be safe and effective. Although rare, certain potential complications are recognized such as occlusion, thrombosis, infection, pneumothorax, migration and fragmentation. Some of these complications are manageable by relevant interventional radiological techniques like snaring out of a broken migrating catheter fragment [Figure - 9] or correction of catheter twist.
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Ahmad Samy Saeed
Interventional Radiology Unit, King Fahd Renal Dialysis And Transplantation Unit, Cairo University Hospitals, Cairo
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6], [Figure - 7], [Figure - 8], [Figure - 9]