Interventional radiology in urology and nephrology

 

Interventional radiology in urology and nephrologyIntroduction:

The advances in vascular catheterization associated with the development of imaging techniques, and in particular the techniques of sectional imaging, have been at the origin of the extraordinary development of interventional radiology. The urinary tract has not been the poor relation in this field, the last two decades seeing many percutaneous techniques appear to allow to treat different affections of the urinary system.

Three main categories of interventions dominate: endovascular interventions, which mainly involve the renal artery and relate to the pathology of the renal artery and the parenchyma, interventions on the upper urinary tract by percutaneous approach, urinary collection drainage interventions , regardless of their topographies.

All these therapeutic techniques concern both the native urinary tract and the transplanted urinary tract. Whatever the type of intervention, they all have the advantage of simplicity, reduced aggressiveness compared to surgical methods and a result that is often equivalent. They also open new therapeutic pathways. However, they must always be the result of a broad medico-surgical consultation, making it possible to determine the most appropriate therapeutic method according to the notions of cost, risk and benefit to the patient.

Endovascular interventional radiology:

Using catheterization techniques, endovascular navigation now allows selective or hyperselective catheterization of different vessels in the urinary tract or their distal branches. These techniques require great skill in vascular catheterization as well as a perfect knowledge of the use of X-ray guidance. Two broad categories of techniques emerge:

– vascular occlusion techniques dominated by embolization;

– Vascular clearing techniques dominated by percutaneous transluminal angioplasty.

EMBOLISM IN URINARY PATHOLOGY:

Embolization consists in introducing, by means of adapted catheters, materials of a diverse nature intended to occlude the vascular light. According to the clinical indication and the therapeutic objective (temporary or definitive embolization, palliative or curative), the vascular occlusion must be proximal or distal, localized or diffuse. This therapeutic objective will also condition the choice of the occlusive agent. The main materials currently used are fragments of calibrated synthetic polymers, metallic balls, releasable balloons, occlusive metallic spirals. Vascular occlusion can also be achieved by injection of sclerosing agent, such as absolute alcohol, or injection of polymeric adhesives. Therapeutic substances may also be associated with the injected fragments, for example anticancer cytotoxic agents: chemoembolization of malignant tumors.

The indications of the embolization of the urinary system concern three great anatomical domains:

– renal artery and renal parenchyma;

– branches of the hypogastric arteries principally intended for vesicoprostatic purposes;

– the spermatic veins.

Renal embolization:

This is by far the most used technique and it is addressed to the affections of the renal parenchyma. The indications are multiple and can be grouped into three categories, schematically.

Preoperative embolization:

They aim to decrease the vascularization of a tumor and thus to facilitate the surgical action, reducing blood loss and promoting surgical dissection by the reaction edema secondary to embolization. The agreement is far from total on the real utility of this technique, the advantages of which are to be balanced with the morbidity of the gesture. It should be reserved for voluminous tumors larger than 8-9 cm, very hypervascularized and in which difficult dissection is foreseeable. Similarly, the existence of a neoplastic extension to the renal vein, which may impede the approach of the artery, is for some an indication to the preoperative embolization.

Symptomatic embolization:

They are most often palliative and aim to treat a symptom, mainly in the context of a non-surgical tumor pathology.

It is either macroscopic haematuria with spoilage anemia, lumbar pain or, more rarely, secondary cardiac insufficiency due to tumor arteriovenous fistula or paraneoplastic signs (hypertension, polycythemia, hypercalcemia). The effectiveness of this gesture is usually temporary, but the embolization is much less aggressive than “clean” surgery and allows a more comfortable survival sometimes prolonged.

On the other hand, the embolization treatment of posttraumatic haematuria, whether there is a false aneurysm or an arteriovenous fistula, represents a particularly effective and attractive solution, since the selectivity of the catheterization makes it possible to preserve as much as possible the healthy parenchyma. The ideal is to be able, thanks to hyperselective catheterization techniques, to occlude only the alimentary artery of the traumatic lesion. This is particularly the case of iatrogenic trauma: hematuria after renal puncture-biopsy or percutaneous approach for percutaneous nephrolithotomy.

The curative treatment by embolization of certain intrarenal lesions, whether hemorrhagic or not, could also be proposed. This is particularly the case for the rare intrarenal vascular malformations (cirsoid aneurysm, congenital arteriovenous fistula). On the other hand, treatment by embolization of aneurysms of the trunk of the renal artery is rarely possible insofar as the anatomical arrangement does not allow a sufficiently precise and reliable positioning of the metallic turns in the aneurysmal sac.

Curative embolization of certain renal angiomyolipomas may also be considered in some clinical situations. The occurrence of a haemorrhagic syndrome, whether persistent haematuria or retroperitoneal hematoma, can be controlled by embolization and it is thus possible to avoid emergency surgery, which almost nephrectomy. These hemorrhagic complications are mainly seen in bulky angiomyolipomas and, for some teams, embolization can be carried out in these preventive cases. In the tuberous sclerosis of Bourneville, where renal involvement is diffuse and bilateral in more than 80% of cases, embolization allows to be at the maximum conservative of the healthy parenchyma, to treat only the hemorrhagic tumor zone.

In total, this category of indications is intended for a wide range of clinical situations, to be discussed on a case-by-case basis, depending on the anatomical accessibility and the justification in terms of effectiveness.

Radiological nephrectomies:

By “sclerosing” the whole of the renal vascularization, it is possible to obtain almost total destruction of the renal parenchyma and to suppress the main functions of this organ. This is particularly valid if the parenchyma has a significant prior destruction. This gesture can represent an effective alternative to surgical nephrectomy, uni- or bilateral, by realizing a real functional exclusion. It has been proposed in cases of malignant hypertension which is difficult to control or in the case of severe nephrotic syndrome with major protein loss, also in the case of an inexhaustible urinary fistula. It is also possible to totally exclude a negligible useful kidney to suppress a difficult management apparatus (permanent nephrostomy for example) and thus to improve the comfort of the patient’s survival. The advantage of embolization is to propose a therapeutic alternative that is as effective but with morbidity and mortality significantly lower than those of surgery, which are approximately 20% and 5% respectively in these particularly fragile subjects.

Side effects :

The risks of renal embolization are limited. Secondary manifestations (postsmall syndrome) in relation to renal infarction are constant and transient: low back pain, nausea and vomiting, sometimes temperature and leukocytosis.All symptoms are resolutive under symptomatic treatment. The migration of embolic reflux fragments into the aorta should be avoided by a very rigorous technique and quality radiological control during surgery.

The possibility of an abcdation of a necrotic tumor home can not be ruled out and justifies in certain situations an antibiotic coverage.

Pelvic arterial embolization:

Selective catheterization of the branches of the hypogastric arteries makes it possible to propose a therapeutic alternative to certain clinical situations. The approach is most often done by femoral, homolateral or contralateral, and more rarely by the axillary route. Selective catheterization may be tricky especially in the elderly whose vascular axes are frequently sinuous.

Selective occlusion of the target arteries is necessary to avoid ischemic complications in neighboring territories.Embolization should generally be bilateral to avoid any resumption of anastomosis between the two hypogastric systems. The indications are limited. They relate to some hematuria of the lower apparatus, difficult to control by other means: bladder tumor, radial cystitis, pelvic trauma, postoperative hemorrhage. Embolization may also be indicated in the treatment of priapism and some erectile dysfunction.

The indication of embolization mainly concerns post-traumatic priapism. It is secondary to an increase in arterial flow in relation to an arteriovenous fistula. The vascular breccia leads to an excess of irrigation of the corpora cavernosa and the embolization must be proposed after failure of conventional treatments less invasive. The efficacy is good and the risk of secondary impotence is low, provided that the embolization is hyperselective and unilateral and that its implementation intervenes early.

The existence of a proximal arteriovenous fistula secondary to perineal trauma is much more rare. It is responsible for a deficit of erection by flight phenomenon. If anatomical accessibility permits, the embolization of the fistula makes it possible to restore the vascularization of the corpora cavernosa and possibly their function.

Embolization of spermatic veins:

It mainly concerns the left spermatic vein in the case of varicocele. Varicocele is the leading curable cause of male infertility. Selective catheterization of the left spermatic vein is generally possible up to the supra-inguinal segment.The occlusion may be performed either by occlusive metal turns or by sclerosing agents. The technical efficiency in terms of occlusion of the varicocele is between 90 and 97%. The rate of recidivism varies from 4 to 11%. These figures compare favorably with those of surgery, where recurrences occur between 10 and 21% of cases. On the other hand, recurrences after embolization are more difficult to treat with new embolization than surgical recurrences, for which embolization allows a success rate of 96%. The technique is very simple and can be carried out in ambulatory, under simple local anesthesia. The complication rate is very low.

Two types of indication may be proposed:

– curative embolization in the case of varicocele with infertility: in these cases, an improvement of the spermogram is observed in 60 to 78% of the cases and the pregnancy rate is between 40 and 60% of the cases;

– preventive embolization in the presence of a varicocele in an adolescent, especially if there is a decrease in the size of the testis: this indication is however discussed.

For most authors, embolization must be carried out in an indisputable manner in the case of recurrence after surgery.On the other hand, in other situations, its use remains more discussed. However, it is the most seductive therapy, due to results comparable to the surgical results and the simplicity of its realization.

ENDOVASCULAR TREATMENT OF OBSTRUCTIVE LESIONS OF THE RENAL ARTERY:

It is dominated by percutaneous transluminal angioplasty of the renal artery (ATPR) for the treatment of chronic stenosis lesions of the renal artery. The treatment of acute occlusions of the renal artery involves a much less frequent situation

Transluminal angioplasty of renal arteries:

Renal artery stenosis (SAR) of the native kidney:

The endovascular management of a SAR was first used by Gruntzig in 1978. Since then, it has become the first-line treatment of a SAR whenever it is feasible. Since 1990, it has benefited greatly from the contribution of endoprostheses. The endoprosthesis is a wire mesh cylinder placed inside the artery at the level of the stenosis, which makes it possible to obtain a perfectly regular internal lumen. The endoprosthesis has improved the immediate results and allows the management of more complex lesions.

The ATPR addresses two types of clinical situation and two types of anatomical lesion. Clinical situations include:

– subjects with isolated hypertension, secondary to a SAR, treatment of stenosis aimed at obtaining better control or even cure of high blood pressure: renovascular hypertension;

– subjects with a threatening SAR for the future of renal function (renal artery stenosis or renal artery stenosis): renascascular disease or ischemic nephropathy.

The lesions responsible are two-thirds of cases of atheromatous origin, integrating into polyvascular involvement. More rarely (a third of the cases), this is a particular framework of localized involvement of the different tunnels of the wall of the renal arteries that are grouped under the term of fibromuscular dysplasia. These affections mainly affect the young woman.

· Technical

The ATPR consists, after prior arteriography, of introducing through the stenosis a suitable metal guide on which a balloon catheter is placed. The size and length of the balloon depends on the size of the artery and the lesion. The dilatation of the balloon makes it possible to distend the stenotic region by dilating the atheromatous plaques. The evaluation of the quality of the result is carried out by radiological and manometric control. Depending on the latter, a stent may be used as a complement. The gesture requires local anesthesia of the puncture site, a more or less deep neuroleptanalgesia and a hospitalization of 48 hours. Follow-up should be regular, clinical, biological and ultrasound.

· Results

They must be considered anatomically and clinically.

At the anatomical level, the ATPR knows about 80% of favorable anatomical results at a distance. Unfavorable results include failures, complications and restenosis. The failures are as follows: impassable stenosis, stenosis impossible to dilate or elastic stenosis reproducing immediately after dilatation. These failures are found mainly in the ostial stenosis secondary to an atheromatous plaque of the aortic wall on which the balloon is ineffective. The rate of failure decreased significantly with the use of stents and the existence of an ostial stenosis led to a wide use of these devices.

Complications are currently rare. They are mostly minor (hematoma at the point of puncture, intrarenal distal thrombosis). However, there are major complications (less than 5% at the hands of an experienced team): temporary or permanent renal failure due to iodine overload, or especially by cholesterol embolism, retroperitoneal hematoma, renal artery thrombosis in general by dissection. The use of an endoprosthesis also decreased the occlusion rate of the renal arteries by allowing the treatment of most of these secondary dissections to dilation. Urgent surgery is required in less than 1% of cases.

Medium-term recurrences are secondary to the intimal hyperplasia generated by parietal trauma. The overall rate is around 15-20%. Their possibility of occurrence is well correlated with the quality of the immediate result. The presence of a residual stenosis greater than 30% and / or a longitudinal dissection in the treated region are factors of recurrence. The use of the endoprosthesis makes it possible to reduce this rate of immediate results of mediocre quality, but the installation of a stent can itself generate restenosis.

Restenosis can be successfully dilated again. Anatomical results are generally higher for lesions of fibromuscular dysplasia than for atheromatous stenoses.

Clinically, the results are most often dependent on the indication and subject to controversy, as their objective evaluation is difficult and the judgment criteria vary with the teams. In the case of renovascular hypertension, the clinical results are not necessarily correlated with the anatomical result. Intrarenal nephroangiosclerosis lesions in the contralateral kidney may induce hypertension despite effective endovascular treatment. Clinical benefit (healing or improvement in blood pressure with decreased medical treatment) is achieved in about 50-70% of the atheromatous stenoses. For lesions of fibromuscular dysplasia, due to the best anatomical result, absence of lesion diffusion, age and early diagnosis, the cure rate is significantly higher and 85-90% benefit of this type of treatment.

In the case of ischemic nephropathy, the results are difficult to assess and are the subject of randomized studies, which should allow an accurate evaluation of the benefits, depending on the type of lesion and the clinical stage. In these often hypertensive subjects, often suffering from severe heart failure, the threat of rapid and definitive deterioration of renal function is significant. The results are generally lower than in the previous category due to the age, complexity and age of the lesions. A clinical benefit (improvement or stabilization of renal function) is obtained in about 50% of cases, but the intervention may be responsible for worsening of renal insufficiency.

· Indications and contraindications

They depend on the clinical presentation of the patient and the type of lesion. ATPR is the background treatment for most significant stenosis of the renal artery. It has undoubted advantages over surgery: simplicity, lower morbidity, quasi-zero mortality, slightly lower results but also significantly lower cost. It can be repeated and does not prevent any surgery. The use of endoprostheses makes it possible to eliminate most failures and insufficient immediate results.This is particularly the case of the ostial stenoses considered hitherto as a poor indication of ATPR.

The recent series have shown that the endoprosthesis makes it possible to obtain results superior to those of the surgery for this type of lesion.

The restenosis rate appears to be slightly lower with the stent and a recent series shows that the first-line use of the stent results in better overall results compared to angioplasty alone for ostial lesions. This must be balanced against the cost of the stent, which is significantly higher than that of the isolated dilation.

A hemodynamically significant SAR should be corrected even if it is not symptomatic, in cases where an associated pathology involves surgery on the contralateral kidney, eg SAR + contralateral kidney cancer.

The contraindications of ATPR are represented by complex lesions of the renal artery, in particular dysplastic with aneurysm, spontaneous dissection and / or extension of lesions to intrarenal branches, complex aortorenal lesions justifying aortic restoration surgery. The main topic of discussion is the very need for direct treatment of the stenosing lesion, given the limited clinical efficacy in certain situations, even if a correct anatomical result is obtained. This discussion concerns mainly complex atheromatous stenoses irrespective of their clinical presentation. The main argument in favor of the treatment of the stenosis is the possibility of an aggravation of the lesion leading to the loss of the kidney. This possibility has been highlighted, but the importance of the risk is not really quantified. The disadvantages of medical treatment are also to be retained: difficulty of compliance, variable effectiveness, deleterious effects. The EMMA study (multicenter versus angioplasty study) showed that endovascular treatment of stenosis allowed control of hypertension with more limited medical treatment but with higher morbidity. As far as ischemic nephropathy is concerned, there is currently no randomized study to evaluate the efficacy of endovascular treatment.However, it seems difficult to avoid treating a patient with tight bilateral stenoses with progressive renal insufficiency.Beyond these discussions and awaiting the results of indisputable studies, the care of these patients must systematically go through a decision

multidisciplinary approach taking into account the risk and benefits of each therapy.

ATPR of the grafted kidney:

SAR of graft kidney is a frequent complication, occurring in 20 to 25% of kidney transplants. The etiologies are numerous and the occurrence of a SAR often multifactorial: arterial trauma during the sampling, problems of suture, graft malposition, arterial plicature, vascular rejection, preexisting arterial lesion, atheroma of the graft artery. The consequences are the occurrence of refractory arterial hypertension, acute occlusion with graft loss and renal failure.The ATPR is an attractive therapeutic alternative in that surgical reoperation presents major risks of graft loss (15%) or even mortality (5%).

A technical success of the ATPR is obtained in 80 to 90% of the cases, the difficulty being related to the surgical assembly and the type of anastomosis.

Similarly, the morbidity of the gesture depends on the technical difficulty associated with the vascular approach. It is about 2% with a graft loss of less than 1%.

Clinical results are difficult to judge because hypertension is multifactorial: 70% of the patients are improved but the rate of restenosis is relatively high, between 20 and 27%. Redilation, especially if the type of anastomosis allows easy access, should be proposed because it can restore prolonged permeability in 75% of these restenosis cases. An endoprosthesis can be proposed in case of multiple restenoses with results sufficiently interesting to be able to retain this hypothesis in preference to the surgery.

Endovascular treatment of acute renal artery obstructions:

These acute obstructions of the renal artery are a rare but sometimes unrecognized pathology. The safeguarding of the kidney may involve an endovascular saving action which has the advantage of being able to be carried out rapidly, immediately after the diagnostic arteriography and whose effectiveness is at least equivalent to that of the surgery. The results of this research are indeed mediocre overall. The effectiveness of the endovascular treatment depends on the anatomical type of the obstruction and its cause, as well as on the time of its implementation. The literature does not provide a significant series but includes occasional observations with often spectacular results, the significance of which remains questionable given the small number of cases presented.

The therapeutic means available to the interventional radiologist are in situ thrombolysis, thromboaspiration and endoprosthesis. The first two techniques are well adapted to the treatment of thrombotic obstructions, whether it is an embolic obstruction or an acute thrombosis on a pre-existing lesion. In the latter case, the treatment of thrombotic occlusion should be supplemented by the endovascular treatment of the causal lesion (dilation of a preexisting stenosis with or without stent placement).

The endoprosthesis is especially indicated for obstructions secondary to dissection of the renal artery, whether it is a traumatic dissection by phenomenon of deceleration, or of the extension to the renal artery of a dissection aortic spontaneous or spontaneous or iatrogenic dissection.

INTERVENTIONAL RADIOLOGY OF VASCULAR ABNORMALITIES FOR DIALYSIS:

Percutaneous treatment of vascular access for dialysis was proposed in the 1980s. Initially, the treatment was dominated by percutaneous transluminal angioplasty and the results were characterized by a rate of immediate failures of the order of 15 to 20% and especially a rate of recurrences reaching 50% to 1 year. The frequency of restenoses has led most teams to propose new dilatations, since access to the pathological area is generally technically simple. Careful monitoring of dialysis parameters is essential for early detection of restenosis prior to thrombotic occlusion.

All authors agree to reject long and irregular strictures as well as old occlusions which are accompanied by a high rate of immediate and medium-term failure as well as a greater morbidity. Technical advances have made it possible to optimize the results gradually, in particular by reducing the rate of immediate failures by the use of high-pressure balloons and, above all, of endoprostheses. The overall results of dilation alone show a higher rate of restenosis for bridging than for fistulas. Endoprostheses have the advantage of virtually eliminating immediate failures and of increasing secondary permeability, which increases to 60% at 2 years, knowing that the lesions are often complex to treat and multi-recurring. Endoprostheses are particularly indicated in “downstream stenoses” (subclavian vein, proximal venous trunks), for which dilation alone is often insufficient. However, stents have the disadvantage of their high price and morbidity greater than the simple dilatation, as well as a not insignificant reduction of the usable venous capital.

In case of acute obstruction of access to the vessels (in general, by thrombosis on unknown stenosis), endovascular techniques also have the first place, either by in situ thrombolysis or by thromboaspiration, which allows almost complete deobstruction as well as treatment concomitant stenosis.

Endoluminal techniques have now proved their effectiveness provided that the indications are wisely and in perfect cooperation between radiologists and nephrologists.

– Acute occlusions of venous access must be unclogged in order to preserve access.

– Short symptomatic stenoses on arteriovenous fistula (excluding short stenoses of the lower two-thirds of the forearm) are considered surgical.

– Recurrent stenoses should be dilated, while rapid recurrences (within 3 months) should be treated with a stent.

– Significant proximal stenoses of the venous side should be dilated even if they are asymptomatic, especially when they touch anatomical areas with low possibility of supplemen- tary circulation.

– Long and irregular stenoses or chronic occlusions should be discussed on a case-by-case basis. Endovascular treatment, in particular the placement of an endoprosthesis, can be discussed as an alternative to surgery.

The advantages of endovascular treatment are manifold: simplicity, low cost and low morbidity, correct efficiency, prolongation of vascular endurance, absence of amputation of venous capital. Finally, endovascular treatment has the advantage of not reducing possible surgical possibilities later.

Interventional radiology of the urinary tract:

Thanks to the precision of the guidance, which is permitted by ultrasound and / or computed tomography (CT), thanks also to its experience in the handling of endovascular catheters, the radiologist is able to perform percutaneously a number of therapeutic gestures on the upper urinary tract. These gestures are not competitive but complementary to endourology gestures.

All these techniques are performed by percutaneous approach of the pyelocalicious cavities, under radiological control, allowing the realization of a percutaneous nephrostomy (NP). This is the fundamental gesture that can be followed, allowing access to the excretory pathways and the ureter, other endoluminal therapeutic techniques.

PERCUTANEOUS NEPHROSTOMY:

This is the basic gesture of urinary interventional radiology, allowing external drainage of the upper urinary tract. This is a simple and effective procedure, which can be performed urgently and which is the first step in more complex endocanal gestures.

Whatever the therapeutic objective, simple external drainage or endocanal treatment, the effectiveness and the safety of the gesture depend on the quality of the percutaneous approach.

Technical:

The principle is to percutaneously puncture posterior intrarenal urinary tract and to set up a drainage catheter. To be the least traumatic possible, the approach of the excretory pathways must obey certain rules:

– the percutaneous approach must be transparent and avoid a direct approach of the pelvis, especially in the extrasinusal position;

– the posterolateral approach is preferable to the posterior approach, for the comfort of the patient, but must be careful to avoid the colon, which can sometimes be retro- nal;

– the approach must be calic rather than pyelic and be done along the transverse axis of the kidney to get as close as possible to the “avascular” line and decrease the risk of haemorrhagic fever.

The methods of detection depend on the action to be performed, on the existence or not of a dilation of the excretory pathways and on the function of the kidney:

– if the excretory pathways are dilated and if it is a simple external drainage, the guidance can be ultrasound;

– if the excretory pathways are not very dilated and / or the ultrasound guidance is difficult, it is possible, according to the anterograde pyelography techniques, to puncture the pelvis with the fine needle, allowing opacification and thus easier radiological identification for the calicious approach and the placement of the catheter;

– if the excretory pathways are weak or not dilated and functional and percutaneous surgery is considered, a simple urographic register with biplane scopy or an opacification of the excretory pathways by retrograde urethral probe can be used.

The choice of the chalice to be punctured is essential. The posterior calyxes must be selected and approached tangentially. The lower calyx is the most used, but for a ureteral approach or for percutaneous surgery, the middle calyxes, sometimes superior, can be punctured, but with an increased risk of translocation.

Placement of the NP catheter is performed on the Seldinger principle by means of a metallic guide placed in the excretory pathways through the puncture needle. For an isolated NP, the examination is carried out under simple local anesthesia after simple sedation. Neuroleptanalgesia is necessary in case of endo-ureteric maneuver. General or epidural anesthesia is used for percutaneous nephrolithotomies. Antibiotic coverage may be necessary, especially in cases of suspected infected urine.

Preliminary checking of haemostasis is essential.

Results and complications:

With the experience of percutaneous approach, the rate of success of setting up a NP is around 95%. The proper functioning of the drainage must be ensured by careful monitoring to avoid catheter mobilization, occlusion or plication.

Complications are rare and of three types:

– haemorrhagic complications: transient haematuria is frequent but yields within a few days. Persistent haematuria, requiring perfusion compensation, is exceptional.

In these cases, renal arteriography should be proposed in search of a vascular wound that can eventually be treated by embolization. The existence of major haemostasis disorders must be contraindicated at first percutaneous urinary tract;

– urinary extravasations: they are generally due to technical faults and are more a hindrance to locating than a real complication. The urinomas are exceptional;

– infectious complications: these are the most serious. The discovery of purulent urine should make the opacification delay because hyperpressure promotes the vascular passage of germs. Bacteremia with septic shock is possible.

Indications:

NP is above all a gesture of external drainage of the upper excretory pathways upstream of an obstacle. This drainage can be done for different reasons, frequently entangled:

– transient decompression of the urinary tract in the case of an acute or chronic obstacle, whatever the cause: this is the case, for example, of the acute obstructive renal failure, for which the emergency NP must immediately follow the ultrasound diagnosis and rapidly reduce obstruction and improve renal function. It is thus possible to envisage the therapeutic management of the causal disease;

– external deviation of the urine upstream of a urinary fistula;

– assessment of residual renal function of an obstructive kidney;

– drainage of infected urine upstream of an acute or chronic obstruction (febrile nephritic colic, pyonephrosis).

These indications vary according to the teams who favor, to a greater or lesser extent, multidisciplinary radiov urological management. Whatever the arguments in favor of a retrograde or anterograde approach, the indications of NP become systematic when the retrograde approach is impossible: failure or impossibility of retrograde catheterization, especially in the case of uretero-intestinal derivation or any intervention or bladder pathology, altering the ureter abutment. In a patient with advanced neoplasia, the establishment of an NP should be discussed, balancing the limited benefit in terms of survival and the discomfort caused by the presence of the probe.

TECHNIQUES DERIVED FROM PERCUTANEOUS NEPHROSTOMY:

Besides the indications proper for NP, it is used as a first step for the percutaneous approach of the upper excretory pathways, in order to allow the realization of very different therapeutic gestures, pure interventional radiology or endo-urological treatment.

Interventional endo-ureteral radiology:

This category of radiological interventions mainly concerns the treatment of ureteral constrictions, and more rarely the treatment of urinary fistulas and ureteral stones. The anterograde pathway is of course used in the event of failure or impossibility of the retrograde pathway. It is the preferred route for intestinal diversion. A combined approach can be used in certain situations by the so-called “cableway” technique, which makes it possible to position an endo-ureteral device more easily, by the retrograde route, at the level of the ureter.

Treatment of ureteral strictures:

By the percutaneous approach, it is possible to put in place a ureteral intubation catheter, either mixed, internal-external, or most often internal: it is the double probe J, multiperforated catheter, connecting the pelvis to the bladder and allowing the evacuation of the urine by the natural ways. The indications and the equipment used are identical to the dual J probes placed by the low channel. The problems of long-term permeability are the same, the average permeability being between 3 and 6 months. The existence of clotting or of a tumoral bladder pathology may be the cause of early occlusion, but it is generally the incrustation of the probe by crystals which causes this occlusion. The latter intervenes inevitably in spite of all the precautions taken.

The change of probe is made more easily by the lower route but, if it is impossible, it can be considered percutaneously. The indications of the double J probe are wide: temporary action in the case of benign lesions, awaiting definitive treatment, or palliative action in case of neoplastic stenosis. It is possible to associate the dilatation of the stenosis using a balloon catheter, especially in benign stenosis, to the placement of a double J probe. This technique is mainly for postoperative stenosis (uretero-intestinal anastomosis), provided that it is a short (less than 3 cm) short stenosis (less than 3 months) and that there is no irradiation. If these conditions are met, a healing rate of 60% can be expected.

The self-expanding metal endoprostheses have been proposed in substitution for the double probe J. They have the advantage of allowing a larger diameter of the permeable light than with a double probe J but can not be removed once implanted. They have the disadvantage of having a very poor and almost identical long-term permeability to double J-probes.

If ureteric intubation treatments fail, whether anterograde or retrograde, it is possible to propose more complex methods using electrocoagulation techniques or the creation of a neotraject parallel to the ureter. stenosis (percutaneous ureteroneocystostomy).

Treatment of urinary fistulas:

Whatever their topography, origin and anatomical type, urinary fistulas pose particularly complex therapeutic problems.Surgical treatment is difficult and has many failures as well as high morbidity. If the NP may be sufficient for small volume fistulas, more complex techniques should be used. In the case of ureteral fistula, the technique most frequently used is ureteral intubation by double probe J.

The anterograde route should be favored, as the failures of the retrograde pathway are of the order of 40 to 60%. The success rate is of the order of 80% provided that the treatment intervenes at an early stage.

In the case of bladder fistula or bilateral ureteral fetula with broad flow, temporary ureteral occlusion techniques can be proposed with intra-ureteral occlusive balloon probes combined with external drainage of urine by NP. This ureteral occlusion can be definitive by placing releasable balloons or polymeric glues. This final occlusion can be considered in the case of a non-functional kidney and must then be accompanied by a renal embolization to destroy the various urinary functions, thus avoiding a definitive NP.

Treatment of urinary lithiasis:

The technique of percutaneous lithiasis dissolution in the case of uratic lithiasis is nowadays used very little because of the length of the treatment, the possible failures and the efficiency of the new techniques of treatment of the ureteral lithiasis (extracorporeal lithotripsy or techniques endo-ureteral). On the other hand, it is possible to envisage percutaneously performing a lithiasic expulsion of a low ureteral calculation located, in particular by the use of balloon catheters.

Endo-Urological Techniques:

The role of radiology is not negligible in the realization of these techniques which systematically use the radioscopic guidance. In addition, in case of difficulty in introducing endoureteral devices (ureteroscopy), the urologist may benefit from the percutaneous insertion of an endovascular metal guide allowing him to catheterize the ureter (technique of “Cableway”).

Many percutaneous techniques use percutaneous approach: mainly percutaneous nephrolithotomy for ablation of calculations, anterograde ureteroscopy or percutaneous surgery (treatment of certain syndromes of the pyelo-ureteral junction or of certain urothelial tumors). As part of this percutaneous approach, the radiologist can bring his know-how in spatial location and radiological guidance. The effectiveness, ease and low morbidity of the intervention are in fact largely dependent on the quality of the percutaneous approach.

SPECIAL CASE OF THE KIDNEY:

Interventional radiology of the urinary tract plays a major role in the management of the urological complications of the renal transplant. These complications are of the order of 2 to 10% according to the series. These are mainly ureteral strictures, and more rarely fistulas. The ease of percutaneous approach (superficial kidney, in extraperitoneal position), the frequent difficulties of retrograde catheterization due to bladder reimplantation, largely explain the preference for percutaneous approach.

Surgical treatment is difficult and can result in graft loss. The importance of early diagnosis and therapeutic management in relation to the quality of the therapeutic outcome must be emphasized.

In stenosis, the therapeutic choice is based on the nature of the stenosis and its date of occurrence. The establishment of an NP is the first step to improve the patient’s condition and renal function and to discuss the most appropriate strategy, depending on the type of stenosis found on the antegrade pyelogram. In cases of early stenosis by anastomotic edema, NP is sufficient. In other cases, a double J probe must be fitted, the effectiveness of which will be all the greater as the stenosis is short and recent. Ureteral dilation with a balloon catheter may be associated with the double J probe, when the stenosis occurs at a distance from the graft.

In the case of a fistula, the NP is also the first step that allows the opacification and the evaluation of the breach size.In case of total discontinuity, surgery should be considered. In other cases, the treatment is based on the placement of a double probe J by anterograde.

Puncture techniques and therapeutic drainage of the urinary tract

Guided biopsies, although invasive techniques, are not, strictly speaking, part of interventional radiology gestures, since they are not therapeutic. They are common practice but are not contemplated in this chapter.

PERCUTANEOUS COLLECTION DRAINAGE TECHNIQUES:

Widely used in the abdominal cavity, these techniques are also useful for all the renal and / or retroperitoneal or pelvic collections, whether urinary, hematic, purulent or mixed. In all cases, the preliminary detection has benefited from the contribution of the techniques of imaging in sections. The CT scan is particularly well suited for topographing the lesion, assessing the best approach, respecting noble structures, and assessing the importance of the collection, its relationships and the degree of compartmentalization. Ultrasound or ultrasound scanning has the advantage of flexibility of use and the possibility of making oblique approaches, avoiding certain structures and scanning the advantage of precision. This guided puncture allows the exact identification of the collection and in particular the bacteriological analysis. It is followed by the installation of the drainage device, carried out under fluoroscopic control.The existence of several pockets or partitions can lead to the installation of several drainage catheters. The caliber of the catheters must be adapted to the more or less thick nature of the collection. The drain allows opacification of the pouch and, in particular, the search for abnormal communication with neighboring structures (urinary tract, digestive tract). The association with urinary tract drainage should be considered in cases of urinoma associated with obstruction of the excretory pathways. Drain monitoring is clinical, radiological (pocket opacification and CT).

The decision to withdraw is made after a prolonged drying-off of catheter flow, prolonged apyrexia, associated with the absence of residual cavity on radiological examinations.

The indications concern the urinomas, communicating or not with the excretory pathways, the postoperative lymphoceles (especially after transplantation) and especially the abscessed collections. In the case of hematomas, drainage should be considered with caution, in case of severe compressional phenomena or suspicion of superinfection. Percutaneous drainage is the treatment of choice for kidney abscesses, perinephritic phlegmons or postoperative abcdal collections. The results are of good quality in 85% of the cases.

Failures occur in the case of multiclocated abscesses, insufficient drainage, premature withdrawal of the drainage catheter or in case of communication with the digestive tract.

SCLEROTHERAPY OF POSTOPERATIVE KYSTS AND LYMPHOCLES:

Simple removal of renal cystic cavities is insufficient to remove the cyst. Sclerotherapy can be proposed by injecting a sclerosing agent inside the cystic cavity: absolute alcohol placed in the cavity for 15 to 20 minutes. The success rate exceeds 90% if the session is repeated at 48-hour intervals. This technique should be reserved for compressive and symptomatic cysts.

An identical technique may be proposed for the treatment of postoperative lymphocele, especially after renal transplantation. However, the effectiveness of this treatment is limited and it is frequently necessary to repeat the sessions of sclerosis, whatever the agent used (alcohol, tetracycline, polyvidone iodine). The efficacy of surgical marsupialization is increasingly preferring this technique to percutaneous sclerotherapy.

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