Main techniques of interventional radiology in urology PDF

‭ ephrology and Urology‬ N ‭Ezio Lanza - Radiology - Lesson 03:‬ ‭ ain techniques of interventional radiology in urology‬ M ‭13/12/2024...

‭ ephrology and Urology‬ N ‭Ezio Lanza - Radiology - Lesson 03:‬ ‭ ain techniques of interventional radiology in urology‬ M ‭13/12/2024 - Group 4 (Awwad and Paolini)‬ ‭ he role of interventional radiology and nephrology and urology:‬ T ‭Interventional radiologists are able to aid urologists in their elective and emergency patients by‬ ‭performing percutaneous and endovascular procedures. The main goals of these procedures are‬ ‭the following:‬ ‭1.‬ ‭To decompress an obstructed kidney‬ ‭a.‬ ‭This is one of the most frequent cases in which interventional radiologists operate.‬ ‭2.‬ ‭To restore renal-bladder flow‬ ‭a.‬ ‭i.e To restore the flow of the ureter.‬ ‭3.‬ ‭To prevent the bursting of an aneurysm.‬ ‭4.‬ ‭To restore of renal artery patency‬ ‭5.‬ ‭To Stop ongoing hemorrhage:‬ ‭○‬ ‭The professor proceeds to describe a case he was involved in:‬ ‭‬ ‭The day prior the professor had performed the emergency embolization of‬ ‭a bleeding angiomyolipoma of the adrenal gland.‬ ‭‬ ‭The patient was a 48 year old, male, truck driver who was otherwise‬ ‭healthy. The patient presented with severe pain in his left flank on the‬ ‭posterior aspect of his abdomen.‬ ‭‬ ‭This angiomyolipoma started bleeding profusely resulting in a large‬ ‭retroperitoneal hematoma.‬ ‭‬ ‭The professor was called by the urology department due to the high risk‬ ‭associated with undergoing a severe surgery in this situation, as well as the‬ ‭fact that they did not know how to go about stopping the bleeding.‬ ‭‬ ‭In this case the surgical option was to undergo a large‬ ‭retroperitoneal ablation , which is quite a significant intervention.‬ ‭‬ ‭Rather than undergoing such a surgery, an emergency embolization was‬ ‭performed and in fact the patient did not need any surgery whatsoever.‬ ‭6.‬ ‭To stop priapism‬ ‭○‬ ‭Priapism is the arteriovenous fistula between the vein and the artery of the penis.‬ ‭○‬ ‭This is an emergency situation as the condition is very painful and may result in‬ ‭the sclerosus of the penis‬ ‭‬ ‭Sclerosus may impact the sexual and urinary function of the penis‬ ‭7.‬ ‭To ablate kidney tumor‬ ‭○‬ ‭This is done frequently, around every week.‬ ‭1‬  ‭○‬ T ‭ his is a way to avoid surgery, sparing renal parenchyma for a patient who is‬ ‭already oncological and therefore may also be undergoing other treatments and‬ ‭may require multiple procedures in their lifetime.‬ ‭8.‬ ‭Drain post-surgical collection‬ ‭○‬ ‭This point is not solely related to urology as it extends to other surgical specialties‬ ‭with which an interventional radiologist may collaborate.‬ ‭Decompression of an Obstructed Kidney‬ ‭ bstructed Kidney:‬ O ‭Kidney obstruction is most frequently due to kidney stones lodged at the ureteropelvic junction,‬ ‭obstructing the flow of urine. Other potential causes of obstruction include urothelial tumors, and‬ ‭strictures. The result of such an obstruction is an engorgement of the kidney resulting in‬ ‭hydronephrosis, a dilation of the renal system. The symptoms of this condition include severe‬ ‭pain, infections, and reduced renal function. If untreated, hydronephrosis may lead to renal‬ ‭insufficiency as the cortex of the kidney scars and becomes fibrotic. Therefore hydronephrosis is‬ ‭considered an emergency. Typically one may wait up to 24 hours before decompressing the‬ ‭kidney, however, the sooner the obstructed kidney is decompressed the better the outcome.‬ ‭Another consideration is that the longer that the collection of urine remains in place the higher‬ ‭the risk of infection, hence the longer one waits the higher the risk of urosepsis. Typically an‬ ‭obstructed kidney is considered an urgent rather than an emergent case. Cases of obstructed‬ ‭kidney with infection, however, are considered emergent and require emergent drainage.‬ ‭Complete recovery of glomerular filtration rate is possible with up to one week of obstruction;‬ ‭there is limited recovery of glomerular filtration after 12 weeks.‬ ‭ irect Catheter Placement into the Renal Pelvis:‬ D ‭The patient is positioned in a slight decubitus or even in a complete lateral decubitus. A probe is‬ ‭used to identify the obstructed kidney. Under ultrasound guidance the kidney is punctured with a‬ ‭21 gauge needle. A 21 gauge needle is considered very small, and is typically used to administer‬ ‭local anesthesia. The needle used is very thin, and long. They are called Chiba needles. Once the‬ ‭dilated renal pelvis is reached, a small metallic guide wire from inside the needle is inserted into‬ ‭the most accessible calyx to access the urinary system. A slightly larger catheter containing a‬ ‭slightly larger guide wire is placed over this initial guidewire. Using this system in which the‬ ‭size of the catheters is continuously increased along these guidewires, a nephrostomy tube is‬ ‭eventually placed. The nephrostomy tube is 8 French (Fr). A French is equivalent to ⅓ of a‬ ‭millimeter, hence the 8 French nephrostomy tube possesses an internal lumen of 2.66mm. The‬ ‭nephrostomy tube is a catheter with a characteristic circular ‘pigtail’ shape at its end. There are‬ ‭many holes in the pigtail allowing the catheter to drain a wide area. The urine inside the calyx is‬ ‭pushed by the pressure into the catheter eventually reaching a urine bag. As a result of this‬ ‭procedure the kidney is decompressed.‬ ‭2‬ ‭ ontrast is initially injected to opacify the urinary system, aiding in the visualization of the‬ C ‭calyxes and enlarged renal pelvis. Once the nephrostomy is placed all the contrast is drained out‬ ‭as the pressure has been relieved and the kidney has been drained.‬ ‭This is a very frequently performed procedure. Both urologists and interventional radiologists are‬ ‭able to perform it. Who performs this procedure is dependent on the availability of the operating‬ ‭room. The interventional radiologist’s access to a hybrid room, which is easier to access, has‬ ‭dedicated personnel making it easier for interventional radiologists to perform this procedure.‬ ‭Urologists need to use the operating room, and therefore must follow its more intense schedule.‬ ‭Postprocedure management includes monitoring for complications such as infection, bleeding or‬ ‭stent displacement. There should be regular follow-ups for catheter management and assessment‬ ‭of renal function recovery.‬ ‭Restore renal-bladder flow‬ ‭ rinary tract obstructures‬ U ‭Most urinary tract obstructions that block the flow of urine from the kidney to the bladder are‬ ‭due to kidney stones, strictures, and tumors.‬ ‭ ercutaneous antegrade ureteral stent placement (PAUS):‬ P ‭A stent can be placed with the same technique used to place a nephrostomy, however, instead of‬ ‭stopping with a nephrostomy a guide wire is placed. The guidewire is inserted, following the‬ ‭course of the ureter to reach the bladder. Over the guidewire a complete stent is placed. In this‬ ‭image the stent is placed above the guidewire which is still inside. This stent also has pigtails‬ ‭which is a typical feature of drainage catheters. This stent has two pigtails (also called double J‬ ‭or double pigtail) so that it may drain the pelvis and the bladder in order to restore the flow‬ ‭between them. These patients typically also have an indwelling bladder catheter. A nephrostomy‬ ‭tube can also be placed in very severe cases with urosepsis in order to completely drain the‬ ‭urinary system immediately.‬ ‭3‬ ‭ his procedure has a high technical success rate at 97% in neoplastic and 100% in‬ T ‭non-neoplastic cases. Potential complications include stent malposition, urinary tract infection,‬ ‭and occlusion. More major complications are related to percutaneous nephrostomy such as‬ ‭hematoma or abscess.‬ ‭ uestion: Since you enter by puncturing the kidney, isn't there the risk of damaging some‬ Q ‭artery?‬ ‭Of course there is such a risk, a possible complication is perirenal hematoma or even severe‬ ‭bleeding. This is why very thin needles are used: this is an advancement from the classical‬ ‭technique in which the kidney was directly punctured with a needle as large as the nephrostomy‬ ‭tube. The evolution away from this was made mainly to avoid the complication you mentioned,‬ ‭the laceration of the kidney. Though this procedure may still incur some damage, particularly in‬ ‭very frail patients or those with coagulation disorders, the risk of doing severe damage with a 21‬ ‭gauge needle is minimal. Other potential complications include the perforation of the renal‬ ‭calyces or the renal pelvis. This is not a major problem. If it happens you can see the contrast‬ ‭leaving the renal pelvis however since it is not a high pressure system it goes on without any‬ ‭issues.‬ ‭ uestion: Is there a way to utilize colour doppler in this procedure to avoid blood vessels?‬ Q ‭Yes, but you can't be sure as the kidney is vascularized by invisible, small arteries. Looking at‬ ‭the kidney from the lateral view, there is a visible bulge. This bulge is at the region in which the‬ ‭two embryological structures fused to form the kidney. Some studies say that this region is the‬ ‭least vascularized, and hence the best to puncture. In the professor’s opinion, this area is not‬ ‭always targetable as a dilated calyx is needed and there may not be one in that area. The rule is to‬ ‭target the most accessible calyx. The more severe the hydronephrosis the easier it is to perform‬ ‭the perfect procedure without complication. In cases where a non-dilated kidney must be‬ ‭drained, for instance if there is a distal laceration of the urinal allowing urine to fall into the‬ ‭4‬ r‭ etroperitoneum, the procedure is much more difficult as non dilated, decompressed calyxes have‬ ‭a much higher risk for bleeding as they typically require several attempts to be reached. To sum‬ ‭it up, if you see a dilated calyx which you are confident can be reached with one move, that is the‬ ‭best target regardless of vascularization. Performing the procedure with a single puncture is the‬ ‭most effect way to minimize the risk‬ ‭Prevent aneurysm burst‬ ‭ neurysm:‬ A ‭An aneurysm is a vascular abnormality. There are many different types of aneurysms.‬ ‭Aneurysms are most common in female patients especially during pregnancy. The risk of‬ ‭aneurysm rupture increases with size, particularly when they grow larger than 2 cm.‬ ‭Hypertension, smoking, atherosclerosis, and genetic factors like fibromuscular dysplasia are risk‬ ‭factors for aneurysm. Though renal artery aneurysms (RAAs) are rare they may occur after an‬ ‭echogenic puncture. Saccular aneurysms are most common. RAAs are difficult to treat‬ ‭surgically, and such an approach typically results in nephrectomy. Since the kidney is highly‬ ‭vascularized and has a high blood flow an ruptured aneurysm in this district is a grave‬ ‭emergency. Such a situation can easily end in the death of the patient due to hypovolemic shock.‬ ‭This is something which requires special attention, including follow ups. If there is an increase in‬ ‭the size of the aneurysm between two scans then some sort of treatment is required.‬ ‭ ndovascular treatment of RAAs:‬ E ‭There are many different materials that may be used in this treatment. The most common‬ ‭treatment involves the coiling of the aneurysm. Coiling is a term that indicates the placement of a‬ ‭metallic coil inside the aneurysm. The coil is usually made of tungsten. These coils are used to‬ ‭stop the flow into a vessel via spontaneous thrombosis. In more complex cases liquid embolic‬ ‭agents, such as a special glue named Onyx, are employed. Overall this procedure has a high‬ ‭success rate and spares much, if not all of the kidney.‬ ‭This is a very large saccular aneurysm of the right kidney. If approached surgically it is a sure‬ ‭nephrectomy. Instead a catheter was placed inside the aneurysm to fill it with a large coil. In‬ ‭order to protect the renal artery a stent was placed so that the coil would not enter it. The result is‬ ‭the complete exclusion of the renal aneurysm without any loss of kidney parenchyma as‬ ‭angiography reveals that the kidney is still completely vascularized. In the third image there is a‬ ‭beaming artifact that the metallic coil creates when studied with CT.‬ ‭5‬ ‭Renal artery stenting.‬ ‭ enal artery stenosis:‬ R ‭Renal artery stenosis (RAS) refers to the narrowing of the lumen of the renal artery. This is‬ ‭commonly caused by atherosclerosis and fibromuscular dysplasia. RAS can lead to hypertension,‬ ‭renal insufficiency, pulmonary edema, and unstable angina. If the renal artery is stenotic, there is‬ ‭no chance for collateral circulation as the kidney possesses a terminal vascularization, therefore‬ ‭the renal artery should be reopened and the kidney revascularized at all costs.‬ ‭ AS stenting:‬ R ‭Instead of closing an aneurysm or an artery, in this case the procedure aims to open the artery. A‬ ‭renal artery stenting or angiography is considered successful if there is less than 30% residual‬ ‭stenosis after the procedure. A measurement of the arterial pressure can also be employed to‬ ‭determine if the procedure was successful. Another option to determine the outcome of the‬ ‭procedure is to measure the GFR.‬ ‭In this renal angiography the renal artery is well enhanced with the exception of a defect at the‬ ‭origin of the artery. This indicates a clinically significant stenosis. The decision was made to‬ ‭treat this stenosis before it could worsen, causing renal failure. A metallic guidewire is advanced‬ ‭into the renal artery, and over the guidewire there is a stent. When satisfied with the position the‬ ‭stent is released and it automatically opens and expands. There are 2 main types of stents. The‬ ‭first is a balloon mounted stent, in which a balloon inflates. expanding the stent and releasing it‬ ‭into the artery. The other type which are non-balloon assisted release of the stent called nitinol‬ ‭stents which open and due to their spontaneous radial force they tend to restore their size creating‬ ‭a radial force which keeps the artery open. Technical reasons and cost may favor the use of one‬ ‭kind of stent over the other. In the renal artery the less costly and simpler balloon stent is‬ ‭preferred as the renal artery does not move. In the carotid however the balloon stent isn't the best‬ ‭option, and it is preferred to use an nitinol stent. The balloon mounted stent is made of steel‬ ‭which when compressed doesn't return to its original size. Instead this alloy of nickel and‬ ‭titanium is more elastic and tends to function better under pressure and different forces. In the‬ ‭final image the stent has been opened and the renal artery is now enhanced homogeneously.‬ ‭6‬ ‭ his procedure is very quick and easy. It can be done either via the femoral or radial axis. The‬ T ‭axis employed is a matter of preference. The advantage of the radial axis is that the patient can‬ ‭be discharged on the same day as the procedure, whereas with the femoral axis there is need for‬ ‭followup on the subsequent day. On the contrary, the radial artery is very small and is not large‬ ‭enough for this procedure in every patient, in particular, small women above 50 years of age as‬ ‭they have tiny radial arteries 1-2 mm.‬ ‭ uestion: Does the stent stay there on its own because the aortic goes into the iliac‬ Q ‭branches?‬ ‭Yes because it's not the iliac legs that keep the aortic stent in place, what keeps the stent in place‬ ‭is the size. If you have a 7mm artery and place a 9mm stent the artery is slightly overextended‬ ‭and its muscular tissue, in return, compresses the stent. So there is an exchange of forces‬ ‭between the stent and the artery. This keeps the stent in place in the first period. After around a‬ ‭few months neo-endothelialization of the stent takes place. New endothelium grows inside the‬ ‭stent causing it to become incorporated into the artery. There are cases of stent dislocation and‬ ‭fracture, especially if the artery is movable. If the brachial or axillary artery are stented, for‬ ‭instance in an emergency after trauma, this may lead to problems. For this reason, even in the‬ ‭carotid artery, a surgical patch is favored over a stent. This also applies to the common femoral‬ ‭artery as a stent would be stretched everytime the thigh is flexed therefore the risk of fracture is‬ ‭high.‬ ‭ uestion: How long does the procedure last?‬ Q ‭Duration depends on the difficulty of the procedure. This is a fairly easy stenosis, as the renal‬ ‭artery only has a single stenosis at the origin. The most frequent site of stenosis of renal artery is‬ ‭the origin. There are no problems entering the artery in this case. Sometimes in severe‬ ‭atherosclerosis, patients that are heavy smokers, or diabetic patients, there is a very diseased‬ ‭artery with several stenoses or a fully obstructive stenosis, meaning that it is not possible to enter‬ ‭with a guidewire. In this scenario you have to fight a little with the stenosis which causes the‬ ‭procedure to last longer as revascularization may be necessary before stent placement. A special‬ ‭guide wire with a pointier edge is used to reopen the flow inside the plaque. Sometimes a‬ ‭subintimal approach is necessary, a new channel in the intima is created if the block is very large.‬ ‭7‬ ‭ hese complications may cause the procedure to last longer. In this case it was a 30 minute‬ T ‭procedure.‬ ‭Stop ongoing hemorrhage‬ ‭ enal hemorrhage:‬ R ‭Renal hemorrhage is a very urgent situation resulting from trauma, neoplasm, or iatrogenic‬ ‭causes. Angiography identifies active bleeding, AV fistula, or pseudoaneurysms. Contrast‬ ‭enhanced CT is always performed to assess the extent of the bleeding. The patient is then rushed‬ ‭to the angiography room to undergo superselective catheterization.‬ ‭ uperselective catheterization:‬ S ‭Liquid embolic agents are preferred to coils in these cases. This is because glue is more effective‬ ‭as it does not rely on spontaneous thrombosis. This is important as there is no time to wait for the‬ ‭blood to coagulate such as in the case of coils, and in addition to this the platelet count in‬ ‭bleeding patients is diminished. Due to these limitations coil is only used in cases where bleeding‬ ‭is limited or in situations where it is possible to wait. Liquid embolic agents achieve an‬ ‭immediate result, however it is important to balance effective hemostasis with renal preservation.‬ ‭As much kidney function as possible should be preserved. After the procedure it is important to‬ ‭follow up with the patient immediately for complications. Long term changes such as renal‬ ‭atrophy or potential hypertension should be considered.‬ ‭ ase of an iatrogenic pseudoaneurysm‬ C ‭Prior to the case here is a quick reminder on the differences between an aneurysm and‬ ‭pseudoaneurysm. A pseudoaneurysm looks like an aneurysm, however, it does not have arterial‬ ‭walls. The pseudoaneurysm is a temporary fix that the body creates around bleeding. There is a‬ ‭bleeding point and the surrounding tissue creates a barrier as a response. This tissue may be‬ ‭retroperitoneal, or renal as it is in the following case. A pseudoaneurysm is not a stable finding, it‬ ‭will inevitably enlarge and result in active bleeding. An aneurysm on the other hand, is‬ ‭something you can reflect on as there is an arterial wall containing the aneurysm allowing the‬ ‭physician to take their time in their approach. An aneurysm must be ruptured to result in active‬ ‭bleeding whereas the pseudoaneurysm is already a form of active bleeding. The pseudoaneurysm‬ ‭in this case was formed due to the placement of a double J Ureteral stent. The pseudoaneurysm is‬ ‭this dense sphere, in the centre of the renal hilum. This patient had hematuria due to connection‬ ‭with the urinary system. Starting with angiography we find that the kidney is in a very oblique‬ ‭position. Using a microcatheter, a catheter contained within another catheter, the‬ ‭pseudoaneurysm is treated by injecting it with glue.‬ ‭8‬ I‭ f you take a closer look at the first image below though contrast has not been injected yet the‬ ‭results are apparent as the glue is dense and hence radiopaque. There is a cast of glue in the area‬ ‭of the pseudoaneurysm. When contrast is injected it flows back to the other branches of the renal‬ ‭artery but does not enhance the pseudoaneurysm anymore. The result is complete preservation of‬ ‭renal function‬ ‭ he case of a polytraumatic patient‬ T ‭This more severe case involves a polytraumatic patient from a motorcycle accident. There is a‬ ‭large retroperitoneal hematoma on the right side. The arrow indicates active bleeding. Renal‬ ‭angiography is performed revealing spasms inside the renal artery due to the active bleeding. The‬ ‭several dots in the second image indicate renal laceration as blood is freely flowing here‬ ‭suggesting that this is a good spot to perform embolization. Super selective catheterization of the‬ ‭lower pole renal artery branches was performed. In the third image you can see the contrast is‬ ‭leaving the kidney. We perform our glue embolization and final contrast angiography, in the‬ ‭fourth image, highlights how the cast of glue has been placed and there is no ongoing bleeding‬ ‭9‬ a‭ nymore, saving the kidney. The only alternative is a very risky emergency kidney nephrectomy‬ ‭with high risk of death. This is because when you open the abdomen in a case like this you only‬ ‭see a huge hematoma. The pressure is relieved causing faster bleeding free to flow at its‬ ‭maximum potential, and you are not even able to see the kidney or renal artery. It's better to treat‬ ‭it conservatively (also perseveres the kidney).‬ ‭6. Stop priapism‬ ‭ riapism‬ P ‭Priapism is not a very common condition. There is no possible surgery in this area which will not‬ ‭leave a scar or a dysfunction of the penis. The primary cause of this condition is trauma leading‬ ‭to an arteriovenous fistula. This may happen to bike riders with trauma to the perineal region‬ ‭after an accident. Laceration of a cavernous artery results in persistent and irregular blood flow‬ ‭to the vascular lacunae of the erectile tissue.‬ ‭Embolization techniques:‬ ‭10‬ ‭ ontrast color doppler is used to identify the arteriovenous fistula. When first line conservative‬ C ‭treatment fails embolization techniques may be employed. It is important to avoid excessive‬ ‭embolization as this may cause erectile dysfunction. Evidence from the literature indicates that‬ ‭the recurrence of priapism after embolization is around 20% however there is a high rate of‬ ‭clinical success and embolization can be repeated. This first image is from outside of Humanitas,‬ ‭and in this case color doppler is used to highlight the AV fistula. This second image is an MRI in‬ ‭which we see contrast enhancement of the left cavernous corpus and angiography of the perineal‬ ‭artery demonstrates AV fistula which in this case is fixed using coils. We may use coils as we are‬ ‭not in a rush as the patient is not bleeding, the coils are more gentle and there is less risk of‬ ‭entering the venous side of the AV fistula. The glue risks glueing the corpus Cavernosum. Small‬ ‭coils instead cause the AV to close with less risk.‬ ‭Ablate kidney tumors‬ ‭ mall renal tumors:‬ S ‭There has been an increase of incidental diagnosis of renal tumors, particularly small renal‬ ‭tumors due to follow up and frequent CT and MRI use. When there is 2 cm renal tumor its old‬ ‭treatment was partial nephrectomy, and nowadays there is robot-assisted resection but it is very‬ ‭expensive and is not free from risks. On the contrary, ablation is a very easy way to burn a tumor.‬ ‭ umor ablation modalities:‬ T ‭Renal tumor ablation is done quite often. Radiofrequency ablation utilizes a high-frequency‬ ‭alternating current to produce heat and cause cell death. This method is effective for tumors‬ ‭under 4 centimeters and is the preferred ablation modality as it is more gentle to the non‬ ‭malignant tissue. Microwave ablation employs electromagnetic waves producing higher‬ ‭temperatures than radiofrequency ablation. This modality is very destructive and must be used‬ ‭with care and precision to avoid excessive ablation, making it better suited for larger tumors or‬ ‭more centrally located tumors. Cryoablation is another option which is very costly but effective.‬ ‭In this technique a probe is used to create extreme cold inside the kidney. Cold is equally if not‬ ‭more effective in destroying tumoral tissue than heat. The ice ball utilized liquid nitrogen which‬ ‭11‬ h‭ as a very low temperature and is able to destroy malignant tissue. It is very expensive and‬ ‭somewhat impractical as the required gas is contained in large containers.‬ ‭ ther ablation modalities:‬‭these modalities were not‬‭mentioned in class however are included‬ O ‭in the slides:‬ ‭Laser ablation uses lasers to deliver light energy which is transformed into heat, this form is best‬ ‭suited for small exophytic lesions. Exophytic refers to solid organ lesions originating from the‬ ‭outer surface of their organ of origin. High-Intensity Focused Ultrasound (HIFU) is a‬ ‭non-invasive option which employs ultrasound waves to raise tissue temperature and induce‬ ‭coagulative necrosis‬ ‭ adiofrequency ablation example:‬ R ‭This procedure is done frequently, “every monday” according to the professor. The procedure is‬ ‭similar to a renal biopsy, only rather than just biopsying the kidney a needle is placed inside the‬ ‭tumor. In this case it's likely a renal cell carcinoma. There is a little bleeding in the image due to‬ ‭the biopsy however it is not a large concern as this area will be burnt. When satisfied with the‬ ‭position of the needle the ablation begins, extreme heat causes gas to form so it is normal to see‬ ‭some bubbles. After about 12 minutes of ablation the procedure is complete, the bleeding has‬ ‭stopped though there is some hematoma around the kidney though it is not of concern as long as‬ ‭it doesn’t grow. This procedure is performed under conscious sedation. No stitch or bandaging is‬ ‭needed. The patient may be discharged the day after the procedure with no pain.‬ ‭ uestion: Do you biopsy the margins to ensure there is no tumor‬ Q ‭No, but we ablate a safe margin so if the tumor is 2 cm ablate 4 cm. If ablation is well performed‬ ‭the results are the same as surgery. There is no difference between resection and ablation, safe‬ ‭margins are also needed in resection otherwise the procedure is not curative.‬ ‭ ryoablation example:‬ C ‭This is an example of cryoablation done under MRI guidance. An ice probe is placed inside the‬ ‭lesion creating a large ice ball. The ball can be extended quite a bit as cold is not as damaging to‬ ‭12‬ h‭ ealthy tissue as microwaves for instance. The temperature is not even throughout the ice ball, as‬ ‭it is warmer on the outside and cooler on the inside so there must be calculation so that the tumor‬ ‭is exposed to the most effective temperature. The end result is very effective though much more‬ ‭expensive.‬ ‭ uestion: Is it possible to not only ablate but to embolize to reduce growth?‬ Q ‭This is not commonly done for the kidney as ablation is both easier to perform and more‬ ‭destructive than embolization. In cases with large tumors, and where nephrectomy is not‬ ‭applicable ablation and embolization can be combined. This is considered a palliative treatment‬ ‭as a large renal tumor that can not undergo surgery has probably metastasized or the patient may‬ ‭be severely compromised. This is the only case in which embolization and thermal ablation are‬ ‭combined as the area of ischemia is much larger in this scenario and there is increased damage to‬ ‭the kidney. In the case of the liver this combination is more practical as the liver is larger and it‬ ‭regenerates. Instead in the kidney typically only ablation or only embolization is performed.‬ ‭To Drain post-surgical collection‬ ‭ ost surgical collections:‬ P ‭Common perioperative complications include lymphoceles, urinomas, and abscesses, especially‬ ‭after renal transplants or pelvis surgery. Diagnosis is done via ultrasound or CT, and ultrasound‬ ‭or CT are used for real-time guidance. Post surgical collections can compress adjacent structures‬ ‭causing pain, infection, and functional impairment. Post-surgical drainage is not limited to the‬ ‭renal urogenital districts and is applicable in a wide range of different surgeries across many‬ ‭districts. In the image below there is a collection of fluid due to pyelonephritis in the left kidney.‬ ‭13‬ ‭ rocedure:‬ P ‭The patient is placed in the prone position and the collection is punctured and a pigtail catheter is‬ ‭placed in order to drain the fluid. The catheter used depends on the fluid of the collection,‬ ‭small-pore pigtail catheters are used for serous fluid and large bore catheters are used for viscous‬ ‭or purulent collections. The success of the procedure is determined by symptom resolution,‬ ‭decreased collection size, and absence of infection or obstruction on follow-up imaging.‬ ‭ uestion: Is the drainage of an infected cyst done by an interventional radiologist or a‬ Q ‭nephrologist?‬ ‭We do it with a CT scan so it is done by interventional radiologist.‬ ‭14‬