Vascular and Renal Interventions

• Interventional radiologists aid urologists with elective and emergency patients through percutaneous and endovascular procedures.

Goals of Interventional Radiology in Urology

• Decompress an obstructed kidney, a frequent operation for interventional radiologists.
• Restore renal-bladder flow, restoring flow of the ureter.
• Prevent aneurysm bursting.
• Restore renal artery patency.
• Stop ongoing hemorrhage.
• Stop priapism.
• Ablate kidney tumors.
• Drain post-surgical collection.

Decompression of an Obstructed Kidney

• Kidney obstruction is commonly caused by kidney stones at the ureteropelvic junction,.
• Other causes include urothelial tumors and strictures.
• Obstruction leads to engorgement of the kidney, resulting in hydronephrosis (dilation of the renal system).
• Symptoms include severe pain, infections, and reduced renal function.
• Untreated hydronephrosis may cause renal insufficiency as the kidney cortex scars and becomes fibrotic.
• Hydronephrosis is considered an emergency, kidney decompression should be immediate.
• Waiting longer increases the risk of infection and urosepsis.
• Obstructed kidney cases are urgent, but obstructed kidneys with infection are emergent requiring immediate drainage.
• Complete recovery of glomerular filtration rate is possible within one week of obstruction, but there is limited recovery after 12 weeks.

Direct Catheter Placement into the Renal Pelvis

• Patient is in a slight or complete lateral decubitus position.
• A probe identifies obstructed kidney.
• A 21 gauge needle punctures the kidney under ultrasound guidance, used to administer local anesthesia.
• Chiba needles are thin and long.
• A small metallic guide wire goes through the needle into an accessible calyx to access the urinary system.
• A slightly larger catheter containing a slightly larger guide wire is placed over the initial guidewire.
• The size of catheters is continuously increased along the guidewires to place a nephrostomy tube.
• The nephrostomy tube is 8 French (Fr), where 1 French is equal to 1/3 of a millimeter.
• Therefore the 8 French nephrostomy tube possesses an internal lumen of 2.66mm.
• The tube has a circular ‘pigtail' shape with holes at its end, drains urine from the calyx into a urine bag, decompressing the kidney.
• Contrast opacifies the urinary system to visualize the calyxes and enlarged renal pelvis.
• Once the nephrostomy is placed, contrast is drained out to relieve pressure and drain the kidney.
• The hybrid room provides easier access and dedicated personnel, helping interventional radiologists perform the procedure.
• Postprocedure management monitors infection, bleeding or stent displacement with follow-ups for catheter management and renal function recovery.

Restore Renal-Bladder Flow

• Urinary tract obstructions block the flow of urine from the kidney to the bladder can be due to kidney stones, strictures, and tumors.

Percutaneous Antegrade Ureteral Stent Placement (PAUS)

• Stent placement uses the same technique as nephrostomy placement.
• A guidewire is placed, inserted, following the ureter to reach the bladder.
• A complete stent goes over wire, the shown stent has pigtails, a typical feature of drainage catheters, also called double J or double pigtail.
• This drains the pelvis and bladder to restore the flow.
• Patients typically have an indwelling bladder catheter.
• Nephrostomy tube is used in severe urosepsis cases to immediately completely drain the urinary system.
• PAUS has a high technical success rate at 97% in neoplastic and 100% in non-neoplastic cases.
• Potential complications include stent malposition, urinary tract infection, and occlusion, major complications involve percutaneous nephrostomy, hematoma, or abscess.
• Risk of damaging an artery is possible and avoided using thin needles.
• A possible complication is perirenal hematoma or bleeding.
• The evolution from directly puncturing the kidney with a large needle was mainly to avoid the complication of kidney laceration.
• 21 gauge reduces the risk of severe damage in frail patients or those with coagulation disorders.
• Other potential complications include perforation of the renal calyces or the renal pelvis.
• Color doppler cannot ensure avoidance of invisible, small arteries.
• The best area is at the bulge.
• The perfect procedure occurs without complication if the hydronephrosis is more severe.

Prevent Aneurysm Burst

• An aneurysm is a vascular abnormality.
• More common in females, especially during pregnancy.
• Aneurysm rupture risk increases with size, mainly growing larger than 2 cm.
• Hypertension, smoking, atherosclerosis, and genetic factors (fibromuscular dysplasia) aneurysm.
• Renal artery aneurysms (RAAs) are rare, but may occur after an echogenic puncture.
• Saccular aneurysms are most common.
• RAAs are difficult to surgically treat, commonly resulting in nephrectomy.
• A ruptured aneurysm in the kidney, which is highly vascularized with high blood flow, is a grave emergency that can result in hypovolemic shock and death.
• Requires special attention and follow-ups. If aneurysm size increases between scans, treatment is required.

Endovascular Treatment of RAAs

• Treatment includes coiling of the aneurysm, placing a metallic coil inside to stop flow.
• The coil is made of tungsten, stopping flow into the vessel via spontaneous thrombosis.
• Complex cases use liquid embolic agents like Onyx with high success and high kidney sparing.
• To protect the renal artery, a stent is placed to block the coil entry, completes renal aneurysm exclusion without any loss of kidney parenchyma.

Renal Artery Stenting

• Renal artery stenosis (RAS) is the narrowing of the lumen of the renal artery, results from atherosclerosis and fibromuscular dysplasia.
• RAS can lead to hypertension, renal insufficiency, pulmonary edema, unstable angina.
• Stenotic renal artery means no chance for collateral circulation because the kidney has terminal vascularization.
• Therefore the renal artery should be reopened and the kidney revascularized at all costs.
• Procedure aims to open the artery.
• Renal artery stenting/angiography is successful with less than 30% residual stenosis after the procedure.
• Arterial pressure is measured.
• GFR determines result.
• Lesion at artery origin indicates clinically significant stenosis.
• A metallic guidewire goes in with a stent.
• Stent is released.
• Main Stent Types: balloon mounted (balloon inflates, expands stent), nitinol stents (non-balloon assisted release, open, restore size).
• The radial force keeps the artery open. Cost may mean using one stent kind.
• Renal artery prefers less costly/simpler balloon stent.
• Carotid prefers nitinol stent.
• Balloon mounted stent steel doesn't return to compressed size, alloy of nickel and titanium is more elastic and functions better under more pressure.

Questions Summary

• Radial axis allows same-day discharge, however, radial artery is very small for some patients over 50 with small arteries that are 1-2mm.
• 9mm Stent in 7mm artery: artery is overextended, the arterial muscular constricts the stent during first period, neo-endothelialization keeps stent in place.
• Moveable arteries (brachial, axillary) increases dislocation and fracture, surgical patch is favored over stent.
• Stretched common femoral artery has fracture risk.
• Stenosis in renal artery origin is easy.
• Special wire with pointier edge reopens flow of plaque.
• 30 minute procedure, usually.

Stop Ongoing Hemorrhage

• Renal hemorrhage is very urgent from trauma, neoplasm, or iatrogenic causes.
• Angiography identifies active bleeding, AV fistula, or pseudoaneurysms.
• Contrast enhanced CT assesses the bleeding.
• Patient is rushed to angiography undergo superselective catheterization.

Superselective Catheterization

• Liquid embolic agents are preferred to coils because glue is more effective as it does not rely on spontaneous thrombosis.
• Important because there is no time to wait for the blood to coagulate with coils (platelet count in bleeding patients).
• Coils are used in bleeding is limited/situations.
• Embolic agents balance hemostasis and renal preservation.
• There is a post operation follow up of complications, renal atrophy/potential hypertension.

Case of an Iatrogenic Pseudoaneurysm

• Pseudoaneurysm does not have arterial walls.
• Pseudoaneurysm is a temporary fix body, creates around bleeding via retroperitoneal/renal tissue.
• Unstable: inevitably enlarges and causes bleeding.
• Renal hilum, patient has hematuria due to urinary disconnection, kidney angled.
• Microcatheter, catheter treated by injecting glue.
• The result is complete preservation of renal function via glue.
• Renal angiography involves spasms showing renal laceration where blood flow suggests embolization is needed.
• The third image shows contrast leaving the kindey. We performed our glue embolization and final contrast which shows how glue has been placed and there is no ongoing bleeding.

Stop Priapism

• Priapism is not very common
• There is no surgery in that area without a scar or dysfunction of the penis.
• Primary cause is trauma arteriovenous fistula and cavernous arteries laceration from trauma (bike riders).
• Results in irregular blood flow to the vascular lacunae of erectile tissue.
• Color doppler identifies fistula, first line conservative treatment that can be treated with embolization may be employed.
• Recurrence of priapism after embolization is 20%, high success and can be repeated.
• Highlight the AV fistula.
• MRI shows contrast enhancement of the left cavernous corpus.
• Angiography of perineal Artery shows AV fistula, fixed using coils (patient is not bleeding, more gentle, less risk), or glue to stop flow.
• The glue can glue the Corpus Cavernosum. Small coils cause the AV to close with less risk.

Ablate Kidney Tumors

• Increased incidental diagnosis of renal tumors from frequent CT/MRI use.
• Old treatment/Partial nephrectomy to treat 2 cm tumor: robot-assisted resection but expensive.
• Ablation is very easy to burn tumor.

Tumor Ablation Modalities

• Renal tumor ablation is done quite often.
• Radiofrequency ablation uses high frequency alternating current causing cell death.
• Effective if under 4 cm, gentle to the non-malignant tissue.
• Microwave ablation by electromagnetic waves produces higher temperatures.
• Should be used carefully for larger tumors, or more centrally located tumors.
• Cryoablation creates extreme cold (using a probe) inside the kidney.
• Is costly but very effective.
• Ball can be extended as cold not as damaging as microwaves.

Other Ablation Modalities

• Laser ablation delivers light energy transformed into heat, best for exophytic lesions.
• High-Intensity Focused Ultrasound (HIFU), non invasive option; uses waves raise tissue temperature and cause coagulative necrosis.

Radiofrequency Ablation Example

• Don every Monday. Needle places inside tumor, renal cell carcinoma.
• Little bleeding. Gas bubbles/heat means ablation occurs, hematoma is fine.
• A 12 minute procedure under conscious sedation, no stitch/banding, patient discharged next day.

Questions Summary

• Ablate a safe margin: 2 cm tumor, ablate to 4 cm. Is well perforformed results for good. There is no difference between resection and ablation because safe margins are needed otherwise the procedure isn't curative.
• Cryoablation: Ice probe placed inside the lesion creating ice ball which may be extended.
• Use in kidney is uncommone, ablation over embolization
• Large tumor is considered palitative because of the metestasized area.
• Kidney means only ablation/embolization performed.

Drain Post-Surgical Collection

• Common perioperative complications include lymphoceles, urinomas, abscesses, after transplants/pelvis surgery.
• Post surgical collections compress adjacent structures causing pain, infection, impairment.
• Not limited to renal urogenital districts, many surgeries districts.
• The temperature in the ice ball is not even/needs calculation to expose to the right temperature making it very expensive.

Procedure

• Patient is placed prone and is punctured and a pigtail catheter is used to drain fluid.
• Catheter type depends on collection of fluid, small (serous), large bore (viscous/purulent).
• The success of the procedure is determined by symptom resolution, which occurs when there is a decreased collection size and absence of infection/obstruction on imaging.

Explore vascular risks like femoral artery stenting and renal artery stenosis sites. Discusses initial steps for treating severe atherosclerosis and the approach for large blockages. Outlines angiography's purpose and embolic agent preferences in renal hemorrhage, contrasting techniques and rationales.