Interventional radiology


Interventional radiology is a medical specialty that performs various minimally-invasive procedures using medical imaging guidance, such as x-ray fluoroscopy, computed tomography, magnetic resonance imaging, or ultrasound. IR performs both diagnostic and therapeutic procedures through very small incisions or body orifices. Diagnostic IR procedures are those intended to help make a diagnosis or guide further medical treatment, and include image-guided biopsy of a tumor or injection of an imaging contrast agent into a hollow structure, such as a blood vessel or a duct. By contrast, therapeutic IR procedures provide direct treatment—they include catheter-based medicine delivery, medical device placement, and angioplasty of narrowed structures.
The main benefits of IR techniques are that they can reach the deep structures of the body through a body orifice or tiny incision using small needles and wires. This decreases risks, pain, and recovery compared to open procedures. Real-time visualization also allows precision guidance to the abnormality, making the procedure or diagnosis more accurate. These benefits are weighed against the additional risks of lack of immediate access to internal structures, and the risks of radiation exposure such as cataracts and cancer.

Types

Common elements

Interventional radiology is a set of techniques that allows access to the internal structures of the body through body orifices or very small incisions and guidance with medical imaging. Regardless of the reason for the intervention, the procedure will likely use common elements such as a puncture needle, guidewires, a sheath, and catheters.
Also common to all intervention radiology procedures are the medical imaging machines that allow the healthcare provider to see what is occurring within the body. Some use X-rays and some do not. In each case, the images created may be modified by computer to better visualize the structures as is in the case with digital subtraction angiography, CT and MRI, or the display of the images improved with virtual reality or augmented reality presentation.

Diagnostic interventional radiology

  • Angiography: Imaging the blood vessels to look for abnormalities with the use of various contrast media, including iodinated contrast, gadolinium based agents, and gas.
  • Cholangiography: Imaging the bile ducts within the liver to look for areas of blockage.
  • Biopsy: Taking of a tissue sample from the area of interest for pathological examination from a percutaneous or transvenous approach.
  • Fine-needle aspiration: obtaining cells from a tissue or organ under ultrasound guidance.

    Therapeutic interventional radiology

Vascular
  • Balloon angioplasty/stent: Opening of narrow or blocked blood vessels using a balloon, with or without placement of metallic stents to aid in keep vessel patent.
  • Endovascular aneurysm repair: Placement of endovascular stent-graft across an aneurysm to prevent expansion or progression of the defective vessel.
  • Embolization: Placement of a metallic coil or embolic substance to block blood through to a blood vessel, either to stop bleeding or decrease blood flow to a target organ or tissue.
  • * Uterine artery embolization or uterine fibroid embolization
  • * Prostate artery embolization
  • * Pulmonary arteriovenous malformation embolization
  • * Hemorrhoidal artery embolization
  • * Splenic artery embolization
  • Thrombolysis: Catheter-directed technique for dissolving blood clots, such as pulmonary embolism and deep venous thrombosis, with either pharmaceutical or mechanical means.
  • IVC filters: Metallic filters placed in the vena cava to prevent propagation of deep venous thrombus.
  • Dialysis-related interventions: Placement of tunneled hemodialysis catheters, peritoneal dialysis catheters, and revision/thrombolysis of poorly functioning surgically placed AV fistulas and grafts.
  • TIPS: Placement of a transjugular intrahepatic porto-systemic shunt for select indications in patients with critical end-stage liver disease and portal hypertension.
  • Endovenous laser treatment of varicose veins: Placement of thin laser fiber in varicose veins for non-surgical treatment of venous insufficiency.
  • Chemoembolization: Combined injection of chemotherapy and embolic agents into the arterial blood supply of a tumor, with the goal of both local administration of chemotherapy, slowing "washout" of the chemotherapy drug, and also decreasing tumor arterial supply
  • Radioembolization: Combined injection of radioactive glass or plastic beads and embolic agents into the arterial blood supply of a tumor, with the goal of both local administration of radiotherapy, slowing "washout" of the radioactive substance, and also decreasing tumor arterial supply
Biliary intervention
  • Placement of catheters in the biliary system to bypass biliary obstructions and decompress the biliary system.
  • Placement of permanent indwelling biliary stents.
  • Cholecystostomy: Placement of a tube into the gallbladder to remove infected bile in patients with cholecystitis, an inflammation of the gallbladder, who are too frail or too sick to undergo surgery.
Catheter placement
  • Central venous catheter placement: Vascular access and management of intravenous devices, including both tunneled and non-tunneled catheters.
  • Drainage catheter placement: Placement of tubes to drain pathologic fluid collections. This may be achieved by percutaneous, trans-rectal, or trans-vaginal approach. Exchange or repositioning of indwelling catheters is achieved over a guidewire under image guidance.
  • Radiologically inserted gastrostomy or jejunostomy: Placement of a feeding tube percutaneously into the stomach and/or jejunum.
Ablative
  • Radiofrequency ablation : Local treatment in which a special catheter destroys tissue with heat generated by medium frequency alternating currents
  • Cryoablation: Local treatment with a special catheter that destroys tissue with cold temperature generated by rapid expansion of compressed argon gas—used mostly to treat small renal cancers and for the palliation of painful bone lesions
  • Microwave ablation: Local treatment with a special catheter that destroys tissue with heat generated by microwaves
Genitourinary
  • Percutaneous nephrostomy or nephroureteral stent placement: Placement of a catheter through the skin, directly into the kidney to drain from the collecting system. This is typically done to treat a downstream obstruction of urine.
  • Ureteral stent exchange: indwelling double-J type ureteral stents, typically placed by urologist using cystoscopy, may be exchanged in retrograde fashion through the female urethra. The IR uses a thin wire snare under fluoroscopy to capture the distal portion of the stent. After partially extracting the distalmost stent, exchange for a new stent can be accomplished over a guidewire.

    Techniques for specific disorders

Gastrointestinal intervention

Gastrointestinal hemorrhage

The treatment of gastrointestinal hemorrhage can range anywhere from monitoring an asymptomatic bleed to supporting and maintaining the hemodynamic function of the patient. The role for the interventional radiologist is to offer patients an image-guided, minimally invasive procedure to alleviate a condition that could be otherwise be potentially life-threatening.
The avenue for the interventional radiologist to dictate the clinical course of a GI bleed is largely influenced by location of bleed, overall patient health and other conditions the patient may have, most notably heart and liver functions. For most cases, collaboration between the gastroenterologist and interventional radiologist optimizes patient outcome but again, is largely dictated by anatomical location of the GI bleed. If a patient is evaluated and determined to be a candidate for an interventional procedure, then the bleed is often treated by embolization. Embolization is a process in which the interventional radiologist accesses the culprit bleeding vessel via a small catheter and interrupts blood flow to the site of bleeding via various mechanisms. Side effects of this procedure are minimal but there is a risk of bleeding and infection—though much less than the equivalent surgical procedure. When successful, the procedure often eliminates the bleed and patients can walk after a few hours of rest.

Hepatobiliary intervention

Transjugular intrahepatic portosystemic shunt

A transjugular intrahepatic portosystemic shunt is a procedure an interventional radiologist performs to create a shunt between the hepatic inferior vena cava and the portal vein, a vessel that returns blood from the intestines to the liver. The portal vein is the site where hypertension can produce a myriad of deleterious effects throughout the liver and small or large intestine.
Primarily, a TIPS functions to alleviate two different conditions: an emergent/life-threatening GI bleed or ascites caused by too high of blood pressure in the portal vein that is otherwise uncontrolled by diet and medications.
The workup for the procedure is straightforward and the interventional radiologist performing the procedure often orders several tests to assess how well the patient will tolerate the procedure. These are often simple blood tests, and an ultrasound of the heart and liver. The procedure is often well tolerated and can result in a permanent reduction or elimination of symptoms. The procedure can take anywhere between 15 minutes to an hour and has lower risks of bleeding or infection compared to an equivalent surgical procedure.
A TIPS may cause temporary confusion or worsening of liver/heart function. The degree of these two side effects largely depends on the health of the patient's heart and liver prior to the procedure and the risk-benefits of the procedure must be thoroughly discussed with their interventional radiologist before beginning. If the post-procedural consequences are more troublesome to the patient than their initial symptoms the artificial conduit created by the procedure can be reversed if the post-procedural side effects outweigh those caused by the prior conditions.
In some cases, a TIPS could form a blood clot, called a thrombus. A interventional radiologist would intervene to open up the shunt again by performing a mechanical thrombectomy. This procedure involves removing the thrombus from the TIPS. This would allow the patient to regain the initial benefits from the TIPS creation.