By Dr SEE Teik Choon, FRCS, FRCR, Consultant Interventional Radiologist, Cambridge, UK

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Interventional Radiology is a relatively new subspecialty of Radiology. It is a subspecialty where minimally invasive procedures are performed under radiological guidance using X rays, ultrasound (US), computed tomography (CT) and lately, magnetic resonance imaging (MRI). The persons who perform the procedures are interventional radiologists, although most radiologists (not necessarily interventional radiologists) are capable of performing some minor or less complicated interventional procedures. All radiologists are fully qualified medical doctors with postgraduate radiology training. Further in depth formal training in Interventional Radiology is usually required (essential in some countries) if one is to pursue a career in Interventional Radiology.

Majority of the interventional procedures are performed in a special ‘interventional suite’ located in the X ray department, with the support from the nursing and radiography staff. Most procedures are done under local anaesthesia with or without conscious sedation (drowsy but not completely out of touch). There are also some cases that are best performed under general anaesthesia.
 

As a result of the less invasive nature of most interventional procedures, it is a technique which is in general less costly with shorter hospital stay and faster recovery.

Here are some of the common Interventional Radiology procedures:

• Tissue Biopsy
• Aspiration or Drainage
• Arteriogram
• Angioplasty
• Endovascular Stenting
• Nephrostomy
• Ureteric Stenting
• Percutaneous Nephrolithotomy
• Percutaneous Transhepatic Cholangiogram, Drainage and Stenting
• Radiologically Placed Gastrostomy
• Oesophageal Dilatation and Stenting
• Bowel Stenting
• Hysterosalpingography and Recanalisation
• Embolisation
• Chemo-embolisation
• Uterine Fibroid Embolisation
• Varicocoele Embolisation
• Arterio-Venous Fistuloplasty
• Central Venous Line Insertion
• Tumour Ablation
• Vertebroplasty

Tissue Biopsy
This is commonly performed in order to find out what is the underlying diagnosis of a lump for example in the neck, breast, liver, lungs etc. This involves passing a ‘biopsy needle’ into the lump and a small sample of the tissue is obtained which is sent to the laboratory for analysis.  

Aspiration or Drainage
This involves inserting a small tube into a body cavity to drain a fluid or pus collection. The tube may be removed immediately (aspiration) or leave it to drain (connected to a bag externally) for a few days if it is a big collection. 

Arteriogram: A normal right internal carotid arteriogram – this shows the one artery and its brances on the right side of the brain

Arteriogram
This is performed to find out if there is any narrowing or blockage of the arterial system (blood vessels) of the body. For example, leg arteriogram if somebody is complaining of severe leg pain preventing walking; heart arteriogram if somebody is complaining of recurrent severe chest pain despite regular medication; head arteriogram if there is clinical suspicion of bleeding or abnormality of the blood circulation in the head.

The procedure usually involves inserting a small tube into the respective arterial system via the groins (usually the right groin). Contrast medium is then injected via the tube while X-rays are activated to record the images. Groin compression is applied following removal of the tube to avoid bleeding at the entry site.

Angioplasty
This is performed in order to dilate the narrowed or blocked artery evidenced from the arteriography or other imaging examinations. The access for the procedure is again usually via one of the groins. A wire is passed across the narrowed or blocked artery. This is followed by dilatation using a balloon catheter/ tube.

Endovascular Stenting
‘Endovascular’ means inside the blood vessels. There are cases when angioplasty alone is insufficient and a stent (basically a hollow tube) may be required to overcome the obstruction. The stent is left in the vessel indefinitely. This may become narrowed in the future when a repeat angioplasty can again be performed. There are now various types of stents available. The procedure can be performed in either the artery (pulsating part of the vessels) or the vein (non pulsating part of the vessels), depending on the clinical condition. Some examples of arterial stenting are carotid artery stenting in the neck, abdominal aneurysm stenting in the tummy, kidney and iliac artery stenting in the tummy.

Nephrostomy
‘Nephro’ means having to do with kidney and ‘stoma’ means an access from an organ of the body to outside the body, usually by means of a tube with or without a drainage bag applied outside the body. This is indicated when the urine is unable to drain from a kidney to the bladder. The underlying cause could be due to stone disease, tumour, narrowed ureter (the tube that connects a kidney to the bladder) and others. Prolonged obstruction to urinary drainage may lead to infection and kidney malfunction.  A tube is inserted via the skin to the affected kidney and connected to a bag externally to drain the urine. Hence this is essentially like a drainage procedure described above. This is almost always temporary while the underlying cause of obstruction is being investigated or treated.

Ureteric stenting
When the urinary obstruction is due to an obstruction along the ureter (the tube that connects a kidney to the bladder), a stent (a hollow tube) may be needed to bypass the obstruction. Ureteric stenting can be performed by Interventional Radiologists following a nephrostomy but it can also be performed by the Urologists (surgeons that look after the kidneys) using a camera scope via the bladder in theatre. Ureteric stenting is usually temporary but the stent can also be left for a longer period if necessary. The stent may become obstructed and lead to infection. Stent removal and replacement (if required) is usually performed by the Urologists.  

Percutaneous Nephrolithotomy (PCNL)
‘Percutaneous’ means through the skin; ‘Nephro’ is related to kidney; ‘lithotomy’ means removal of stones. This is one of the treatments for kidney stone disease. The aim of the procedure is to remove kidney stones through a small hole on the back (near the respective kidney) without undergoing a major operation. This is performed in operating theatre by a radiologist in conjunction with a urologist, usually under general anaethesia.

Percutaneous Transhepatic Cholangiogram (PTC) and Drainage (PTD) and Stenting (PTS)
‘Percutaneous’ means through the skin; ‘hepatic’ means liver; ‘cholangiogram’ means images showing the bile ducts (which drain bile from the liver to gall bladder and to the bowel).  

This procedure is indicated when somebody is jaundiced (yellowing of the skin and itch) and prior clinical investigations raised the possibility of obstruction to the drainage of the bile in the liver. PTC involves passing a small needle via the skin to a bile duct of the liver. Contrast medium is then injected via the needle to fill up the bile ducts and X-rays images are taken. This will show the site and possibly the cause of the obstruction. 

If there is an obstruction along the bile duct, this will require drainage to relief jaundice and prevent infection. PTD is performed following PTC by passing a wire across the obstruction of the bile duct and subsequently inserting a tube across the obstruction. The tube can then be connected to a bag externally. Hence this is essentially a type of drainage procedure described above. PTD is a temporary procedure while waiting for more definitive treatment of the underlying cause.

In some cases a stent (a hollow tube) is required to allow drainage of bile across the obstruction in the usual manner (i.e. to the bowel). Like PTD, this is performed by passing a wire across the obstruction of the bile duct and subsequently deploying a stent across the obstruction. Unlike PTD, no external tube or bag is required following stenting. 

Radiologically Placed Gastrostomy (RPG)
‘Gastro’ means anything related to the stomach and ‘stoma’ means an access from an organ of the body to outside the body, usually by means of a tube with or without a drainage bag applied outside the body. RPG is indicated in somebody who is unable to swallow food or fluid in the normal way due to disease of the gullet (food pipe) or central nervous system supplying the function of the gullet. The procedure is performed by inserting a special tube (gastrostomy) via the skin to the stomach. Feeding (nutritious fluid formula) can then be instituted via the gastrostomy directly to the stomach. The gastrostomy may become blocked in the future but this can be replaced using the same access. 

Oesophageal Dilatation and Stenting
‘Oesophagus’ is the gullet which is the passage between the mouth and the stomach. This may become narrowed in certain disease condition. The narrowed segment can be dilated by passing a wire across followed by a balloon catheter.  

In late stage of oesophageal cancer, the gullet is severely obstructed by the growth. Balloon dilatation in this situation is not recommended due to high risk of rupturing the gullet. A stent (a hollow tube) can be inserted instead.  

Oesophageal dilatation and stenting can also be performed with the assistance of a camera scope. 

Bowel Stenting
Stenting can also be performed in the small and large bowel, similar to oesophageal stenting described above. This is usually indicated in late stage cancer disease to provide symptomatic relief of obstruction. This can also be performed with the assistance of a camera scope. 

Hysterosalpingography (HSG) and Recanalisation
‘Hystero’ means uterus (womb), ‘salpinx’ means fallopian tube (the tube that allows passage of eggs from the ovary to the uterus). Hysterosalpingography [Intro to HSG, click here; FAQ to HSG, click here] is a procedure where a tube is inserted into the uterus followed by injection of contrast medium to outline the anatomy of the uterus and the fallopian tubes. This is one of the main tests in investigating the cause of infertility in women.  

If the fallopian tubes are blocked, this can sometimes be unblocked by passing a wire across the obstructions. This process is called recanalisation. 

Embolization
Embolization is a procedure where a blood vessel is blocked intentionally. This is indicated in situations such as to stop bleeding due to trauma, tumour, or abnormal enlargement of the vessels (aneurysm). It can also be performed to block blood supply to a tumour e.g. cancer of the liver. The idea of tumour embolization is to cause cessation of blood supply to tumour cells hence this forms one of the treatments in certain tumours not suitable for surgery. 

The procedure involves gaining access to the respective artery (usually via one of the groins) with a catheter (small tube). An embolic agent is then injected via the catheter to block the respective blood supply. There are different types of embolic agents available, the choice depends on what type of embolization required in each clinical condition. 

Chemo-embolization
This is commonly performed for liver tumours not suitable for surgery. Embolization is performed as described above. In addition, a chemotherapy agent is instituted using the same route. 

Uterine Fibroid Embolization (UFE)
Uterine fibroids may cause pain, bleeding and other related symptoms. The traditional treatment for fibroids is surgery which may involve removal of the uterus (womb). In some women who may want to preserve fertility (i.e. who may want to get pregnant in the future) UFE may be considered.  

The procedure involves gaining access to the uterine artery (usually via one of the groins) with a catheter (small tube). An embolic agent is then injected via the catheter to block the blood supply to the fibroid. 

Varicocoele Embolization
‘Varicocoele’ is abnormal dilatation of veins (non pulsating part of the blood vessels) due to failure of blood to return to the heart. This results in engorgement of blood in the veins. This may occur in different parts of the body. If this happens in a testicular vein in a man, this may cause pain and very importantly, may reduce the fertility potential. Traditionally the vein can be ligated surgically but varicocoele embolization is now a recognized alternative. This involves inserting a small catheter (tube) into the vein (usually via the groin) and injecting an embolic agent (usually coils) to block the vein.  

Arterio-Venous Fistuloplasty
‘Fistula’ refers to a surgically constructed site where an artery (pulsating part of the vessels) is joined to a vein (non-pulsating part of the vessels). This is done in patients with kidney failure that requires regular dialysis. The site of fistula is usually at the wrist. Like any blood vessel, the arterio-venous fistula may be blocked or narrowed with time. Fistuloplasty is a procedure whereby a balloon catheter is used to dilate the area of narrowing, not dissimilar to angioplasty described above. 

Central Venous Line Insertion
A vein is the non pulsating part of the blood vessels. A central vein refers to a big vein in the chest as supposed to a peripheral vein which is smaller and located in the arms or legs. A line or tube may be inserted to a central vein to allow institution of chemotherapy, nutrition, long term antibiotics, or for temporary dialysis. A peripheral vein is not suitable for these purposes.  

The procedure involves inserting a line into a big vein on the neck or below the collar bone. It is not uncommon to ‘tunnel’ part of the line under the skin (for stability and to prevent infection). Different types of ‘tunneled lines’ are available, a common example is the Hickman line.

Tumour Ablation
This is a technique whereby a tumour is destroyed using heat, cold gas, sound wave therapy and others. It is an option for treatment of some tumours when surgery is not suitable. It involves passing a special needle (which is connected to a special machine) into the tumour and delivers the respective mode of the treatment. An example is radiofrequency ablation of liver or kidney tumours using heat. 

Vertebroplasty
This is a procedure to treat pain and instability resulting from fracture of the spine secondary to osteoporosis. Osteoporosis is a process of bone demineralization with age. This results in formation of fragile bones and may lead to fracture. Compression fractures (‘compression’ because there is a reduction in the height of the spinal bone) of the spine are difficult to treat and usually patients are given pain relief and external support. Vertebroplasty involves injecting special bone cement into the spine. This provides symptomatic pain relief, stabilizes the fracture site, and prevents further compression of the spine.  

Further Reading
For another introduction to Interventional Radiology, check this chapter from the book for the general public - Radiology Inside the Human Body published by the College of Radiology (then Malaysian Radiological Society) in 1997.

http://www.radiologymalaysia.org/Archive/RITHB/interventionalradiology.html

Please click here for more!
 

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Last Updated:
Tuesday, 15 January 2008