History of Interventional Radiology
It wasn't long after x-rays were discovered that scientists began experimenting with interventional procedures. Early in the 20th century, a dedicated scientist injected contrast into one of his own arteries, and the field of angiography was born. Within a few decades, radiologists were looking at the arteries that supply the legs, the aorta and its branches in the chest and abdomen, the arteries in the head and other areas of the body.
The preferred means of access became the femoral artery in the groin, which connects to just about every artery in the body. Different catheters were developed to allow access to small arteries. During the 1960s, the use of angiograms reached its first peak. There were few options back then, and angiograms became an important, although invasive, way of looking at many organs. Radiologists could, for example, inject dye right into the renal arteries and view exquisite renal vascular anatomy and tumors quite clearly.
It became possible to see arteries that were bleeding internally for any number of reasons. The dye is seen to "extravasate" or lie outside the artery in which it was supposed to have been confined. Now what? Suppose we could get a catheter into the artery that was bleeding and inject something through it that would stop the bleeding. We could inject vasopressin (substance that causes the artery to constrict), a porous, gauze material (ultimately absorbed by the body), or coils to clog the artery and stop the bleeding.
Radiologists were now able to map the vascular supply of the entire body and perhaps even stop internal bleeding. Back then, the radiologists would simply tell the surgeons what was going on, and the surgeons would decide what to do next. That was old-fashioned radiology.
Today, when an area in an artery is severely narrowed, instead of calling the surgeon and scheduling the patient for the operating room, in many cases an interventional radiologist can insert a catheter that has a balloon at its tip. When the section of the catheter that holds the deflated balloon is positioned right across the narrowed area, the radiologist inflates the balloon to "crack the plaque" and dilate the vessel. He may do this two or three times. Most of the time the vessel will stay open. If not, the radiologist can insert a small, reinforced tube (stent) to keep the artery open. This can be done to arteries in the heart (coronary angioplasty), to vessels in the belly (renal artery angioplasty), and to vessels supplying the legs and elsewhere.
What about the carotid arteries in the neck, the ones that supply the brain and have a tendency to get narrowed by plaque? Why not dilate them with balloons?
This would be a dangerous undertaking. First of all, when the balloon is dilated and kept dilated for 10 seconds or so, the artery is completely occluded and there is no flow of blood through that artery at all. Also, when the plaque is cracked, small fragments of the plaque, or small blood clots, may flake off and cause damage. The damage inflicted by the balloon is generally tolerated in the legs and even in the coronary arteries, but the brain is not so forgiving.
Investigators continue to work on the problem, however, and carotid artery angioplasty may someday become a recognized, safe procedure.
During the period in which angiography was being developed, special procedures took on an additional role. Interventional radiologists are able to locate masses (e.g., cysts, tumors) in the body and insert a needle to aspirate cells or the core of the mass. For example, before ultrasound, CT scan, and MRI scan, we saw all sorts of masses in kidneys that were nothing more than benign renal cysts that had almost no clinical significance. The problem was that we did not know which of these masses were malignant tumors. So what we did was place needles into these masses, under fluoroscopy; drain some of the material; and send it to the lab for analysis.
It was the advent of the ultrasound and CT that really made the difference here. We could see much more and could even sample tiny lymph nodes in the abdomen because we could guide our needles to it by CT. Or we could biopsy small lesions in the breast because we could see them on ultrasound and could actually watch on the screen as our needle was approaching the cyst or tumor. Biopsy of hidden body parts through the skin (percutaneous) became a specialty unto itself.
If you can take the fluid out of a renal cyst, why not drain other fluid collections in the body, for example, abscesses in the abdomen? Since radiologists can put needles into these abscesses for diagnostic purposes, why not just drain them and make surgery unnecessary? Not many abscesses can be drained with the same thin needles used for diagnostic purposes, so something a bit bigger, like a tube, is needed. Of course, inserting tubes increases complications and reduces patient comfort level. Complications, however, can usually be avoided with a good technique and experience. If surgery can be avoided, it is certainly worth a try.
Sometimes it's necessary to drain a fluid collection in the renal pelvis. For whatever reason, the tube leading from the kidney to the bladder (the ureter) becomes blocked and the part of the kidney that collects the filtered urine (the collecting system) gets dilated. Pressure builds up, causing the kidney to stop filtering, a backflow into the tissues around the kidney, or an infection.
If the obstruction cannot be fixed by putting a tube into the bladder and ureter, it may be necessary to relieve the pressure by putting a tube directly into the collecting system from the skin surface (percutaneous nephrostomy or "perc"). The patient would probably need conscious sedation. Ingenious systems have been devised to help the radiology team perform this procedure, and in good hands it is successful in the vast majority of patients. Once a tube is in, the kidney can be drained and the obstruction removed.