Interventional radiology: An overview

Several breakthrough developments in instrumentation have contributed to considerable growth in interventional radiology. The introduction of the minimally traumatic thin-caliber Chiba needle has not only rekindled interest in transhepatic cholangiography but paved the way for transhepatic biliary drainage, access to the portal venous system for venous blood sampling, and embolization of esophageal varices. Such 'fine needles' (20 to 22 gauge) also allow low-risk aspiration biopsies. Catheterguided embolotherapy was first applied to gastrointestinal (GI) bleeding, which arterial vasopressin infusion had failed to control. Introduction of a variety of embolic materials such as the 'coil-spring embolus' and flowdirected detachable balloons expanded applications of embolotherapy. Not only has the angiographic catheter become a tool for therapeutic uses in blood vessels but it can also be used for nonvascular applications such as drainage of bile, urine, and intra-abdominal fluid collections Finally, an ingenious catheter modification inaugurated by Porstmann, the so-called 'caged balloon', allowed expansion of a catheter-mounted balloon to a predetermined diameter. Using a different plastic material, Gruntzig and co-workers introduced the limited expansion balloon catheter now most widely used for so-called 'transluminal angioplasty.' Development of the sonographic biopsy transducer brought organs such as the pancreas, the liver, and the kidneys into reach of visually guided needle entry. Using the percutaneous catheterization principle developed by Seldinger, the way was opened for sonographically guided catheter placement for drainage of deep-seated abscesses and fluid collections. Recently introduced percutaneous transluminal extraction of renal pelvic or ureteric stones proves that there is no fundamental barrier between entering the kidney with a 22-gauge needle and widening this tract within minutes to 10 times the needle diameter, allowing percutaneous introduction of endoscopes and retrieval instruments. Most of these techniques owe their existence to diagnostic angiographers familiar with remote guidance of needles and catheters. From among the numerous interventional radiology procedures whose detailed description has already filled textbooks, we shall discuss those of particular interest to the readership, emphasizing indications and risks, as well as immediate and long-term effects as applicable.