The next major step in the diagnosis of a renal mass came with the introduction of renal angiography, performed safely by radiologists in the radiology department. Abdominal aortography had previously been performed by surgeons, and required an arterial cutdown on the femoral artery and insertion of a catheter into the aorta. Because the procedure was significantly invasive, it was rarely used in renal mass diagnosis. Visualization of the aorta and renal arteries was performed by some urologists utilizing translumbar aortography, another significantly invasive procedure which also suffered from considerable morbidity and low diagnostic accuracy, except in hypervascular neoplasms.3
In 1953, Seldinger (Seldinger 1953) devised a method of percutaneously putting a catheter into the aorta. Eventually, the renal arteries and all the branches of the aorta were selectively catheterized. This was greatly aided by the introduction of image intensification for fluoroscopy, and the introduction of rapid film changers and power injectors. (It must be remembered that prior to the introduction of image intensification in fluoroscopy, red goggles were used for dark adaptation, which was needed for fluoroscopy performed in a darkened room. The fluoroscopic image, prior to the development of image intensification equipment, was of fairly low quality compared to present standards.)4
The initial work using the Seldinger technique was performed by Swedish radiologists (O. Olssen and E. Boijsen) in the 1950s. (Many of us traveled to Sweden to learn their techniques). Arteriography quickly became adopted and practiced around the world. By the 1960s the technique was well established, and added stature to the specialty of radiology because diagnoses, which previously had never been made preoperatively, were possible for the kidneys and of course throughout the rest of the body as well. Radiologists were much more appreciated by their clinical colleagues and were now valued as more than just “film readers.” 5 While the diagnostic accuracy of differentiating a renal cyst from tumor with selective arteriography was high (in the range of 95%),6 angiography couldn’t be performed on everyone with a renal mass. So, nephrotomography (even modified by introducing contrast by bolus and drip infusion, or just drip infusion through a smaller-bore needle) was used to triage renal masses so that angiography would be performed only on questionable or positive cases. Renal arteriography was readily embraced by urologists as it enabled preoperative visualization of the vascular anatomy of the kidney, greatly aiding the surgical approach as well as providing improved preoperative staging of malignancy.
Sonography was in development in the late 1960s and early 1970s and it proved to be an important modality in all areas of abdominal and pelvic radiology and in the triaging of renal masses. Imaging with ultrasound started with A mode, advanced to B mode (FIGURE 5), and progressed to “real time” and grey scale with continuous improvement in accuracy following advances in instrumentation. The technique, like others, had limitations, and accuracy was very dependent on the experience, persistence, and ability of the individual performing the study, but sonography was able to separate simple benign cysts from other masses that required more study. As sonography developed, its ability to clearly and accurately diagnose a simple cyst (by far the most common renal mass) without the need for contrast injections or radiation exposure was in itself a great contribution to renal mass evaluation.7
Figure 4. Epinephrine enhanced angiogram in renal cancer. (A) Left renal arteriogram reveals a
few abnormal-appearing vessels at the upper pole of the left kidney, indicating probable renal neoplasm. (B) Renal
arteriogram performed after the intra-arterial injection of epinephrine. Note that the peripheral renal vessels are not
filled because they are constricted by the epinephrine, while contrast flows into abundant tumor vessels at the upper
pole since these “abnormal” vessels are not affected by epinephrine, establishing the diagnosis of neoplasm.
In the 1970s, with the invention of computed tomography by Sir Godfrey Hounsfield (Hounsfield 1980) (Isherwood 2004), we witnessed the greatest advance in imaging of the body since the discovery of x-rays by Wilhelm Roentgen in 1895. If angiographywas a great step forward in the progression of radiology, the development and use of computed tomography was a colossal step, further securing the important role that radiology plays in the practice of medicine. CT was initially applied to the brain but shortly thereafter the body was studied as well. CT scanners were available on a limited basis in the mid and late 1970s, but by the 1980s the technology was available in most hospitals around the world (FIGURE 6). Over the years since its introduction, CT has been continually updated and improved. CT scans of the body on the early units (e.g., second-generation scanners, the EMI 5005) obtained single-axial slices of 13 mm thickness in 27 seconds per slice. An abdominal examination took an hour to perform because of the constraints of tube cooling, reconstruction time, and disc storage space. Now, of course, with multi-detector computed tomography (MDCT) an axial slice of less than 1 mm can be obtained in less than one second, and an entire scan of the abdomen can be obtained in much less time than it took to get a single slice on the early scanners. (The introduction of non-ionic contrast agents further expanded the value and use of CT.) With the discovery of CT, the computer age and radiography were united, and modern radiology was born.8
The introduction of magnetic resonance imaging (MRI) was a further giant advance in imaging of the body.9 Its rapid development and widespread use were aided to a great extent by the “concepts of digital data acquisition, sophisticated interactive display systems, and powerful image processing” that were used in the development of CT (Isherwood 2004). MRI has continued to improve since its introduction, with the use of higher field-strength magnets, the use of surface coils, and advances in pulse sequences. This technique has already proven to be even more important than CT in imaging many areas of the body. The future of MR seems almost limitless, with the introduction of more powerful magnets and the development of diffusion techniques and spectroscopy. However, at this time, in imaging of the kidney for renal cancer, CT remains the more important technique, although MRI has a significant role since it eliminates the use of ionizing radiation and iodinated contrast medium; also, because of its superior contrast resolution, MRI can be helpful in evaluating some renal masses which are inconclusive on CT. MRI is valuable in staging renal cancer and, due to its direct multiplanar imaging ability, provides an excellent roadmap for surgical removal or ablation of renal lesions (MDCT can provide excellent resolution in interpolated planes as well).
As a radiologist and former angiographer who spent many hours in the angiography suite, and who at one time or another catheterized almost all the vessels of the aorta (including the middle adrenal, bronchial, and brachiocephalic arteries) (Bosniak 1963), I find the superb vascular images obtained with CTA and MRA both astounding and almost unbelievable. When I think of what the patient and the angiographer had to go through to get the images that are now available relatively pain-free on CTA and MRA, it is almost incomprehensible, and at the same time, something at which to marvel. If these advances can occur in 50 years, one has to wonder what is coming next.
Figure 5. “B” scale sonogram diagnosing a cyst of the left kidney.
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