Uroradiology Notes From RSNA 1999
Written by Jeffrey H. Newhouse, M.D..
The 1999 Scientific Program of the 85th Annual Assembly of the RSNA contained a large number of abstracts and scientific exhibits dealing with diagnostic uroradiology. The increasingly international flavor of the meeting was reflected by the large number of contributions from overseas.
CT and Stones
The utilization of non-contrast abdominal CT for investigating possible urinary stone disease continues to be investigated and refined. CT urography was found to be as effective in children as in adults, and to be cost-effective as well. Multi-slice exams were shown to work as well as single-slice CT, and a moderate increase in pitch was found to reduce dose without a significant reduction in sensitivity. Secondary signs of obstruction were not always seen in patients with acute ureteral stones; their likelihood was shown to be directly proportional to the duration of obstruction. Non-contrast CT exams are not always easy to analyze: pitfalls in diagnosing and excluding ureteral stones were described. The list of alternative diagnoses sometimes encountered in patients with symptoms suggesting stones was expanded, and CT was shown to be better, although not statistically significantly so, than ultrasound in investigating patients with possible stone disease. Elderly patients who underwent extracorporeal shock wave lithotripsy were found to have an increased risk of subsequent hypertension. Contrast-enhanced CT urography was shown to be effective in displaying diseases causing calyceal filling defects.
Obstruction
Ureteral obstruction continues to be investigated, both with advanced ultrasound techniques, such as contrast-enhanced harmonic imaging and planimetry, and by various static and dynamic and gadolinium-enhanced MR urography techniques. The former were used to assess changes in renal blood flow associated with obstruction and to demonstrate that vascular compliance changes were a major part of the visualized abnormalities, and to show that renal parenchymal volumes correlated well with nuclear medical assessments of function in patients with hydronephrosis. MR was shown able to assess both experimental and clinical obstruction morphologically and functionally, to demonstrate the role of accessory vessels in ureteropelvic junction obstruction, and to distinguish some malignant from some benign causes of ureteral obstruction.
Reflux
Vesico-ureteral reflux continues to be investigated by ultrasound. Contrast-enhanced ultrasonography was shown to be able to replace some radiographic voiding cystourethrograms and thus reduce radiation dose. Contrast-enhanced Doppler ultrasound was shown to correlate well with functional studies and biopsy results in patients with transplanted kidneys. Resistive indices were found to be elevated in patients with severe reflux, but the presence of mild hydronephrosis was not shown to be useful in predicting whether an infant had reflux.
Infectious Disease
Inflammatory disease continues to be investigated, primarily by ultrasound and CT. The diagnosis of acute pyelonephritis by standard ultrasound and pulse inversion harmonic ultrasound (especially with contrast agents) was demonstrated. Power Doppler ultrasound was shown to be comparable with DMSA scans for demonstrating acute pyelonephritis in children. Helical CT findings were shown to be comparable to those for standard CT; the excretory phase was most accurate in depicting areas of pyelonephritis in the cortico-medullary phase. Ultrasound findings in orchitis were reviewed. Radiography, urography, CT and ultrasound of the various manifestations of tuberculosis in all parts of the urinary tract were demonstrated. Finally, an exhibit on Fournier's gangrene concentrated on the differentiation of this disease from other sources of air in the scrotum.
Trauma
All of the manifestations of renal trauma were demonstrated by a nice exhibit. Delayed post-contrast images of the kidney during CT of trauma patients were found to improve visualization, but not to warrant routine performance in trauma. Penile trauma was shown to be well evaluated by MRI.
Vascular Imaging
Renal vascular imaging studies continues to show progress. Doppler ultrasound and nuclear scintigraphy showed diminution in perfusion of ptotic kidneys and harmonic Doppler imaging was found to be promising for evaluating renal artery stenosis. The ever-troublesome technical difficulties in performing renal vascular ultrasound were addressed by a detailed exhibit demonstrating tricks and techniques. MR angiography continues to be refined; a number of contributions demonstrated its utility in screening for and evaluating renal artery stenosis and its functional consequences, and for evaluating renal artery aneurysms as well. Both MRA and CTA were demonstrated to be very accurate in evaluating potential kidney donors (with the exception of tiny accessory vessels) and the visualization of ever-smaller renal artery branches were shown to be possible using dual-phase multi-detector helical CTA.
Transplantation
Vascular and flow imaging in renal transplant patients continues to be developed. MRA was reinforced as a satisfactory technique, and triggered pulse inversion images with contrast agents were shown to be especially good at visualizing vascularity. Color Doppler flow studies correlated well with other functional studies in patients with chronic graft rejection; physiologic functional imaging was pursued. It was demonstrated that flow-mediated vascular reactivity could be assessed by color Doppler ultrasound and shown to be different in pancreas-kidney transplant patients from those in patients who received a kidney alone. An exhibit described the imaging of renal transplant vascular complications involving the iliac arteries. MRI diffusion and perfusion imaging was shown to be feasible in transplanted kidneys.
Adrenal Imaging
There were relatively few presentations on adrenal imaging. An algorithm to deal with the commonly-encountered incidentaloma was described, and a nice exhibit demonstrated the variety of appearances of adrenal masses. MIBG scintigraphy was compared with MRI in pediatric patients with adrenal and sympathetic chain tumors; since neither was perfectly accurate, a combination of the two was proposed.
Neoplasms
Oncologic imaging received a good deal of attention. Refinements in detection algorithms were presented: fast MRI, CT virtual cystoscopy, contrast-enhanced CT urography, normalization of PSA rating with MRI-evaluated peripheral prostate volume, and imaging of the urachus all proved to be efficacious in the initial diagnosis of tumors. MRI and MRA continue to evolve as appropriate pre-operative evaluation measures for patients with renal cell carcinoma, as does contrast-enhanced ultrasound. MRI findings were shown to be good predictors of outcome in bladder cancer, and MRI with node-seeking superparamagnetic agents was found to improve detection of metastases in non-enlarged nodes. MRI and ultrasound continue to show effectiveness in evaluation of testicular and extratesticular scrotal masses. Finally, both cryotherapy and RF ablation have been shown to be efficacious in the therapy of small renal carcinomas.
Further progress was reported in the imaging of prostate cancer. Transrectal ultrasound was shown to be able to demonstrate flow abnormalities that correlated well with tumoral microvessel count, in guiding interstitial gene therapy, and for successful seminal vesicle biopsy for staging. Multiplanar transrectal ultrasound was better than standard exams in demonstrating the site and size of tumors and overall gland volume. Improvements in technique were reported: local antisepsis and a double prophylactic sheath used during biopsies without antibiotics were found to have no effect on infection rates compared to antibiotic-covered biopsies. Recent ejaculation was shown to increase vascularity as assessed by transrectal Doppler, a finding which should help in interpreting the significance of vascular findings. Two papers showed the efficacy of MRI in detection and differential diagnosis of prostate cancer in patients whose transrectal ultrasound was not definitive, and MR spectroscopic imaging was shown to be able to find recurrent local disease after brachytherapy. MRI was also able to demonstrate intraprostatic and perioprostatic changes following interstitial therapy.
CT of nodal metastases in testicular cancer performed early during chemotherapy was found to be a good predictor of further chemotherapeutic response and may therefore be of aid in planning extensive therapy.
Cystic Diseases
The spectrum of findings in the various renal cystic diseases was well demonstrated in an exhibit, as was the effect of a beam-hardening artifact in the evaluation of simple renal cysts.
Scrotum and Male Infertility
Two exhibits demonstrated the wide range of ultrasound-demonstrable abnormalities leading to male infertility. Ultrasound was also found to be able to demonstrate frequent changes in the vas and epididymis in patients who had had vasectomies.
Scrotal imaging was well reviewed. Exhibits of the scrotal sonographic appearance of virtually all kinds of intrascrotal pathology, especially including extratesticular masses, tuberculosis, torsion, orchitis and Fournier's gangrene were presented.
Ultrasound demonstrated a wide variety of extratesticular scrotal pathology in mountain bikers. Scrotal ultrasound was found to be of little use in patients with chronic scrotal pain but normal physical examinations. The prevalence of microlithiasis and its associated relative increase in tumor risk was outlined. In both humans and animals, gadolinium-enhanced MRI was found to be helpful in demonstrating testicular ischemia.
Anatomy
Precise anatomic studies were presented. In particular, an automated program to estimate renal parenchymal volume by CT was shown to be highly accurate, internal surface coil MR imaging demonstrated very detailed anatomy of the pelvic floor, and CT angiography of the renal artery and its branches showed progression of the capacities of the technique to demonstrate ever-smaller vessels. The normal anatomy of penile structures was shown to be well demonstrated by MRI.
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