IMAGING

CT urography of urinary diversions with enhanced CT digital radiography: preliminary experience
Sudakoff GS, Guralnick M, Langenstroer P, Foley WD, Cihlar KL, Shakespear JS, See WA
Department of Radiology, Medical College of Wisconsin, Froedtert Hospital, Milwaukee, WI, USA
AJR Am J Roentgenol. 2005; 184: 131-8

• Objective: The purpose of this study was to determine if 3D-rendered CT urography (CTU) depicts both normal and abnormal findings in patients with urinary diversions and if the addition of contrast-enhanced CT digital radiography (CTDR) improves opacification of the urinary collecting system.
• Materials and Methods: Thirty CTU and contrast-enhanced CTDR examinations were performed in 24 patients who underwent cystectomy for bladder cancer. Indications for evaluation included hematuria, tumor surveillance, or suspected diversion malfunction. All examinations were evaluated without knowledge of the stage or grade of a patient’s tumor and were compared with the clinical records. Opacification of the urinary collecting system was evaluated with 3D CTU alone, contrast-enhanced CTDR alone, and combined CTU and CTDR.
• Results: Nine abnormalities were identified including distal ureteral strictures (n = 4), vascular compression of the mid left ureter (n = 1), scarring of the mid right pole infundibulum (n = 1), bilateral hydronephrosis and hydroureter (n = 1), urinary reservoir calculus (n = 1), and tumor recurrence invading the afferent limb of the neobladder (n = 1). Eight of the nine detected abnormalities were surgically or pathologically confirmed. All abnormalities were identified on all three imaging techniques but were best seen on 3D CTU and enhanced CTDR images. Incomplete opacification of the urinary collecting system occurred in 17 patients with CTU alone, 12 patients with contrast-enhanced CTDR alone, and nine patients with combined CTU and contrast-enhanced CTDR. Compared with CTU alone, the combined technique of 3D CTU and contrast-enhanced CTDR improved opacification by a statistically significant difference (p = 0.037).
• Conclusion: CTU with 3D rendering can accurately depict both normal and abnormal postoperative findings in patients with urinary diversions. Adding enhanced CTDR can improve visualization of the urinary collecting system.
  
  
• Editorial Comment
  Radiologic evaluation of urinary diversion has 4 main objectives: the detection of postoperative complications, the detection of newly developed urothelial tumors, to monitor upper tract distention and to detect metastasis. Various surgical techniques that are used in continent and noncontinent diversions alter the normal anatomy and make the radiologic interpretation difficult. An accurate interpretation can be made only if radiologists become familiar with the various surgical procedures and the appearances of various postoperative anatomic changes.
  The type of imaging procedure and the frequency of imaging is dictated by the urologist preference. In most cases, early complications require urgent radiographic evaluation, usually with intravenous urography or CT. Late complications of urinary diversion are more often insidious, and several imaging techniques has been used: intravenous urography ,contrast enhanced CT, pouchograms, fluoroscopic loopogram or CT loopogram. The authors present their results where a multidector 3D-CT urography associated with a digital scout view of the abdomen and pelvis after intravenous contrast injection (enhanced CTDR), was performed in 24 patients treated by cystectomy or cystoprostatectomy with subsequent urinary diversion. They compared the 2 types of images in the opacification of the urinary collecting system and evaluated whether one technique was superior or complementary to the other for the detection of any type of abnormalities. These patients presented with ileal conduits, right colonic pouches and ileal neobladders. The combined imaging technique of CTU and enhanced CTDR allowed total opacification of the urinary tract in 21 (70%) of 30 cases studied. They found that the middle and distal left ureteral segments and the left ureteroenteric anastomosis were the most common sites that failed to opacify on either CTU alone, enhanced CTDR, or combined CTU and enhanced CTDR. Even with this drawback, there are numerous advantages of CTU over IV urography and fluoroscopic loopogram. The advantage include better evaluation of distal ureter narrowing, tumor recurrence, better detection and localization of urinary calculi and fistulae, identification and characterization of small renal masses, and detection of extra urinary disease. Main limitations of loopogram include: incapacity of retrograde opacification of the upper urinary tract, incapacity of evaluate renal function, and limitation to detect renal masses, tumor recurrence or extra urinary disease. We have used the same technique presented by the authors, for the evaluation of 16 patients with urinary diversions. Similarly, we have observed more difficulties for adequate opacification of the distal portion of the left ureter. In order to improve this visualization, we have added recently, a 250-mL saline bolus during excretory phase. This modification in the technique allowed us to obtain improved opacification of the distal portion of left ureter in 37% of patients. This modification was also useful for better demonstration of narrow fistulas in 2 patients. This is a very good, very well written and nicely illustrated paper. As a radiologist, I found it extremely useful for understanding all the surgical details of the more common surgical procedures used for urinary diversion. There is no doubt that multidector CTU with 3D rendering has the potential to be the imaging technique of choice for the initial evaluation of patients with urinary diversion.

Dr. Adilson Prando
Chief, Department of Radiology
Vera Cruz Hospital
Campinas, São Paulo, Brazil