Effectiveness of abdominal compression during helical renal CT

Rationale and Objectives. The authors performed this study to assess the ef fect of abdominal compression on opacification and distention of the proxim al renal collecting system during helical computed tomography (CT). Materials and Methods. Abdominal compression was applied during helical CT in 31 patients who were scanned 150 and 300 seconds after initiating a dyna mic bolus injection of contrast material. Two reviewers assessed renal coll ecting system opacification and measured the maximal short-axis diameter of the collecting system at three locations: the upper pole, the lower pole, and the proximal ureter. A similar evaluation was performed in a control gr oup of 29 patients who under-went CT without compression at 300 seconds aft er initiating the injection of contrast material. Results. Both reviewers noted collecting system opacification at all locati ons in 52 of 56 noncompressed collecting systems scanned at 300 seconds, 57 of 59 compressed collecting systems scanned at 300 seconds, but only 26 of 59 compressed collecting systems scanned at 150 seconds. Measured collecti ng system distention was statistically significantly greater at 300 seconds in patents who received compression than in patients who did not (P = .001 3). For patients who received compression, measured collecting system diste ntion was statistically significantly greater on scans obtained at 300 seco nds than on scans obtained at 150 seconds (P = .0001). Conclusion. Abdominal compression during renal helical CT produces a detect able increase in renal collecting system distention. In patients who receiv e compression, scanning at 300 seconds rather than at 150 seconds results i n greater collecting system distention and more consistent opacification.