Influence of bladder distension control on postoperative intensity-modulated radiotherapy in rectal cancer patients

A prospective study was undertaken to reduce bladder volume variation and the irradiated small bowel injury by irrigating the bladder during postoperative pelvic IMRT in rectal cancer patients.

12 consecutive patients underwent three sets of computed tomography scans during the treatment course: Group I, a distended (not empty) bladder before the radiation course; Group II, a distended bladder at the end of the fourth week; Group III, an irrigated bladder at the end of the fourth week. A seven-field coplanar intensity- modulated radiotherapy plan of 50.4 Gy was made to the clinical target volume. The total volume of regions of interest and volume within every isodose level, their maximum dose and mean dose were analysed.

Compared with group I, the median reduction of bladder volume was 147.7 cm3 (24.3%), and the median increment of small bowel was 122.4 cm3 in group II. The volume of small bowel within every isodose level was increased (P<0.05). Statistical analysis showed a correlation between the volume change of bladder and small bowel. The mean radiation dose (Dmean) of small bowel and bladder was increased in group II compared to groups I and III (P<0.05).

Bladder volume declines significantly during the course of radiotherapy, leading to an increment in irradiated small bowel volume. Bladder irrigation is a feasible method to guarantee a consistent bladder volume and reduce small bowel radiation exposure.