Neorectal irritability after short-term preoperative radiotherapy and surgical resection for rectal cancer

Preoperative radiotherapy followed by rectal resection with total mesorectal excision (TME) and colo-anal anastomosis severely compromises anorectal function, which has been attributed to a decrease in neorectal capacity and neorectal compliance. However, to what extent altered motility of the neorectum is involved, is still unknown. The aim of the study was to compare the motor response to (prolonged) filling of the (neo-)rectum in patients after preoperative radiotherapy and rectal resection with that in healthy volunteers (HV).

Neorectal function (J-pouch or side-to-end anastomosis) was studied in 15 patients (median age 61 years, 10 males) 5 months after short-term preoperative radiotherapy (5 x 5 Gy) and rectal resection with TME for rectal cancer and compared with that of 10 volunteers (median age 41 years, 7 males). Furthermore, patients with a colonic J-pouch anastomosis (n=6) were compared with patients with a side-to-end anastomosis (n=9). (Neo-)rectal sensitivity was assessed using a stepwise isovolumetric and isobaric distension protocol. (Neo-)rectal motility was determined during prolonged distension at the threshold of the urge to defecate.

The neorectal volume of patients at the threshold of the urge to defecate (125 +/-45 ml) was significantly lower when compared with that of HV (272+/-87 ml, P<0.05). The pressure threshold, however, did not differ between patients (26+/-9 mm Hg) and HV (21+/-5 mm Hg) and neither did the pressure threshold differ between patients with a J-pouch and those with side-to-end anastomosis. In HV, no rectal contractions were observed during prolonged rectal distension. In contrast, in all 15 patients, prolonged isovolumetric and isobaric distension induced 3 (range 0-5) rectal contractions/10 min, which were associated with an increase in sensation in half of the patients.

Patients who underwent preoperative radiotherapy and rectal resection with TME, but not HV, developed contractions of the neo-rectum in response to prolonged distension. We suggest that this neorectal "irritability" represents a new pathophysiological mechanism contributing to the urgency for defecation after this multimodality treatment.