• double incontinence;
  • lower gastrointestinal tract;
  • lower urinary tract;
  • manometry;
  • neurogenic pelvic organ dysfunction

Background:  Both the lower urinary tract (LUT) and the caudal part of the lower gastrointestinal tract (LGIT) are innervated by the sacral spinal cord. We aimed to compare the normal physiology of the LUT and LGIT using the same videomanometry method.

Methods:  We recruited fifteen healthy volunteers (eight men and seven women; mean age, 60 years). The videomanometric measures included fluoroscopic images, subtracted bladder/rectal pressures, urethral/anal sphincter pressures, sphincter electromyography, and urinary/fecal flow.

Results:  During the resting phase, the urethral/anal sphincter pressures showed almost the same values (mean, 70 cmH2O and 68 cmH2O, respectively). During the storage phase, the volumes at first sensation and maximum capacity for the LGIT (129 mL and 320 mL) were slightly smaller than those for the LUT (170 mL and 405 mL). Compliance of the LGIT (65 mL/cmH2O) was almost as high as that of the LUT (99 mL/cmH2O). However, the LGIT showed spontaneous phasic rectal contractions (SPRC) that were never seen in the bladder. None of the subjects experienced leakage during bladder/rectal filling. During the evacuation phase, rectal contraction on defecation (14 cmH2O) was present, but was weaker than bladder contraction on micturition (42 cmH2O; P < 0.01). Abdominal strain on defecation (70 cmH2O) was greater than that on micturition (25 cmH2O; P < 0.01). Sphincter pressure increase on defecation (13 cmH2O) was greater than that on micturition (−52 cmH2O). An illustrative case of SPRC that were seen during urodynamic recording was shown.

Conclusion:  SPRC and abdominal strain are features of the LGIT, whereas micturition bladder contraction is a feature of the LUT. These features can aid in understanding the possible rectal ‘artifacts’ of videourodynamics and neurogenic pelvic organ dysfunction.