Pain and mechanical properties of the rectum in patients with active ulcerative colitis.
BACKGROUND
The pain, urgency, and incontinence in ulcerative colitis may be related to changes in viscoelastic properties of the gut wall or to alterations of the sensory pathways. In the present study, we used an advanced rectal probe to study the mechanosensory and smooth muscle properties in patients with active disease.


METHODS
Nine patients with ulcerative colitis (mean age 39.5 years) with exacerbation limited to the rectum and sigmoid colon and 17 age-matched healthy subjects were included. The rectum was distended before and after pharmacological relaxation of the smooth muscle until moderate pain was reported, and the cross-sectional area, volume, pressure, tension, and strain were computed. To investigate central integration of a tonic stimulus, the bag was finally distended to the pain threshold; then, the cross-sectional area was held constant for 2 min.


RESULTS
The patients were hypersensitive to mechanical stimuli as assessed by the cross-sectional area (F = 21.7; P < 0.001). There were no differences in compliance or stiffness between the 2 groups, but the hypersensitivity was abolished after muscle relaxation. Together with the muscle analysis, this finding demonstrated that the smooth muscles were tonically contracted in the inflamed rectum, resulting in a decreased rectal circumference. The tonic distensions did not evoke central integration of the pain response, indicating that hyperalgesia is more likely related to peripheral factors.


CONCLUSIONS
Patients with active ulcerative colitis have hypersensitivity and increased tone of the smooth muscles, which may explain the symptoms. Drugs that affect smooth muscle contraction may be helpful in difficult cases.
Drewes
Asbjørn Mohr
AM
Center for Visceral Biomechanics and Pain, Department of Gastroenterology, Aalborg University, Denmark. drewes@smi.auc.dk
Frøkjaer
Jens Brøndum
JB
Larsen
Ejnar
E
Reddy
Hariprasad
H
Arendt-Nielsen
Lars
L
Gregersen
Hans
H
D000328:Adult; D003093:Colitis, Ulcerative / Q000150:complications / Q000503:physiopathology*; D018450:Disease Progression; D004548:Elasticity; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D009130:Muscle, Smooth / Q000503:physiopathology; D010146:Pain / Q000209:etiology / Q000503:physiopathology*; D010147:Pain Measurement; D010812:Physical Stimulation; D010865:Pilot Projects; D012007:Rectum / Q000503:physiopathology*; D012720:Severity of Illness Index