Diseases of the COLON /r RECTUM Vol. 30 September 1987 No. 9 Is Paradoxical Contraction of Puborectalis Muscle of Functional Importance? P. N. JONES, B.Sc., D. Z. LUBOWSKI, M.B., F.R.A.C.S., M. SWASH, M.D., F.R.C.P., M.R.C.PATH., M. M. HENRY, M.B., F.R.C.S. Jones PN, Lubowski DZ, Swash M, Henry MM. Is paradoxical contrac- tion of puborectalis muscle of functional importance? Dis Colon Rec- tum 1987;30:667-670. Paradoxical contraction of the puborectalis muscle during simulated defecation straining (anismus) has been cited as a cause of constipation. The functional specificity of this phenomenon was evaluated in 79 patients, 50 with constipation, 21 with idiopathic perineai pain, and eight with solitary rectal ulcer syndrome. Eiectromyogram evidence of paradoxical puborectalis contraction was observed in 38 (76 percent), ten (48 percent), and four (50 percent) of these patients, respectively. All patients with solitary rectal ulcer syndrome had difficulty defecating; defecation was normal in all patients with perineal pain. These obser- vations suggest that paradoxical contraction of the puborectalis muscle is not a specific finding, and that it is not the sole cause of constipation in patients with anismus. [Key words: Constipation; Electromy- ography; Anorectum; Pelvic floor disorders] PARADOXICALCONTRACTIONof the puborectalis mus- cle is defined as contraction rather than relaxation of this muscle during simulated defecation straining, as demon- strated by defecating proctographic or electromyographic (EMG) studies. It has been suggested that this paradoxical activation of the puborectalis muscle causes functional obstruction of the pelvic floor outlet, leading to the defe- catory disorder termed anismus ~ or "spastic pelvic floor Receivedfor publication March 9, 1987. This study was supported by the St. Mark's Hospital Research Foundation and the F. H. Muirhead Trust. P. N. Jones was attached to the Sir Alan Parks PhysiologyLaboratoryduring an elective period by arrangement with The Medical School of The Universityof Leeds. Address reprint requests to Dr. Swash: St. Mark's Hospital, City Road, London EC1V 2PS, United Kingdom. From the Sir .4 lan Parks .4norectal Physiology Laboratory, St. Mark's Hospital, London, United Kingdom syndrome."z The latter term is misleading, however, since there is no evidence that paradoxical puborectalis con- traction is due to a lesion of the corticospinal tract. It is somewhat surprising that surgical division of the pubo- rectalis muscle in patients with constipation associated with paradoxical puborectalis activity has failed to pro- duce marked functional improvement) This disorder of puborectalis activity has been noted not only in patients with constipation but also in those with solitary rectal ulcer syndrome. 4-6 This paper reports observations suggesting that para- doxical puborectalis activity is a relatively nonspecific finding that cannot be directly related to any particular clinical presentation. Patients and Methods Fifty patients referred to St. Mark's Hospital with con- stipation, 21 with idiopathic perineal pain and eight with solitary rectal ulcer syndrome, were studied. All patients with constipation experienced no more than two bowel movements weekly. The mean age of these constipated patients was 46 (range, 17 to 74) years. The patients with idiopathic perineal pain reported a continuous, dull, throbbing pain and a sensation likened to a ball in the anal canal (chronic idiopathic anal pain), but some had a continuous ache with exacerbations. A sudden crescendo pain that stopped spontaneously (proctalgia fugax) oc- 667