Constipation and spina bifida occulta: is there an association?

Spina bifida occulta (SBO) is an abnormality in the posterior arch formation, most commonly found at the level of the S1 vertebra. It has recently been implicated in the aetiology of urinary voiding problems. We have therefore investigated its incidence in female patients with constipation due to outlet obstruction (anismus) and slow colonic transit. The plain abdominal radiographs of 52 females with constipation, and 48 age-matched controls were reviewed by one radiologist, looking for both the incidence of SBO and the incidence of abnormally high posterior sacral arc opening (S3 and above) in each group. Seventeen (32.6%) patients compared to 11 (22.9%) control subjects had SBO (chi 2 1.183, P = 0.4). Fourteen (26.9%) patients compared to six (12.4%) control subjects had an abnormally high posterior sacral arc opening (chi 2 2.406, P = 0.2). Three of seven patients (42.6%) with anismus were found to have SBO. Of 19 patients with slow colonic transit five (26.2%) had SBO and of seven patients with a mixed picture, three (42.6%) had SBO. There was no significant difference in the incidence of SBO in any of these three patient subgroups when compared to the control group. These results suggest that there is no association between spina bifida occulta and constipation.