Anorectal manometry with balioon distension was performed on 28 patients with diarrhoea predominant irritable bowel syndrome, 27 patients with constipation predominant irritable bowel syndrome and 30 normal controls. In the diarrhoea predominant group balloon volumes required to perceive the sensations of gas, stool, urgency of defecation and discomfort were significantly lower than in controls or constipation predominant patients (p<0-001). Diarrhoea predominant patients also had a significantly lower rectal compliance than controls or constipation predominant patients (p<003) but showed no difference in motor activity induced by distension. When the constipation predominant patients were compared with controls the only significant difference that emerged was in the volume at which discomfort was perceived. No significant differences between constipated subjects and controls were found in the distension induced motor activity. Symptom severity and psychological parameters were also recorded and the diarrhoea predominant patients were found to be more anxious than those with constipation (p=0.04). It proved possible (by comparison with the control group) to identify three abnormal rectal subtypes in patients with irritable bowel syndrome. These were a sensitive rectum (low sensation thresholds, normal or low rectal pressure), a stiff rectum (normal or low sensation thresholds, high pressure) and an insensitive rectum (high sensation thresholds, normal or high pressure) and their distribution varied considerably depending on bowel habit. Some form of rectal abnormality was identified in 75% ofdiarrhoea predominant patients compared with 30% of constipation predominant subjects (p=0002). A sensitive rectum was a particular feature of diarrhoea predominant patients being observed in 57% of patients compared with only 7% of the constipated group (p<0001).

The urinary excretion of lactulose, 51Cr-labelled ethylenediaminetetra-acetate (51Cr-EDTA), L-rhamnose and polyethyleneglycol 400 (PEG-400) has been measured after intravenous and oral administration in healthy volunteers. Intestinal permeation of the probes was compared after their ingestion in iso-osmolar, hyperosmolar and cetrimide-containing test solutions. Urinary recovery of lactulose and 51Cr-EDTA after intravenous administration reached 75% by 5 h, and exceeded 90% at 24 h, and these values were 62 and 72%, respectively, for L-rhamnose. Recovery of PEG-400, however, varied with the relative molecular mass (Mr) of each polymer from 25.9 to 68.5% in 24 h. Intestinal permeation of ingested lactulose and 51Cr-EDTA was low, but that of L-rhamnose was 45-fold, and that of PEG-400 100-fold, greater. Permeation of lactulose and 51Cr-EDTA was markedly increased by cetrimide and hyperosmolar stress, whereas that of L-rhamnose showed little change. PEG-400 permeation was not affected by cetrimide, but was slightly increased by hyperosmolar stress. The 5 h permeation of lactulose, but not of L-rhamnose or PEG-400, correlated with that of 51Cr-EDTA (r = 0.98, P less than 0.001). These findings are compatible with three distinct pathways of unmediated mucosal permeation, L-rhamnose (radius less than 0.4 nm) passing mainly through small aqueous 'pores' of high incidence, lactulose and 51Cr-EDTA (radius greater than 0.5 nm) through larger aqueous 'channels' of low incidence susceptible to cetrimide and hyperosmolar stress, and PEG-400, which has appreciable lipid solubility, by partition through cell membrane lipid as well as the aqueous 'pores'.

No abstract

Abdominal distension is one of the principal features of irritable bowel syndrome.'~' Characteristically, patients report that distension is absent in the morning and progressively appears during the day with eating being the most frequent exacerbating factor.4 The cause is entirely unclear and many question whether it is even a real phenomenon. Explanations to account for this symptom include excessive intraabdominal gas, depression of the diaphragm, increased lumbar lordosis, and voluntary protrusion of the abdomen.' There has been little or no investigation of the subject, however, not even to the extent of documenting whether girth does actually alter during the day.It was the purpose of this study to confirm or refute the existence of abdominal distension by objective measurements and then examine possible mechanisms with the aid of computed tomography.

The results of this study justify evaluation of the therapeutic potential of selective 5-HT antagonists in both functional dyspepsia and irritable bowel syndrome.