The stimulation of the colon after eating is within most individuals' experience and an exaggerated response is frequently a problem in patients with functional diarrhoea or irritable bowel syndrome. Early studies showed that fatty meals stimulated colonic pressure waves more than carbohydrate meals, whereas amino acid meals tended, if anything, to inhibit motility. Although these initial studies recorded only from the rectum and distal sigmoid colon we now know that the whole colon responds, though the response is less pronounced and of shorter duration in the proximal compared with the distal colon. As well as stimulating phasic activity, eating also increases colonic tone both proximally and distally.1

Modern, solid state manometric systems, which use strain gauges mounted on tubes as in the study by Rao et al (see page 205), have a much smaller diameter and are more comfortable for the patients than the older water perfused manometry catheters and permit prolonged ambulatory studies. Twenty hour recordings have shown a noticeable circadian rhythm, with pronounced activation on wakening and after eating. These recordings also make it possible to get an accurate estimate of the frequency of infrequent forceful propulsive waves, known as high amplitude propagated contractions (HAPCs). These are characterised by high …