Chronic Fatigue Syndrome (CFS) is a descriptive term used to define a classifiable pattern of symptoms that cannot be attributed to any alternative condition 1. It can be associated with immunological alterations, neuro-endocrine changes 2, sleep disturbance and disturbed neurocognitive performance with abnormal cerebral perfusion 3, but the pathophysiological significance of these is uncertain. Skeletal neuromuscular function is usually normal in CFS sufferers 4.

Many with CFS have gastro-intestinal (GI) symptoms, which are often unrecognised as being part of CFS. The commonest of the upper GI symptoms include fullness and bloating after a small meal, abdominal distension, nausea, and loss of appetite. Lower GI tract symptoms have considerable overlap with irritable bowel syndrome 5.

The hypothesis explored in this paper is that symptoms of possible upper gastrointestinal origin are more common in patients with CFS and are related to upper gastrointestinal motility as assessed by radionuclide methods.

Thirty-two (32) CFS patients (22F), with a mean age of 38.5 years had gastric emptying studies. Forty-five (45) control subjects undertook the questionnaire. The demographic details of the controls vs. patients are shown in table 1 Gastro-intestinal symptoms were more common in the CFS group (mean symptom score {MSS] 1.01 ± 0.87) than controls (MSS 0.24 ± 0.34) (table 2).

The overall, grouped gastric emptying studies of CFS subjects showed no significant slowing of oesophageal clearance p = 0.45 from the control population, and no significant correlation between emptying and oesophageal symptom score (r = 0.15) although 5 of the symptomatic and 2 of the asymptomatic subjects 7/32 (22%), were slower than the 95% confidence limits, (fig 1), this did not reach statistical significance. The major abnormality shown is a delay in the emptying of the liquid phase in 23/32 72% of the patients, whereas 12/32 (38%) of solid emptying was delayed compared with the historic controls (t comparison of means, figs 2 and 3, group p ≪ 0.005). When the gastric emptying results were compared to the mean symptom score there was a highly significant correlation of solid (r = 0.81) and liquid (r = 0.65) delay which increased with the symptom score (p ≪ 0.001).

G-I symptoms are common in patients with CFS. Abdominal pain is distressing 10, often requiring analgesia for relief. A previously unrecorded symptom in CFS patients is nocturnal diarrhoea, which disrupts an already disturbed sleep pattern. The most common upper GI symptom is fullness and bloating after a small meal. The usual medical explanation for the gut symptoms is 'irritable bowel'. Unless specific G-I questions are put to the CFS patient they will not spontaneously discuss these symptoms.

An abnormality in solid or liquid emptying or combinations of these study parameters was more common in the more symptomatic patients, and liquid was more frequently affected. This is the opposite of the abnormality seen in diabetic subjects 8, where the major abnormality, delay in the solid phase of gastric emptying has been ascribed to autonomic dysfunction or hyperglycaemia. A group of elderly subjects with a number of neurological defects showed a delay in the liquid rather than the solid emptying 11.

Symptoms and delayed gastric emptying in diabetic gastroparesis studies have not correlated well. In this study there is a good correlation with symptoms. The commonest of these was early satiety, fullness and bloating after eating. There was though a poor correlation with oesophageal symptoms and a disorder of oesophageal emptying.

GI motility is complex, with central, local neuromuscular and humoral influences. Non-specific endocrine disturbances have been demonstrated in CFS, but the relevance of these is unknown with regard to GI disturbances. Skeletal muscle fatigue appears to be of central rather than peripheral origin, but again it is not known whether this may be extrapolated to visceral muscle.

Inconclusive central changes have been documented. The impact of disturbed sensory function is unknown, and this could also involve peripheral nerves or the central processing of sensory information.

Diagnostically, there is overlap between CFS, functional dyspepsia and fibromyalgia and all may be related to abnormal sensory processing 101213. Altered gastric emptying has been shown in association with irritable bowel syndrome 14.

These observations indicate that there is measurable disturbance in upper gut motility corresponding with symptoms in CFS. Although the cause for these findings is not apparent in this study, the more prominent delay in liquid rather than solid emptying may point to a central rather than a peripheral aetiology. The gastro-intestinal tract and function should be properly investigated and the symptoms not necessarily be ascribed to irritable bowel syndrome.

The author(s) declare that they have no competing interests.

RB examined the patients and analysed the clinical data, BC performed the Nuclear Medicine studies, drafted the manuscript and performed the statistics. Both read and approved the final manuscript.