1601pathy. Only one abnormal ratio was found in the 75 diabetics of grades 0 and 1, in whom autonomic function was normal on conventional testing. In grade 2, 41 of the 47 diabetics gave abnormal or borderline results. The ratios in the 12 with symptomatic autonomic neuropathy (grade 3) were all well below the normal range.Repeat measurements of the E:I ratio varied little; the coefficients of variation were 8 9°in healthy subjects and 5 3%/ in diabetics. DiscussionMeasurement of variation in heart rate during deep breathing is generally agreed to be a sensitive index of autonomic dysfunction, comparing favourably with tests based on changes in posture.1 3 Adaptation of a repeated deep breathing test for use with a conventional electrocardiogram to obtain an E:I ratio was first described by Sundkvist et al,11 which represented a considerable simplification in technique over previous methods. These authors did not define the influence of age on this ratio but set the lower limit of normal at an E:I ratio of 1-1. When applied to the ratios measured here this limit gave three falsepositive and 16 false-negative diagnoses. The age-related normal range described in this report increases the diagnostic value of the E:I ratio test since there were only one false-positive and six false-negative results.There does not appear to be any advantage in averaging the variations in heart rate from a sequence of forced respirations compared with measuring the change resulting from a single deep breath. The change in rate is greater on the first breath1 12 and, in contrast to the mean, is not affected by the resting heart -rate,5 which simplifies the construction of a normal range.I conclude, therefore, that the E:I ratio test of sinus arrhythmia is an accurate and reliable method of screening diabetic patients for autonomic dysfunction. It may be performed rapidly by a nurse or technician with any electrocardiographic apparatus and immediate reference made to the normal range. It is thus appropriate for use in the diabetic clinic.I am grateful to the British Diabetic Association for financial support, Professor S E Smith for statistical advice, and Professor P H Sonksen and Dr C Lowy for allowing me to study their patients. ReferencesMackay Microscopic colitis-a cause of chronic watery diarrhoea JEREMY G C KINGHAM, DAVID A LEVISON, JOANNA A BALL, ANTHONY M DAWSON Abstract Six patients with severe watery diarrhoea were found to have microscopic total colitis. None had any abnormality detectable by conventional tests used to diagnose inflammatory bowel disease-namely, barium radiology and endoscopy. The diagnosis could only be made by microscopic examination of biopsy specimens from the apparently normal colon. Anaemia, raised erythrocyte sedimentation rate, hypokalaemia, and hypoalbuminaemia were common findings. Smallbowel function was normal in all, though three patients had jejunal lesions of uncertain relevance but seemingly unrelated to the diarrhoea. The five patients given anti-inflammatory drugs showed a satisfactory re...

Clinical and pathological aspects of six patients with collagenous colitis are presented. These patients have been observed for between four and 15 years and the evolution of the condition is documented in three (cases 1, 3 and 5). Management and possible pathogenetic mechanisms of this enigmatic condition are discussed. The term collagenous colitis was introduced by Lindstrom' in 1976 to describe the microscopical changes seen in the rectal biopsies of a patient with longstanding watery diarrhoea. Since then over 20 isolated cases have been reported mainly from continental Europe.220 The clinical and pathological descriptions have all been similar. The patients are predominantly middle aged women, essentially well apart from watery diarrhoea and abdominal pain. Clinical examination, including sigmoidoscopy, is usually unremarkable as are laboratory investigations. The condition is unresponsive to conventional treatment used in inflammatory bowel disease. The cause of the abnormally thick band of collagen underlying the colonic epithelium is speculative as is its relationship to the diarrhoea, but it is tempting to attribute the latter to the former. Some have proposed2 10 12 14 19 that the pathogenesis lies in the abnormal differentiation of the pericryptal fibroblastic sheath,21 but the primary aetiology is obscure. The paucity of published cases implies this condition to be exceptionally rare. One of us has seen and followed six new cases in the past 13 years in the course of general gastroenterological practice, which suggests collagenous colitis to be commoner than generally supposed. We report the clinical and pathological aspects of these six patients.

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