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is no guarantee against disease, particularly in the sigmoidcolon of patients with diverticular disease where even largepolyps are missed by good-quality radiological examination.

There. is a trend in the USA towards a short 30-35 cmflexible sigmoidoscope (truly a flexible version of thetraditional rigid instrument), the longer 60 cm instrumentbeing restricted by the understandable "closed shop"attitude of the American Society for Gastrointestinal

Endoscopy, which nonetheless is trying to establish trainingprogrammes both for interns and for primary care physicians.In other medical systems, including the National HealthService, any doctor competent to use a rigid sigmoidoscopecould probably convert without difficulty to a flexibleinstrument after basic tuition; with expert tuition and

experience he or she will get even better results. Flexiblesigmoidoscopy is a rich man’s version of rigidsigmoidoscopy; it is not a poor man’s version of colonoscopy.Every gastroenterologist should aim to become "a rich man".

X-RAYS IN CHILDHOOD ASTHMA

WHEN asked whether a child with asthma should have achest X-ray on at least one occasion, a group of specialistswith an interest in childhood asthma were strongly in

favour-83% for, 17% against.’ There are two basicindications for requesting a chest X-ray in a child with anapparent attack of asthma-firstly, to exclude a complicationthat requires a prompt change in management (eg, pneumo-thorax or pneumonic consolidation); and, secondly, when thechild is very young or the clinical history not entirely straight-forward, to help exclude pulmonary disorders simulatingacute asthma, such as congenital anomalies, radio-opaqueforeign bodies, and cystic fibrosis. In clinical practice a clearradiograph of a tachypnoeic but adequately treated childdoubtless brings comfort to the inexperienced physician andthe anxious parent, but are such X-rays worthwhile? Gersheland co-workers2 analysed 371 standard posteroanterior andlateral chest radiographs in first-time wheezers seen in theemergency room over one year (average age 42 months). Asexpected 350 (94-3%) films were compatible with the

diagnosis of uncomplicated asthma-ie, they showed hyper-aeration, peribronchial thickening, increased central

markings, and segmental atelectasis. 21 radiographs (5-7%)revealed, in order of frequency, atelectasis and pneumonia,segmental atelectasis, pneumonia, multiple areas of atelec-tasis, and a pneumomediastinum. Pneumothorax and otherpulmonary conditions associated with wheeze were not seenin this group of young asthmatic children. 22 of the 350 filmswere initially misinterpreted by house-staff as showinginfective changes and antibiotics were needlessly prescribed,and only 10 (out of21) of the abnormal X-rays were correctlyidentified in the emergency room. There seemed to be acorrelation between the severity of asthma (respiratory rate60, pulse rate 160, fever 38’3°C, localised crepitations ordecreased breath sounds) and abnormal radiological findings.These observations agree broadly with earlier studies3,4 andsuggest that not every child with acute asthma requires achest X-ray on admission to hospital.

1. Henry RL, Milner AD. Specialist approval to childhood asthma: does it exist? Br Med J1983; 287: 260-61

2. Gershal JC, Goldman HS, Stein HS, Shelov SP, Ziprkowski M. The usefulness of chestradiographs in first asthma attacks. N Engl J Med 1983; 309: 336-39.

3. Hodson ME, Simon G, Batten JC. Radiology of uncomplicated asthma Thorax 1974;29: 296-303.

4 Bierman CW. Pneumomediastinum and pneumothorax complicating asthma in

children Am J Dis Child 1967; 114: 42.

Whatever the radiological appearances of uncomplicatedasthma, none of the features is pathognomonic of the condi-tion and all may occur in other chronic lung disorders. Thusit is essential to review the patient and the X-ray until bothreturn to normal. Failure to do so results in missed and

delayed diagnoses of cystic fibrosis, vascular ring, foreignbody inhalation, respiratory disease due to gastro-

oesophageal reflux, and (very occasionally) an upper airwaytumour. Moreover, when an inhaled foreign body is

suspected clinically but the standard posteroanterior film isnormal, the next move should be inspiration-expirationradiography or even computerised tomography. Serious

complications of acute asthma, such as pneumothorax orpneumomediastinum, are associated with severe and chronicdisease and are age-related-hence the low incidence in theUS study.2 Thus before requesting an urgent chest X-ray oneshould consider the severity and duration of the attack, theage of the child, the clinical history, physical findings, peak-flow meter readings and, when available, arterial blood gasvalues. All these are helpful pointers to whether a radiographwould be of practical value in management. Certainly, if achild does not respond quickly to treatment, a portable X-rayshould be taken forthwith and the patient’s clinical coursediscussed with a knowledgeable medical or radiologicalcolleague. Such a simple practice would assist greatly ineducating the clinician, eliminate some of the errors of filminterpretation, and reduce the number of unnecessary chestX-ray requests.

PRECAUTIONS WITH LEGIONELLA

IN our editorial of Sept 24 (p 716) we said that Legionellapneumophila "is no longer classified in the UK as a BI

pathogen, though it must still be handled with respectaccording to WHO risk category 2". The first part of thissentence was incorrect, though the reclassification may sooncome to pass. The Advisory Committee on DangerousPathogens has recommended that Legionella may be handledin clinical laboratories as "risk group 2", but until formalapproval by the Department of Health and others it shouldcontinue to be treated as a B 1 pathogen. An organism in riskgroup 2 is defined by the Advisory Committee’ as "A

biological agent that may cause human disease and whichmight be a hazard to laboratory workers, but is unlikely tospread in the community. Laboratory exposure rarelyproduces infection and effective prophylaxis and treatmentare available." Work with such organisms should be per-formed in the laboratory according to "containment level 2"and the staff concerned must have received "training inhandling pathogenic agents and an appropriate standard ofsupervision of the work must be maintained." However, ingeneral, the work "may be conducted on the open bench, butcare must be taken to minimise the production of aerosols.For manipulations such as vigorous shaking, mixing andultrasonic disruption, etc, a microbiological safety cabinetshould be used (class 1; BS 5726; 1979) or equipment which isdesigned to contain the aerosol." These recommendations ofthe Advisory Committee, if and when approved, will domuch to encourage diagnostic culture of clinical material forLegionella organisms and will bring the UK into line withmany other countries and WHO.

1. Advisory Committee on Dangerous Pathogens. Characterisation of pathogensaccording to risk and categories of containment. Report no I submitted to the Healthand Agriculture Ministers and the Health and Safety Commission for consultationJanuary, 1983.