Renal artery stenosis (RAS) is the commonest secondary cause of hypertension and may result in renal ischaemia with resultant renal failure. Recent studies hve suggested that colour Doppler ultrasound, with spectral analysis of the intrarenal waveforms, can identify those patients with a significant RAS. A prospective study was performed in which colour Doppler ultrasound was compared with angiography in 73 patients (143 kidneys) presenting for renal angiography. Colour Doppler ultrasound was unsuccessful in 16% of kidneys due to a combination of technical failures and small kidney size. Accessory renal vessels were present in 14% of kidneys on angiography but none was detected by ultrasound. Of the 120 kidneys that had both examinations, no significant difference in intrarenal pulsatility or resistive index was noted between the angiographically stenosed and normal arteries. There were significant differences for intrarenal peak and end diastolic velocities, and acceleration time and index. Of these measurements, acceleration time was the best indicator of RAS. The probability of detecting a high grade RAS in an individual patient did not reach 90% until the acceleration time was prolonged to more than 0.12 s. Intrarenal colour Doppler ultrasound is not a general screening test for RAS and it should be reserved for selected patient groups where the incidence of disease is high. Patients with prolonged acceleration times of more than 0.12 s have a high likelihood of at least 70% RAS and should proceed directly to angiography.

SUMMARYTo assess whether an accurate diagnosis of pneumothorax can be made on a single chest film, 233 pairs of inspiratory (I) and expiratory (E) chest films taken in an accident and emergency (A&E) department for suspected pneumothorax were reviewed by two A&E officers and three radiologists. The films were assessed for the presence of pneumothorax by viewing the I film in isolation and, after an interval, by viewing the paired I and E films together. Fifty-four of the patients had a pneumothorax. The five observers missed 23 pneumothoraces (8.5% of total) on the I film alone which were correctly diagnosed on the paired I and E films, the three radiologists missed 10/162 pneumothoraces on the I film alone which were correctly identified on the I and E films (6%) and the two A&E officers 13/108 (12.5%). The use of a single inspiratory chest film for suspected pneumothorax could result in pneumothoraces being missed, particularly by less experienced observers and therefore we believe that paired I and E films should continue to be used routinely for suspected pneumothorax.

Many different imaging modalities and techniques have been used in the past for the diagnosis of renal artery stenosis. The ideal accurate, non-invasive and inexpensive diagnostic test has yet to be found but there have been promising developments during the last few years. In this review we consider in detail the use of the following tests for the diagnosis of renal artery stenosis; intravenous urography, B Mode ultrasound, Doppler ultrasound, renal scintigraphy with angiotensin-converting

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