Assessment of microtransducers in anorectal manometry

It has been reported that microtransducer-tipped catheters (transducer) produce reliable reproducible measurements which correlate well with water-filled balloon systems. Maximum resting pressure (MRP) and maximum voluntary contraction pressures (MVC) were compared using a standard station pull-through technique in 12 patients. There was a poor correlation for both MRP: microballoon, 115 cmH2O (60-160 cmH2O); transducer 60 (20-110), r = 0.62, P less than 0.05, and MVC: microballoon, 202 (60-375); transducer, 175 (60-210), r = 0.42, n.s. To determine whether this was due to radial variation in pressures measured by the transducer, we studied a further 39 patients with both systems. At each station, transducer measurements were made at each of four quadrants. We found better correlation for MRP: microballoon, 100 (40-175); transducer, 66 (34-120), r = 0.72, P less than 0.001, and MVC: microballoon, 225 (55-650); transducer, 180 (50-470), r = 0.87, P less than 0.001, but a significant radial variation for the transducer where rotation reduced MRP pressure measurements by 21 per cent (0-600 per cent), and MVC 17 per cent (0-76 per cent). Moreover there was a significant difference between anterior and posterior MRP in the upper anal canal, anterior 35 (5-80) versus posterior 25 (10-60), P less than 0.05. These results account for the poor correlation between random positioning of the microtransducer-tipped catheter and indicate that radial orientation must be taken into account.