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Editor,—We read with interest the commentary by Al-Musawi and Williamson (Gut1998;43:454–5) and the paper in the same issue by Smythe et al(Gut1998;43:571–8). We agree with Al-Musawi and Williamson that six months is an inadequate follow up time, that identification of cystic duct abnormalities is important and in particular that cholecystokinin (CCK) scintigraphy is a more accurate technique than either ultrasound or oral cholecystography. We however disagree with their view that the CCK provocation test, based solely on the reproduction of pain, is of diagnostic value.
The value and accuracy of CCK scintigraphy has been well documented by several groups1-4 including our own.5-7 The true positive rates for all these studies are in the range 94–97%. Our most recently reported data7 are from an eight year prospective study of 235 patients, with follow up (mean 4.5 years) of all patients, surgical and non-surgical, with both normal and abnormal gall bladder ejection fractions. This demonstrates 96% sensitivity, 92% specificity and 95% overall accuracy for CCK scintigraphy in predicting gall bladder dysfunction and long term clinical outcome. These findings are in agreement with the 6% false negative rate obtained by Fink-Bennett and colleagues1 in a retrospective study. In our series, abnormal cystic ducts were found in 12% of patients who underwent surgery, all of whom were symptom-free on long term follow up.
In their introduction, Smythe et al state that Yap and colleagues3 and ourselves5 claim some efficacy for the CCK provocation test. This is incorrect. Both papers clearly describe the efficacy of CCK scintigraphy and the measurement of gall bladder ejection fraction. We have never advocated pain reproduction as an indicator of gall bladder dysfunction. Despite using a fast (three minutes) infusion of CCK,8 thought to be more likely to induce pain and cause spasm of the cystic duct, we have found no correlation between the reproduction of pain following CCK infusion and either gall bladder ejection fraction or subsequent surgical outcome.7 We agree with Smytheet al that pain reproduction following CCK infusion is not a diagnostic predictor.
Our experience of using CCK scintigraphy in over 300 patients over a 10 year period (manuscript in preparation) is that an abnormal gall bladder ejection fraction is highly predictive of gall bladder dysfunction and is a good predictor of long term clinical outcome following surgery.
CCK scintigraphy is an accurate, objective technique and in our view should be the investigation of choice for suspected gall bladder dysfunction in patients without gallstones.
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