Introduction
Currently, cholescintigraphy is considered the procedure of choice for diagnosing acute cholecystitis. A previous review suggested that the sensitivity and specificity of cholescintigraphy may be as high as 94 -100%". However, conventional imaging protocols frequently require delayed imaging for up to 4 hours post injection of the radiotracer", or for even up to 24 hours in patients with several intercurrent disease", to achieve a sufficiently high level of accuracy. Delayed imaging can be logistically inconvenient and potentially disadvantageous to the patient, and may not be feasible in some clinical settings.
The intravenous administration of morphine results in significant contraction of the sphincter of Oddi. This, in turn, causes an increase in the intraductal pressure and forces the bile flow from the common bile duct into the gallbladder(GB) if the cystic duct is patent. For this reason, morphine-augmentation has been used as an alternative to delayed imaging to shorten the total imaging time required to diagnose acute cholecystitis3´. The entire study can be terminated in 90 minutes in contrast to the 4 or more hours with delayed imaging. Previous studies of patients with suspected acute cholecystitis have indicated that the morphine-augmentation is as useful as, or more useful than, delayed imaging").
However, another comparison of the efficay of the two techniques would appear warranted for several reasons.
1. Most investigators did not compare the two techniques in a single series using comparable patient populations. Only one of the 7 morphine reports that we reviewed compared the efficacy of the two techniques directly 3).
2. The efficacy of delayed imaging alone has not been independently evaluated. The reported effica cy of morphine-augmentation is based primarily´ on study designs which excluded cases of early GB visualization without morphine´-", while most__ delayed imaging protocols included these cases.
3. Some concerns have been raised about false-negative -augmented studies, which need to be exam; ined"-"´. The consequences of a false-negative study can be grave if it results in delayed surgical intervention. H We compared the efficacy of morphine-augmenta´
tion with delayed imaging in those cases in which the
GB was not visualized during the first hour of study.
Materials, Methods, and Results(Read Ref; erence 12 for more detailed data and ding; cussion)
r
Of 306 consecutive patients who were scanned to rule out acute cholecystitis, the GB was visualized,, within 1 hour in 215 cases. 210 patients did not have_ acute cholecystitis. Therefore, GB visualization with in one hour has an negative-predictive value of 98%.. In the remaining 91 cases with GB nonvisualizati6n within 1 hour, 46 patients had delayed imaging(1Z true+, 10 true-, 19 false+, and 0 false-), and 45 had morphine -augmentation(24 true +, 15 true-, 4 , false+, and 2 false-). The data indicate that delayed imaging has a significantly lower specificity and positive-predictive value for acute cholecystitis than morphine-augmentation, and a slightly higher (statistical-; ly insignificant) sensitivity and negative-predictive value.
We have also reviewed the literature on morphine-´ augmentation3-" and conventional imaging´-´-"´, and, the data which excluded cases with early GB
visuLiiization were reanalyzed. When cases with early GB visualization were excluded from the analysis, delayed imaging had on overall sensitivity of 98 % (97
100%), and a specificity of only 71%(33%-94%). A total of 283 patients with morphine-augmentation in 6 reports´ 5-v´ were analyzed. Overall sensitivity of
morphine-augmentation was 96 % (range : 94%-100 %) that is similar to 98%-sensitivity of delayed im
aging(p=0.25). Morphine imaging had a specificity of 87%(69%-100%) that is significantly higher than 71% of delayed imaging(p=0.028). When the disease prevalence in each group was, although not as low as the value in our series, still significantly lower than that(87%) of morphine-augmentation(p=0. 014), and the recalculated negative-predictive values
f the two groups were similar(97 % and 96%).
E L- findings are consistent with our results.
Conclusion
Our findings appear to agree with previous reports
t have suggested that GB visualization within one ,ur has a very high negative-predictive value for ute cholecystitis(1).
.However, nonvisualization on the delayed images pears to be a nonspecific finding. Morphine-augntation can be quite helpful in these cases. It ms to have a reasonably good specificity and posi
ve-predictive value which are significantly better
that of delayed imaging. These results appear to supported by a reanalysis of previous reports in literature.
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