THE ROLE OF ULTRASONOGRAPHY IN THE DIAGNOSIS OF PYLORIC-STENOSIS - A DECISION-ANALYSIS

Background/Purpose: The appropriate role for ultrasonography (US) as a replacement for the upper gastrointestinal series (UGI) in vomiting i nfants remains undefined. The authors have used decision analysis tech niques to determine whether the use of ultrasonography as an initial s creen in vomiting infants is cost effective when compared with the UGI as the only study. Methods: Two diagnostic strategies were compared: 1) UGI alone and 2) ultrasonography followed by an UGI series in 50% o f cases when ultrasonography scan was negative for pyloric stenosis. T he test sensitivity (US, 0.9; UGI, 1.0) and test specificity (US, 1.0; UGI, 1.0) and the incidence of pyloric stenosis among vomiting infant s presenting to the community pediatrician (0.30) or after a negative examination by an experienced examiner (0.02 to 0.18) were obtained fr om a review of the literature. The relative charges for ultrasonograph y and UGI were obtained from a national survey from which the cost rat io of US to UGI was estimated to range from 0.67 to 1.81 with a median of 1.06. Results: Under these baseline assumptions, UGI only was the preferred strategy. The results of the decision analysis were sensitiv e to, or dependent on, assumptions made regarding the incidence of pyl oric stenosis, the US to UGI cost ratio, the sensitivity of the US, an d the proportion of patients that proceed to UGI when the US scan was negative for pyloric stenosis. When at least 50% of patients whose US scan was negative for pyloric stenosis proceeded to a UGI, UGI remaine d the preferred strategy for all cost ratios examined (0.6 to 1.7). Ev en when no patients proceeded to UGI, the cost ratio of US to UGI had to be less than 0.7 under the typical incidence (0.30) of pyloric sten osis among vomiting infants presenting to the community pediatrician f or US to be cost effective. Finally, only UGI was indicated when an ol ive was not appreciated by an experienced examiner. Conclusion: Under assumptions that fit most clinically relevant circumstances, the UGI a s the initial study is the most cost-effective radiological diagnostic test in the evaluation of the vomiting infant. Copyright (C) 1998 by W.B. Saunders Company.