Survival is not improved by elective repair of abdominal aortic aneurysms smaller than 5.5 cm, even when operative mortality is low.

A high degree of precision is possible in CT measurement of AAA diameter, but this precision may not be obtained in practice because of differences in measurement techniques. Differences between imaging modalities increase variability further. Variations in AAA measurement of 0.5 cm or more are not uncommon, and this should be taken into account in management decisions. Efforts to reduce variation in measurement are warranted and might include (1) seeking agreement between surgeons and radiologists on a precise definition of AAA diameter, (2) limiting the number of radiologists who measure AAAs, and (3) use of calipers and magnifying glass for CT measurements.

Gallbladder stasis may be an important factor in the pathogenesis of cholesterol-gallstone formation in some individuals. We investigated gallbladder function in a group of nondieting, gallstone-free, healthy subjects with normal (22 +/- 1 kg/m2) and high (36 +/- 1 kg/m2) body mass indexes. Fasting gallbladder volume (28.2 +/- 4.4 ml) and residual volume after maximal emptying (8.4 +/- 2.3 ml) in high-body-mass index subjects were not significantly different from those of normal-body-mass index subjects (20.5 +/- 2.5 ml and 4.2 +/- 1.3 ml, respectively). The percentage of gallbladder emptying (71% +/- 5%) and the rate of gallbladder emptying (-1.9 +/- 0.3 x 10(-2) min-1) in high-body-mass index subjects in response to a maximal emptying stimulus was similar to the percentage of emptying (78% +/- 6%) and rate of emptying (-2.3 +/- 0.6 x 10(-2) min-1) in normal-body-mass index subjects. A liquid meal containing less than 1 gm fat, 14 gm protein and 6 gm carbohydrate resulted in both a decreased rate of gallbladder emptying and an increased residual gallbladder emptying and an increased residual gallbladder volume in both groups. The addition of 10 or 20 gm (but not 4 gm) of fat to the liquid meal restored gallbladder emptying to the maximal-stimulus level. These results demonstrate that gallbladder emptying in response to a single liquid meal stimulus is not altered in obesity and that dose-response relationships to fat are similar in obese and normal-weight individuals.(ABSTRACT TRUNCATED AT 250 WORDS)

nized factors in cholesterol gallstone formation; bile which is Obese persons are at risk for cholesterol gallstones saturated with cholesterol is essential for crystals to form, because their bile is saturated with cholesterol. The risk nucleation factors can influence whether crystals form in satincreases during rapid weight loss by means of certain urated bile, and gallbladder stasis can allow crystal growth. very-low-calorie diets or gastric bypass surgery. GallObesity is associated with increased bile cholesterol secrestone risk factors during rapid weight loss include intion and saturation index. 6 Several studies suggest that bile creased bile cholesterol saturation index and gallbladsaturation index increases further during rapid weight der stasis. Obese subjects were randomized to one of two loss. 1,6,7 In one study, 10 subjects losing weight on a 1,000-low-calorie liquid diets for rapid weight loss: a 520-kcal kcal diet showed reduced output of all bile lipids, but 6 of the diet with less than 2 g fat/d, and a 900-kcal diet with 30 10 increased their bile saturation index. 6 On the other hand, g fat/d (including one 10-g fat meal to stimulate maximal several studies have reported decreased bile saturation index gallbladder emptying). Bile and blood lipids, saturation after 6 to 20 days of fasting. 8,9 Cholesterol may be mobilized index, leukocyte 3-hydroxy-3-methylglutaryl coenzyme from tissue stores to be secreted into bile during rapid weight A (HMG CoA) reductase activity, and ultrasonographic loss. 6 Decreased bile acid synthesis has also been detected gallbladder emptying were measured repeatedly during during diet-induced weight loss and fasting. 6,9,10 Thus, rapid dietary treatment. Both diets produced comparable weight loss may alter secretion of cholesterol and bile acids weight loss of 22%. Bile cholesterol saturation index inin a manner conducive to gallstone formation. creased during both diets (26%), but fell to 15% below Pro-and antinucleating proteins and mucins are described prediet level after weight loss. Compared with subjects' in gallbladder bile, and may predispose to gallstones. These maximal gallbladder emptying fraction of 66%, the 520-factors could change during rapid weight loss. Shortened kcal diet provided poor gallbladder emptying (35%), crystal nucleation time has been observed during very-lowwhereas the 10-g fat meal of the 900-kcal diet provided calorie liquid diets. 7 Mucin and calcium increased in gallbladmaximal emptying. Gallstones developed in four of six der bile of obese subjects forming gallstones after gastric by-520-kcal subjects and none of seven 900-kcal subjects (P pass. 11,12 Å .021), an unanticipated difference that resulted in preGallbladder emptying may also participate in gallstone formature study termination for ethical reasons. Blood lipmation. 13 Studies of meal-stimulated gallbladder emptying in ids and HMG CoA reductase activity in mononuclear leuobese subjects have given variable results. [14][15][16][17] We and others kocytes fell at week 8 durin...