Value of CT in the diagnosis and management of gallstone ileus

Abstract

Aim: To retrospectively establish the diagnostic criteria of gallstone ileus on CT, and to prospectively apply these criteria to determine the diagnostic accuracy of CT to confirm or exclude gallstone ileus in patients who presented with acute small bowel obstruction (SBO). Another purpose was to ascertain whether the size of ectopic gallstones would affect treatment strategy.

Methods: Fourteen CT scans in cases of proved gallstone ileus were evaluated retrospectively by two radiologists for the presence or absence of previously reported CT findings to establish the diagnostic criteria. These criteria were applied in a prospective contrast enhanced CT study of 165 patients with acute SBO, which included those 14 cases of gallstone ileus. The hard copy images of 165 CT studies were reviewed by a different group of two radiologists but without previous knowledge of the patient's final diagnosis. All CT data were further analyzed to determine the diagnostic accuracy of gallstone ileus when using CT in prospective evaluation of acute SBO. The size of ectopic gallstone on CT was correlated with the clinical course.

Results: The diagnostic criteria of gallstone ileus on CT were established retrospectively, which included: (1) SBO; (2) ectopic gallstone; either rim-calcified or total-calcified; (3) abnormal gall bladder with complete air collection, presence of air-fluid level, or fluid accumulation with irregular wall. Prospectively, CT confirmed the diagnosis in 13 cases of gallstone ileus with these three criteria. Only one false negative case could be identified. The remaining 151 patients are true negative cases and no false positive case could be disclosed. The overall sensitivity, specificity and accuracy of CT in diagnosing gallstone ileus were 93%, 100%; and 99%, respectively. Surgical exploration was performed in 13 patients of gallstone ileus with ectopic stones sized larger than 3 cm. One patient recovered uneventfully following conservative treatment with an ectopic stone sized 2 cm in the long axis.

Conclusion: Contrast enhanced CT imaging offered crucial evidence not only for the diagnosis of gallstone ileus but also for decision making in management strategy.

Figure 1

Ectopic gallstone (arrow) showed totally calcified component (A) and rim-calcified component (B).

Figure 2

Diseased gallbladder (arrow) was replaced by gas (A); mixed air and fluid (B); and fluid with irregular wall (C).

Figure 3

False negative case showed poor differentiation between less calcified rim of the ectopic gallstone (arrow) and the enhanced bowel wall (case 8).

Figure 4

Axial contrast enhanced CT delineated wall thickening (between arrows) of duodenum second portion >1 cm (case 3).

Figure 5

Axial contrast enhanced CT showed rim-calcified ectopic gallstone in the proximal ileum (A). CT section located 3 cm caudal to (A) reveal segmental edematous wall thickening of small intestine (arrow) proximal to transition zone, which indicated transient ischemic change secondary to bowel obstruction (B) (case 2).

Figure 6

Rim-calcified ectopic stone (arrow) sized 2 cm in the long axis with SBO but evacuated spontaneously following conservative treatment (case 9).