Type:
Educational Exhibit
Keywords:
Obstruction / Occlusion, Acute, Diagnostic procedure, CT, Conventional radiography, Gastrointestinal tract, Emergency, Abdomen
Authors:
J. P. Zawaideh1, S. Banderali2, L. Bacigalupo2, G. A. Rollandi2; 1Genova/IT, 2Genoa/IT
DOI:
10.1594/ecr2018/C-1546
Findings and procedure details
Plain abdominal film is still often used as the first imaging modality for acute abdomen.
Fig. 1 It is possible to observe the Rigler’s triad:
(1) pneumobilia,
(2) aberrantly located radio-opaque gallstone,
(3) intestinal dilatation/obstruction.
The Rigler triad can be considered pathognomonic.
When diagnosis is still doubtful,
an abdominal ultrasound (US) can be indicated for gallbladder stones,
confirming the presence of choledocholithiasis.
The use of US in combination with abdominal films to increase the sensitivity of diagnosis.
However,
the diagnosis of the ectopic gallstone is difficult and requires an expert sonographer.
CT provides an optimal definition of the Rigler’s triad findings,
multi-planar reconstruction can help to identify the gallstone.4 Fig. 2
However,
since only 10% of gallstones are radio-opaque and pneumobilia may be limited; gallstone ileus may be misdiagnosed.
Radiological ancillary signs to be aware of are the change of gallstones position when compared to previous imaging.9
The standard protocol for acute abdomen with intravenous contrast using portal or venous phase is usually sufficient.
Non-contrast enhanced CT has the benefit of easier localization of ectopic stone regardless of the degree of calcification.
Non-enhanced CT may be sufficient in patients who have renal impairment or risk of contrast allergy.
It is prudent to be aware that additional stones may be present in the bowel proximal to the site of obstruction and to correctly report them so that the surgeons can search for them during the surgery.
Fig. 3
At CT the gallstone may appear to be rim-calcified or completely calcified.
Sometimes it may be difficult to visualize due to the radiolucency nature of the stone or if the stone is deeply impacted in an inflamed mucosa.
This could lead to a pitfall,
underestimating the true size of the impacted gallstone.4 Fig. 4