Out of the box

A 72-year-old male ex-smoker, presented with fatigue and shortness of breath. He was referred for a CT scan due to persistent opacification in the right costophrenic angle on CXR. He had hypertension, hypercholesterolemia, hiatus hernia with Barrett’s oesophagus and past history of gall stone pancreatitis a few years prior with interval cholecystectomy.

Chest radiograph demonstrates patchy opacification and blunting of the right costophrenic angle. Additionally known hiatus hernia..

Contrast-enhanced staging CT of the thorax in arterial phase and upper abdomen in portal venous phase shows multiloculated wall enhancing pleural collection along the right costophrenic recess posterolateral to the diaphragm. It is infiltrating into the posterolateral chest wall. There is associated subsegmental atelectasis of the adjacent right lateral basal segment.

Inferiorly, there are calcific foci within the collection. No air locules within the collection. No calcified pleural plaques.

 A subsequent USS of the right chest wall reveals calculi with posterior acoustic shadowing within the collection extending into the chest wall.

We present an unusual case of patchy right costophrenic opacification in a patient which was clinically concerning for malignancy. On staging contrast-enhanced CT this was demonstrated to be due to a right pleural fluid collection with calcific foci within. Further targeted US scan showed calcific foci with posterior acoustic shadowing in the collection consistent with appearances of calculi.

We also reviewed prior imaging which revealed a previous episode of gallstone associated pancreatitis four years ago seen on CT.  Dropped gall stones within the abdomen were seen on a CT scan performed one-year post-cholecystectomy.

The constellation of the findings on CT and USS with review of previous imaging helped to make the diagnosis of pleural fluid collection secondary to dropped gallstones.

It was explained to the patient that his symptoms were related to gallstones and he opted for surveillance imaging in favour of surgical retrieval.

Dropped gallstones are an infrequent occurrence, reported in 1 to 20% of the cases following laparoscopic cholecystectomy. Amongst these, 20% of the cases may go on to have further complications, including granulomas and abscesses [1]. A dropped gallstone acts as an inflammatory nidus and incites a low-grade granulomatous response [2]. In rare instances, dropped gallstones may migrate superiorly and enter the pleural cavity, possibly as a result of diaphragmatic defects in elderly patients [2, 3]. Pleural empyema and abscesses have been reported numerous times in association with dropped gallstones [1, 2, 3].

Diagnosis is challenging and frequently delayed because of the atypical clinical presentations, unexpected locations of dropped gallstones, and inability to visualise radiolucent calculi with conventional imaging-like radiographs [2]. Imaging is needed to rule out any sinister pathology being considered and assure the requesting physician that the pathology is benign [2]. It is crucial to keep this diagnosis in mind, as the history of surgery may be remote, and the patient may be afebrile with normal inflammatory markers [2].

Incidental asymptomatic dropped gallstones are easily identified with CT and ultrasound when they are large and calcified [2, 3]. It is recommended to always look for prior imaging, as in this case there were dropped gallstones in the abdomen that had migrated to the pleura [3]. Figure 6 shows a contrast-enhanced CT axial image of the abdomen taken four years prior when the patient presented with acute necrotising pancreatitis associated with gallstones. In figure 7, the contrast-enhanced CT axial image of the abdomen post-interval cholecystectomy for the same patient one year after the episode of pancreatitis shows the dropped gallstones posterior to the liver.

Take-Home Message/Teaching Points:

Dropped gallstones can cause recurrent and indolent abscesses in uncommon and extra-abdominal locations.

Presentation is often remote from the time of the actual procedure.

Granulomatous inflammation can mimic malignancy with infiltration into adjacent structures.

Careful history taking and evaluation of the previous imaging helps to point towards the diagnosis.

Multimodality imaging with CT and US or MRI is needed for making a confident diagnosis.