CT cholangiogram – when should we order one?

12th November 2023, NIA Diagnostic Imaging

epigastric pain

Epigastric pain has to be one of the most common presenting symptoms in primary care. The differential diagnoses include cholelithiasis and cholecystitis. With increasing prevalence of obesity and type 2 diabetes, the prevalence of gallbladder disease is also increasing. Often, abdominal ultrasound can confirm or exclude gallbladder disease but sometimes, the results are inconclusive or we suspect additional bile duct obstruction. CT cholangiogram is a fast, widely available and non-invasive alternative technique to image the gallbladder and biliary tree [5]. This imaging technique enables three-dimensional visualisation of the detailed anatomical structures of the biliary tree including very small bile ducts such as aberrant branches [1].

Endoscopic Retrograde Cholangiography [ERC] is considered as the gold standard for visualising biliary trees [4]. However, ERC is invasive, user-dependent and can cause pancreatitis [4]. Ultrasound and MRC (MR cholangiography) are commonly used. Ultrasound is also user-dependent and the images are not easily appreciated by clinicians especially during surgical planning [4]. MRC is costly, not widely available and not suitable for patients with MRI contraindications. In MRC, the result is inconclusive if there is air within the biliary system, e.g. post Whipple’s operation and Billroth 2 [4]. Artefacts caused by surgical clips post cholecystectomy can imitate ductal cancer or a stone in MRC [4]. Therefore, CT cholangiogram utilisation should be considered.

Indications [3, 5]:

Second line of imaging after ultrasound where the results are inconclusive
Biliary tree obstruction
Gallstones
Bile duct stenosis
Post-operative setting where bile duct injury or retained gallstones are suspected
Patients with contraindications for MRC

Technique:
A non-contrast CT of the abdomen and pelvis is done. A second CT acquisition of the same area is done 60 minutes post drip infusion of Biliscopin (meglumine iotroxate). Biliscopin is excreted by the biliary system thus allowing for the depiction of biliary system without structural modification [1].
Post processing work-ups are done to produce 3D, volume rendering (VR), and maximum-intensity projection (MIP) images. 3D images allow for the depiction of the complexity of the biliary tree. VR enables specialists to stereoscopically view the path of the biliary system. MIP aids in the visualisation of small bile ducts such as aberants branches and caudate branches [1]. These anatomical variations are potential sources of surgical complications [1].

Contraindications [5]:
• Bilirubin level <30 μmol/L nor should it be rising rapidly (contrast excretion in bile is affected by the impaired excretory ability of hepatocytes)
• Severe renal or hepatic dysfunction
• Thyroid dysfunction
• Iodinated-contrast adverse reactions

Efficacy:
In the detection of choledocholithiasis, the sensitivity and specificity of CT cholangiogram are comparable to that of MRC. CT has a sensitivity of 86-93% while MRC is 80-95%. CT has a specificity of 94-100% and MRC is 88-96% [4]. Besides, CT cholangiogram is less prone to artefact than MRC [2].
In conclusion, CT cholangiogram is an excellent alternative to image the biliary system where ECR, ultrasound and MRC are not suitable or fail to give conclusive results. CT cholangiogram is cost effective, fast, widely and readily available and provides high-resolution images which assist treating clinicians in detecting a wide range of biliary system pathologies.

Case Study:
A 60-year-old patient with biliary colic and abnormal LFTs had an ultrasound of the upper abdomen at NIA Diagnostic Imaging, which showed tapering area of the gallbladder (figure 1), dilatation of the CBD and mild dilatation of the intrahepatic ducts.

A CT cholangiogram was performed at NIA later on to further investigate the cause of ductal dilatation and the tapering area. The result from the scan showed that there is mild prominence of extrahepatic ducts however, no obstruction was found as contrast can be seen in the duodenum and proximal jejunum (Figure 2-4).

Figure 3 & 4. MIP slices show that there is no complete blockage

References:

HYODO, T, KUMANO, S, KUSHIHATA, F, OKADA, M, HIRATA, M, TSUDA, T, … MURAKAMI, T 2012, ‘CT and MR cholangiography: advantages and pitfalls in perioperative evaluation of biliary tree’, British Journal of Radiology, vol. 85, no. 1015, pp. 887–896.
O’Connor OJ, O’Neill S, Maher MM 2011. ‘Imaging of biliary tract disease’. AJR Am J Roentgenol, vol 197, no, 4, doi: 10.2214/AJR.10.4341
Health South Western Sydney Local Health District, CT Cholangiogram 2015, South Western Sydney Local Health District, viewed 09 October 2023 https://www.swslhd.health.nsw.gov.au/medicalImaging/serv_CT_cholangiogram.html
Persson, A, Dahlström, N, Smedby, O & Brismar, TB 2006, ‘Three-dimensional drip infusion CT cholangiography in patients with suspected obstructive biliary disease: a retrospective analysis of feasibility and adverse reaction to contrast material’, BMC Medical Imaging, vol. 6, no. 1, pp. 1–1.
Weerakkody Y, Yap J, Murphy A, et al. CT cholangiography [protocol] 2023, Radiopaedia.org, viewed 09 Oct 2023 https://radiopaedia.org/articles/35600

PFO Closure

Furlan AJ, Reisman M, Massaro J, et al. Closure or medical therapy for cryptogenic stroke with patent foramen ovale. N Engl J Med 2012; 366: 991–

A multicenter, randomized, open-label trial of closure with a percutaneous device, as compared with medical therapy alone, in patients between 18 and 60 years of age who presented with a cryptogenic stroke or transient ischemic attack (TIA) and had a patent foramen ovale. The primary end point was a composite of stroke or transient ischemic attack during 2 years of follow-up, death from any cause during the first 30 days, or death from neurologic causes between 31 days and 2 years.

Results:

Primary end point was 5.5% in the closure group as compared with 6.8% in the medical-therapy group (adjusted hazard ratio, 0.78; 95% confidence interval, 0.45 to 1.35; P = 0.37)

Conclusion:

“In patients with cryptogenic stroke or TIA who had a patent foramen ovale, closure

with a device did not offer a greater benefit than medical therapy alone for the

prevention of recurrent stroke or TIA”

2 Saver JL, Carroll JD, Thaler DE, et al. Long-term outcomes of patent foramen ovale closure or medical therapy after stroke. N Engl J Med 2017; 377: 1022–

A multicenter, randomised, open-label trial ,randomly assigned patients 18 to 60 years of age who had a patent foramen ovale (PFO) and had had a cryptogenic ischemic stroke to undergo closure of the PFO (PFO closure group) or to receive medical therapy alone (aspirin, warfarin, clopidogrel, or aspirin combined with extended-release dipyridamole; medical-therapy group). The primary efficacy end point was a composite of recurrent nonfatal ischemic stroke, fatal ischemic stroke, or early death after randomisation.

Results:

Recurrent ischemic stroke occurred in 18 patients in the PFO closure group and in 28 patients in the medical-therapy group, resulting in rates of 0.58 events per 100 patient-years and 1.07 events per 100 patient years, respectively (hazard ratio 0.55; 0.31 – 0.999; P = 0.046)

Conclusion:

“Among adults who had had a cryptogenic ischemic stroke, closure of a PFO was associated with a lower rate of recurrent ischemic strokes than medical therapy alone during extended follow-up.”

Meier B, Kalesan B, Mattle HP, et al. Percutaneous closure of patent foramen ovale in cryptogenic embolism. N Engl J Med 2013; 368: 1083–

A prospective, multicenter, randomised, event-driven trial, randomly assigned patients to medical therapy alone (anti-platelet or warfarin therapy) or closure of the patent foramen ovale.

Results:

9 patients in the closure group and 16 in the medical-therapy group had a recurrence of stroke (hazard ratio with closure, 0.49; 0.22 – 1.11; P = 0.08). The primary analysis of the intentionto- treat cohort showed a nominal 51% hazard rate reduction with closure, but the reduction did not reach significance.

Conclusions:

” …there was no significant benefit associated with closure of a patent foramen ovale in adults who had had a cryptogenic ischaemic stroke.”

Sondergaard L, Kasner SE, Rhodes JF, et al. Patent foramen ovale closure or antiplatelet therapy for cryptogenic stroke. N Engl J Med 2017; 377: 1033–

Multinational trial involving patients with a PFO who had had a cryptogenic stroke, randomly assigned patients to undergo PFO closure plus antiplatelet therapy or to receive antiplatelet therapy alone.

Results:

During a median follow-up of 3.2 years, clinical ischemic stroke occurred in 6 of 441 patients (1.4%) in the PFO closure group and in 12 of 223 patients (5.4%) in the antiplatelet-only group (hazard ratio, 0.23; 0.09 to 0.62; P=0.002).

Conclusions:

“Among patients with a PFO who had had a cryptogenic stroke, the risk of subsequent ischemic stroke was lower among those assigned to PFO closure combined with antiplatelet therapy than among those assigned to antiplatelet therapy alone; however, PFO closure was associated with higher rates of device complications and atrial fibrillation.”

Mas JL, Derumeaux G, Guillon B, et al. Patent foramen ovale closure or anticoagulation vs. antiplatelets after stroke. N Engl J Med 2017; 377: 1011–

In a multicenter, randomised, open-label trial patients 16-60 years of age who had had a recent stroke attributed to PFO, to transcatheter PFO closure plus long-term antiplatelet therapy, antiplatelet therapy alone or oral anticoagulation.

Results:

No stroke occurred among patients in the PFO closure group, whereas stroke occurred in 14 of the 235 patients in the antiplatelet- only group (hazard ratio, 0.03; 0 to 0.26; P<0.001). Large number of patients discontinued anti-coagulation in the anti-coagulant group and statistical significance was not analysed because the study was not adequately powered to compare outcomes.

Conclusion:

“Among patients who had had a recent cryptogenic stroke attributed to PFO with an associated atrial septal aneurysm or large interatrial shunt, the rate of stroke recurrence was lower among those assigned to PFO closure combined with antiplatelet therapy than among those assigned to antiplatelet therapy alone. PFO closure was associated with an increased risk of atrial fibrillation.”

Lee PH, Song J-K, Kim JS, et al. Cryptogenic stroke and high-risk patent foramen ovale: the DEFENSE-PFO Trial. J Am Coll Cardiol 2018; 71: 2335–

Patients with cryptogenic stroke and high-risk PFO were divided between a transcatheter PFO closure and a medication-only group.

Results:

No events occurred in the PFO closure group. 12.9% of patients in the medication group had an event (p= 0.023).

Conclusion:

“PFO closure in patients with high-risk PFO characteristics resulted in a lower rate of the primary endpoint as well as stroke recurrence”