Complications of gadolinium use
The use of gadolinium-based contrast agents can lead to two main adverse events:
- Nephrogenic systemic fibrosis (NSF). This is a specific complication associated with high doses of certain agents. The main trigger is severe renal failure. Precipitating factors include inflammation, cumulative contrast medium dose (CM), and elevated phosphate levels. The best prevention is the complete avoidance of such contrasts in patients with severe renal pathology.
- Gadolinium deposition in the brain. Hyperintensity of the basal ganglia can be observed on T1-weighted images. This is due to the accumulation of the substance; however, to date, it has not been proven to cause any clinical symptoms (clinical sequelae).
Non-contrast MR angiography (MRA)
Due to the risks associated with gadolinium, magnetic resonance angiography techniques without the use of contrast are actively developing.
The classical technique is time-of-flight MRA (Time-of-flight, TOF). Its disadvantages include long scanning times due to long repetition intervals, poor performance in axial scanning, and the risk of overestimating vessel stenosis due to flow-related artefacts (flow-related artefacts).
Modern and promising methods include:
- Flow encoding (flow-encoding) and spin labeling.
- 4D phase-contrast MRA.
- ECG-gated 3D fast spin-echo (cardiac-gated 3D fast spin-echo).
- Arterial spin labeling (arterial spin labelling, ASL).
- Balanced SSFP (bSSFP).
The main drawback of the new approaches is their strong dependence on the specific scanner and operator, which slows down their widespread adoption.
CT angiography in the evaluation of aortic aneurysms
Prior to endovascular treatment of an abdominal aortic aneurysm (EVAR), precise anatomical assessment is necessary. Although both MRA and CT angiography (CTA) have high accuracy, CTA is the method of choice. It better demonstrates the extent of vessel wall calcification.
When planning EVAR surgery based on CTA, the following are measured:
- Distance from the aneurysm neck to the renal arteries.
- Dimensions of the iliac arteries.
- Relationship of the neck to the mesenteric arteries.
These parameters are critical for selecting the correct stent size and type. For juxtarenal aneurysms located close to the artery ostia, special fenestrated (fenestrated) and customised (customised) stents are used.
Endoleaks and postoperative follow-up
The goal of aortic stent-graft placement is to exclude the aneurysm from the systemic circulation. A complication where blood continues to flow into the aneurysm sac is called an endoleak (endoleak).
Endoleaks are often asymptomatic, but extremely dangerous: blood pressure can cause further expansion and rupture of the aneurysm. On CTA or MRA scans, an endoleak appears as a collection of contrast medium outside the stent graft. This is precisely why patients after EVAR require lifelong imaging surveillance.
Note: Sometimes on CTA it is difficult to distinguish contrast within the vessel lumen from wall calcification, which can lead to a false diagnosis of occlusion. This problem is resolved by using dual-energy computed tomography.
Briefly: answers to topical questions
What are the types of endoleaks after stent-graft placement?
There are five types of endoleaks (leaks) occurring after endovascular aneurysm repair:
- Type I (Type I) — secondary leakage due to inadequate sealing at the stent-graft fixation site.
- Type II (Type II) — retrograde filling of the aneurysm sac via branch arteries (lumbar, inferior mesenteric, or internal iliac arteries).
- Type III (Type III) — mechanical damage to the graft or separation of its modular components.
- Type IV (Type IV) — secondary leakage due to the porosity of the graft material.
- Type V (Type V) — endotension (Endotension), which is the expansion of the aneurysm sac without visible abnormalities on CT angiography.
Which contrast agents belong to the high-risk group for the development of nephrogenic systemic fibrosis?
The development of nephrogenic systemic fibrosis (nephrogenic systemic fibrosis) is associated with the use of gadolinium-based contrast agents. The risk is specific to particular agents; in particular, the complication occurs after the administration of certain older contrast media when using high doses. The exact names of high-risk agents are not specified in the sources.
What are the absolute contraindications to the administration of iodinated contrast agents?
The sources indicate the following contraindications to the administration of iodinated radiopaque agents:
- Renal impairment.
- burdened allergological history.
- Elevated thyroid hormone levels (thyrotoxicosis).
If contraindications are present, consultation with a nephrologist and an allergist-immunologist is necessary.
Class and exam questions
In which case is gadolinium strictly contraindicated?
Gadolinium-based contrast agents should not be used in patients with severe renal impairment due to the risk of nephrogenic systemic fibrosis.
Where does gadolinium deposit and is it dangerous?
Gadolinium can be deposited in the basal ganglia of the brain, which is visible on T1-weighted MRI. No clinical consequences of this phenomenon have been identified yet.
Why is CT angiography preferred over MRA before aortic aneurysm surgery?
CT angiography better visualizes the presence and exact location of vessel wall calcification, which is critically important for planning stent placement.
What is an endoleak after stent-graft placement?
An endoleak is a complication where blood flow persists inside the aneurysm sac outside the installed stent, which can lead to its rupture.
What else to study on this topic
- Pathogenesis of nephrogenic systemic fibrosis (NSF)
- Types of artifacts in time-of-flight MRA (TOF)
- Classification of endoleaks by type
- Working principle of dual-energy computed tomography
- Features of the use of fenestrated stent-grafts
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