“Contrast harms the kidneys” — this belief has been present among patients for years, and sometimes also among physicians. In clinical practice, it may raise concerns about imaging examinations and procedures that use contrast agents.
A recent study published in the journal Neurology, co-authored by researchers from Wroclaw Medical University, shows that in patients with ischemic stroke treated with mechanical thrombectomy, renal complications following contrast administration are rare. Moreover, the risk of their occurrence can be estimated even before the procedure.
As emphasized by Prof. Maciej Guziński, co-author of the publication and a radiologist who performs thrombectomy procedures, contrast agents are essential for the diagnosis and treatment of vascular diseases.
– CT examinations with contrast and vascular procedures, including thrombectomy in stroke, require the administration of iodinated contrast, which allows precise visualization of blood vessels and enables rapid decision-making to initiate treatment that saves the brain or life,- explains Prof. Guziński. – However, it is natural for patients and their families to ask whether contrast is safe for the kidneys.
Where did the concerns come from?
Contrast-associated kidney injury was first described in the 1950s, when contrast agents in use were significantly less safe than those available today. Over the decades, the belief became established that contrast frequently leads to serious complications.
– Since then, it has been established that the issue is much more complex and depends on many factors, not only on the potential nephrotoxicity of contrast – explains Marta Nowakowska-Kotas, MD PhD from the Department of Neurology, co-author of the study.
The risk is influenced by the patient’s age, comorbidities, and overall health condition.
Patients after stroke
Mechanical thrombectomy is currently one of the most effective methods of treating ischemic stroke. The procedure involves mechanical removal of a clot from a cerebral vessel and restoring blood flow.
During the procedure, physicians administer contrast to precisely visualize the vessels and control the course of the intervention.
– During mechanical thrombectomy, a relatively large amount of contrast is administered, and these are often older patients with multiple comorbidities, making them more susceptible to acute kidney injury – says Michał Puła, MD, a radiology resident and co-author of the publication.
Therefore, renal function in these patients is closely monitored.
The CAN-REST score
One of the most important outcomes of the study was the development of the CAN-REST index, which allows estimation of the risk of deterioration in renal function even before the procedure.
– Based on the collected data, parameters were selected that make it possible to identify patients at increased risk of developing this complication, explains the researcher.
The most important factors include, among others, renal filtration parameters (GFR), hemoglobin levels, glucose concentration, history of kidney disease, medications used, and the patient’s neurological status.
Importantly, the analysis also showed that the amount of contrast used during the procedure did not significantly improve the accuracy of the prediction.
– It can therefore be concluded that the information available before the procedure alone allows identification of patients particularly at risk of adverse outcomes – emphasizes Nowakowska-Kotas, MD PhD.
Is contrast safe?
The most important conclusion from the study is reassuring. Renal complications following contrast administration occurred in less than 5% of patients undergoing thrombectomy.
– Acute deterioration of renal function after contrast administration occurs in approximately 5% of patients. In the vast majority of cases, however, this is a transient disorder that resolves within a few days. More persistent deterioration of renal function affects approximately half a percent of all patients – explains Prof. Maciej Guziński.
In clinical practice, this means that the decision to administer contrast should not delay diagnosis or treatment, especially in emergency situations.
– In the case of stroke, the benefits of performing imaging and the procedure clearly outweigh the potential risks. Thrombectomy often allows avoidance of severe disability or death – emphasizes the neurologist.
The new CAN-REST prognostic tool may additionally help physicians better identify patients at particularly high risk of complications and implement preventive measures at an early stage.
Rapid diagnosis and immediate treatment save brain tissue, the patient’s functional status — and often their life.
When can contrast be harmful to the kidneys?
Not every patient carries the same risk of complications following contrast administration. Physicians pay particular attention to several factors that may increase the risk of deterioration in renal function.
The most important include:
- chronic kidney disease or reduced renal filtration (GFR),
- advanced age,
- diabetes,
- dehydration,
- anemia,
- use of certain medications that burden the kidneys.
For this reason, before contrast-enhanced examinations, physicians often check creatinine levels or GFR. This allows assessment of the examination’s safety and — if necessary — the implementation of additional precautions.
This material is based on the article:
Contrast-Associated Acute Kidney Injury After Thrombectomy for Ischemic Stroke
Prognostic Impact and CAN-REST Predictive Score
Neurology