# Contrast CT booked on three kidney screening questions, without a routine blood test beforehand

Source: https://onco.cc/ideas/idea-pu-contrast-ct-screening-questions/  
OnCo record `idea-pu-contrast-ct-screening-questions` (Idea). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Many hospitals still ask for a kidney blood test within three months before a CT scan with contrast dye, and cancel scans when it is missing. Since 2024 NICE has said a test from the past six months will do, and that when there is none, three questions about kidney disease and acute illness can decide whether a test is needed. How safely and how widely this works is not measured.

## Summary

The recommendation. NICE NG148 (updated October 2024) says that before a non-urgent contrast CT the requester should use an eGFR from the past 6 months if there is one; if there is none, ask whether the person has kidney disease or a kidney transplant, has seen or is waiting to see a kidney specialist, kidney surgeon or urologist, or has symptoms of acute illness likely to cause acute kidney injury; and, if the answers do not suggest kidney disease and the person is clinically stable, consider proceeding "without the need for further blood tests before the scan" (1.1.10 to 1.1.12). The European ESUR 2026 handbook instead measures eGFR within 7 days for inpatients and the acutely ill and within 3 months for others, either in everyone or in those with a listed history.

Why it would matter. NICE's committee wrote that in current practice "a person is required to have an eGFR test in the 3 months before undergoing contrast media CT scanning", that this "often results in delayed scans", and that the change is likely to reduce eGFR testing and short-notice cancellations. People with cancer have many contrast scans, so each avoidable test and cancellation recurs.

Why it is untested. The same committee found the evidence for risk questionnaires "lacking in both quantity and quality" and made the recommendation on its own knowledge and expertise, with a research recommendation on validated tools. No study OnCo found measures how many trusts have adopted the questions, how many tests and cancellations they save, or how many people with unrecognised kidney impairment they miss.

## Fields

- Kind: Idea
- Last checked: 2026-11-11
- Tags: protocol-upgrade; upgrade:untested; evidence:insufficient
- Hypothesis: Booking non-urgent contrast CT on the three NICE screening questions, with an eGFR only when an answer is positive or no result exists from the past six months, reduces pre-scan blood tests and cancellations by at least half without an increase in contrast-associated acute kidney injury.
- Rationale: The threshold for extra care is an eGFR below 30 in all three major guidelines, and the risk above it is low; a three-month blood-test rule therefore spends tests and scan slots on people who are almost all safe. The questions are cheap, but their sensitivity for finding the few who are not safe is unknown.
- Proposed test: A before-and-after or stepped-wedge study across imaging departments adopting the questions, measuring blood tests per scan, cancellations, and acute kidney injury at 48 to 72 hours in a sample of people who screened negative and had an eGFR checked after the scan.
- Maturity: early-clinical
- Actor: clinic

## Sources

- NICE guideline NG148, Acute kidney injury: prevention, detection and management, recommendations 1.1.5 to 1.1.12 (2024): https://www.nice.org.uk/guidance/ng148/chapter/Recommendations
- NICE guideline NG148, Rationale and impact: assessing risk factors in adults having iodine-based contrast media (2024): https://www.nice.org.uk/guidance/ng148/chapter/Rationale-and-impact
- ESUR Contrast Media Safety Committee Guidelines 2026: https://www.esur.org/wp-content/uploads/2026/10/Guidelines-2026.pdf

## Connected records

- ideas: [Eating and drinking normally before a contrast CT scan](https://onco.cc/ideas/idea-pu-no-fasting-before-contrast/)
- fronts: [Imaging](https://onco.cc/fronts/imaging/)
- technologies: [CT (computed tomography)](https://onco.cc/technologies/ct/), [Iodinated and barium contrast for CT and X-ray](https://onco.cc/technologies/iodinated-contrast-media/)
- institutions: [National Institute for Health and Care Excellence](https://onco.cc/institutions/nice/)
- bottlenecks: [Fragmented care and guideline gaps](https://onco.cc/bottlenecks/b-care-fragmentation/), [Knowledge reaches practice too slowly](https://onco.cc/bottlenecks/b-knowledge-diffusion/)
- protocols: [Iodinated contrast for CT: kidney function checks, kidney protection and metformin](https://onco.cc/protocols/iodinated-contrast-kidney-and-metformin/)

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