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Bleeding and an aneurysm are different findings

Emergency investigation asks whether bleeding has occurred and, if it has, what caused it. Planned vascular imaging may instead ask whether an aneurysm is present or has changed. A scan that detects an arterial bulge is not automatically proof that it ruptured; clinicians consider the pattern of blood and whether the aneurysm fits the bleeding source. Other causes of subarachnoid hemorrhage exist. Sudden severe headache or acute neurological symptoms require local emergency assessment, even when a person already has an “unruptured” diagnosis.1

Investigating an acute presentation

Non-contrast CT of the head can identify blood in the subarachnoid space. Its diagnostic performance depends on timing and interpretation, as well as the clinical presentation. NICE gives separate recommendations for scans performed early and later after onset, with radiologist reporting and senior clinical discussion. This is a clinical pathway, not an instruction to count hours and rule out bleeding yourself.1

Clinicians may select further investigations when needed, including lumbar puncture to examine cerebrospinal fluid. Laboratory evidence and timing matter. A sample that looks bloody is not by itself a universal proof of aneurysmal hemorrhage: blood may have other explanations, and locating the source is a separate step. NICE's diagnostic recommendation concerns evidence of bilirubin, or xanthochromia, using spectrophotometry. The team interprets the result alongside the presentation and imaging.1

CT angiography (CTA) uses CT and contrast to visualize arteries. Magnetic resonance angiography (MRA) uses MRI techniques to assess vessels. Catheter angiography, also called digital subtraction angiography, provides detailed vascular images through an invasive procedure. The team selects among them according to the question, image quality, procedural risks and what previous tests show. An aneurysm not seen on one examination may require specialist interpretation or further investigation in the appropriate context.12

Screening concerns people without an acute presentation

Screening seeks an aneurysm in someone without symptoms prompting emergency investigation. Family history can increase the likelihood of having or developing an aneurysm, particularly when multiple close relatives have had aneurysmal subarachnoid hemorrhage. Ask a clinician to review which relatives were affected, their diagnoses and ages, and your own history.2

Autosomal dominant polycystic kidney disease (ADPKD) has its own screening guidance. KDIGO 2025 recommends screening for people with ADPKD and a personal history of SAH or relevant family history, when treatment is an option and life expectancy is reasonable. It also supports informed discussion in additional situations. Those are risk-group recommendations, not a general-population rule. Choices include potential benefits, incidental findings, anxiety and the implications of ongoing imaging or treatment.3

Questions after an imaging result

Ask whether the finding is definite, whether prior images are comparable, and what question the next test would answer. A follow-up plan should explain who reviews the images, how results will be communicated and what would change management.2

References

  1. National Institute for Health and Care Excellence. NG228. Subarachnoid haemorrhage caused by a ruptured aneurysm: diagnosis and management. 2022. Source ↩
  2. Etminan N et al. European Stroke Journal. 2022;7: LXXXI–CVI. doi:10.1177/23969873221099736. Source ↩
  3. KDIGO. 2025 Clinical Practice Guideline for Evaluation, Management, and Treatment of ADPKD. Kidney International. 2025;107(Suppl 2S). Chapter 6. Source ↩