What Tests Are Done After a Car Accident?
Most people expect imaging and get a physical exam first. That order is deliberate. Clinicians run a validated decision rule before ordering neck imaging, and being cleared without a scan is often the rule working correctly rather than a corner being cut.
When testing does happen, the sequence usually runs from X-ray for bone, to CT for bleeding and complex fractures, to MRI weeks later for soft tissue. Each of those tools has a documented blind spot, which is the part that rarely gets explained and the part that matters most if your symptoms outlast your scans. In California, there is a second question layered on top: who pays for any of it.
Key Takeaways
- A physical exam and a validated decision rule usually determine whether you get imaged at all.
- Plain X-rays are good at finding fractures and poor at finding them in the neck. One prospective study found X-rays missed more than half of clinically significant cervical spine injuries.
- MRI is routinely normal in acute whiplash, and CT is routinely normal in concussion. A clean scan is not evidence that nothing happened.
- California has no personal injury protection coverage, so diagnostic bills run through health insurance, optional medical payments coverage, a lien, or the settlement itself.
- Recoverable past medical expenses in California are tied to what was actually paid, not what was billed.
Where People Go, and What Each Provider Checks
| Test | What it finds | What it misses | Typically ordered |
|---|---|---|---|
| Physical exam | Range of motion loss, tenderness, neurological deficits, vital sign changes | Anything requiring visualization inside the body | First, at every visit |
| X-ray | Fractures, dislocations, alignment problems | Soft tissue, ligament, disc, and brain injury. More than half of significant neck fractures | Initial evaluation |
| CT scan | Bleeding in the skull, complex fractures, organ injury | Most concussions. Ligament and disc detail | Emergency setting, higher-energy crashes |
| MRI | Disc herniation, ligament tears, spinal cord and nerve involvement | Frequently shows nothing in acute whiplash despite real symptoms | Follow-up, usually weeks later |
| FAST ultrasound | Free fluid in the abdomen | Solid organ injury without free fluid. Sensitivity varies widely by operator | Trauma bay, blunt abdominal injury |
| ECG with troponin | Blunt cardiac injury | Non-cardiac chest injury | After chest impact |
| Blood work | Blood loss, organ stress, coagulation problems | Structural injury of any kind | Emergency setting |
What Happens Before Anyone Orders Imaging
Clinicians run a decision rule before they order neck imaging, and the rules are well validated. The two in common use are the NEXUS Low-Risk Criteria and the Canadian C-Spine Rule, both of which sort patients into those who need imaging and those who can be cleared clinically.
They do not perform identically. A nine-hospital prospective study of 8,283 patients compared the two directly and found the Canadian rule was 99.4 percent sensitive for clinically important cervical spine injury against 90.7 percent for the NEXUS criteria. Across 169 patients with important injuries, the Canadian rule would have missed one, and NEXUS would have missed sixteen.
Understanding this changes how you read your own visit. Being sent home without a scan is frequently the correct application of a validated rule rather than an oversight. It also means the rule is only as good as the history you give, so symptoms you downplay in triage can route you away from imaging you would otherwise have received.
What Imaging Finds, and What It Misses
X-ray. Fast, cheap, widely available, and considerably less sensitive for neck injury than most people assume. A prospective trauma study comparing plain films against multislice CT found plain radiography was 45 percent sensitive and missed 15 of 27 clinically significant cervical spine injuries. CT caught all of them. X-ray also shows nothing about soft tissue, ligaments, discs, or the brain.
CT. Near-complete detection of fractures and the standard tool for finding bleeding inside the skull. It is not ordered reflexively, and the reason is dose. The FDA puts diagnostic CT in the range of 1 to 10 millisieverts and estimates that a 10 millisievert exam may carry roughly a 1 in 2,000 increase in the possibility of fatal cancer. An abdomen and pelvis CT sits near the top of that range.
MRI. The best tool for soft tissue, and frequently unremarkable in exactly the patients who hurt the most. A prospective study of 100 acute whiplash patients found a trauma-related abnormality in one of them and concluded MRI has no role in the routine workup of acute whiplash where plain films are normal, and there is no neurological deficit. A separate one-year prospective trial reached the same conclusion: early MRI findings did not predict who still had symptoms twelve months later.
Concussion imaging. The CDC is explicit that a brain scan is not needed to identify a mild traumatic brain injury, and is used mainly to check for bleeding in patients at risk of it. Concussion diagnosis is clinical. It comes from history and examination.
Why a Normal Scan Does Not Mean You Were Not Hurt
Negative imaging is the expected result in the two most common collision injuries. Whiplash and concussion both produce real, sometimes lasting symptoms with nothing visible on a standard scan, and the clinical literature treats that as unremarkable rather than suspicious.
The numbers hold up on this. Somewhere between 18 and 31 percent of mild traumatic brain injury patients have symptoms that persist despite normal imaging. Research using more sensitive protocols has found that when patients whose initial CT was normal are re-imaged with MRI two to three weeks out, close to a third show abnormalities the first scan did not.
None of that changes how a claim gets valued in practice. Objective findings are easier for an adjuster to concede than a patient’s account of pain, so a file with clean imaging and persistent symptoms tends to draw more resistance. The response is documentation rather than more scans: consistent visits, measured findings, and specific functional limitations recorded over time. If symptoms surfaced days after the crash rather than at the scene, our piece on delayed concussion covers that pattern.
This article is general information, not medical or legal advice. For care, see a licensed medical professional.
The Tests That Are Not Imaging
FAST ultrasound. A bedside scan for free fluid in the abdomen, used in the trauma bay to identify who needs surgery in the next few minutes. Specificity runs high, around 97 to 99 percent, but sensitivity swings with the operator and the timing. One study measured initial sensitivity at 31 percent, rising to 72 percent on a repeat exam. It also cannot detect solid organ injury that has not produced free fluid.
ECG and troponin. After blunt chest trauma, the Eastern Association for the Surgery of Trauma recommends an admission ECG for anyone with suspected blunt cardiac injury and notes that a normal ECG combined with a normal troponin level rules it out. Adding troponin to the ECG moves the negative predictive value from 95 percent to 100 percent.
Blood work. A complete blood count, chemistry panel, coagulation studies, and lactate together indicate blood loss, organ function, clotting problems, and tissue perfusion. Lactate is the one that catches trouble early, because it can flag inadequate perfusion while vital signs still read normal. None of it says anything about structural injury.
Who Pays for Tests After a Car Accident in California?
California has no personal injury protection requirement, which is the reason this question is harder here than in Florida, Arizona, or the other no-fault states. Nothing pays automatically. The bill runs down one of four paths, and each has a different effect on what you keep at the end.
- Health insurance. Pays at negotiated rates on a normal claims cycle, then typically asserts a reimbursement or subrogation claim against your eventual settlement. Self-funded employer plans enforce reimbursement under federal law and are often the least flexible on reduction.
- Medical payments coverage. Optional first-party coverage on your own auto policy that pays medical bills regardless of fault. California has never included it in the mandatory minimums, so plenty of drivers do not carry it and find that out after a crash. Where it does exist, the insurer generally holds a contractual reimbursement right against you rather than a direct claim against the at-fault driver, which the California Supreme Court addressed in a 2009 decision.
- A lien or letter of protection. A provider treats now and secures payment against the settlement. Hospitals have a statutory lien; outpatient providers generally work through a contractual arrangement instead. See our explainer on letters of protection.
- Medi-Cal. Pays, then recovers from the settlement under a statutory formula. The Department of Health Care Services requires written notice within 30 days of filing a claim, reduces its lien by 25 percent for attorney fees plus a pro rata share of costs, and cannot take more than half your net recovery.
Every one of those paths except medical payments coverage creates something that comes out of the settlement later. Our pieces on medical bills after a California crash and negotiating medical liens go through the mechanics.
Does a More Expensive Test Make Your Claim Worth More?
No, and California law is specific about why. Recoverable past medical expenses are limited to what was actually paid and accepted, not what the provider billed. The California Supreme Court settled that in 2011, and a 2013 appellate decision extended it to keep billed amounts away from the jury entirely.
An MRI billed at $3,200 and settled with the insurer for $600 contributes $600 to the medical specials. Stacking imaging inflates the billed total and does very little to the recoverable figure.
Testing that the treating clinician orders because the clinical picture calls for it is a different matter. It documents the injury, it guides treatment, and it makes the causal connection harder to dispute. Testing ordered to build a bigger number does neither.
Talk to Someone Who Handles These Claims
Reading your own imaging reports, figuring out which insurer is supposed to pay, and tracking what comes out of a settlement at the end is a lot to carry while you are still recovering.
DK Law handles injury claims throughout California, and there is no cost to talk through where your case stands. Reach out whenever you are ready.
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