Lower back pain often does not require imaging

Here is a lesson in why defensive medicine should be avoided: it costs a lot, it doesn't help patients, and it has the potential to hurt them. Chou et al. published a study in the Lancet showing that in patients presenting with lower back pain without serious clinical symptoms (more on this in a second) imaging does not improve outcomes.

Lower back pain is a common presentation in clinic. It is pretty prevalent with about 15 percent of Americans reporting having had it. However, in most cases it isn't anything to be alarmed about. In the majority of cases, it goes away pretty quickly and can be treated with Advil or Tylenol. Only in a small fraction of cases does this pain indicate some sort of systemic pathology, and in most cases it is attributed to mechanical or musculo-skeletal pain of unknown origin.

The problem is that some doctors are in the habit of ordering routine imaging in cases of uncomplicated lower back pain. By uncomplicated, I mean that there are several "red flags" that indicate that the patient might be in the fraction of people with a systemic pathology.

These "red flags" include:

• Traumatic injury (or even milder injury if someone is >50)
• Unexplained weight loss -- which makes you worry that they might have an undetected tumor pressing on their spine
• Unexplained fever, history of immunosuppression (from drugs or HIV), history of IV drug abuse, or in-dwelling urinary catheter -- all indicating an infection (sometimes in the bladder) that may be causing the pain
• Osteoporosis, prolonged use of steroids -- possible indicating a spinal break, steroids cause you to lose bone mass
• Focal neurologic deficits -- tingling, numbness, weakness, etc. which could indicate many things such as sciatica or cauda equina syndrome
• Duration longer than a month to six weeks

All of these red flags are bad news. They indicate that something might be seriously wrong. They should definitely make your physician want to order a CT, MRI, or plain X-ray.

However, absent symptoms of this nature, Chou et al. conclude that imaging in unnecessary and does not improve patient outcomes. They examined the literature of published studies looking at the outcomes following lower back pain. They conclude that outcomes such as improvement in pain or function, mental health, quality of life, and patient satisfaction do not improve with imaging:

Our meta-analysis of randomised controlled trials showed that immediate, routine lumbar-spine imaging in patients with low-back pain and no features suggesting serious underlying conditions did not improve clinical outcomes compared with usual clinical care without immediate imaging. Results were limited by small numbers of trials for some analyses, but seemed consistent for the primary outcomes of pain and function, and for quality of life, mental health, and overall improvement. Data for patient satisfaction could not be pooled, but showed no clear difference. In addition to non-significance, pooled estimates were small or close to zero and, in some cases, slightly favoured the non-imaging strategy. This result suggests that, even if statistical power could be increased by other trials, clinically important benefits from routine lumbar imaging are unlikely, assuming that future results are similar to those currently available. Based on lower limits of 95% CIs, maximum plausible benefits on pain or function with routine imaging would be small (SMD [Standardized Mean Difference] 0·29 for short-term function) or trivial (SMD <0·2).

Further, using one particular imaging modality -- say CT vs. X-ray -- did not make a difference.

To be fair, this study does have limitations. First, it pools together many studies with diverse populations. But that is true of basically any meta-analysis out there. Second, and more significant, studies that looked at outcomes longer than a year after presentation are very rare. We don't know if presentation with back pain one year might result in a serious problem several years later. However, I would argue that individuals likely to have a problem much later are also likely to have extended pain and keep showing up at clinic. Such individuals are very likely to eventually fall under the red flags category.

In spite of some clear recommendations on the issue, many physicians do send patients with lower back pain straight to imaging, even in the absence of red flags. This is a problem for three reasons. One, imaging is expensive. It is a horrible waste of money to be doing MRIs on people to no clinical benefit. Two, when we do imaging we sometimes find things that merit further investigation, but a lot of those times it was nothing to worry about. False positives on imaging could lead to many unnecessary and potentially invasive procedures. One particular problem is that imaging of the lumbar spine often finds things like degenerated discs or arthritis, but these are not strongly correlated with back pain -- you often find them in pain-free patients. Three, with CTs and X-rays, there is radiation involved. I don't know about you, but I don't want someone irradiating my pelvis for no reason.

The critical take-home from this study is that we need to educate physicians and patients. Patients will often request or expect certain procedures to make them feel better and to convince them that they are getting the best care. Physicians will often request extra procedures to protect them from lawsuits if they miss something. Coming up with clear practice guidelines helps them both. Physicians can feel better not ordering a test if they know that it does not improve outcomes, and patients can feel better in that they actually are getting the best care available -- more is not always better.

Hat-tip: Science Daily

Roger Chou, Rongwei Fu, John A Carrino, Richard A Deyo (2009). Imaging strategies for low-back pain: systematic review and meta-analysis The Lancet, 373 (9662), 463-472 DOI: 10.1016/S0140-6736(09)60172-0