Friday, October 12, 2012

Appendicitis: Accurate diagnosis or no radiation. You make the call.

Amid the mounting concern about radiation exposure and future increases in cancer rates comes a report from Washington State describing the benefits of imaging, particularly CT scanning, for the diagnosis of appendicitis.

The authors collected data from some 55 hospitals of all types and sizes over a six-year period for more than 19,300 patients older than age 15; 91% of patients underwent one or more imaging studies. There were 16,852 (87.2%) CT scans, 1160 (6.0%) ultrasounds and 108 MRIs (0.6%) with 1677 (8.7%) patients having no imaging.

If a patient had an imaging study, the rate of normal appendix removal was only 4.5% compared to 15.4% for those who were not imaged, p < 0.001. Stated another way, on multivariate analysis a patient who had no imaging was over 3 times more likely to have a normal appendix at surgery. Only 4.1% of those undergoing CT scan had a normal appendix compared to 10.4% of those who had only an ultrasound, p < 0.001.

The difference in the rate of normal appendix removal was true regardless of gender—men 3% with imaging vs. 10% without and women 6.9% vs. 24.7%, both statistically significant differences. In other words, nearly 1/4 of all women who were not imaged had a normal appendix at surgery.

Perforated appendicitis occurred in 15% of all patients, a figure that has remained constant over many years and has not been influenced by imaging.

The Washington appendicitis experience is probably generalizable because in most hospitals, CT scan is the preferred imaging modality over ultrasound, which is more operator-dependent, less accurate and less available during off hours than CT scan.

My personal experience is similar to that of the authors of the study. My rate of removal of a normal appendix when operating for the presumed diagnosis of appendicitis is 4.3% for my last 200 cases. Only 18 (9%) of my patients, all young males, had no imaging and just 1 had a normal appendix. CT scans were the only studies performed in 99% of my patients who were imaged.

I have previously written that patients and their families seem to prefer an accurate diagnosis over a theoretical slightly higher cancer risk 20 or 30 years later. The paper from Washington also confirms that a high accuracy rate of CT scanning for appendicitis is achievable outside of academic centers.

For many reasons, I can’t imagine the rate of CT scans for the diagnosis of patients with right lower quadrant pain decreasing. The accuracy of CT is no longer an issue. Most ED MDs are scanning everyone with right lower abdominal pain. They may tell you it’s because surgeons insist upon it, but whatever the reason, a lot of CT scans are being done. Another advantage of CT scanning is if the diagnosis is something other than appendicitis, the CT will very often reveal what is wrong with the patient. In a previous blog, I have mentioned before that it would be impractical to ask surgeons to examine every patient with abdominal pain, one of the more frequent complaints of patients presenting to emergency departments.

Face it, CT scanning for the diagnosis of appendicitis is here to stay. Whether implementation of protocols to lower the radiation dose of the devices will calm all the doomsday prophets remains to be seen.

[Thanks to Dr. Frederick Thurston Drake, lead author of the paper from Washington, for providing me with information not published.]


Keeweedoc said...

Hey there,
just a few thoughts
do you ever not image and take the serial exam approach?
How do you counsel for radiation risk?
Is a 14% normal appendix rate too high? what about 10%?

felt the need to play devils advocate on this one.

Skeptical Scalpel said...

Good questions. We do occasionally admit patients for observation and serial exams, but it is just so much easier to get an immediate answer with a CT scan.

I do not think the ED MDs are telling patients much about the radiation risks. On the rare instance when I see a patient before a scan is done, I do mention the possibility of an increased risk of cancer in the future. Read some of my other posts on appendicitis for more details about this.

A normal rate above 10% is unacceptable in 2012. It should be about 5%.

Milind said...

In developing countries CT scan may not be available for all patients. I still believe & teach that repeated clinical exam if possible by the same doctor is the best method to diagnose or rule out appendicitis. The costs & radiation hazards of CT can't bd ignored.

Skeptical Scalpel said...

Milind, I can't argue with you. However, in the US, the standard of care is to get a CT scan. I am sure that if you observed a patient with serial exams who later had a complication, a plaintiff's lawyer would say you should have done a CT. And the jury would agree.

Brian Sabb said...

Dear Dr. Scalpel,

I completely agree with your comment about standard of care in the US. Furthermore, there can be standards of care in subsections of the US. For instance, if your patient is in a very remote area of the US, CT may not be possible. In this situation, what Dr. Milind advises certainly makes sense. However, I know that where I practice, in Southeast Michigan, if the suspected diagnosis is appy...the patient will get a CT. That is definitely the standard of care around here.

Thanks for the excellent and educational blogging!


Brian Sabb

Skeptical Scalpel said...

Brian, I appreciate your agreeing with me and your kind comments about the blog. I hope you keep reading it.

Keeweedoc said...

Just jumping back in here to play the devils advocate again.
To clarify patients are not treated expectantly because of the risk of litigation.
Do you think this style of management would reduce the radiation exposure and negative appendicitis rates?

Skeptical Scalpel said...

I can't speak for all surgeons but admission for observation is not done often where I work.

Regarding the risk of litigation, I haven't searched this topic. It is just a theory of mine that observation followed by perforation would be hard to successfully defend.

Observation would reduce radiation exposure but I doubt it would lead to decreased rates of negative appendectomy. Observation is what we used to do and negative appy rates were 15-20%.

Keeweedoc said...

Ok so radiation dose reduced but using serial USS or physical exams wouldnt reduce neg appy rate?
already saying its about 10% with USS, repeating this wouldnt help?
I guess what I am saying is radiation risk is sorta an unknown. is there someway we can reduce this risk until we know more about it?

Skeptical Scalpel said...

To my knowledge, serial ultrasound for right lower quadrant abdominal pain has not been investigated.

As I mentioned in the blog, some centers are adopting protocols to reduce the radiation dose of CT. Also, limiting the CT to focus on the area of the appendix would help.

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