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Think You Have Appendicitis? Here, Pee In This.

A promising new test for appendicitis involves only a patient’s urine sample.

In an Annals of Internal Medicine article published June 23, 2009 (still not online at this time), researchers at Children’s Hospital in Boston have found that the body excretes many proteins during acute inflammation of the appendix. The protein that was found to be most consistently present in acute appendicitis cases is called leucine-rich alpha-2-glycoprotein, or “LRG” for short. According to the Time article, the protein is specific to immune cells in the appendix, and LRG testing has “statistically negligible rates of false results,” meaning that it was very good at separating those who had appendicitis from those who did not. Unfortunately, the test has only been validated in children thus far, so more testing is necessary to see whether the test can be validated in adults.

The implications of this test are huge. Appendicitis is one of the more difficult diagnoses to make clinically and missed appendicitis is an often-litigated issue, prompting many physicians to order expensive CT scanning in anyone with right lower quadrant pain. As many as 30% of appendectomies end up showing no appendicitis. If LRG testing has a low false positive rate (i.e. test is positive when there is no appendicitis) and a low false negative rate (i.e. test is negative when appendicitis is really present), it would save a lot of unnecessary surgeries, would decrease the number of CT scans being performed, and would significantly reduce the transit times in ED patients who have lower abdominal pain.

Unfortunately, as GruntDoc often says, “the devil is in the details.” I suspect that other inflammatory conditions of the bowel such as diverticulitis, colitis, and even gastroenteritis will also cause extra amounts of the protein to be secreted, causing “false positive” tests. My guess is that LRG testing will be similar to D-dimer testing for pulmonary emboli in the future – useful to exclude appendicitis if it is “normal” but requiring more testing to definitively pin down a case of appendicitis in an adult if it is positive.

Nevertheless, this could be one more bullet in a physician’s diagnostic arsenal that will hopefully improve patient care. I just hope it doesn’t become one of those things that gets ordered as part of a battery of tests on an abdominal pain patient while docs just do a CT scan anyway.

Kudos to the researchers at Children’s Hospital in Boston for thinking outside the box on this one.

4 Responses to “Think You Have Appendicitis? Here, Pee In This.”

  1. paul says:

    sounds like it’s going to become the “d-dimer” of abdominal pain. good rule-out test (if your pretest probability is low), not so good rule-in test.

  2. Shalom (R.Ph.) says:

    Funny you should write this just now. As it happens, I just spent this past Sunday afternoon at the ED having a CT scan to R/O appendicitis or diverticulitis. It would have been nice if I could have just peed in a cup and been told, “No, you don’t have appendicitis, go home.”

    (It was neither, by the way. Had no other symptoms, beyond the feeling that someone was stabbing me repeatedly with a hot knitting needle right at McBurney’s spot, but my MD suggested I still go to the ED. Still don’t know what the hell it was, but it resolved spontaneously after another day.)

    False positives on a test like this aren’t so bad; you’d have had to do the CT anyway, so you’re not losing anything beyond the cost of the lab. False negatives would bother me much more.

  3. [...] A urine test for appendicitis? Would be useful! (via WhiteCoat) [...]

  4. Mirjam says:

    Interesting. I was sent to the ED with such suspicions and also had a CT-scan done, which showed nothing. From what they told me I didn’t have enough body fat to identify the appendix. They wanted to do an ultrasound at first, which would have been the best thing to do as it turned out when I had a laparoscopy that an ovarian cyst had ruptured.

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