Dear Wise Owl? How Many Licks DOES it take?: A Brief Synopsis of AFP's "Appropriate and Safe Use of Diagnostic Imaging"

A Brief Synopsis of;
Appropriate and Safe Use of Diagnostic Imaging
BRIAN K. CROWNOVER, MD, and JENNIFER L. BEPKO, MD, Nellis Air Force Base Family Medicine Residency, Nellis Air Force Base, Nevada
http://www.aafp.org/afp/2013/0401/p494.html
Am Fam Physician. 2013 Apr 1;87(7):494-501.


     In the world of defensive medicine and the absolute need for an immediate diagnosis over a thorough differential diagnosis, imaging has taken a prominent role. Recent knowledge tells us that much of the imaging is unnecessary, wasteful, and harmful to the patient. According to this article, up to 2% of future cancers will be due to radiation from CT's. A chest CT will give a patient the same amount of radiation as 769 chest x rays. A barium enema is the equivalent of 615 chest x rays. An ERCP is about the same radiation as 308 chest x rays. A TIPS procedure? -you are looking at 5,385. A poor differential and chasing zebras could really cost the patient a lot on unwanted exposure.
     So what will happen? Well, besides the obvious potential for cancer, the patient may also be at risk for nephrogenic systemic fibrosis.  This is "characterized by scleroderma-like changes in the skin, internal organs, eyes, and blood vessels. This is seen mostly in gadolinium-based MRI contrast agents. Gadolinium contrast should be avoided in patients with late stage chronic kidney disease.
     The next few chapters will discuss which imaging is best for certain suspected diseases. I will add the number of equivalent chest x rays in quotations next to the imaging for fun, when available.
     In suspected ischemic stroke, a non-contrast head CT (154) should be done to rule out bleeding within three hours of onset. Beyond that, and within 24 hours, a head and neck CT angiogram or an MRA (preferred) should be performed.
     Headaches generally do not require imaging. Symptoms such as suspected meningitis, new onset in pregnancy, immunosuppression, focal neurological signs, or thunderclap onset may trigger a CT or MRI.
     Imaging for a suspected pulmonary embolism should be entertained only after the provider has determined the Wells score. A chest helical CT should be ordered if the score suggests an intermediate or high risk probability.  If the chest CT is negative and there is a very high probability, then a V/Q scan or pulmonary angiogram (1,154) can be done.
     An MI needs to be ruled out in patients presenting with chest pain. Myocardial perfusion imaging (923-2,231, depending on the contrast media) or coronary angiography (1,231) can be done. If the pain is non-recurrent, the ECG is negative, or the troponins, etc are negative, exercise stress testing can be done.
     An abdominal (769) and pelvic (538) CT is recommended for patients with RLQ pain and suspected appendicitis. If the patient is pregnant or a child, an ultrasound is preferred.  Ultrasound is the imaging of choice for cholecystitis as well. If the patient is suspected of having diverticulitis, a CT abdomen/ pelvis with contrast is done first. Women of child bearing age should have an ultrasound in this case to rule out gynecological causes, to avoid the radiation.
     Low back pain should not routinely be imagined unless the patient has pain longer than 6 weeks, age over 70 years, a history of cancer, immunosuppression, IVDA, alcohol abuse, long term corticosteroid use, trauma, or unexplained fever, weight loss, or night pain. MRI can be used at this point, but there are a lot of unrelated abnormal findings, which may be found. Although these findings may fit the picture, often times they have no role in the symptoms.
     In whole body scanning, the average patient finds 3 abnormalities, which is why it is not recommended.