A scan too many: How much is too much radiation?

June 12, 2018 - 9:23am

DEAR DR. ROACH: A year ago, I had surgery for bladder cancer, and had a small stroke and pulmonary clot. During this past year, I've had five CT scans, three chest X-rays and a couple of other scans to diagnose the stroke and clot. I also had some kind of scan in radiology to put in and then take out an IV blood filter. I am having another CT scan to check kidney function and another chest X-ray in May. Now my GP says I'm due for a mammogram. How much is too much radiation? I know it's cumulative. -- R.W.
       ANSWER: People get nervous about radiation. Fear of radiation can be rational or irrational. The irrational part is nonetheless very human: There is something fundamentally terrifying about a force you can't see or sense in any way but that can cause terrible damage. Especially for those of us who grew up worried about atomic bombs and atomic testing, radiation is disturbing on a deep level.
       There also are rational reasons to be concerned about excess medical radiation. Six CT scans in a year is a lot (the blood filter was most likely placed with ultrasound, which uses sound waves, not X-rays). It is reasonable to question the necessity for any additional X-rays.
       Fortunately, the amount of radiation in a mammogram is very small. The amount of radiation in a CT scan is roughly 20 times the amount in a mammogram. If you are between 50 and 74, the benefits of mammogram screening almost certainly outweigh the risks of the radiation.    

  DEAR DR. ROACH: I am a 65-year-old male, quite active and weight appropriate. I have been taking hydrochlorothiazide for several years. Due to a glitch with the pharmacy, I ran out of the meds for a week. During the time I was off the medicine, I took my BP five times per day for four days straight. The average of the 20 checks was 125/74. After finally getting the refill, and restarting it, I again took my BP five times per day for four days straight. The average of the 20 BP checks while on HCTZ was 127/71. My blood pressure while on and off the HCTZ look very close. Am I getting enough benefit from taking this prescription to outweigh any kidney damage or other effects of long-term use? What would you recommend? -- D.B.
       ANSWER: It's very helpful to have this level of detailed information, especially since yours is an unusual situation. The most important information are the readings while not taking the medication. If the readings you have represent the time after the HCTZ has worn off, then it would be unlikely that you would be recommended to start on treatment, since your risk for developing a problem with a blood pressure of 125/74 is low.
       It is also remarkable that the HCTZ was not effective at lowering your blood pressure. Twenty-five milligrams of HCTZ normally lowers the blood pressure by about 8 systolic points and 3 diastolic points in people with high blood pressure; however, it has been shown to reduce stroke risk in people over 65 with hypertension better than some other agents.
       I'm not sure you need any medication. You should discuss discontinuing it with your doctor. If you jointly decide that you still need medication, I would consider a different class.
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