Dear Dr. Roach: In August 2014, my urologist ordered a CT scan to confirm a possible recurrence of kidney stones. The stone results were negative; however, the scan report described findings of a small, low-density lesion in the pancreas measuring 4.3 millimetres in the proximal tail. 听
In the past 11 months, my gastroenterologist has ordered two ultrasounds and two MRCPs. All test results were negative. He did not order another CT scan because of the radiation exposure. Upon my suggestion, he recently had two radiologists review a CD of the CT scan, and neither could find any indication of a pancreatic lesion. What鈥檚 going on? 听
GM
It is very frustrating for patients to be presented with conflicting results, but it is far more common than you might realize. There are two possibilities here. The first is that you do not have a pancreatic mass. In that case, the initial review of the CT scan must have been wrong. This is called a false-positive, because the scan had a positive finding, a 4.3-mm lesion, and false if it turns out not to be true. CT scans are very accurate for larger tumours (greater than 20 mm is a large tumour), if the scan is done in a way to look specifically for pancreatic masses.
This probably wasn鈥檛 done, since initially they were looking for kidney stones. However, it is much less accurate for smaller masses. (For comparison, a pencil eraser is 6 mm in diameter.) So 4.3 mm is at a level where I would be concerned about there being a false-positive.
The fact that two radiologists reviewed it and couldn鈥檛 find it makes a false-positive very likely.
The second possibility is that you do have a pancreatic mass and all the other tests were false-negatives. This is unlikely: MRCP (magnetic resonance cholangiopancreatography) is a pretty good test, able to pick up about 84 per cent of masses that turned out to be pancreatic cancers. Ultrasound also is sensitive, picking up 90 per cent of such lesions.
I think it鈥檚 unlikely that these both were repeatedly wrong. It鈥檚 not possible to be 100 per cent sure, but I think that by far the more likely possibility is that the reading of the original CT scan 鈥� probably not the kind designed for finding pancreatic masses 鈥� was wrong.
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