Other Radiology Bits and Pieces of Lore




(1)
Department of Radiology, UMDNJ-New Jersey Medical School, Newark, NJ, USA

 



Abstract

In the proceeding essay, my theme was well-established misconceptions under the heading. “It ain’t what you don’t know it’s what you do know that ain’t so.” If you are game, lets continue with some more examples.


In the proceeding essay, my theme was well-established misconceptions under the heading. “It ain’t what you don’t know it’s what you do know that ain’t so.” If you are game, lets continue with some more examples.


Pills


Occasionally on plain films of the abdomen and on CT’s, one or several discrete non-calcific opacities are recognized [1]. They are characteristically homogeneously dense and differ also from most stones by their smooth outline and by the fact that their density varies inversely with the extent of the “area” they present to the X-ray beam. That is, when the beam brings into view a larger “area” of the opacity it appears less bright than when a smaller area is presented, when it is correspondingly more radiodense. This is because these opacities are disc-shaped, unlike the more spherical configuration stones tend to assume. So by the characteristics of their conformation alone, one is apt to say that they are pills. Typically the radiologists report is limited just to that phrase. That is, pills are present.

I submit that such a brief interpretation is inadequate because we know more and should say so. I routinely ask senior medical students and residents—all of whom are at least 2 years beyond physiology class a simple question. Where is iron absorbed? Unless tipped off, almost all of them will say in the ileum and a few others will offer up the jejunum. Yet they have forgotten that iron is absorbed only in the twelve inches of the duodenum—not more distally.

How is that relevant? Well if we are to see a pill in the gut on X-ray, it must be intact and therefore it has resisted dissolution. Moreover beyond the duodenum it is of no value even if it could dissolve. And of course it must be opaque to begin with. Now, the only medications that satisfy both those criteria are Pepto Bismol tablets which are typically triangular in configuration and iron pills which have a range of shapes.

Besides being absorbed only in the duodenum, iron is irritating to the stomach. Hence solid iron-containing preparations are enteric-coated to bypass dissolution in the gastric lumen and therefore they are prepared to dissolve in the duodenum. This requires a pharmaceutical tour-de-force if you will. Enteric coats become more resistant the older the patient and the longer its shelf life before being ingested. Hence, often the pill is still intact as it enters the jejunum and thus it will not be absorbed.

The implication of this fact should not be avoided by the radiologist. The presence of a pill beyond the duodenum—and it is always an iron pill if it is rounded—is that the treatment of anemia for which the pill was administered is now recognized as being ineffective. The radiologists’ report should mention this clinically relevant conclusion. Moreover, the referring physician should be specifically notified about this manifestation of a therapeutic failure. Merely to say pills are present should be regarded in this circumstance as inadequate reporting by a radiologist.

Apr 27, 2016 | Posted by in GENERAL RADIOLOGY | Comments Off on Other Radiology Bits and Pieces of Lore
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