Hickam's Victims: Misdiagnosis & Treatment of an Incidentaloma in Guillain-Barre Syndrome and Careless Citation Practices

I'm following citations to our paper explicating Hickam's Dictum (HD) and Ockham's Razor (OR) as applied to diagnostic decision making, published two years ago. It was my hope that this paper would lead to a more thoughtful consideration of these allegedly conflicting clinical saws, but alas I was too sanguine about that prospect. It would seem that most people citing our paper are not even reading it. Rather, it appears that they conclude that they have identified a case of HD, write a case report about it, then seek supporting references and cite our paper without reading it or applying its insights to their case.

Nonetheless, I'm happy to have our paper cited for any perspicatious and curious readers of these case reports. And, the problem of careless citation practices is rampant. Often when I check citations to see if they support the referenced statements, I'm gobsmacked: not only do many citations fail to support the authors' statements, sometimes they directly undermine them. Commonly, an author makes claims as though starting from truth rather than uncertainty, then searches for supporting references, but does not carefully evaluate the references or their relation to his claim -- or even read the papers he's referencing. Rather, he reads the title or abstract ingenuously and cites the paper. This is not scholarship, this is confirmation bias and motivated reasoning in action. It is abetted and exacerbated by the tendency of authors to overextend themselves in their abstracts, arriving at conclusions that are broader and firmer than warranted by the data. This phenomenon has a tendency to magnify and replicate flimsy claims, so we wind up with wholly unsupported concepts that persist for decades, viz, immune dysregulation in sepsis. (Just think about this for a second and decide if it makes sense:"Some people die of sepsis; therefore, evolution of mamallian immunology stalled, failed, or overshot, and the immune system is dysregulated.") Yet this concept accompanies almost every single article about sepsis for going on a generation; you gotta reference it in your sepsis paper. So, you go to pubmed, type it in, find the latest abstract that mentions  it, import it into EndNote, cite it. Done. Specious concept propagated yet again.

In this case report alleging the simultaneous presentation of Guillain-Barre Syndrome (GBS) and a pancreaticoduodenal artery aneurysm PDAA with "impending rupture," the author invokes Hickam's dictum becaues the patient has two diseases that were discovered at the same time. The schema outlined in Figure 3 of our paper shows that there are four possibilities for the relations between two (or more) disease: incidentalomas, pre-existing diseases, diseases causally connected to the principal diagnosis, and lastly, two symptomatic, independent, temporally coincident diseases. This last possibility is decidecly the least common, but it's what the author settled upon.

The patient had a preceeding viral illness (setting the stage for GBS) and a week later developed numbness and back pain, two common symptoms of GBS. She went to an ER and because of the back pain, had a CT of the abdomen, and a PDAA was discovered. The case report describes it as having an "impending rupture," but we are not told how this determination was made. (Can it be made?) It was embolized and her back pain (maybe? kinda?) resolved. Days after the embolization, they discovered the true cause of her numbness and back pain: GBS.

Not described in the report is the well-established fact that the vast majority of unruptured PDAA are totally asymptomatic and discovered incidentally on imaging as in this case. Furthermore, when they are symptomatic they cause epigastric and abdominal pain, not back pain. Risk of rupture is not clearly correlated with size, so size alone cannot be used to infer "impending rupture." Just that background knowledge is enough to establish that this is an incidentaloma. 

In real time, considering that these aneurysms take years to form and are mostly incidentally discovered and don't cause back pain should lead the wary clinician to question whether this is an incidentaloma and the real disease is still lurking in the background. Her symptoms should be more carefully explored, information about the patient and the diagnostic possibilities further investigated and synthesized.

If we find incidentalomas and treat them with invasive therapies without careful consideration, we are liable to cause iatrogenic problems. Though PDAAs warrant embolization because of a high risk of later rupture, we may not want to place it high on the list of management priorities depending on the acute disease (here, GBS) we're dealing with. Imagine that this lady had presented just a bit later when she had respiratory muscle weakness, and had been taken for urgent embolization, and then she coded during conscious sedation for the procedure. Or, imagine if, as almost happened in this case, that the principal diagnosis (the one which explains the chief complaint: GBS) was missed and she had respiratory arrest because PDAA with "impending rupture" was misidentified as the principal problem and her weakness was misattributed to residual sedation effects.

Analysis of this case report makes clear that this is not a purely pedagogical or pedantic exercise. Knowledge structured according to our Figure 3 heightens awareness that we can always be chasing incidentalomas or anchoring on known diseases, missing the true principal diagnosis, or failing to make connections between causally related facets of the presenting illness, invoking multiple diagnoses --sometimes highly unlikely combinations of rare diseases -- rather than a unifying one.

Some of these case reports alleging HD are downright embarrassing. They expose fundamental errors of diagnostic logic that persist even after the effort to write up the case for full publication has been undertaken. As we showed in our paper -- the one that apparently nobody reads -- most of the time when you invoke HD it means you missed the big picture and were surprised by an unsurprising set of multiple diagnoses because of incomplete or flawed understanding of the case. 

Medicine is hard.