A truly bizarre line of thought about Descartes's death. Descartes died very suddenly, so rumors about poisoning began almost at once. But the reason historians say he died of pneumonia is that all of the definite evidence is that he did, in fact, die of pneumonia, probably with the contributing factor of being severely weakened by aggressive bloodletting as part of his treatment: he had a fever and congestion of lungs, and the circumstances under which he became ill are consistent with pneumonia. It was also diagnosed as pneumonia a the time.
Of course, if one wants to say that Descartes was poisoned, Baillet (who is not always reliable) does tell us that the doctor who was put in charge wanted to see Descartes dead -- a far more plausible candidate to accuse of being a poisoner than anyone else in the whole scenario, and indeed, the rumors of poisoning at the time were rumors that he had been poisoned by Weulles (Johan van Wullen). By the time Viogué was called in, Descartes was already far gone -- Viogué was called in to do last rites when it was already clear that Descartes was unlikely to survive, and there are far more plausible enemies who had far more plausible opportunities to do damage to Descartes. The proposed motive for Viogué doesn't even make sense -- Descartes himself believed in transubstantiation, he was widely believed to be trying to convert Queen Christina to Catholicism, and even if Viogué thought Cartesian view too like Calvinism, it wouldn't have mattered because Christina was Lutheran, not Calvinist.
But it's possible, too, that there's more to the argument than just the one point, briefly mentioned, about the urine; newspapers are not good sources for seeing how complicated arguments are put together, and any decent argument for the claim that Descartes was poisoned would have to be a complicated one, since all the straightforward evidence suggests pneumonia.