Tag: X-rays

Balding black holes – a shaggy dog story

Resurrecting an analogy from a dead metaphor?

Keith S. Taber

Now there's a look in your eyes, like black holes in the sky…(Image by Garik Barseghyan from Pixabay)

I was intrigued by an analogy in a tweet

Like a shaggy dog in springtime, some black holes have to shed their "hair."

The link led me to an item at a webpage at 'Science News' entitled 'Black holes born with magnetic fields quickly shed them' written by Emily Conover. This, in turn, referred to an article in Physical Review Letters.

Now Physical Review Letters is a high status, peer-reviewed, journal.

(Read about peer review)

As part of the primary scientific literature, it publishes articles written by specialist scientists in a technical language intended to be understood by other specialists. Dense scientific terminology is not used to deliberately exclude general readers (as sometimes suggested), but is necessary for scientists to make a convincing case for new knowledge claims that seem persuasive to other specialists. This requires being precise, using unambiguous technical language."The thingamajig kind of, er, attaches to the erm, floppy bit, sort of" would not do the job.

(Read about research writing)

Science News however is news media – it publishes journalism (indeed, 'since 1921' the site reports – although that's the publication and not its website of course.) While science journalism is not essential to the internal processes of science (which rely on researchers engaging with each other's work though  scholarly critique and dialogue) it is very important for the public's engagement with science, and for the accountability of researchers to the wider community.

Science journalists have a job similar to science teachers – to communicate abstract ideas in a way that makes sense to their audience. So, they need to interpret research and explain it in ways that non-specialists can understand.

The news article told me

"Like a shaggy dog in springtime, some black holes have to shed…
Unlike dogs with their varied fur coats, isolated black holes are mostly identical. They are characterized by only their mass, spin and electric charge. According to a rule known as the no-hair theorem, any other distinguishing characteristics, or "hair," are quickly cast off. That includes magnetic fields."

Conover, 2013

Here there is clearly the use of an analogy – as a black hole is not the kind of thing that has actual hair. This would seem to be an example of a journalist creating an analogy (just as a science teacher would) to help 'make the unfamiliar familiar' to her readers:

just as

dogs with lots of hair need to shed some ready for the warmer weather (a reference to a familiar everyday situation)

so, too, do

black holes (no so familiar to most people) need to lose their hair…

(Read about making the unfamiliar familiar)

But hair?

Surely a better analogy would be along the lines that just as dogs with lots of hair need to shed some ready for the warmer weather, so to do black holes need to lose their magnetic fields…

An analogy is used to show a novel conceptual structure (here, relating to magnetic fields around black holes) maps onto a more familiar, or more readily appreciated, one (here, that a shaggy dog will shed some of its fur). A teaching analogy may not reflect a deep parallel between two systems, as its function may be just to introduce an abstract principle.

(Read about science analogies)

Why talk of black holes having 'hair'?

Conover did not invent the 'hair' reference for her ScienceNews piece – rather she built her analogy on  a term used by the scientists themselves. Indeed, the title of the cited research journal article was "Magnetic Hair and Reconnection in Black Hole Magnetospheres", and it was a study exploring the consequences of the "no-hair theorem" – as the authors explained in their abstract:

"The no-hair theorem of general relativity states that isolated black holes are characterized [completely described] by three parameters: mass, spin, and charge."

Bransgrove, Ripperda & Philippov, 2021

However, some black holes "are born with magnetic fields" or may "acquire magnetic flux later in life", in which case the fields will vary between black holes (giving an additional parameter for distinguishing them). The theory suggests that these black holes should somehow lose any such field: that is, "The fate of the magnetic flux (hair) on the event horizon should be in accordance with the no-hair theorem of general relativity" (Bransgrove, Ripperda & Philippov, 2021: 1). There would have to be a mechanism by which this occurs (as energy will be conserved, even when dealing with black holes).

So, the study was designed to explore whether such black holes would indeed lose their 'hair'.  Despite the use of this accessible comparison (magnetic flux as 'hair'), the text of the paper is pretty heavy going for someone not familiar with that area of science:

"stationary, asymptotically flat BH spacetimes…multipole component l of a magnetic field…self-regulated plasma…electron-positron discharges…nonzero stress-energy tensor…instability…plasmoids…reconnection layer…relativistic velocities…highly magnetized collisionless plasma…Lundquist number regime…Kerr-schild coordinates…dimensionless BH spin…ergosphere volume…spatial hypersurfaces…[…and so it continues]"

(Bransgrove, Ripperda & Philippov, 2021: 1).

"Come on Harry, you know full well that 'the characteristic minimum plasma density required to support the rotating magnetosphere is the Goldreich-Julian number density' [Bransgrove, Ripperda & Philippov, 2021: 2], so hand me that hyperspanner."
Image from Star Trek: Voyager (Paramount Pictures)

Spoiler alert

I do not think I will spoil anything by revealing that Bransgrove and colleague conclude from their work that "the no-hair theorem holds": that there is a 'balding process' – the magnetic field decays ("all components of the stress-energy tensor decay exponentially in time"). If any one reading this is wondering how they did this work, given that  most laboratory stores do not keep black holes in stock to issue to researchers on request, it is worth noting the study was based on a computer simulation.

That may seem to be rather underwhelming as the researchers are just reporting what happens in a computer model, but a lot of cutting-edge science is done that way. Moreover, their simulations produced predictions of how the collapsing magnetic fields of real black holes might actually be detected in terms of the kinds of radiation that should be produced.

As the news item explained matters:

Magnetic reconnection in balding black holes could spew X-rays that astronomers could detect. So scientists may one day glimpse a black hole losing its hair.

Conover, 2013

So, we have hairy black holes that go through a balding process when they lose their hair – which can be tested in principle because they will be spewing radiation.

Balding is to hair, as…

Here we have an example of an analogy for a scientific concept. Analogies compare one phenomenon or concept to another which is considered to have some structural similarity (as in the figure above). When used in teaching and science communication such analogies offer one way to make the unfamiliar familiar, by showing how the unfamiliar system maps in some sense onto a more familiar one.

hair = magnetic field

balding = shedding the magnetic field

Black holes are expected to be, or at least to become, 'hairless' – so without having magnetic fields detectable from outside the event horizon (the 'surface' connecting points beyond which everything, even light, is unable to 'escape' the gravitational field and leave the black hole). If black holes are formed with, or acquire, such magnetic fields, then there is expected to be a 'balding' process. This study explored how this might work in certain types of (simulated) black holes – as magnetic field lines (that initially cross the event horizon) break apart and reconnect. (Note that in this description the magnetic field lines – imaginary lines invented by Michael Faraday as a mental tool to think about and visualise magnetic fields – are treated as though they are real objects!)

Some such comparisons are deliberately intended to help scientists explain their ideas to the public – but scientists also use such tactics to communicate to each other (sometimes in frivolous or humorous ways) and in these cases such expressions may do useful work as short-hand expressions.

So, in this context hair denotes anything that can be detected and measured from outside a black hole apart form its mass, spin, and charge (see, it is much easier to say 'hair')- such as magnetic flux density if there is a magnetic field emerging from the black hole.

A dead metaphor?

In the research paper, Bransgrove, Ripperda and Philippov do not use the 'hair' comparison as an analogy to explain ideas about black holes. Rather they take the already well-established no-hair theorem as given background to their study ("The original no-hair conjecture states that…"), and simply explain their work in relation to it  ("The fate of the magnetic flux (hair) on the event horizon should be in accordance with the no-hair theorem of general relativity.")

Whereas an analogy uses an explicit comparison (this is like that because…), a comparison that is not explained is best seen as a metaphor. A metaphor has 'hidden meaning'. Unlike in an analogy, the meaning is only implied.

  • "The no-hair theorem of general relativity states that isolated black holes are characterized by three parameters: mass, spin, and charge";
  • "The original no-hair conjecture states that all stationary, asymptotically flat BH [black hole] spacetimes should be completely described by the mass, angular momentum, and electric charge"

(Read adbout science metaphors)

Bransgrove and colleagues do not need to explain why they use the term 'hair' in their research report as in their community it has become an accepted expression where researchers already know what it is intended to mean. We might consider it a dead metaphor, an expression which was originally used to imply meaning through some kind of comparison, but which through habitual use has taken on literal meaning.

Science has lots of these dead metaphors – terms like electrical charge and electron spin have with repeated use over time earned their meanings without now needing recourse to their origins as metaphors. This can cause confusion as, for example, a learner may  develop alternative conceptions about electron spin if they do not appreciate its origin as a metaphor, and assumes an electron spins in the same sense as as spinning top or the earth in space. Then there is an associative learning impediment as the learner assumes an electron is spinning on its axis because of the learner's (perfectly reasonable) associations for the word 'spin'.

The journalist or 'science writer' (such as Emily Conover), however, is writing for a non-specialist readership, so does need to explain the 'hair' reference.  So, I would characterise the same use of the terms hair/no-hair and balding as comprising a science analogy in the news item, but a dead metaphor in the context of the research paper. The meaning of language, after all, is in the mind of the reader.

Work cited:

Not me, I'm just an ugly chemist

Keith S. Taber

Actress Francesca Tu playing an 'ugly chemist', apparently.

The 1969 film 'The Chairman' (apparently released in the UK as 'The Most Dangerous Man in the World') was just shown on the TV. I had not seen it before, but when I noticed it was on I vaguely recalled having heard something about it suggesting it was a film worth watching, so thought I would give it a try. And it had "that nice Gregory Peck" in it, which I seem to recall was the justification given for one of my late wife's sweet little Aunties going to see 'The Omen' (wasn't that also about the The Most Dangerous Man in the World?).

Nobel prize winner AND man of action

Dr John Hathaway (played by Gregory Peck): scientist and international man of mystery

Peck plays a Nobel laureate chemist, so I got interested. He had received a letter from a Chinese scientist, an old mentor who had worked with him at Princeton, warning him not to go to visit him in China, which (a) piqued his interest as (i) he had had no contact with the colleague for a decade, and (ii) he had no plans to go to China, and (b) told us viewers he would be off to China.

Peck's character, Hathaway, is an American who is currently a visiting professor at the University of in London. He contacts his embassy, suspecting there must be something of international significance in the message.

Hathaway's love interest (played by Anne Heywood) is seen teaching in the biophysics department

It transpires that this Nobel prize winning chemist had some kind of background in "the game" – intelligence work (of course! Well, at least this gets away from the stuffy stereotype of the scientist who never leaves the lab.), but had reached an epiphany three years earlier when his wife had been killed in a road accident while he was driving, and the experience of being with her as she died had led to him deciding that every life was unique and precious (as he later explained to Mao Zedong, the eponymous Chairman of the title) and he would no longer take on a job that would oblige him to kill. (Later in the film Hathaway seemed to have forgotten his high principles when he accepted a pistol as he made an escape in a stolen armoured car.) The intelligence communities had become aware that China had identified a natural product that could be extracted in tiny quantities, an enzyme which allowed any crop to be grown under any conditions.

The film seemed to be intended to make some serious points about detente, the cold war, the cultural revolution and the cult of Mao, and political and moral imperatives.

It is the responsibility of all to cultivate themselves, and study Marxism-Leninism deeply. / [Thinks: Sure, as soon as we've finished cultivating this rice.]
The allies argue that China will keep the new discovery to itself and use it to bring developing countries with food shortages into its sphere of influence, and Hathaway seems motivated to ensure all of humanity should share the benefits, thus he accepts the mission to go to China; later Mao agrees to provide a written promise that if Hathaway helps in the research then he can leave China at any time he likes and take with him whatever information he wishes to share with the world.

For the rest of the film to make any sense, Hathaway and the viewer have to assume that the promise and document will not be honoured (and it seems to be assumed that a character simply suggesting this is all Hathaway, or indeed any of us, need to be convinced of this). Yet, (SPOILER ALERT) when Hathaway is safely back in London, and has decoded the structure, he is told that the Western authorities have decided not to share the discovery.

I was not sure what a young audience who do not remember the context might make of some aspects of the film. We are told that the operation to obtain the enzyme, operation Minotaur *, has according to the US officer in charge cost half a billion federal dollars (which seems a lot for 1969, even allowing for some exaggeration) and was supported by the UK with a contribution a British intelligent officer suggests was likely "two pounds ten" (i.e., £2.50).

I wondered whether Chinese agents actually operated so easily in moving into and out of Hong Kong as is suggested, and there was some interesting brief news footage  playing on a hotel television suggesting (British) Hong Kong police were responding to civil unrest in a way that does not seem so different from contemporary reports under the already notorious 2020 Hong Kong national security law.

Anyway, I will try and avoid too many plot spoilers, but suffice to say I was interested and intrigued in how matters would pan out for the first three quarters of the film (until people started firing guns and throwing grenades, at which point I lost any investment I'd had in what would happen.)

Science in the media in 1969

The science in the film was far-fetched, but perhaps not too far fetched for a general audience in 1969. 1969 was after all, a different age. (In 1969 the Beatles were still together, 'In the Court of the Crimson King' was released, and NASA's landing on the moon showed just what the USA could achieve when a President believed in, and encouraged, and resourced, the work of scientists and engineers.)

A transmitter made of undetectable plastic parts, suppposedly

Hathaway was bugged (through a sinus implant) such that his US /UK handlers (and USSR observer) could hear everything he said and everything said to him from half a world away through a bespoke satellite that the Chinese had not noticed recently appearing over their territory. The Americans initially had serious trouble with signal:noise and just made out the odd consonant, and so could not understand any speech, but a UK intelligence officer suggested simply filling in the gaps with uniform white noise, which, amazingly, and (even more amazingly) immediately at first attempt, gave a much cleaner sound than I can get on FaceTime or Zoom or Skype today (Implied message: the British may be the poor relatives, but have the best ideas?)

High stakes communication

What Hathaway did not know (but perhaps he should have been paying more attention when he was told the implanted transmitter was a 'remedy' in case the Chinese would not let him leave the country?) was that the implanted transmitter also had an explosive device that could be used if he needed to be terminated.

Indeed there was supposedly enough plastic explosive that when Hathaway was invited to meet Chairman Mao (was he meant to be 'the most dangerous man in the world'?) it raised the issue of whether the device should be used to remove the Chairman as he played table tennis with Hathaway (asking us to believe that democratic governments might sanction the violent summary execution of perceived enemies, without due legal process, in foreign lands) *.

Is it stretching credibility to believe that democratic governments would sanction the violent summary execution of perceived enemies, without due legal process, on foreign soil?

The command code to explode the device was stored on magnetic tape that took over thirty seconds to execute the instructions (something that seems ridiculous even for 1969, and was presumably only necessary to provide faux tension at the point where the clock counts down and the audience are supposed to wonder if the British and Americans are going to have to kill the film's star off before the movie is over).

Equally ridiculous, the implant supposedly had the same density as human tissue so that it would not show up on  X-rays. (A wise precaution: when in  Hong Kong, Hathaway is lured to some kind of decadent, Western, casino-cum-brothel where Chinese agents manage to covertly X-ray him from the next room as he enjoys a bowl of plain rice with a Chinese intelligence officer – quite a technical feat).

Of course, human tissue is not all of one 'density' (in the sense of opaqueness to X-rays), or else there would be little point in using X-rays in medical diagnosis – actually a sinus should show up on an X-ray as an empty cavity!

Would blocked sinuses show on an X-ray?

Highly technical information appeared on screens at the listening post as displays little more complex than sine waves – not even the Lissajous figures so popular with 1970s sci-fi programmes.

I think it's just the carrier wave, sir

At one point Hathaway broke into a room through a thick solid metal floor by using just a few millilitres of nitrohydrochloride acid (aqua regia) that was apparently a standard bench reagent in the Chinese biochemistry laboratory (these enzymes must be pretty robust, or perhaps Professor Soong had a side project that involved dissolving gold), and which Hathaway was quite happy to carry with him in a small glass bottle in his jacket pocket. The RSC's Education in Chemistry magazine warns us that "because its components are so volatile, [aqua regia] is usually only mixed immediately prior to use". Risk assessment has come on a lot since Dr Hathaway earned his Nobel.

Laboratory safety glasses: check. Bench mat: check. Gloves: check. Lab coat: check. Fume cupboard: check.

The focal enzyme was initially handled rather well – the molecular models looked convincing enough, and the technical problem of scaling up by synthesising it seemed realistic. The Chinese scientist could not produce the enzyme in quantity and hoped Hathaway could help with the synthesis – a comparison was made with how producing insulin originally involved the sacrifice of many animals to produce modest amounts, but now could be readily made at scale. I seem to recall from my natural products chemistry that before synthetic routes were available, sex hormones were obtained by collecting vast amounts of 'material' from slaughterhouses and painstakingly abstracting tiny quantities – think the Curies, but working with with tonnes of gonads rather than tonnes of pitchblende.

Before Hathaway had set out on his mission he had pointed out that the complexity of an enzyme molecule was such that he could never memorise the molecular structure as it would contain anything from 3000 to 400 000 atoms. So, the plot rather fell apart at the end (SPOILER ALERT) as he brings back a copy of Mao's little red book, in which his mentor had hidden the vital information – as the codes for three amino acids.

Ser – Tyr – Pro

Hm.

Beauty and the chemist

You are beautiful, just like your mother – but OBVIOUSLY not as clever as your dad.

But, what sparked me to wrote something about this film, was some dialogue which brought home to me just how long ago 1969 was (I was still in short trousers – well, to be honest, for about half the year I am still in short trousers, but then it was all year round). Hathaway is flown to China from Hong Kong, and on arrival is met by the daughter of his old mentor:

Soong Chu (Francesca Tu): I am Professor Soong's daughter

Dr. John Hathaway (Peck): You look a great deal like your beautiful mother.

Soong Chu: Not I. I am just an ugly chemist

Hathaway: I read your recent paper on peptides. I thought it was brilliant – for a woman.

Soong Chu: Oh, I agree, but my father helped a great deal.

Working in the dark to avoid any more comments on her looks?

I was taken aback by the reference to just being an ugly chemist, and had to go back and check that I'd heard that correctly. Was the implication that one could not be beautiful, and a chemist? Nothing more was said on the topic, but that seemed to be the implication. And what is meant by being 'just' a chemist?

Hathaway's comment that Soong Chu's paper had been brilliant, was followed by a pause. Then came "…for a woman". Did he really say that?

Not bad for a girl

I was waiting for the follow-up comment which would resolve this moment of tension. This surely had to be some kind of set up for a punch line: "It would have been beyond brilliant for a man", perhaps.

But no, Soong Chu just agreed. There did not seem to be intended to be any tension or controversy or social critique or irony or satire there. So much for Soong Chu's membership of the Red Guard and all the waving of the thoughts of the Chairman (she would have known that "Women represent a great productive force in China, and equality among the sexes is one of the goals of communism").

"The red armband is the most treasured prize in China…[representing] responsibility…[as] a leader of our revolution"
Soong Chu had needed the help of her father to prepare her paper, but he had presumably declined to be a co-author, not because his input did not amount to a substantial intellectual contribution (the ethics of authorship have also come on a bit since then), but because his daughter was a woman and so not able to stand on her own two feet as a scientist.

This dialogue is not followed up later in the film.

So, this is not planting a seed for something that will later turn out to be of significance for character development or plot, or that will be challenged by subsequent scenes. It is not later revealed that Soong Chu has a parallel career as Miss People's Republic of China (just as Hathaway is a chemist and also a kind of James Bond figure). Nor does it transpire that Professor Soong had been senile for many years and all of his work was actually being undertaken for him by his even more brilliant daughter.

Sadly, no, it just seems to be the kind of polite conversation that the screenwriters assumed would be entirely acceptable to an audience that was presumably well aware that females cannot be both beautiful and scientists; and that women need help from men if they are to be successful in science.

Times have changed … I hope.

 

 

* Interestingly, I've now found a poster for the film which seems to suggest that the whole purpose of the operation was not to acquire the enzyme structure at all, but to get Hathaway close enough to Mao to assassinate him.

Getting viewers to watch the film under false pretences

This seems to describe a very different cut to one I watched – where the audience with Mao seems to have surprised everyone, and the senior intelligence officers contacted their governments to alert them of this unexpected opportunity!

Is 6% kidney function just as good as 8% kidney function?

A case of justifying dubious medical ethics by treating epistemology as ontology

Keith S. Taber

Image by Mohamed Hassan from Pixabay

I was puzzled by something I heard a hospital doctor say regarding kidney functioning. The gist of his comments were that

  • once kidney function was below about 10% of normal functioning…
  • then protecting remaining kidney function was not important…
  • because estimates of function at that level are unreliable.

I thought this was an illogical argument as it confused ontology (the state of the kidneys and their functioning) and epistemology (how well we can measure kidney function).

The kidneys are essential organs that regulate hydration levels and eliminate toxic materials from the body. They are 'essential' in the sense that without kidney function someone soon dies. Typically healthy people have plenty of scope for contingency in the capacity of their kidneys. (Living kidneys donors give up one of their two kidneys for transplantation, so, after donation, they will only have, at best, 50%,of normal functioning.) So when people's kidneys start to deteriorate due to disease the patient can continue with normal life for some time. I am not an expert, but from what I understand, a person can manage a normal life with 20% of normal functioning.

Of course there reaches a point in progressive kidney disease when the remaining capacity is not enough to keep someone alive for an extended period. So if kidney function drops to something like an eighth of normal healthy functioning, the situation gets critical.

Kidney dialysis

These days people can have dialysis if their kidneys fail. Someone with 0% kidney function – someone who never excretes any urine at all – can be kept alive indefinitely by dialysis. However this is not ideal. The patient has to attend a clinic and have treatment for 3-4 hours at a time, usually three times a week. No time off – no holidays from dialysis if the patient wants to continue living (and some decide they would rather not continue living, although most 'tolerate' the treatment). Often patients feel unwell on, or after, dialysis – they may say they feel 'washed out', for example. Dialysis also costs the health service (or in some countries, the patient) a good deal of money.

Dialysis patients also have to be very careful about diet and avoid some foods (e.g., eating bananas can lead to dangerously high levels of potassium that can interfere with heart function and could lead to a heart attack), as sessions of dialysis (with no, or very little, blood filtration occurring in-between) is never as good as having constantly functioning kidneys.

Then there's the problem of fluid intake

Dialysis patients are asked to limit their intake of fluids. A healthy person who drinks a lot (whether tap water, tea, beer, etc.) simply produces more urine. Most dialysis patients, however, produce little, if any, urine, and the difference between what they 'should' excrete (to maintain homeostasis), and what they can actually excrete, needs to be removed during the dialysis process. So, whatever water a patient takes in drinks during the 45 or so hours between sessions (and is not lost through some other mechanism such as sweating or breathing), is all taken off during three or so hours on the machine. This brings about changes in the blood volume much more quickly than is comfortable. As the body cannot remove excess fluid via the kidneys, fluid intake means the fluid levels build up between dialysis sessions which can lead to various complications such as increases in blood pressure.

Dr McCoy is unimpressed by 20th Century medicine (Star Trek IV: The Voyage Home, Paramount Pictures)

So, having kidney function of, say, 10% or less of normal is a real pain and requires reorganising your entire life around your dialysis sessions (or perhaps getting a transplant if you are strong enough for surgery and are lucky enough that a good match can be found).

That provides some background in considering whether, once kidneys have deteriorated below, say 10%, it really makes any difference in worrying about the actual level. If you have 8% of normal functioning and are on dialysis for life, why would it matter if that fell to 6%?

An actual case

The context of this question was a patient with kidney failure or end-stage renal disease (a haemodialysis* patient, who would only live a matter of days without regular treatment) who was given a CAT scan** using a contrast medium*** to show up features that would not be observable otherwise. Such media are widely considered to have some toxicity in relation to the kidneys (Ahmed, Williams & Stott, 2009), but in a healthy person they are eliminated through the kidneys quite quickly and any risk is considered small. A person with kidney failure does not eliminate toxins in this way, and so when a scan is indicated, it can be scheduled for just before their next dialysis session.

"In every study comparing patients with and without some degree of renal insufficiency [kindeys not functioning adequately], renal insufficiency increased the likelihood of RCIN [radiocontrast-medium-induced nephropathy, i.e., kidney damage due to the use of contrast media]"

"Both peritoneal and hemodialysis remove substantial amounts of the contrast medium (50% to 90% of the dose); hemodialysis is more effective."

Solomon, 1998: 230, 236.

This patient, however, was admitted to a hospital very ill. The emergency department doctor ordered an immediate scan – late at night, at a weekend – but told the patient that the on-call dialysis staff could be called in to give dialysis after the scan. At the X-ray department, the radiographer then said that this was not needed, as long as the patient had dialysis within 24 hours of the scan.

The renal doctor's viewpoint

The next afternoon, the patient had still not gone for dialysis when the hospital renal doctor visited the patient. This doctor took the view that as the patient was due their regular dialysis the following day (i.e., about 38 hours after the scan), there was no point sending the patient for an additional dialysis session, as – after all – the kidneys had already failed sufficiently for the patient to be relying on dialysis for survival.

The patient's viewpoint

The counter-argument presented to the renal specialist (by the patient's spouse) was that even at this point further deterioration should be avoided if possible – that even if 8% of normal kidney function was not good, it was inherently better than 6% of normal kidney function.

After all, if for some reason a patient was further compromised (by an unrelated illness, or by delay in accessing normal dialysis due to some unexpected contingency) a few percentage points – making a small difference in how much the body could remove toxins and excess fluid from the blood by itself between dialysis sessions – could still be the critical factor in determining whether the person survived. (Those attending hospital dialysis notice the high frequency of fellow regular patients who, suddenly, are no longer attending for treatment.)

The renal doctor's justification

The doctor responded to this with the counter-argument that once kidney function was this low, there was no reason to be concerned about a change in measured kidney function from (say) 8% to 6% as the difference between such measurements was within the usual variations in measurements found in patients from time to time.

There are two issues here of interest.

Consent that is conditional is not consent if the conditions are broken

One issue relates to ethics (here, medical ethics). A patient consented to a diagnostic procedure with a possible risk of side effects on the understanding that a suitable counter measure would be taken immediately after the procedure to minimise any detrimental effect. The hospital undertook the procedure, but then decided (when it was too late for the patient to withdraw consent) not to follow through on the promised counter-measure. In effect, a procedure was carried out without consent as the consent was (as was made absolutely clear by the patient) conditional on the scan being followed by dialysis.

Reasons for refusing to provide treatment

The second issue relates to the justification given by the doctor as reported above.

The day after the explanation about measurement not clearly distinguishing between 8% and 6% functioning had been made, when dialysis was finally provided, another renal specialist offered a different justification entirely – that the potential risk to kidneys of the contract medium was just a myth. However, the earlier conversations

  1. in the emergency department;
  2. in the X-ray department; and
  3. with the first renal doctor within 24 hours of the scan,

were all clearly undertaken on the basis that both patient and medical staff thought the contrast medium was potentially damaging to kidneys.

"These contrast media can occasionally cause kidney damage, especially in patients who already have kidney disease"

Ahmed, Williams & Stott, 2009

In the context of that discourse, the first renal specialist had argued that because (a) the precision of estimates of kidney function was not great enough to reliably measure a difference between 6% and 8% functionality, then (b) there was no need to be concerned about treatment which could potentially cause damage bringing about deterioration of this order.

Presumably,

  • at any one time, a person's kidney function will be at a certain level.
  • If the kidney is then further damaged by toxins then that functionality will drop.
  • A more damaged kidney is inherently less desirable than a less damaged (better functioning) kidney.
  • So further damage to an already damaged kidney is inherently undesirable,
  • and should be avoided if possible, if the costs of doing so are not too high.

The state of a diseased person's kidneys could vary slightly 'naturally' in response to various factors related to their general health, diet, environment, etcetera. This is an ontological consideration – the actual state of the kidneys changes. This may well mean that changes of a few percent between measurements could just be natural fluctuation.

It may therefore be difficult to tell if a person's kidneys have become more damaged due to a particular event, such as a diagnostic scan. That is an epistemological issue – the limitation on how well we can identify a specific change that is masked by noise.

Presumably, there are also various factors that limit the precision of such estimates – all measurements are subject to errors, and small (real) differences may be difficult to identify if they are at the level of the likely measurement error. That is also an epistemological issue.

But, just because an effect cannot be clinically measured (epistemology), that does not mean it is not real and will not have consequences (ontology). A drop from 8% kidney function to 6% kidney function is only a change of 2% compared with normal functioning, BUT it is a loss of 25% of the patient's actual kidney function.

A small deterioration in already severely compromised kidneys may seem insignificant to the renal doctor because he does not think he could reliably measure the change. One day it could be the difference between life and death to the kidneys' owner.

Sources cited:
  • Ahmed, A., Williams, G., & Stott, I. (2009). Patient information-What I tell my patients about contrast medium nephrotoxicity. British Journal of Renal Medicine, 14(3), 15-18.
  • Solomon, R. (1998). Contrast-medium-induced acute renal failure. Kidney international, 53(1), 230-242.

* haemodialysis involves the patient having permanent 'plumbing' installed that allows their vascular system to be connected to a dialysis machine, so the blood can be diverted to the machine to be cleaned. This usually done using blood vessels in the arm. In the case discussed the surgeon cut into the neck and chest (with the patient fully conscious), and connected tubing to a vein in the neck. The tubing was run beneath the skin to exit in the chest below the neckline, where a fitting acted as a tap and connector for the external tubing to the machine. Very special care has to be taken to keep the area clean, and the dressing dry, as the plumbing provides a direct route into the bloodstream. (Baths, swimming, hot-tubs, etc. are not advisable.)

[Peritoneal dialysis is an alternative treatment that involves a catheter being implanted in the abdomen, and being used to allow a solution into the abdominal cavity, which is later removed after it has absorbed waste materials. The patient can manage the process at home, but needs to change the solution in the abdomen a number of times each day.]

** computerised tomography: a process that uses a series of X-ray bursts to collect data that can be compiled into a 3-D image.

*** a substance that shows up on X-ray scans, and which when injected into the blood helps detect vascular structures. (The term is generic – it also applies to substances swallowed  before scans of the alimentary canal.)

Note: this post was originally prepared in October 2015, but was not published at the time when the patient was alive and attending for treatment.