From: Steve Harris <sbharris@ix.netcom.com>
Newsgroups: sci.med
Subject: Re: Vitamins and Colonoscopy
Date: 4 May 2005 19:05:51 -0700
Message-ID: <1115258751.245615.31180@f14g2000cwb.googlegroups.com>

>>There's nothing wrong with vitamins before a colonoscopy, but vitamins
that contain iron, as many do, may make for some black stool in there
that could be confused with upper GI bleeding (melena) at the time of the
colonoscopy and samples can cause false positives for occult blood. <<

COMMENT:

Not if you're using guaiac reaction cards, it won't. That's an urban
medical myth. Those cards require the catalytic properties of
heme-iron, and the only false positives they return is if you're eating
lots of stuff with heme iron.  Like steak tartar and wasabi sauce (all
that green heme-containing horseradish peroxidase is why wasabi is
exactly snot green, and why shot is green too, as a result of a similar
enzyme in eosinophils), etc. Eating iron supplments (which contain
ferrous iron) won't cause false positive stool occult blood tests,
although it *will* produce a somewhat dark stool. This is hard to
confuse with melena for those who have seen and smelled real melena,
but in any case, the guaiac test tells the truth of the tale.

Large amounts of vitamin C can cause a false NEGATIVE on guaiac, since
they inhibit the oxidation which is at the center of that test (and
which happens when you put the hydrogen peroxide on the little card).
But that's only for stool with so little blood you wouldn't see it it
anyway. Melanotic stool will be guaiac positive no matter how much
vitamin C you take.

The true reason why GI docs don't like vitamin pills is they hate to
see the undigested things in a colonoscope....

SBH

From: "Howard McCollister" <nospam@nospam.net>
Newsgroups: sci.med
Subject: Re: Vitamins and Colonoscopy
Date: 5 May 2005 10:17:03 -0500
Message-ID: <427a3876$0$73635$bb4e3ad8@newscene.com>

Steve Harris <sbharris@ix.netcom.com> wrote in message
news:1115258751.245615.31180@f14g2000cwb.googlegroups.com...

> Not if you're using guaiac reaction cards, it won't. That's an urban
> medical myth. Those cards require the catalytic properties of
> heme-iron, and the only false positives they return is if you're eating
> lots of stuff with heme iron.  Like steak tartar and wasabi sauce (all
> that green heme-containing horseradish peroxidase is why wasabi is
> exactly snot green, and why shot is green too, as a result of a similar
> enzyme in eosinophils), etc. Eating iron supplments (which contain
> ferrous iron) won't cause false positive stool occult blood tests,
> although it *will* produce a somewhat dark stool. This is hard to
> confuse with melena for those who have seen and smelled real melena,
> but in any case, the guaiac test tells the truth of the tale.
>
> Large amounts of vitamin C can cause a false NEGATIVE on guaiac, since
> they inhibit the oxidation which is at the center of that test (and
> which happens when you put the hydrogen peroxide on the little card).
> But that's only for stool with so little blood you wouldn't see it it
> anyway. Melanotic stool will be guaiac positive no matter how much
> vitamin C you take.
>
> The true reason why GI docs don't like vitamin pills is they hate to
> see the undigested things in a colonoscope....
>

Dark stool, such as might occur with iron supplements, can cause a false
postive interpretation based on distingishing the dark stool from the blue
color that appears on the card. The vitamin C issue is an interesting lab
experiment, but has no practical application.

I respect your experience in this arena, Steve. I doubt that it exceeds
mine.

HMc

From: Steve Harris <sbharris@ix.netcom.com>
Newsgroups: sci.med
Subject: Re: Vitamins and Colonoscopy
Date: 5 May 2005 15:46:49 -0700
Message-ID: <1115333209.785617.255760@z14g2000cwz.googlegroups.com>

I dunno, Howard. It's hard to tell who's telling who's granny how to
suck eggs. Unless you do digital exams for a living? I don't know how
many thousands of guaiac's I've done. Blue is BLUE. It doesn't look in
the least like iron-darkish-green.  And if you're smearing so thickly
you're seeing *any* color but faint-brown or yellowish brown, you're
smearing it too thickly.

[Smearing it on a bit thickly here}

Humbly Yrs,

SBH

From: "Howard McCollister" <nospam@nospam.net>
Newsgroups: sci.med
Subject: Re: Vitamins and Colonoscopy
Date: 5 May 2005 19:44:02 -0500
Message-ID: <427abd58$0$91654$bb4e3ad8@newscene.com>

Steve Harris <sbharris@ix.netcom.com> wrote in message
news:1115333209.785617.255760@z14g2000cwz.googlegroups.com...
> I dunno, Howard. It's hard to tell who's telling who's granny how to
> suck eggs. Unless you do digital exams for a living? I don't know how
> many thousands of guaiac's I've done. Blue is BLUE. It doesn't look in
> the least like iron-darkish-green.  And if you're smearing so thickly
> you're seeing *any* color but faint-brown or yellowish brown, you're
> smearing it too thickly.
>
> [Smearing it on a bit thickly here}
>
> Humbly Yrs,
>

Well, actually I was referring to colonoscopy and the visual appearance of
iron-containing stool rather than the appearance on a developed guaiac card.
Perhaps I overstated my case? Let me restate after trying to tame my ego a
little....

I see that you're correct - iron may cause a false-positive guaiac in vitro,
but oral iron does not in vivo. Fortunately, DRE for screening isn't a
routine part of my practice and my basis for that exam is palpation rather
than Hemoccult. Patient's are referred to me pre-guaiac'ed.

From a practical standpoint, my point was that at colonoscopy, from a visual
standpoint, iron or iron-containing medications/vitamins could conceivably
be confused with acid hematin and forms the basis for trying to exclude such
compounds as part of a colonoscopy prep. On that, I stand firm as the rock
of Gibralter...unless you have something else I should know...?

HMc

From: Steve Harris <sbharris@ix.netcom.com>
Newsgroups: sci.med
Subject: Re: Vitamins and Colonoscopy
Date: 5 May 2005 16:53:17 -0700
Message-ID: <1115337197.267396.115230@g14g2000cwa.googlegroups.com>

> wasabi sauce (all
> that green heme-containing horseradish peroxidase is why wasabi is
> exactly snot green


>>Huh?  It's coloured with vegetable dye.  Fresh wasabi is slightly
yellow. <<

COMMENT:

Ah so desu ka?  I learn something!  Okay, replace what I said by
"exactly snot yellow..."

SBH

From: Steve Harris <sbharris@ix.netcom.com>
Newsgroups: sci.med
Subject: Re: Vitamins and Colonoscopy
Date: 6 May 2005 15:27:00 -0700
Message-ID: <1115418420.526129.139830@f14g2000cwb.googlegroups.com>

>>I see that you're correct - iron may cause a false-positive guaiac in
vitro, but oral iron does not in vivo.<<

COMMENT:
Yep. There are some conditions where iron ions CAN do the trick, but
not at the pH of the colon, where they're all precipitated out. So in
practice you don't see it. Maybe if you were guaiacing NG tube return
you might see a false positive from iron pills, but not with stool.

>>Fortunately, DRE for screening isn't a routine part of my practice and
my basis for that exam is palpation rather than Hemoccult.<<


COMMENT:
Mine usually also, of course. Feeling prostates, mostly. But if you get
stool, one tends to use it (your patients may be as bad at remembering
to mail things as you are).


>>From a practical standpoint, my point was that at colonoscopy, from a
visual standpoint, iron or iron-containing medications/vitamins could
conceivably be confused with acid hematin and forms the basis for trying
to exclude such compounds as part of a colonoscopy prep. On that, I stand
firm as the rock of Gibralter...unless you have something else I should
know...? <<

COMMENT:
I just wanted to point out that nobody trusts their impression of "acid
hematin" from what they see in a colonoscope screen anyway, so what's
the point? I think this is one of those things like taking not taking
vitamin E before plastic surgery, or with Coumadin, which gets
ingrained, and just goes on and on because everybody knows it's so.
Sort of like not letting patients even drink water the evening before
surgery, not letting them get out of bed for weeks after an MI, and
never giving a narcotic to anybody complaining of abdominal pain. These
things all seemed reasonable at one time. Now we know better. Some hard
and fast rules aren't every hard and fast, and others should not even
be rules. Always question.

If your patient is taking 365 mg of FeSO4 t.i.d. for iron deficiency
anemia (I never give that much, but some docs do), and that's how they
come to you for colonoscopy, I can see why some doctors would want them
off, since this much will stain everything green, and is irritating to
the stomach enough to cause many people to be guaiac pos from REAL
blood.  But somebody who forgot to not take their Theragram M?  Bah.

SBH