What is GFR( glomerular Filtration Rate ) & what is its relevance in Gynaecolgical
surgery , Obstetrics and Obstetric
Medicine?? Why we should read this
note at all ??
Logic:: As more and more women with
established DM/ SLE and woman with renal
transplant are conceiving so we must be aware of basic
physiology of kidneys not to speak of acute shut down of kidneys due to
ureteric insults by surgery(monopolars) and nephrotoxic drugs, Additila basic
knowledge is warranted for undesirable
mismatched blood transfusions.. Here is
the relevance Ans:-The glomerular filtration rate is used to evaluate renal function.
It varies with age, gender, size and even nutrition of women. The concept of
normal renal function is complex.
But : We the practicing gynaecologits
who come across DM/ SLE cases with some
form gynecological /Obstetric problems and more recently more and more women
are conceiving with renal transplant as well. should remember
that “The GFR value only decreases when 50%
of the glomeruli are affected “. It is time for practsing Obstetrician
to remember that “ a normal GFR does not imply the exclusion of
early renal disease”. That is why we the gynaecologist must pay more relevance on
renal functional reserve rather than GFR only
in 3 kinds of medl diseases as mentioned
like DM/SLE/Renal transplants. We just can’t refer her to nephrologists all the
time for many reasons including financial commitments.
What
is the baseline GFR ?? Logic:: As more and more women with
established DM/ SLE and woman with renal
transplant are conceiving so we must be aware of basic
physiology of kidneys not to speak of acute shut down of kidneys due to
ureteric insults by surgery(monopolars) and nephrotoxic drugs, Additila basic
knowledge is warranted for undesirable
mismatched blood transfusions.. Here is
the relevance Ans:-The glomerular filtration rate is used to evaluate renal function.
It varies with age, gender, size and even nutrition of women. The concept of
normal renal function is complex.
But
: We the practicing gynaecologits who come across DM/ SLE cases with some form gynecological /Obstetric problems and more recently more and more women
are conceiving with renal transplant as well. should remember
that “The GFR value only decreases when 50%
of the glomeruli are affected “. It is time for practsing Obstetrician
to remember that “ a normal GFR does not imply the exclusion of
early renal disease”. That is why we the gynaecologist must pay more relevance on
renal functional reserve rather than GFR only
in 3 kinds of medl diseases as mentioned
like DM/SLE/Renal transplants. We just can’t refer her to nephrologists all the
time for many reasons including financial commitments.
What
is baseline glomerular Filtration Rate?? Baseline GFR is approximately 120ml/min/l.73 m
and 110 ml/min/1.73 m in men and
women respectively .
When it gets
persistently lowered below
60 ml/min/ `1.73 m one usually speaks of chronic renal
insufficiency and when it
falls rapidly one speaks
of acute renal
insufficiency .
Relation
of GFR with Age??
Ans:--It decreases physiologically with age at about 0.8 ml/mm/
1.73 m per year after the age of 30 years.
How can we mathematically estimate GFR at OPD / personal clinic?? Ans:-In a clinic we the
gynaecologits can estimate GFR -à as the GFR is globally estimated by clinicians from serum
creatinine level using different formulae.
But the
latest being the CKD - EPI formula
The KDIGO 2012 classification on CRI combines eGFR
and the measurement of Albuminuria. It enables the clinician to orientate
his/ her management. It could nevertheless be falsely reassuring.
How,
then we calculate “Renal functional
reserve”?
RFR (reserve) is the capacity of the kidney
to increase its activity in
response to certain pathological
or physiological stimuli . RFR
decreases with age. A study carried out in 2010 compared the GFR values in two groups
healthy men and women of extreme
ages. The conclusion that the
maximal increase of GFR of the young
group was 84% whilst it was only 39% in the old group
How
GFR can falsely reassure clinicians who are nephrologist?? Ans:-Only half of the glomeruli
are needed to maintain a GFR
within the norms and so its calculation is a poor marker of the functional capacity of the kidneys. It
would seem that in renal insufficiency
there is a concomitant decrease
of RFR (functional reserve) and GFR but
proportionally the decrease of RFR(renal reserve) is more rapid
than that of GFR. The more advanced the Chr Renal Diseases(CKD) , the
less will be the RFR. This typically
happens in long standing uncontrolled DM which we may miss in naked unless you
read this comments which I am preparing for weeks since the initiation of lock
down at India.
The fact that RFR can be measured would give much more precise information
on renal function and would enable for example the anticipation of the occurrence of renal reserve which seems to lower the reserve. The return to a normal GFR after acute renal shut down (mismatched
blood transfusion) does not mean a complete restoration of renal function thus
Acute renal shut down (drugs/ tying both ureters accidentally) . Reserve should no longer be considered as a isolated episode
but as a risk factor
for developing CKD. Likewise
renal without an impact on the GFR
could be a sub clinical disease.
The mechanism involved in the
mobilization of the GFR is only partially understood
In a person without any renal
disease it probably comes
from the recruitment of a
large number of glomerules
from hyper filtration but
mostly from the increase of renal blood flow . But what happens in a woman
with CKD?? In such women the
increase in the filtration
fraction of the glomerule always through
increase in renal blood flow would be mediated by the release of nitric oxide and prostaglandins vasodilatory substances.
Some examples of renal
functional reserve
It is
important to note that a diet
which is poor in proteins could
probably facilitate rediscovery
of a renal functional reserve in
patients with renal insufficiency
In the same manner a pregnant lady
without renal disease increase her
GFR through the increase
in cardiac flow and thus decreases her renal functional
reserve .Nevertheless the maximal GFR is not modified . The RFR could thus be useful to detect situation
of risk in these women.
Usefulness
of determining renal functional reserve
The kidney
could permanently increase its emunctories function of the person by increase of the glomerular filtration rate,
like hepatic cells regeneration . This adaptation inevitably involves
recruiting of the reserve Force( Renal Reserve—RFR) .
How
to asses Renal health of patients , not by creatinine as we are accustomed?? How USG Doppler can offer an
overview of Renal reserve ? Ans:- Henceforth measuring the RFR will offer a more
specific vision of the state of renal health of patients. It measurement is hardly invasive less expensive and does
not necessitate a demanding technique. It is applicable to patients who are in bed and could
even be evaluated by Ultrasound Doppler
.It enables the clinician to better understand why two
patients with the same GFR value and an identical muscular mass do not
show the same renal sensitivity to a
given renal stress. It also facilitates the understanding of why elderly
persons are more exposed to renal disease. It could also have practical
implications For example it could
enable a better follow up of
patients who have acute renal failure or who have poor Renal reserve and therefore
present with an increased risk of
developing CKD. Follow up would also be better for hypertensive and diabetic patients with polycystic renal disease or with only
one kidney in who a lowered RFR would
signal a subclinical disease.
Is there any Role of estimating renal reserve in Preopertaive assement?? Ans:- Determining the RFR
could form a part of the evaluation of risk for surgery or a procedure
on the renal function. The perfusion of
amino acids enabled an increase in the
GFR and
in diueresis. Knowing the RFR
could determine the chances of recuperation when there is acute renal insufficiency
in a patient with CKD and would
pre empty the placement of a useless
arteriovenous fistula(often needed in Dialysis) . The RFR could prove to be very useful in
specifying the risk of delay in functioning in caes of a renal
transplant and the duration of survival
of the transplant women . It would also furnish significant information
in the case of live donors in
whom it would seem logical that a low
RFR puts them at risk for progression
towards a CRI. A systematic
measurement before proceeding with
nephrectomy could be done in the future
in the same manner
as the maximal respiratory capacity
is measured before a pneumectomy
Renal functional
reserve is a measurement of the maximal
capacity of the kidney to respond
to a physiological or pathological stimulus. It urges one to differently
perceive acute renal insufficiency or any other
renal stress. It would be desirable to be able to measure it in clinical practice in
patients at risk for developing a CRI
in intensive care and in
transplantation.
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