A balanced view of calcium and
phosphate homeostasis in
chronic kidney disease
Calcium balance in normal individuals and in patients
with chronic kidney disease on low- and high-calcium
diets
Calcium balance in chronic kidney
disease: walking the tightrope
You must be logged in to post a comment.
Is there a major difference between non-dialysis CKD patients and HD or PD patients regarding calcium balance?
Dialysis patients are expected to be at a higher calcium balance because they have lost excretory function compared to CKD patient . Dialysates in HD and PD solutions with high calcium concentrations could cause a positive calcium balance in patients with ESKD. Normal serum calcium concentrations do not indicate calcium loading and cannot be used as a reference to determine calcium balance.
Treatments such as vitamin D analogues, calcimimetics, and PO4 that increase in late CKD must be considered.
Here is a suggested answer:
Dialysis patients are expected to be at a higher calcium balance. Dialysates in HD and PD solutions with high calcium concentrations could cause a positive calcium balance in patients with ESKD and limited/none kidney capacity to excrete this calcium overload.
I think positive calcium balance is more prevalent in PD> HD> non dialysis CKD.
A study found that subjects with late stage 3 and stage 4 CKD were in slightly negative to neutral calcium balance on a daily intake of 800 mg, but were in marked positive balance on 2000 mg/day.
Evidence suggests that calcium mass balance is positive with a DCa 3.5 mEq/L, negative or neutral with the use of DCa 2.5 mEq/L, whereas both positive and negative balances have been observed with the use of DCa 3.0 mEq/L.
Overall, the use of DCa >2.5 mEq/L is usually associated with an increase in serum calcium level and a decrease in serum PTH level and use of lower vitamin D analogue dose, with the opposite effects usually observed with the use of lower DCa. Most of the available evidence is from small-sized and crossover studies; hence, evidence should be regarded with caution and applied in a patient-specific manner.
Patients on PD are continuously exposed to dialysate for several hours during dwelling time. Although guidelines recommend a dialyse calcium concentration (D[Ca]) between 1.25 and 1.50 mmol/L , a D[Ca] of 1.75 mmol/L is still prescribed to up a large proportion of patients on PD around the world,reaching 50 % of those in the USA.
Whereas D[Ca] of 1.75 mmol/L produces soft-tissue calcification and adynamic bone disease, D[Ca] of 1.25 mmol/L stimulates PTH secretion, and therefore, has been recommended to reduce the risk of adynamic bone disease.
Is there a major difference between non-dialysis CKD patients and HD or PD patients regarding calcium balance?
serum calcium cannot be used as a guide to evaluate calcium balance, and normal serum calcium concentrations do not preclude calcium loading.
we hve to consider treatment like vit d analogues calcimimetics, and PO4 which increase in late ckd ( lower klotho effect and less response to FGF23)
in ckd stage 3 or stage 4 CKD are in slightly negative balance to neutral calcium balance on 800mg calcium intake but in marked positive balance when ingesting 2000 mg of elemental calciumintake resulted in lower 1,25D and iPTH but did not result in overall net decreased calcium absorption or an increase in the serum calcium concentration, suggesting that the calcium is being deposited in tissue..
Dialysis patient
lower 1-25dihydroxy calciferol
less residul kidney function lower urine Ca excretion
same GIT absorption of ca that means theres CA load
dilyzate Ca should be considered
easily to be on positive balance on lower ca intake than nondialysis ckd
According to a study data dialysis patients, predicting negative balance when intake is 800 and positive balance when calcium intake exceeds 1500 mg/day.
With the advancement in CKD, decrease in Clotho, increase in FGF-23, and decrease in alpha-hydroxylase, there is a decrease in calcium absorption and secondary hyperparathyroidism. This increases depending on the decrease in GFR. Son, in the end-stage with anuria, the safety of urinary Ca excretion is lost.
In addition, in HD patients, it depends on dialysate calcium, the amount of vitamin D and analogues, and phosphorus binders. In peritoneal dialysis, they seem to have a similar situation (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4079479/). In my opinion, PD patients may be better in terms of calcium balance because of continuous dialysis depending on dialysate and modality CAPD/APD etc. This needs to be further studied
non-dialysis CKD nondialysis patients;in CKD stages 3-4, there was somewhat a bit to the natural balance in lower calcium intake, but in a higher calcium diet,
in dialysis, there was also a negative balance in lower calcium intake.
CKD nonD
Still have regulatory mechanism, less use of calcium binder, lower PTH, better GI absorption of calcium which decrease as CKD progress
HD and PD patient
Loss of residual renal function, more PTH level, more s.Phosphorous level , decrease GIT absorption, less vitamin D level, decrease urinary excretion of calcium.
Also in PD solution there is Calcium which might affect s. Level
Thanks, Dr. Israa. Do you think that HD and PD patients are more prone to a positive calcium balance?
Yes , so we perform more frequent evaluation of Ca, P , PTH levels in dialysis patients and optimal level of PTH is different between dialysis and non dialysis patients
In addition, nutritional requirements differ between HD and PD patients
Thanks Dr Mohammed. However, the calcium levels are not good indicator of calcium balance. Please follow up the topic as we are going to submit the suggested answers by midnight.
In CKD regulatory mechanisms still partially intact, in HD and PD patients mostly they lost , also dialysate calcium content play a role .
Thanks Dr Ahmed. Can you explain what are these mechanisms?
In CKD-ND
The regulatory mechanisms still intact
There is early hypophosphatemia
The patient may be in positive or negative calcium balance
70% of patients have vascular calcification
In HD or PD :
Loss of the regulatory mechanisms
Loss of renal mass
Loss of residual renal function
hyperphosphatemia, hypocalcemia, secondary hyperparathyroidism.
Positive calcium balance
The dailysate content of calcium and bicarbonate may affect calcium balance.
Long dewel time in PD patients enhance positive calcium balance.
Thanks Dr Asmaa
points to be taken into consideration While evaluating net calcium balance
so supposed HD pts have the lowest calcium balance unless supplemented
Nice comment Dr Marwa and you have also the 3rd source of calcium; bone. With progression of CKD, more patients will have ROD, and both Low and High bone turnover could lead to positive calcium balance.
CKDs
intact regulatory mechanism
residual renal function
AdvanceCKD and Dialysis
Hyperphosphatemia/Hypocalcemia require supplement/binders
severity of HPT
Vascular and soft tissues calcification
Thanks Dr Mahmoud. Could you highlight the effect of these factors on the net calcium balance?
As CKD progresses, kidneys become less able to excrete Ca and patients tend to have positive Ca balance
So Dialysis CKD have more +ve Ca balance than non-dialysis CKD
Furthermore, PD patients may have less +ve Ca balance as they maintain their residual renal function for longer periods.
Thanks Dr Hassan. You are right regarding PD, however they also have a high calcium dialysate.
Thanks Dr Ashraf for your comment
Thanks dr Ashraf for your comment, PD patients have higher incidence of dynamic bone disease due to high calcium content in the peritoneal dialysate. PD solutions have different calcium concentration 1.25mmol/L, 1.5mmol/L, 1.75 mmol/L, using low calcium dialysate 1.25mmol/L is beneficial in ABD CASES
In CKD- in no dialysis
There is still a regulatory mechanism
No need for an early Ca supplement
Phosphorus is to some extent regulated especially with residual renal function in the early CKD stage
In Advance and CKD-D
Hyperphosphatemia ensues
Hypocalcemia necessitate supplement
sever secondary hyperparathyroidism with possible nodularity and hypo sensible gland
Vascular calcification
Ca in dialysate??
Yes there were differences between the CKD and non ckd and hd or pd pt depend on stage of CKD
Ca supplement and presence of residual renal functions neutritional state of pt
And we need to maintain positive ca balance according to each pt to prevent vascular calcification
Thanks Dr Rabab, I think you meant we need to “avoid”. Am I correct?
The CKD patient non-dialysis could be in positive or negative Ca balance, but most probably will have a positive Ca balance as these patients on Ca supplements and on VIT d and both of them will increase the total Ca pool.
hd and PD PATIENT also will diffidently have high positive Ca balance due to loss of excretion adding to Ca phosphate binder
Thanks Dr Rihab for your comment
I think dialysis patient will have more postive calcium balance as they have lost excretory function compared to CKD patient
pd patient sometimes have residual urine output and can have less positive balance than HD patient
i feel its probably better to avoid calcium binders in dialysis patient but tho clinical practice is not such?
I agree with you Dr Muhammed.
THANKS, DR Muhammed, for your question, really, we can’t say that calcium supplement should be avoided, because each case has its special criteria according to which you can manage it, but keeping patient on normal calcium balance even toward the negative balance is recommended.
-Is there a major difference between non-dialysis CKD patients and HD or PD patients regarding calcium balance?
Thanks for your detailed answer. Even in early stages of CKD there is an evidence that those patients have ROD.
https://www.sciencedirect.com/science/article/pii/S2468024922012025
Non HD patient with advace ckd may be on slightly negative or positive calcium balance if taking calcium supplement.
With decreased residual urine , patient are more prone to positive calcium balance
So hemodialysis patient without residual urine function and taking calcium supplement will be mostly positive in calcium , then PD patiens because they mostly still have residual urine function.
It also depends on dialysate, and if patient take calcium or calcium containing phosphate binders what is frequently the case.
So positiv calcium balance increase as following:
HD patient>PD patient >advanced CKD
Great, Dr Nour.
CKD-key MBD’s metabolic abnormalities at various stages With GFR < 20–30 ml/min, serum calcium and phosphate levels fall and rise, respectively. Calcitriol decreases early in CKD (GFR 70–80 ml/min), but calcidiol and PTH rise later, from GFR 60–70 ml/min.
Patients with ESRD have extensive renal impairment with very little or no excretory activity, making them more sensitive to calcium overload due to the lack of excretory function.
Thanks Dr Weam
Thank, Dr Weam for your comment, please don’t forget the effect of high calcium dialysate either in HD or in PD that play a key role in calcium balance in these patients.
Is there a major difference between non-dialysis CKD patients and HD or PD patients regarding calcium balance?
1- HD or even PD patients have advanced renal impairment with very little or even excretory function therefore more susceptible to excess calcium loading.
2- for either HD or PD, dialysate composition regarding bicarbonate and calcium content affects greatly the calcium balance.
3- PD patients have longer times of dialysate exposure with more susceptibility to +ve calcium balance.
I agree.
In a recent study when we measured urinary calcium in patients, we found that GFR correlates with urinary calcium. so the more GFR you lose the less urinary calcium you will have in urine. Patients without kidney reserve are more susceptible to calcium overload.