Decreased kidney function's internal effect

Dr. Agar,
When one reaches the point of decreased kidney function with no urine output, are there other internal effects to the body other then simply to the kidneys?

When residual function is lost …

I seem to remember answering something about residual function before: if you look back to December 1st and 2nd 2009 under the then thread heading of "What Factors Influence Residual Function on Dialysis?’ asked by Crobake 12 (Dan) and then some further questions from yourself within the same thread, I think most of this question was actually answered then.

However, again … and more briefly this time than the last … residual renal function (and the urine output that accompanies it) offers two main benefits:

   1.  additional solute excretion over and above that obtained from dialysis

   2.  the advantage of added volume control

Any residual function is a benefit. More solute (salts, wastes) is removed - and especially this is so between dialysis treatments.

Any additional solute removal over and above dialysis alone is a good thing.

In addition, most haemodialysis membranes are non-protein-losing membranes … so substances that are protein-bound cannot pass across the membrane and ‘escape’ via dialysis. P-cresol is one such substance, but indoles and a range of other known and potential ‘toxins’ are also poorly cleared in conventional haemodialysis.

Protein-leaky membranes are now available but are not widely or routinely used, currently being reserved for short term use in conditions like mutliple myeloma with cast nephropathy (so-called high cut-off therapy).

However, the availability - or the sustaining - of residual renal function preserves some capacity to excrete larger molecular weight or protein-bound substances - though this capacity clearly diminishes to ‘nil’ as residual function declines to nil and is thus lost over time … (please see the previous thread for this explanation).

As residual function declines and urine output falls away (again, please re-read my previous posts about this), the added benefit of volume control outside simple fluid removal on dialysis falls too. The benefit of a (or any) urine output for patient comfort and for volume and blood pressure control cannot be over-emphasised.

Again, though this was dealt with before and is also covered at my website, if all fluid removal is dependent on dialysis with no urine output between treatments to permit additional fluid losses, the expansion of the intravascular volume between treatments is magnified. This places extra strain on the circulation, the heart, the blood vessels, the lungs … all the ills that accompany excessive fluid retention and hyper-expansion of the circulation.

Then, on dialysis, all the fluid consumed by mouth minus any fluid lost through insensible (unmeasured) losses: skin, bowel, respiration, must be removed in the short time dedicated to the next dialysis treatment.

This contracts the blood volume … dealt with in the two Webinars on solutes and fluids that are available for replay at the HDC home-page. This then drops the blood pressure, risks ‘flats’, turns on thirst and drives the post dialysis fluid intake such that excessive fluid accumulation is again an issue.

In prior posts which have dealt with compliance, I have made the point that we commonly blame a patient for ‘non-compliance’ when it is the treatment that is at fault … too short, too infrequent, too brutal.

So … yes … the loss of residual renal function can have significant consequences - beyond just the kidneys - both in the accumulation of ‘middle molecules’ and protein-bound substances and in the loss of patient control over volume and the resulting consequences of volume overload and their cardiovascular risks.

Sorry for not being more specific. I was trying to picture what the internal damage inside the body looks like when one no longer has urine output and how it might change the shape/size of the organs. LIke you mention the strain it puts on the circulation, heart, blood vessels, lungs. Are any other organs affected and do their shape, size or positioning change?

No, Jane, not in any way that I sense you seem to picture.

‘Drainage’ isn’t quite a concept I would apply to the function of the kidneys.

As far as the effect of the reduced volume control that accrues as the urine output is lost through the gradual attrition (and it usually is gradual in most patients) of residual renal function after commencing dialysis … this has a sequence of congestive effects on the circulation - the blood volume, the heart, the blood vessels - and has the potential to thus cause ‘congestion’ of other organs - the lungs, the liver etc.

When I have discussed this previously, as I have several times with you before in these pages, I believe I have used the analogy of blocking a river and preventing the free forward flow of water down the river.

Block the river - the free forward flow of water from the intake above (rain on the hills) to the outflow into the sea beyond. Then … look back upstream. What do you see? As the river dams, water begins to pool behind the dam, it then swells the feeding streams and begins to break through the upstream river and stream banks, it then floods the surrounding plains, it causes the underfoot to become sodden and water-logged. This is ‘congestion’ … this is fluid overload … it has many names but, in the simplest words I can use to again describe it for you, Jane, it is that everything just gets soaked and wetter than it ought to be.

So, too, does it happen inside us.

As urine output falls, it is like we have ‘dammed’ our forward flow. Our blood vessels begin to swell, they begin to extrude fluid into the tissues, the organs become congested, a congestion which ultimately affects their function - especially first the heart and lungs but, later, other organs too. We get wet. We get sodden. Eventually we flood … and when that happens in the lungs, we get short of breath and can’t breath well.

Residual renal function is like ensuring that there is still some forward flow down the river to help prevent the backlog behind the dam. Over time, this tends to dwindle to a trickle and then, finally, it stops. As it does, the flooding behind the dam occurs ever more easily (and fast).

Now, dialysis comes along. Every so often - and the more often the better - and three times a week is not enough in my view, as you will know.

Dialysis is like opening the sluice gates in the dam and letting out a whole lot of the water behind the dam. It lets some of the fluid that has accumulated behind the dam escape … out from behind the dam. It lessens and/or controls the effects of all the back-flooding that would otherwise occur.

The two best ways (other than installing a whole new system - eg: a transplanted kidney) to reduce the congestion I have described above are to (1) open the sluice gates more often and for longer (extended hour and frequency dialysis) and/or (2) to lessen the water coming down the stream from higher up … ie: reduce fluid intake.

I favour emphasis on the former - more frequent dialysis. Some favour fluid restriction. In truth, it’s a bit of both. But you know how hard it is to stop drinking! So … more frequent and better dialysis is a good answer.

In truth, Jane, that’s the best I can do for you and I am sorry if you still don’t get a sense of this. If you are still confused about it all, I am sorry, but I have done my best.