Interesting Renal Phys Question...

[metalmd06]

I was just imparting some knowledge upon my girlfriend about the large percentage of the cardiac output that flows through both kidneys (22-25%). She then asked me, post nephrectomy, does the renal blood flow through the remaining viable kidney increase to that basal level of 22-25% of the cardiac output? My initial guess is that increasing the blood flow to 100% above normal would be detrimental to the remaining kidney. Discuss.

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[hanky1982]

My initial guess is that increasing the blood flow to 100% above normal would be detrimental to the remaining kidney. Discuss.

Not sure, but I think that this is accurate.

 

[Hokie06]

i'm not a medical student yet but I'll try taking a stab at this using my premedical education,

Post nephrectomy, the afferent arterioles of the remaining kidney experiences highly elevated pressure, so to maintain homeostasis, brain signals the vessel to increase resistance to restore the glomerular filtration rate to within normal limits of that remaining kidney. As the cardiac output to that kidney persists, your body becomes habituated and develops a new basal level for that kidney. Kind of like thermoregulation where negative feedback allows your body to regulate the amount of heat that is retained or given off by constriction of blood vessels and shivering. Eventually, what was so cold is not so cold anymore. But then I think that since blood is not being "efficiently" filtered of waste material as well as before (2vs1), one needs to constantly get blood work done to check for pH changes and maybe even dialysis in extreme cases.

I think the basal level would change for the remaining kidney. Because if the same amount of blood was routed to that one kidney, afferent arteriole would pick up on this via the dialated afferent arteriole and make physiological changes similar to what would happen if an individual had high blood pressure. of course all of this would only make sense if we assume that the result of having only one kidney causes an increase in pressure.

I guess the other hypothetical answer is that the basal level stays the same, but it takes a greater amount of time for the same liters of blood to get processed in a given time.

 

[J-Rad]

I'm not that interested in intensive review of renal physiology (not my organ of preference), but Campbell's Urology:

"Patients are often concerned about how the removal of a kidney will affect their renal function. After nephrectomy for unilateral renal disease, the opposite kidney undergoes compensatory hypertrophy, and the glomerular filtration rate is ultimately maintained at 75% of the normal value ( Aperia et al, 1977 ; Robitaille et al, 1985). Several long-term studies have shown no increase in hypertension or proteinuria, stable overall renal function, and normal life expectancy after unilateral nephrectomy with a normal contralateral kidney ( Kretschmer, 1943 ; Goldstein, 1956 ; Anderson et al, 1968 ). This information should be shared with patients to alleviate their anxiety before surgery."

I think in this scenario, GFR may proximate GFR.

 

[bigDinLV]

I'm not that interested in intensive review of renal physiology (not my organ of preference), but Campbell's Urology:

"Patients are often concerned about how the removal of a kidney will affect their renal function. After nephrectomy for unilateral renal disease, the opposite kidney undergoes compensatory hypertrophy, and the glomerular filtration rate is ultimately maintained at 75% of the normal value ( Aperia et al, 1977 ; Robitaille et al, 1985). Several long-term studies have shown no increase in hypertension or proteinuria, stable overall renal function, and normal life expectancy after unilateral nephrectomy with a normal contralateral kidney ( Kretschmer, 1943 ; Goldstein, 1956 ; Anderson et al, 1968 ). This information should be shared with patients to alleviate their anxiety before surgery."

I think in this scenario, GFR may proximate GFR.

Beat me to it...

 

[J-Rad]

...

I think in this scenario, GFR may proximate GFR...

Oops, I meant GFR may proximate CO (to the beans, or bean in this case)

 

[Ki45toryu]

I'm not that interested in intensive review of renal physiology (not my organ of preference), but Campbell's Urology:

"Patients are often concerned about how the removal of a kidney will affect their renal function. After nephrectomy for unilateral renal disease, the opposite kidney undergoes compensatory hypertrophy, and the glomerular filtration rate is ultimately maintained at 75% of the normal value ( Aperia et al, 1977 ; Robitaille et al, 1985). Several long-term studies have shown no increase in hypertension or proteinuria, stable overall renal function, and normal life expectancy after unilateral nephrectomy with a normal contralateral kidney ( Kretschmer, 1943 ; Goldstein, 1956 ; Anderson et al, 1968 ). This information should be shared with patients to alleviate their anxiety before surgery."

I think in this scenario, GFR may proximate GFR.

and we have the winner...interesting to note no increase in unilat hypertension as a result of the increased flow/compensation

 

[Hokie06]

hm i thought it was become you now have ADH only acting on 1 kidney as opposed to two. so you expect to have greater water retention and therefoe increased hypertension. at least this was my reasoning