Question

For each finding A–E related to renal transplantation, where both donor and recipient are adult, select the most appropriate variable related to that finding from the following list. 

1. Glomerular filtration rate. 

2. Renal plasma flow. 

3. Brainstem death. 

4. Persistent vegetative state. 

5. Tissue compatibility. 

6. Coma due to drug overdose. 

7. Immunological rejection. 

8. Erythropoietin. 

9. Renin. 

10. Aldosterone. 

A. Prior to removal of the donor kidney, it had been established that the unconscious, artificially ventilated donor had persistently absent corneal and pupillary reflexes, there was no eye movement response to ice cold water in the external auditory meatus, nor was there any ventilatory response to carbon dioxide when the donor was temporarily disconnected from the ventilator. 

B. A careful comparison of recipient and donor showed that their cells share an encouraging number of common antigens. 

C. A month after transplantation the creatinine clearance is reported to be 85 ml/minute, which is regarded as satisfactory. 

D. On the same occasion the para-aminohippurate clearance is reported to be 55 ml/minute, which does not seem compatible with the result reported in (C). 

E. On a later occasion the patient is found to have a blood haemoglobin level of 143 g/litre, whereas prior to renal transplantation and while maintained satisfactorily on dialysis, the level was usually around 110 g/litre.

Answer 1

A. Option 3 Brainstem death. The reflex responses mentioned are all mediated through the brainstem and their persistent absence suggests death of the brain stem and hence of the brain since the brain stem is the least sensitive part of the brain; brainstem function is retained in the persistent vegetative state. Drug-induced coma is potentially reversible and organ donation is thus not considered. 

B. Option 5 Tissue compatibility. Tissue typing is analogous to but involves more factors than determining blood group; shared antigens reduce the risk of transplant rejection. 

C. Option 1 Glomerular filtration rate. Creatinine is freely filtered but not appreciably reabsorbed or secreted, so its clearance is a practical indicator of glomerular filtration rate. This result, over half the value for two normal kidneys, will provide excellent renal function. The value tends to rise in the weeks after transplantation, as the disturbances associated with the upheaval of transplantation settle down. In addition, the kidney tends to hypertrophy, as would happen in someone who had one kidney removed with the other one normal. 

D. Option 2 Renal plasma flow. Para-aminohippurate is normally completely eliminated from the circulation as it passes through the kidney, so indicates the renal plasma flow. With a normal haematocrit, the result would indicate a renal blood flow of 100 ml/minute, less than 10 per cent of normal and inconsistent with the above good creatinine clearance. 

E. Option 8 Erythropoietin. Dialysis can correct many disturbances of renal failure, but the lack of erythropoietin means the patient is subject to anaemia; the transplanted kidney provides adequate erythropoietin for a normal hemoglobin level.