The functional pattern of the transplanted living-donor kidney during the early posttransplant period

The functional pattern of the transplanted kidney during the first year

Prospective studies on kidney function have been carried out 1-14 months after transplantation in two groups of recipients of renal transplants. Both groups were characterized by immediate graft function. The first group had transplants from living donors, the second had received cadaveric kidneys. In the first group a functional maximum (as measured by 125iothalamate, creatine and 131I-hippuran clearances) was reached during the first three weeks after transplantation, approximating 70% of the donors' bilateral preoperative function. In the second group kidney function was constant during the period of study, the values being almost identical with those observed in the first group. At investigation 12-14 months after transplantation, the two groups were compared with the remaining cadaveric transplants carried out during the period of study, the latter being primarily graft anuric. Graft function in the primarily anuric grafts was found to be poorer than in those with initial function. Graft survival, too, was poorer at one year in the group characterized by primary graft anuria than in the other groups. Graft survival at one year was 68% in cadaveric kidney transplants with good initial function.

Influence of the recipient's size upon renal function following kidney transplantation. An experimental and clinical investigation

The influence of the size of the recipient upon posttransplantation renal function was investigated in an experimental study of inbred rats as well as in a retrospective analysis of juvenile recipients of adult donor kidneys. The experimental study revealed either augmentation of the compensatory response, in case of a juvenile donor kidney transplanted into an adult recipient, or attenuation of this response, in case of an adult donor kidney transplanted into a juvenile recipient. Various workers have reported an augmentation of renal function in humans in case of adult recipients of juvenile donor kidneys. In contrast, attenuation of renal function in case of adult donor kidneys transplanted into juvenile recipients, has not been reported. This attenuation was substantiated in our retrospective clinical study. We found that 3 weeks after transplantation, the absolute creatinine clearance (mL/min) was lower in a group of recipients under 12 years old than in a group of recipients older than 12 years. The experimental as well as the clinical investigation indicated that the size of the recipient plays an important part in the functional outcome after renal transplantation. It appeared that the transplanted kidney behaves like a single organ pertaining to the recipient.

Intrarenal hemodynamics in the transplanted rat kidney

Regional and single glomerular blood flow conditions in the transplanted rat kidney after various periods of cold ischemia were investigated with use of the microsphere method. Intravascular injection of a silicon rubber compound (Microfil) allowed identification and sampling of single glomeruli. The periods of ischemia were two hours (minor damage), 12 hr (intermediate damage), and 16 hr (severe damage). After two hours of cold ischemia, the regional and total renal blood flows were fairly normal. After 12 hr and 16 hr of cold ischemia, the total and regional blood flows were reduced five minutes after recirculation, the reduction being pronounced in the deep cortex and juxtamedullary glomeruli. In the 12-hr group, the blood flow showed complete restitution after 65 min, whereas in the 16-hr group, the blood flow in the inner cortex and juxtamedullary glomeruli remained decreased. An impairment of medullary circulation would seem to be an important component in the pathophysiology of acute renal failure in this model.

Nephron function of the transplanted rat kidney

Tubular function in the early phase (one to three hours) after transplantation of rat kidneys was analyzed with respect to glomerular filtration, vascular and tubular pressures, and excretory variables. Kidneys exposed to a short period of cold ischemia (two hours) functioned almost normally, except for a polyuria. After 12 and 16 hr of cold ischemia, nephron heterogeneity appeared with 1) "normal" tubules, 2) dilated tubules, and 3) collapsed tubules. In the "normal" tubules, the pressure was increased to 20 mm Hg, and the filtration was reduced in proportion to the mean net driving force. The dilated tubules had no filtration due to a more or less complete tubular obstruction, probably located in the thin loop of Henle and in the collecting ducts. The collapsed tubules had no filtration due to glomerular ischemia, which in turn might be the consequence of afferent arteriolar constriction. The total GFR was greatly reduced since only the "normal" tubules contributed to the total filtration. Concentrating ability and potassium secretion were also impaired. We interpreted this impairment as being due to medullary dysfunction, which would explain the isosthenuria and the impaired potassium transport.