How little kidney tissue is enough?

Article Abstract:

The capacity of the human kidneys to filter and regulate the blood far exceeds the requirements of normal human physiology. This is most obvious in the case of voluntary kidney donors. One kidney may be completely removed; the remaining kidney enlarges to take up the slack, and the donor is none the worse for wear. The actual individual filtration units within the kidney are called glomeruli; patients with progressive kidney disease may still be able to maintain satisfactory fluid balance when as few as 10 percent of the glomeruli left. Studies on rats, however, suggested that when more than half of the total kidney mass is removed, the remaining tissue may be damaged by the very process of trying to keep up the work. When one kidney is removed completely from an experimental rat, and the other is partially removed, the rate of blood filtration through the remaining glomeruli appears to be so great that the glomeruli are damaged and kidney failure will be the inevitable result. Interventions such as special diets may slow the inexorable decline in kidney function in these experiments. However, other experiments have suggested that the observations made in rats are not directly applicable to humans. Therefore, the question of how much kidney tissue is needed to maintain the human body remains unanswered. In the October 10, 1991 issue of The New England Journal of Medicine, researchers shed some new light on this question. The examined the effects of the removal of kidney tissue from patients who had already lost one kidney, most often to cancer. Once the cancerous area in the remaining kidney was removed, the kidney tissue left was completely normal, thereby eliminating the complications introduced by studying patients with diseased kidneys. Of 14 patients, only two experienced kidney failure, despite removal of as much as three-fourths of the one remaining kidney. However, nine patients had proteinuria, or excessive protein in their urine. This proteinuria is considered as an indicator of stress on the glomeruli, and correlated strongly with the total amount of kidney tissue removed. The animal studies have shown that proteinuria always preceded the kidney failure which resulted from inadequate kidney tissue. Although the patients in the present study were followed for periods ranging from five to 17 years, the proteinuria may foreshadow kidney failure which may develop slowly in years to come. (Consumer Summary produced by Reliance Medical Information, Inc.)

editorial

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Long-term follow-up after partial removal of a solitary kidney

Article Abstract:

Single kidneys are removed for a variety of reasons, ranging from kidney cancer to organ donation. The remaining kidney seems able to manage the needs of the body without ill effects. In experiments with animals, it is found that when some of the remaining kidney is removed, the filtration apparatus of the kidneys apparently suffers under the increased demands, and eventually will begin to deteriorate, leading to total kidney failure. It is uncertain, however, to what degree these observations may be applicable to human beings. A long-term study of kidney function was conducted in 14 patients who, after already having one kidney removed, needed surgery for the removal of a portion of the one remaining kidney. In 12 patients, the first kidney was removed because of cancer, while in two others the first kidney was congenitally abnormal. In all 14 patients, kidney cancer necessitated the removal of some of the remaining kidney. The amount of remaining kidney tissue which had to be removed varied from patient to patient, ranging from 25 to 75 percent. Total kidney failure occurred in two of the 14 patients. The kidney function of the remaining 12 patients appeared to be stable over follow-up periods which ranged from five to 17 years. However, proteinuria was common even among the patients with stable kidney function. This condition, the presence of excess protein in the urine, is an indicator of abnormal kidney function. It was found that the patients who had lost the greatest amount of kidney tissue were also the ones with the most severe proteinuria. The results of this study indicate that the human body can sustain the loss of even more kidney tissue after losing an entire kidney. However, this loss puts strain on the remaining kidney tissue which is evident as proteinuria. (Consumer Summary produced by Reliance Medical Information, Inc.)

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Management of a solitary thyroid nodule

Article Abstract:

Patients with a solitary thyroid nodule should undergo evaluation to rule out the possibility of thyroid cancer. A solitary thyroid nodule is usually characterized by the development of a discrete swelling in the thyroid gland. The risk of developing a thyroid nodule increases with age, and women have a higher risk than men. Many different types of thyroid disease are characterized by the development of thyroid nodules. Most thyroid nodules are benign, but a certain percentage are caused by thyroid cancer. Individuals suffering from a thyroid nodule should undergo a history and physical, and those suspected of having thyroid cancer should undergo a fine-needle aspiration biopsy. Different types of radiographic imaging are also used to evaluate patients with thyroid nodules. Patients diagnosed with thyroid cancer should undergo surgery to remove the nodule.

Care and treatment, Tumors, Endocrine gland tumors

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