RENAL DIABETES AS A CONGENITAL TUBULAR DYSPLASIA

The early introduction of percutaneous renal biopsy in Italy

BACKGROUND

Percutaneous renal biopsy, based on the use of an aspiration needle and the patient in the sitting position, was first described by Iversen and Brun in 1951. In 1954, Kark and Muehrcke described the use of the cutting Vim-Silverman needle on patients in the prone position, with a substantial improvement in the rate of success. The 1961 CIBA Foundation Symposium on renal biopsy marked the coming of age of this technique. During the 1950s in Italy, several individuals played a part in promoting and developing percutaneous renal biopsy. Because this pioneer work has received insufficient attention, we describe the contributions of Italians to the early introduction of this technique.

METHODS

The Italian and international literature about percutaneous renal biopsy of the period 1951 through 1965 was reviewed. In addition, structured interviews with surviving members of the Italian researchers who first used renal biopsy were conducted.

RESULTS

The first renal biopsies in Italy were performed in 1951 in Pisa by the group of Ernico Fiaschi (1913-1989). In their hands, renal biopsy became a tool to investigate the pathogenesis of renal diseases in particular, while simultaneously using the early application of immunofluorescence and electron microscopy. In 1954, Pietro Leonardi (1914-1991) and Arturo Ruol (born 1924) introduced renal biopsy in Padova; they used this technique extensively and published one of the first monographs on the subject. In 1957, Vittorio Bonomini (born 1928) introduced renal biopsy in Bologna, and in subsequent years used this technique to focus on the study of pyelonephritis.

CONCLUSIONS

Our historical research shows that Italian groups were among the first to use and develop percutaneous renal biopsy both as a clinical tool and an investigative tool. This article gives international credit to their work.

Renal glucosuria

Normal urine contains small amounts of glucose, called basal glucosuria, and other carbohydrates. Increased amounts of glucose beyond the basal excretion rates i.e. frank glucosuria, reflect reduced activity of tubular glucose reabsorption. Clinically, there are two conditions which are known to appear with a primary disturbance of epithelial glucose transport: intestinal glucose-galactose malabsorption and benign familial renal glucosuria. In the latter, both the renal threshold for glucose and maximal tubular glucose reabsorption are diminished. The degree of glucosuria is variable; the most severe defect demonstrates minimal glucose threshold values and extremely low levels of maximal glucose reabsorption (type 0). The moderate and mild types show variable reductions of both functional parameters. It is questionable whether these should be subdivided into type A and type B glucosurias. Data in the literature reveal that two distinct entities do not exist, but that there is instead a continuous transition from low to normal values. The defect is transmitted genetically, either in an autosomal dominant or autosomal recessive manner. It seems plausible that the different defects might be produced either by mutations on different gene loci, or by multiple alleles of the same gene locus that determines the synthesis of the glucose carrier.

The effect of pregnancy on the renal handling of glucose

Tubular reabsorption of glucose has been measured during glucose infusion in 29 healthy women during and after pregnancy. All the women had normal glucose tolerance to an oral load, and normal glucose excretion when not pregnant, but exhibited a wide range of daily glucose excretion in pregnancy. Throughout pregnancy the renal reabsorption of glucose is less effective than in the non-pregnant state and, in general, the greater the amount fo glycosuria which develops in pregnancy, the less effective is the reabsorption during infusion. Post partum, women with minor degrees of glycosuria during the preceding pregnancy return to a normal highly efficient reabsorption performance during infusion, but women who exhibit greater degrees of glycosuria have a reduced capacity to reabsorb even though they are no longer glycosuric after the pregnancy. It is concluded that pregnancy imposes some specific change in the glucose reabsorptive capacity of the proximal tubule and that women with more than usual degrees of glycosuria in pregnancy may, in addition, have an element of tubular damage. This is discussed in relation to other renal function changes in pregnancy in an attempt to explain the characteristic intermittency of clinical glycosuria in pregnancy.

Observations on the mechanisms of glucosuria during glucose loads in normal and nondiabetic subjects

The study of 14 normal young men by glucose titration procedures has defined the magnitude of splay in this population, differing from previously reported data in its unexpected deviation from the line of theoretic unity high on the titration curve. Compared to these normal subjects, a group of glucosuric men could be divided into two subclasses, those with normal maximal rate of glucose reabsorption (Tm(G)) and those with subnormal Tm(G), both with comparably abnormal splay. Most consistent glucosurics fall into the latter group. Nephritic patients studied were not such a homogeneous group in terms of age and sex, but did manifest an abnormal splay during their titration curves in most cases. They also demonstrated a greater than normal reabsorptive rate of glucose per unit measured glomerular filtration rate. It is concluded that renal glucosuria must be defined not only in terms of the concept of Tm(G) but also by deviation of the glucose titration curve expressing an unusual degree of splay. The latter is presumed, as has been suggested by others, to be a characteristic of nonhomogeneity of glucose handling units in the kidney. This seems subject to exaggeration in the adaptations which accompany chronic renal disease.