No abstract

To determine the reliability of creatinine as a measure of the glomerular filtration rate (GFR), we compared the simultaneous clearance of creatinine to that of three true filtration markers of graded size in 171 patients with various glomerular diseases. Using inulin (radius [rs] = 15 A) as a reference marker, we found that the fractional clearance of 99mTc-DTPA (rs = 4 A) was 1.02 +/- 0.14, while that of a 19 A rs dextran was 0.98 +/- 0.13, with neither value differing from unity. In contrast, the fractional clearance (relative to inulin) of creatinine (rs = 3 A) exceeded unity, averaging 1.64 +/- 0.05 (P less than 0.001), but could be lowered towards unity by acute blockade of tubular creatinine secretion by IV cimetidine. Cross-sectional analysis of all 171 patients revealed fractional creatinine secretion to vary inversely with GFR. This inverse relationship was confirmed also among individual patients with either deteriorating (N = 28) or remitting (N = 26) glomerular disease, who were studied longitudinally. As a result, changes in creatinine relative to inulin clearance were blunted considerably or even imperceptible. We conclude that true filtration markers with rs less than 20 A, including inulin, are unrestricted in glomerular disease, and that creatinine is hypersecreted progressively by remnant renal tubules as the disease worsens. Accordingly, attempts to use creatinine as a marker with which to evaluate or monitor glomerulopathic patients will result in gross and unpredictable overestimates of the GFR.

Salmonella mycotic aneurysms of the thoracic aorta are exceedingly rare. We describe what we believe is only the third reported case involving the aortic arch. The patient was treated with surgical intervention and a prolonged course of antibiotics, which resulted in long-term survival. We review 13 previously reported cases of salmonella mycotic aneurysms of the thoracic aorta. The overall outcome was abysmal, with 10 of 13 patients dying within 1 month after the diagnosis was made. We discuss the pathogenesis, clinical presentation, diagnostic approach, and management (including surgical intervention and duration of antibiotic therapy) of this condition on the basis of the findings in these cases.

A differential solute clearance technique was used to evaluate glomerular capillary wall function in 20 patients with membranous glomerulopathy and massive proteinuria. The clearance of inulin, the filtration fraction, and the fractional clearance of uncharged dextrans of a radius of 28-48 A were depressed significantly below control values in 20 healthy volunteers (P < 0.01). In contrast, the fractional clearance of dextrans of radius >50 A was elevated markedly. A theoretical model of solute transport that depicts the major portion of the glomerular capillary wall as an isoporous membrane and the minor portion as a nondiscriminatory shunt pathway revealed the calculated gomerular ultrafiltration coefficient to be five times lower and mean pore radius of the major membrane component to be 4 A smaller than control values. However, the fraction of filtrate volume permeating the shunt pathway was three-to fourfold above control values and correlated strongly in individual patients with the fractional clearance of albumin (r = 0.76) and of IgG (r = 0.80). Lowering renal plasma flow by 24% during indomethacin therapy in seven patients resulted in a 74% reduction in proteinuria accompanied by a corresponding diminution of filtrate formed through the shunt pathway. Morphometric analysis ofglomerular ultrastructure revealed the magnitude of depression of the glomerular filtration rate and of urinary protein leakage to be related strongly to changes in the epithelial layer of the glomerular capillary wall, but not to the density of subepithelial immune deposits. We conclude (a) that glomerular capillaries in membranous glomerulopathy are characterized by a loss of ultrafiltration capacity and of barrier size-selectivity, and (b) that subepithelial immune deposits do not provide a structural basis for these functional alterations.

We report a 13-year-old boy with refractory nephrotic syndrome (minimal change with mesangial proliferation) who failed the standard treatment protocols. There was some temporary response to large steroid doses, but even the Mendoza protocol could not induce remission. We show suppression of the proteinuria with Infliximab (Remicade) with tapering of steroids. Serial serum levels of tumor necrosis factor (TNF)-alpha are shown and discussed. We suggest studying the TNF-alpha blocking agents as optional treatment for nephrotic syndrome.

Ten patients with lupus nephritis and marked proteinuria (3.9 g or more/d) that did not respond adequately to treatment with prednisone alone or prednisone in combination with azathioprine were treated with total lymphoid irradiation in an uncontrolled feasibility study. Within 6 weeks after the start of total lymphoid irradiation, the serum albumin level rose in all patients in association with a reduction in the serum level of anti-DNA antibodies, an increase in the serum complement level, or both. Improvement in these variables persisted in eight patients followed for more than 1 year, with the stabilization or reduction of the serum creatinine level. Urinary leakage of albumin was substantially reduced in all patients. Side effects associated with radiotherapy included transient constitutional complaints in ten patients, transient blood element depressions in three, localized viral and bacterial infections in four, and ovarian failure in one. The results suggest that total lymphoid irradiation may provide an alternative to cytotoxic drugs in the treatment of lupus nephritis.

To elucidate the mechanisms by which indomethacin lowers proteinuria, we studied 20 patients with the nephrotic syndrome. We performed differential macromolecule clearances before and after 3 days of therapy (150 mg/24 h). The fractional clearances of albumin and immunoglobulin G (IgG) decreased by 42 +/- 7 and 44 +/- 10%, respectively (P less than 0.05). Separation of IgG into fractions by preparative electrofocusing in eight selected individuals revealed a proportionate reduction of fractional clearances among anionic (pI = 5.0), neutral (pI = 7.5), and cationic species (pI = 8.5) of IgG. Indomethacin elevated the fractional clearance of uncharged dextrans of radius 28-44 A, while depressing those of dextrans of radius 50-60 A. A heteroporous model that depicts the major portion of the glomerular capillary wall as an isoporous membrane (pore radius = 56 A) and the minor portion as a nondiscriminatory shunt, revealed the former to be unchanged and the latter to be less prominent following indomethacin. A lower fraction of total filtrate volume permeating the shunt, together with a concomitant lowering of overall glomerular filtration rate by 24%, reduced the absolute rate of flux of macromolecule-rich fluid through the shunt pathway from 0.40 to 0.25 ml.min-1.73(-2) (P less than 0.01). We conclude that indomethacin lowered the filtered protein load by restoring barrier size-selectivity while reducing the rate of glomerular ultrafiltration.

Colloid volume expansion magnifies proteinuria in subjects with the nephrotic syndrome. To elucidate this phenomenon, we performed differential solute clearances prior to and following infusion of hyperoncotic albumin in 21 nephrotic subjects and seven healthy controls. Urinary excretion rate and fractional clearance of albumin (radius = 36 A) and immunoglobulin G (radius = 55 A) increased significantly in nephrotic subjects. However, urinary albumin excretion rate was unchanged in controls. The fractional clearances of dextrans of broad size distribution (radii = 28 to 58 A) were markedly altered in both groups following albumin infusion. A heteroporous model which depicts the major portion of the glomerular capillary wall as an isoporous membrane (pore radius approximately 55 A) and the minor portion as a non-discriminatory shunt, revealed the latter to be much more prominent in nephrotic subjects than in controls, and to be enlarged further following albumin infusion. By contrast no increase in pore size of the non-shunt pathway occurred in either group. We infer that enhancement of a pre-existing defect of glomerular size-selectivity in nephrotic subjects accounts, in large part, for exaggerated proteinuria in the colloid volume-expanded state. Increases in glomerular perfusion rate and pressure associated with plasma hypervolemia may mediate this alteration in glomerular membrane-pore structure.