Intradialytic Oral Iron Therapy

In order to test the limits of what can be achieved with oral iron therapy and eliminate the factor of noncompliance, we conducted a series of observational studies in an 140-patient inner city dialysis unit. In these studies the patients received supervised iron therapy as 3-4 ferrous sulfate (325 mg) tablets during each dialysis. Acceptance and tolerance was high, less than 10% refusing to take the tablets. In two separate observational studies oral intradialytic iron yielded a hematocrit 28% in 69% of patients and 30% in 42-52%. There was no correlation between the final hematocrit and serum ferritin or transferrin saturation. The response to iron therapy could frequently not be predicted by the ferritin levels or transferrin saturation. We conclude that in view of the known hazards of intravenous iron dextran, oral intradialityc therapy should be tried first and that a good response can be expected in one half to two thirds of hemodialysis patients.

The significance of trace proteinuria

BACKGROUND

The clinical significance of a trace protein reading on urinalysis is unclear, and such a result is often ignored by the clinician.

METHODS

We examined 185 samples of urine with trace proteinuria by both Chemstrips and sulfosalicylic acid testing, and compared the results with those of urinary albumin and total protein concentrations.

RESULTS

Taking for the purposes of this study an arbitrary upper limit of normal of 20 mg/l for albumin and 100 mg/l for total protein concentration, we found abnormal albumin excretion in 87% and abnormal total protein excretion in 88% of trace samples. In this study, a negative urinalysis for protein excluded microalbuminuria in 87% and proteinuria in 78% of cases.

CONCLUSION

Qualitative testing for protein by urinalysis has a high sensitivity and specificity for diagnosing or ruling out microalbuminuria. Trace proteinuria usually means microalbuminuria; negative proteinuria tends to rule it out.

Renal disease in the inner city

For various ethnic and socioeconomic reasons the pattern of renal disease in the inner city displays distinctive features. Hypertension is frequent, often intractable, and generally conditioned by salt sensitivity and a high sodium intake. Chronic hypertensive nephrosclerosis, found predominantly in African Americans, comprises marked cardiomegaly, renal shrinkage, and hypertensive retinopathy. It has been overdiagnosed in the past, but actually accounts for less than 20% of end-stage renal disease (ESRD) in African Americans. Malignant hypertension, less frequent nowadays, may cause renal shutdown, which is reversible in a few cases; the heart and kidneys are often of normal size. Idiopathic focal segmental glomerulosclerosis is the most common cause of the primary nephrotic syndrome in blacks, but its incidence has also been rising in whites and Hispanics; it does not respond well to treatment, and almost one half of the patients develop ESRD within 10 years. Systemic lupus erythematosus is also more common in African Americans, in whom the severe proliferative forms of lupus nephritis pursue a more virulent course: one half of such patients develop ESRD in 5 years. Cocaine, the use of which has assumed epidemic proportions, may cause accelerated hypertension, acute renal failure from rhabdomyolysis, and progression of preexisting renal disease. Heroin nephropathy has all but disappeared and has been replaced by human immunodeficiency virus (HIV) nephropathy. The prognosis of HIV-infected patients maintained by dialysis has greatly improved. Sickle glomerulopathy, consisting of mesangial expansion, basement membrane duplication, and the absence of immune deposits, may cause the nephrotic syndrome in 4% of patients with severe sickle cell anemia, heralding death within 2 years in one half of patients and ESRD in two thirds; survival has not improved with dialysis. Diabetes is now the most common cause of ESRD. Familial aggregation of ESRD is frequently encountered. Interventions useful in the general population, such as vascular bypass procedures, should be undertaken with great caution and restraint in dialysis patients.

Differential effects of enalapril and irbesartan in experimental papillary necrosis

This study was undertaken to determine whether angiotensin receptor blockers are as renoprotective as angiotensin-converting enzyme inhibitors in an experimental model of chronic interstitial renal disease. Groups of rats received one of the following treatments for 1 week: (1) enalapril, (2) diltiazem, (3) a cocktail of hydralazine, reserpine, and hydrochlorothiazide, or (4) irbesartan (an AT1 antagonist). The animals were injected with bromoethylamine (200 mg/kg), and antihypertensive treatment continued for 1 month. All drugs were effective in lowering the mean arterial pressure. The bromoethylamine-treated rats developed albuminuria and sustained a 40-50% decrease in creatinine clearance. Enalapril and irbesartan reduced albuminuria, but only enalapril partially prevented the decline in creatinine clearance and lowered the number of ED-1-positive cells. Diltiazem and cocktail had no effect on proteinuria, creatinine clearance, or ED-1 cells. In this experimental model, the effects of enalapril and irbesartan were not identical. Both drugs reduced proteinuria, but enalapril was more effective in protecting the renal function. The fact that the AT1 antagonist protected against albuminuria but did not affect the clearance of creatinine implies that the results seen with angiotensin-converting enzyme inhibition may be in part due to an effect on angiotensin II via AT2 receptor blockade or through an effect on bradykinin.

Relaxin decreases renal interstitial fibrosis and slows progression of renal disease

BACKGROUND

Relaxin, a hormone of the insulin-growth factor family, promotes collagen remodeling. In rodent models of pulmonary and dermal fibrosis, relaxin reduced interstitial fibrosis. To study relaxin's effect in renal disease, we used the experimental bromoethylamine (BEA) model that leads to severe renal interstitial fibrosis, a decrease in glomerular filtration rate, and albuminuria at one month.

METHODS

Rats were injected with BEA one week prior to implantation of an osmotic pump delivering relaxin (2 microg/hour) or vehicle continuously for 28 days.

RESULTS

BEA caused a significant decrease in creatinine clearance, which was partially prevented by relaxin. In the relaxin-treated BEA rats, serum creatinine was normal, and albumin excretion was slightly decreased. By morphometric measurement, relaxin administration was associated with a significant decrease in interstitial fibrosis at the corticomedullary junction. This was accompanied by a decrease in the number of ED-1 positive cells (an index of macrophage infiltration) and in the intensity of immunohistochemical staining for transforming growth factor-beta. This antifibrotic effect of relaxin did not appear to be mediated by systemic hemodynamic changes since the mean arterial pressure was not significantly different among the groups.

CONCLUSIONS

Relaxin may have a useful application in decreasing interstitial fibrosis and thereby slowing the progression of renal disease.

Can total urinary protein measurements predict microalbuminuria?

We re-addressed the question of whether routine total urinary protein determinations can be used to predict the presence of microalbuminuria by studying 61 patients who attended a diabetic clinic and tested negative or had one positive protein by dipstick. Total urinary protein was measured by the Biorad dye-binding method in undialyzed urine (UND), in dialyzed urine (DIAL), and in dialyzed urine in which albumin and globulins were separated, measured separately with albumin and globulin standards and the results added together to obtain total urinary protein (A + G). The results were compared with albumin measurements obtained by radioimmunoassay (RIA). Compared to DIAL, urinary protein measurements were 43% higher with A + G and 22% higher with UND. Microalbuminuria correlated moderately with UND (r =0.81) and better with the other methods (r=0.87 for DIAL, r=0.91 for A + G). None of the methods predicted microalbuminuria reliably. Taking a protein-to-creatinine ratio of 0.15 and an albumin-to-creatinine ratio of 0.03 as upper limits of normal, we found that UND had a 72% positive predictive value (28% false positives) and 85 % negative predictive value (15% false negatives). DIAL had 90% positive predictive value (10% false positives) and 78% negative predictive value (22% false negatives). A + G had 65% positive predictive value (35% false positives) but 91% negative predictive value (9% false negatives). A + G, which uses the correct standards, would be the most suitable method for screening, having the least number of false negatives, but has more false positives because it is more sensitive. In practice, most routine chemical laboratories find it expedient to use only UND, but physicians interpreting the results of this method should be aware of its limitations.