Course of preeclamptic glomerular injury after delivery

We evaluated the early postpartum recovery of glomerular function over 4 wk in 57 women with preeclampsia. We used physiological techniques to measure glomerular filtration rate (GFR), renal plasma flow, and oncotic pressure (πA) and computed a value for the two-kidney ultrafiltration coefficient ( Kf). Compared with healthy, postpartum controls, GFR was depressed by 40% on postpartum day 1, but by only 19% and 8% in the second and fourth postpartum weeks, respectively. Hypofiltration was attributable solely to depression, at corresponding postpartum times, of Kf by 55%, 30%, and 18%, respectively. Improvement in glomerular filtration capacity was accompanied by recovery of hypertension to near-normal levels and significant improvement in albuminuria. We conclude that the functional manifestations of the glomerular endothelial injury of preeclampsia largely resolve within the first postpartum month.

Effect of l-Arginine Therapy on the Glomerular Injury of Preeclampsia

OBJECTIVE

To assess the benefit of l-arginine, the precursor to nitric oxide, on blood pressure and recovery of the glomerular lesion in preeclampsia.

METHODS

Forty-five women with preeclampsia were randomized to receive either l-arginine or placebo until day 10 postpartum. Primary outcome measures including mean arterial pressure, glomerular filtration rate, and proteinuria were assessed on the third and 10th days postpartum by inulin clearance and albumin-to-creatinine ratio. Nitric oxide, cyclic guanosine 3'5' monophosphate, endothelin-1, and asymmetric-dimethyl-arginine and arginine levels were assayed before delivery and on the third and 10th days postpartum. Healthy gravid women provided control values. Assuming a standard deviation of 10 mm Hg, the study was powered to detect a 10-mm Hg difference in mean arterial pressure (alpha .05, beta .20) between the study groups.

RESULTS

No significant differences existed between the groups with preeclampsia before randomization. Compared with the gravid control group, women with preeclampsia exhibited significantly increased serum levels of endothelin-1, cyclic guanosine 3'5' monophosphate, and asymmetric-dimethyl-arginine before delivery. Despite a significant increase in postpartum serum arginine levels due to treatment, no differences were found in the corresponding levels of nitric oxide, endothelin-1, cyclic guanosine 3'5' monophosphate, or asymmetric-dimethyl-arginine between the two groups with preeclampsia. Further, there were no significant differences in any of the primary outcome measures with both groups demonstrating similar levels in glomerular filtration rate and equivalent improvements in both blood pressure and proteinuria.

CONCLUSION

Blood pressure and kidney function improve markedly in preeclampsia by the 10th day postpartum. Supplementation with l-arginine does not hasten this recovery.

LEVEL OF EVIDENCE

I.

Examining chronic kidney disease management in a single center

AIMS

The management of patients with chronic kidney disease in outpatient clinics was assessed for the ability to achieve targets of care advocated in clinical practice guidelines.

METHODS

272 records of outpatients with increased serum creatinine (> or = 1.5 mg/dl for women, > or = 2.0 mg/dl for men) were reviewed for details of their assessment and management. Prevailing data on blood pressure, anemia, bone disease and lipid status as well as therapeutic changes were evaluated.

RESULTS

The subjects were aged 64 +/- 18 years, serum creatinine 2.6 +/- 1.1 mg/dl, and calculated GFR (MDRD formula) 19.2 +/- 9.9 ml/min. Median UproV was 1.0 (0.024 - 12.4) g/day. Causes of CKD were diabetes (33.5%), HTN (8.8%), GN (19.5%), and adult PKD (3.3%). Treatment targets were BP < 130/85 mmHg, Hct > or = 36%, serum Ca++ > or = 8.5 mg/dl, serum Po4 < 4.5 mg/dl and cholesterol < 200 mg/dl. Of the patients with abnormal findings, mean values for SBP were 153 +/- 17 mmHg, DBP 93 +/- 6 mmHg, Hct 31.7 +/- 2.9%, Ca++ 8.0 +/- 0.7 mg/dl, PO4 5.6 +/- 1.0 mg/dl, and cholesterol 236 +/- 37 mg/dl. Only a minority of patients with abnormal values had their treatment altered. Furthermore, only 54% of patients with hypertension were treated with either ACEi or ARB therapy. Finally, only 6% of patients with hypercholesterolemia had fasting lipid levels measured.

CONCLUSION

This data suggests that treatment of patients with CKD has improved, but that many opportunities exist to optimize their care.

The dynamics of glomerular filtration in the puerperium

We evaluated the glomerular filtration rate (GFR) during the second postpartum week in 22 healthy women who had completed an uncomplicated pregnancy. We used physiological techniques to measure GFR, renal plasma flow, and oncotic pressure and computed a value for the two-kidney ultrafiltration coefficient (K(f)). We compared these findings with those in pregnant women previously studied on the first postpartum day as well as nongravid women of reproductive age. Healthy female transplant donors of reproductive age permitted the morphometric analysis of glomeruli and computation of the single-nephron K(f). The aforementioned physiological and morphometric measurements were utilized to estimate transcapillary hydraulic pressure (Delta P) from a mathematical model of glomerular ultrafiltration. We conclude that postpartum day 1 is associated with marked glomerular hyperfiltration (+41%). A theoretical analysis of GFR determinants suggests that depression of glomerular capillary oncotic pressure, the force opposing the formation of filtrate, is the predominant determinant of early elevation of postpartum GFR. A reversal of the gestational hypervolemia and hemodilution, still evident on postpartum day 1, eventuates by postpartum week 2. An elevation of oncotic pressure in the plasma that flows axially along the glomerular capillaries to supernormal levels ensues; however, GFR remains modestly elevated (+20%) above nongravid levels. An analysis of filtration dynamics at this time suggests that a significant increase in Delta P by up to 16%, an approximately 50% increase in K(f), or a combination of smaller increments in both must be invoked to account for the persistent hyperfiltration.

The dynamics of glomerular filtration after Caesarean section

The objective of this study was to determine whether the glomerular hyperfiltration of pregnancy is maintained even after Caesarean section and, if so, to define the responsible hemodynamics. The dynamics of glomerular filtration were evaluated in 12 healthy women who had just completed an uncomplicated pregnancy and were delivered by Caesarean section. Age-matched but non-gravid female volunteers (n = 22) served as control subjects. GFR in postpartum women was elevated above control values by 41%; 149+/-10 versus 106+/-3 ml/min per 1.73 m2, respectively (P < 0.001). In contrast, corresponding renal plasma flow was the same in the two groups, such that the postpartum filtration fraction was significantly elevated by 20%. Computation of glomerular intracapillary oncotic pressure (piGC) from knowledge of plasma oncotic pressure and the filtration fraction revealed this quantity to be significantly reduced in postpartum women, 20.6+/-1.7 versus 26.1+/-2.0 mmHg in control subjects (P < 0.001). A theoretical analysis of glomerular ultrafiltration suggests that depression of piGC, the force opposing the formation of filtrate, is predominantly or uniquely responsible for the observed postpartum hyperfiltration.

Nature of glomerular dysfunction in pre-eclampsia

BACKGROUND

Pre-eclampsia is characterized by hypertension, proteinuria and edema. Simultaneous studies of kidney function and structure have not been reported. We wished to explore the degree and nature of glomerular dysfunction in pre-eclampsia.

METHODS

Physiologic techniques were used to estimate glomerular filtration rate (GFR), renal plasma flow and afferent oncotic pressure immediately after delivery in consecutive patients with pre-eclampsia (PET; N = 13). Healthy mothers completing an uncomplicated pregnancy served as functional controls (N = 12). A morphometric analysis of glomeruli obtained by biopsy and mathematical modeling were used to estimate the glomerular ultrafiltration coefficient (Kf). Glomeruli from healthy female kidney transplant donors served as structural controls (N = 8).

RESULTS

The GFR in PET was depressed below the control level, 91 +/- 23 versus 149 +/- 34 ml/min/1.73 m2, respectively (P < 0.0001). In contrast, renal plasma flow and oncotic pressure were similar in the two groups (P = NS). A reduction in the density and size of endothelial fenestrae and subendothelial accumulation of fibrinoid deposits lowered glomerular hydraulic permeability in PET compared to controls, 1.81 versus 2.58 x 10(-9) m/sec/PA. Mesangial cell interposition also curtailed effective filtration surface area. Together, these changes lowered the computed single nephron Kf in PET below control, 4.26 versus 6.78 nl/min x mm Hg, respectively.

CONCLUSION

The proportionate (approximately 40%) depression of Kf for single nephrons and GFR suggests that hypofiltration in PET does not have a hemodynamic basis, but is a consequence of structural changes that lead to impairment of intrinsic glomerular ultrafiltration capacity.

Predictors of mortality and the provision of dialysis in patients with acute tubular necrosis. The Auriculin Anaritide Acute Renal Failure Study Group

To explore the natural history of critically ill patients with acute renal failure due to acute tubular necrosis, we evaluated 256 patients enrolled in the placebo arm of a randomized clinical trial. Death and the composite outcome, death or the provision of dialysis, were determined with follow-up to 60 d. The relative risks (RR) and 95% confidence intervals (95% CI) associated with routinely available demographic, clinical, and laboratory variables were estimated using proportional hazards regression. Ninety-three (36%) deaths were documented; an additional 52 (20%) patients who survived received dialysis. Predictors of mortality included male gender (RR, 2.01; 95% CI, 1.21 to 3.36), oliguria (RR, 2.25; 95% CI, 1.43 to 3.55), mechanical ventilation (RR, 1.86; 95% CI, 1.18 to 2.93), acute myocardial infarction (RR, 3.14; 95% CI, 1.85 to 5.31), acute stroke or seizure (RR, 3.08; 95% CI, 1.56 to 6.06), chronic immunosuppression (RR, 2.37; 95% CI, 1.16 to 4.88), hyperbilirubinemia (RR, 1.06; 95% CI, 1.03 to 1.08 per 1 mg/dl increase in total bilirubin) and metabolic acidosis (RR, 0.95; 95% CI, 0.90 to 0.99 per 1 mEq/L increase in serum bicarbonate concentration). Predictors of death or the provision of dialysis were oliguria (RR, 5.95; 95% CI, 3.96 to 8.95), mechanical ventilation (RR, 1.53; 95% CI, 1.07 to 2.21), acute myocardial infarction (RR, 1.95; 95% CI, 1.24 to 3.07), arrhythmia (RR, 1.51; 95% CI, 1.04 to 2.19), and hypoalbuminemia (RR, 0.56; 95% CI, 0.42 to 0.74 per 1 g/dl increase in serum albumin concentration). Neither mortality nor the provision of dialysis was related to patient age. These observations can be used to estimate risk early in the course of acute tubular necrosis. Furthermore, these and related models may be used to adjust for case-mix variation in quality improvement efforts, and to objectively stratify patients in future intervention trials aimed at favorably altering the course of hospital-acquired acute renal failure.

Renal artery stenosis in kidney transplants

Transplant renal artery stenosis (TRAS) is an increasingly recognized complication of renal transplantation, with a reported incidence of between 1% and 23%. The clinical features include refractory hypertension, new-onset hypertension, allograft dysfunction, and the presence of a bruit over the graft. In this report, we describe the investigation and treatment of one such patient and review the current diagnostic approaches and therapy in this setting.

Pretransplant renal dysfunction predicts poorer outcome in liver transplantation

The postoperative courses of 115 liver transplant recipients were reviewed to monitor for outcomes of acute renal failure and mortality. An analysis of baseline (preoperative) variables with particular attention to baseline renal function was accomplished to establish predictive variables for a complicated postoperative course. Acute renal failure requiring dialysis occurred in 27 cases (23%) and was associated with a prolonged ICU stay, greater infectious complications, greater hospital charges and a high mortality rate (46 +/- 11% vs. 9 +/- 3%) as compared to patients who did not experience acute renal failure. Death occurred in 20 patients (17%) overall prior to discharge. In order to assess the contribution of renal function, the population was divided arbitrarily into two groups based on preoperative serum creatinine. Group 1 (n = 50) had a preoperative serum creatinine < 1.0 mg/dl (mean +/- SD = 2.2 +/- 0.2 mg/dl) and Group 2 (n = 65) had a preoperative serum creatinine < or = 1.0 mg/dl (0.7 +/- 0.1 mg/dl). The groups experienced similar operative courses. Group 1 patients experienced significantly longer ICU stays (18 +/- 3 vs. 10 +/- 2 days), higher rates of acute renal failure requiring dialysis (52 +/- 7 vs. 5 +/- 2%), higher hospital charges (231,454 +/- 17,088 vs. 178,755 +/- 14,744 $, US) and a greatly increased mortality rate (32 +/- 1 vs. 6 +/- 1%), as compared to Group 2 patients. A multifactorial regression analysis demonstrated that of all pretransplant factors analyzed, elevation in the serum creatinine was significantly associated and was the strongest predictor of both outcomes: acute renal failure requiring dialysis (ROC = 0.89) and death (ROC = 0.83). The presence or absence of hepatorenal syndrome did not influence the results of this analysis. This study demonstrates that cirrhotic patients with renal dysfunction, as indicated by an elevated serum creatinine, experience a poor surgical outcome following liver transplantation. These patients may require special attention in the perioperative period. Alternatively, these data may influence the selection of ideal candidates for liver transplantation, where scarce resources need to be applied appropriately.

Anaritide in acute tubular necrosis. Auriculin Anaritide Acute Renal Failure Study Group

BACKGROUND

Atrial natriuretic peptide, a hormone synthesized by the cardiac atria, increases the glomerular filtration rate by dilating afferent arterioles while constricting efferent arterioles. It has been shown to improve glomerular filtration, urinary output, and renal histopathology in laboratory animals with acute renal dysfunction. Anaritide is a 25-amino-acid synthetic form of atrial natriuretic peptide.

METHODS

We conducted a multicenter, randomized, double-blind, placebo-controlled clinical trial of anaritide in 504 critically ill patients with acute tubular necrosis. The patients received a 24-hour intravenous infusion of either anaritide (0.2 microgram per kilogram of body weight per minute) or placebo. The primary end point was dialysis-free survival for 21 days after treatment. Other end points included the need for dialysis, changes in the serum creatinine concentration, and mortality.

RESULTS

The rate of dialysis-free survival was 47 percent in the placebo group and 43 percent in the anaritide group (P = 0.35). In the prospectively defined subgroup of 120 patients with oliguria (urinary output, < 400 ml per day), dialysis-free survival was 8 percent in the placebo group (5 of 60 patients) and 27 percent in the anaritide group (16 of 60 patients, P = 0.008). Anaritide-treated patients with oliguria who no longer had oliguria after treatment benefited the most. Conversely, among the 378 patients without oliguria, dialysis-free survival was 59 percent in the placebo group (116 of 195 patients) and 48 percent in the anaritide group (88 of 183 patients, P = 0.03).

CONCLUSIONS

The administration of anaritide did not improve the overall rate of dialysis-free survival in critically ill patients with acute tubular necrosis. However, anaritide may improve dialysis-free survival in patients with oliguria and may worsen it in patients without oliguria who have acute tubular necrosis.

Profound hypophosphatemia and isolated hyperphosphaturia in two cases of multiple myeloma

We describe the development of severe hypophosphatemia and urinary phosphate wasting in two patients with multiple myeloma. In both cases, the serum phosphorus was repeatedly less than 1.0 mg/dL despite vigorous replacement, and the calculated fractional excretion of urinary phosphorus was greater than 100%. Neither patient demonstrated other tubular defects typical of Fanconi's syndrome. With treatment of the myeloma, both patients achieved normalization of the serum phosphorus and no longer required phosphorus supplementation. We believe that multiple myeloma should be considered in the differential diagnosis in patients with profound hypophosphatemia, urinary phosphate wasting, and otherwise intact tubular function.

Acute renal failure due to postinfectious glomerulonephritis during pregnancy

Acute renal failure is a rare but potentially devastating complication of pregnancy. Among its many potential causes is acute postinfectious glomerulonephritis. We describe a case of acute renal failure during pregnancy, provide the histologic features of the renal biopsy, and discuss the differential diagnosis. Postinfectious glomerulonephritis can present rapidly after clinical infection and cause acute renal failure in pregnancy.

Preventing disease progression in chronic renal failure

Progression toward end-stage renal disease is usually inexorable in patients with diabetic and nondiabetic nephropathy. These patients can be identified at an early stage based on history, abnormal urinalysis or reduced glomerular filtration. Recent advances have made it possible to slow the progression of chronic renal failure. Major interventions include antihypertensive therapy, dietary protein restriction and, in patients with diabetes, strict glycemic control and angiotensin-converting enzyme inhibitor therapy. Collaboration with a nephrologist can help guide the family physician in the appropriate use of these modalities and help avoid common complications. Major efforts in slowing the progression of renal failure may lead to a decreased incidence of end-stage renal disease, with savings in morbidity, mortality and cost.

The effects of blood pressure reduction on cyclosporine nephrotoxicity in the rat

The effects of blood pressure reduction on cyclosporine nephrotoxicity were studied over 12 months in four groups of rats. Group 1 received no drugs and served as controls. Groups 2, 3, and 4 received cyclosporine (CyA), approximately 9 mg/kg.day, in their food. In addition, Group 3 received enalapril and Group 4 received minoxidil, hydrochlorothiazide, and reserpine. Time-averaged monthly systolic blood pressure was equal in Groups 1 and 2 (136 +/- 1 and 135 +/- 1 mm Hg, respectively). Antihypertensive agents reduced average systolic blood pressure in Groups 3 and 4 (116 +/- 1 and 117 +/- 1 mm Hg, respectively). Morphometric studies showed that 12 months of CyA treatment caused interstitial fibrosis with an increase in the fractional volume of cortical interstitium (VvInt: Group 2, 20 +/- 1%; Group 1, 11 +/- 1%) and a reduction in mean glomerular volume (VG. Group 2, (2.00 +/- 0.06) x 10(6) mu 3; Group 1, (2.48 +/- 0.06) x 10(6) mu 3). These structural changes were accompanied by a significant reduction in GFR (Group 2, 2.27 +/- 0.10 mL/min; Group 1, 2.76 +/- 0.10 mL/min). Cotreatment with enalapril reduced interstitial fibrosis (VvInt, 14 +/- 1%) and maintained VG (2.23 +/- 0.08 x 10(6) mu 3) and GFR (2.56 +/- 0.08 mL/min) at near-normal values in Group 3. In contrast, the combination antihypertensive regimen increased the extent of interstitial fibrosis (VvInt, 24 +/- 1%) and further lowered VG (1.72 +/- 0.05 x 10(6) mu 3) and GFR (1.72 +/- 0.05 mL/min) in Group 4. These results show that sustained treatment with a moderate dose of CyA causes interstitial fibrosis and impairs renal function in rats. The administration of enalapril, but not minoxidil, reserpine, and hydrochlorothiazide, limits renal injury in this model.

Effects of angiotensin II receptor blockade on remnant glomerular permselectivity

This study examined the mechanisms by which angiotensin II (Ang II) receptor blockade improves glomerular barrier function in rats with reduced nephron number. Proteinuria was measured at four weeks after 5/6 renal ablation, and rats were then divided into a group which received the Ang II receptor blocker MK954 and a group which received no treatment. Studies performed one week later showed that Ang II receptor blockade reduced proteinuria without altering GFR in renal ablated rats. Micropuncture studies showed that Ang II blockade reduced both mean arterial pressure (142 +/- 7 mm Hg, ablation without treatment; 105 +/- 2 mm Hg, ablation with treatment) and glomerular transcapillary pressure (54 +/- 3 mm Hg, ablation without treatment; 43 +/- 1 mm Hg, ablation with treatment). Dextran sieving studies showed that untreated rats developed a size-selective defect characterized by increased transglomerular passage of neutral dextrans with radii 54 to 76 A and a charge-selective defect characterized by an increased transglomerular passage of anionic dextran sulfate with a radius of approximately 18 A. Ang II blockade reduced fractional clearance values for large neutral dextrans near to values observed in normal rats but had no effect on the fractional clearance of dextran sulfate (0.68 +/- 0.11, ablation without treatment; 0.66 +/- 0.08, ablation with treatment; 0.46 +/- 0.05, normal rats). These findings indicate that reducing Ang II activity improves size-selectivity without affecting charge-selectivity in injured remnant glomeruli.

Angiotensin II receptor blockade limits glomerular injury in rats with reduced renal mass

The effects of angiotensin II (AII) blockade were compared with the effects of angiotensin converting enzyme inhibition in rats with reduced nephron number. Rats were subjected to five-sixths renal ablation and divided into four groups with similar values for blood pressure and serum creatinine after 2 wk. Group 1 then served as untreated controls, while group 2 received the AII receptor antagonist MK954 (which has previously been designated DuP753), group 3 received the converting enzyme inhibitor enalapril, and group 4 received a combination of reserpine, hydralazine, and hydrochlorothiazide. Micropuncture and morphologic studies were performed 10 wk later. Converting enzyme inhibition, AII receptor blockade, and the combination regimen were equally effective in reversing systemic hypertension (time-averaged systolic blood pressure: group 1, 185 +/- 5 mmHg; group 2, 125 +/- 2 mmHg; group 3, 127 +/- 2 mmHg; group 4, 117 +/- 4 mmHg). Micropuncture studies showed that glomerular transcapillary pressure was reduced significantly by converting enzyme inhibition and by AII blockade but not by the combination regimen (delta P: group 1, 49 +/- 1 mmHg; group 2, 42 +/- 1 mmHg; group 3, 40 +/- 2 mmHg, group 4, 47 +/- 1 mmHg). Reduction of systemic blood pressure was associated with the development of markedly less proteinuria and segmental glomerular sclerosis in rats receiving enalapril and MK954 but not in rats receiving the combination regimen (prevalence of glomerular sclerotic lesions: group 1, 41 +/- 4%; group 2, 9 +/- 1%; group 3, 9 +/- 1%; group 4, 33 +/- 6%). These results indicate that the effects of converting enzyme inhibition on remnant glomerular function and structure depend on reduction in AII activity and are not attributable simply to normalization of systemic blood pressure.