Acute kidney injury aggravated by treatment initiation with apixaban: Another twist of anticoagulant-related nephropathy

Anticoagulant-related nephropathy (ARN) was initially described in patients on warfarin (as warfarin-related nephropathy) and recently in those using dabigatran. Herein, we report clinical history and kidney biopsy findings in a patient on apixaban (Eliquis). Initiation of treatment with apixaban resulted in aggravation of preexisting mild acute kidney injury (AKI). A few days after apixaban therapy, the patient became oligoanuric, and kidney biopsy showed severe acute tubular necrosis with numerous occlusive red blood cell casts. Only one out of 68 glomeruli with open capillary loops had small segmental cellular crescent. Therefore, there was major discrepancy between the degree of glomerular injury and the glomerular hematuria. Considering that the onset of this AKI was associated with apixaban treatment initiation, we propose that this patient had ARN associated with factor Xa inhibitor (apixaban), which has not previously been described. Monitoring of kidney function is recommended after initiation of anticoagulant therapy.

Oral warfarin and the thrombin inhibitor dabigatran increase blood pressure in rats: hidden danger of anticoagulants?

BACKGROUND

Hypertension is a common comorbidity in patients with chronic kidney disease (CKD). We reported earlier that oral anticoagulants, including warfarin and dabigatran, may induce acute kidney injury. No effects of oral anticoagulants on blood pressure (BP) have been previously reported. The aim of this study was to examine in detail the relationship of anticoagulant therapy and BP in rats.

METHODS

Sham-operated and 5/6 nephrectomy rats were treated with different doses of oral anticoagulants (warfarin and dabigatran), superoxide scavenger N-acetylcysteine (NAC), vitamin K, and protease activated receptor 1 (PAR-1) inhibitor SCH79797. BP was measured by a tail cuff daily.

RESULTS

Warfarin and dabigatran both increased systolic BP in sham-operated and 5/6 nephrectomy rats in a dose-dependent manner. SCH79797 also increased systolic BP in a dose-dependent manner. Vitamin K prevented warfarin-induced increase in BP but did not affect BP when administered alone. NAC delayed the warfarin-associated increase in BP. Warfarin effects on BP were similar in 5/6 nephrectomy rats with different CKD stages.

CONCLUSIONS

Both warfarin and dabigatran increase systolic BP in rats. The mechanism of this effect is not clear, but our data suggest that it is related to decreased thrombin activity associated with anticoagulant treatment. The superoxide scavenger NAC delayed, but did not prevent, warfarin-induced hypertension.

Novel gelsolin variant as the cause of nephrotic syndrome and renal amyloidosis in a large kindred

Familial Amyloidosis of Finnish type (FAF) is a rare type of autosomal dominant hereditary amyloidosis associated with genetic variants of gelsolin. Three amyloidogenic mutations have previously been reported characteristically presenting with ophthalmologic abnormalities, progressive cranial neuropathy and cutis laxa. We report a novel gelsolin variant in a 62-year-old man with nephrotic range proteinuria of 13.2 grams/day as the only presenting symptom. Renal biopsy followed by laser micro-dissection and mass spectrometry showed amyloidosis derived from gelsolin. DNA sequencing revealed the novel gelsolin mutation (c.633C > A) encoding p.N211K protein variant. Four of 13 asymptomatic family members were found to be heterozygous for the p.N211K mutation, three of whom had proteinuria of varying degree including one who proceeded to renal biopsy and was confirmed to have renal amyloidosis. Follow-up of these cases might give us more insight into pathogenicity and potential treatment strategy of this atypical presentation of gelsolin amyloidosis.

Warfarin-related nephropathy is the tip of the iceberg: direct thrombin inhibitor dabigatran induces glomerular hemorrhage with acute kidney injury in rats

BACKGROUND

Excessive anticoagulation with warfarin can result in acute kidney injury (AKI) by causing glomerular hemorrhage and renal tubular obstruction by red blood cell (RBC) casts in some patients, especially in those with chronic kidney disease (CKD). This condition was described as warfarin-related nephropathy (WRN). Recent evidence suggests that WRN-like syndromes are not confined to anticoagulation with warfarin, but may be seen with other anticoagulants, such as dabigatran. The aim of this study was to investigate dabigatran effects on kidney function in an animal model of CKD and possible pathogenic mechanisms of AKI.

METHODS

Control and 5/6 nephrectomy rats were treated with different doses of dabigatran and protease-activated receptor 1 (PAR-1) inhibitor SCH79797.

RESULTS

Dabigatran resulted in changes in coagulation in rats similar to those in humans at 50 mg/kg/day. Dabigatran resulted in a dose-dependent increase in serum creatinine (Scr) and hematuria in both control and 5/6 nephrectomy rats. SCH79797 also increased Scr and hematuria, more prominent in animals with CKD. Morphologically, numerous RBC tubular casts were seen in 5/6 nephrectomy rats treated with either dabigatran or SCH79797 and only occasional RBC casts in control rats.

CONCLUSIONS

Our data indicate that WRN represents part of a broader syndrome, anticoagulant-related nephropathy (ARN). ARN, at least partially, is mediated via PAR-1. Our findings suggest that not only CKD patients, but other patients as well, are at high risk of developing AKI if the therapeutic range of anticoagulation with dabigatran is exceeded. Close monitoring of kidney function in patients on dabigatran therapy is warranted.

N-acetylcysteine ameliorates acute kidney injury but not glomerular hemorrhage in an animal model of warfarin-related nephropathy

Warfarin-related nephropathy (WRN) occurs under conditions of overanticoagulation with warfarin. WRN is characterized by glomerular hemorrhage with occlusive tubular red blood cell (RBC) casts and acute kidney injury (AKI). Herein we test the hypothesis that oxidative stress plays a role in the AKI of WRN. 5/6 Nephrectomy rats were treated with either warfarin (0.04 mg·kg⁻¹·day⁻¹) alone or with four different doses of the antioxidant N-acetylcysteine (NAC). Also tested was the ability of our NAC regimen to mitigate AKI in a standard ischemia-reperfusion model in the rat. Warfarin resulted in a threefold or greater increase in prothrombin time in each experimental group. Serum creatinine (Scr) increased progressively in animals receiving only warfarin + vehicle. However, in animals receiving warfarin + NAC, the increase in Scr was lessened, starting at 40 mg·kg⁻¹·day⁻¹ NAC, and completely prevented at 80 mg·kg⁻¹·day⁻¹ NAC. NAC did not decrease hematuria or obstructive RBC casts, but mitigated acute tubular injury. Oxidative stress in the kidney was increased in animals with WRN and it was decreased by NAC. The NAC regimen used in the WRN model preserved kidney function in the ischemia-reperfusion model. Treatment with deferoxamine (iron chelator) did not affect WRN. No iron was detected in tubular epithelial cells. In conclusion, this work taken together with our previous works in WRN shows that glomerular hematuria is a necessary but not sufficient explanation for the AKI in WRN. The dominant mechanism of the AKI of WRN is tubular obstruction by RBC casts with increased oxidative stress in the kidney.

When size matters: diagnostic value of kidney biopsy according to the gauge of the biopsy needle

BACKGROUND

Kidney biopsy is a vital tool in the diagnosis of kidney disease. Although it has become a routine procedure, it is not complication-free. Some serious complications of percutaneous kidney biopsy include retroperitoneal hemorrhage and death. There is an increased belief that smaller biopsy needle size results in a lower complication rate. As renal pathologists, we witness an increased number of kidney biopsies performed with a small needle size (as low as gauge 22), which results in inadequate tissue sampling and often non-diagnostic biopsy results. Herein we report the diagnostic value of kidney biopsies according to the size of the biopsy needles.

METHODS

We performed kidney biopsies from nephrectomy specimens using biopsy needles of different sizes. Morphologic parameters were analyzed.

RESULTS

We found that biopsies performed by small needles (gauges 20 and 22) contain significantly lower numbers of glomeruli and blood vessels, which limits pathologic evaluation. Data from our institution do not show differences in kidney biopsy complication rates between 16- and 18-gauge needles.

CONCLUSIONS

Our data indicate that small biopsy needles do not provide sufficient material for diagnosis, and they increase the likelihood for a repeat biopsy.

5/6 nephrectomy as a validated rat model mimicking human warfarin-related nephropathy

BACKGROUND/AIMS

We previously reported that patients with chronic kidney disease (CKD) receiving warfarin therapy and whose international normalized ratio increases to >3.0 may develop acute kidney injury (AKI) as a result of glomerular hemorrhage and formation of obstructive red blood cell (RBC) casts. We named this condition warfarin-related nephropathy (WRN). We also previously reported that acute excessive anticoagulation with brodifacoum (superwarfarin) induces AKI in 5/6 nephrectomy (5/6NE) rats. Limitations of the brodifacoum model precluded a careful assessment of dose-response relationships.

METHODS

Warfarin treatment was used in 5/6NE.

RESULTS

Herein we report that warfarin treatment of 5/6NE rats resulted in a dose-dependent increase in serum creatinine (SC). The increase in SC following warfarin treatment was greater at 3 and 19 weeks after the ablative surgery, than that observed 8 weeks after the ablative surgery. The SC increase was correlated with the prothrombin time increase. Morphologically, 5/6NE, but not control rats, had acute tubular injury with RBC and RBC casts in the tubules. Treatment with vitamin K prevented SC increase and morphologic changes in the kidney associated with warfarin treatment. A single episode of WRN did not affect the progression of CKD in 5/6NE.

CONCLUSION

(1) The 5/6NE model of CKD is an appropriate animal model to study the pathogenesis of WRN. (2) The pharmacokinetics of warfarin is better suited to the study of WRN than that of brodifacoum. (3) The more advanced stages of 5/6NE are more susceptible to WRN than the earlier stages. (4) Vitamin K treatment prevents WRN.

Discrepancies in glomerular and tubulointerstitial/vascular immune complex IgG subclasses in lupus nephritis

Background and objectives: Lupus nephritis is characterized by glomerular and extraglomerular immune complex deposition in the kidney. It is unclear whether the same circulating immune complexes deposit in the glomeruli and in extraglomerular structures, or whether they are pathogenetically different. Differences in the IgG subclass composition may point towards different pathways in the formation of glomerular and extraglomerular immune complexes. Therefore we investigated IgG subclass distribution in the immune complex deposits at these anatomic sites.

Design: A total of 84 biopsies diagnosed as lupus nephritis and classified according to the International Society of Nephrology/Renal Pathology Society (ISN/RPS) 2003 classification, were examined by direct immunofluorescence staining for IgG subclasses. The IgG subclass composition in the glomerular, tubular basement membrane (TBM) and vascular wall deposits was compared. We also correlated the presence/absence of interstitial inflammation and IgG subclasses in the TBM and vascular deposits. Lastly, we looked for correlation between staining for IgG subclasses and complement C1q and C3 staining.

Results: IgG staining was present in the TBM in 52/84 biopsies, and in the vascular walls in 40/84 biopsies. IgG subclass distribution was discrepant between glomerular and TBM deposits in 36/52 biopsies, and between glomerular and vascular deposits in 27/40 biopsies. Interstitial inflammation did not correlate with the presence of IgG staining or distribution of IgG subclasses in the TBM. Interstitial inflammation was more common in biopsies of African–American patients than Caucasian patients. The IgG subclass staining correlated with C1q staining in all the three compartments.

Conclusions: The antibody composition of the glomerular and extraglomerular immune complex deposits appear to differ from each other. They may not represent the same preformed immune complexes from the circulation. It is likely that their pathogenesis and site of formation are different.

Warfarin-related nephropathy modeled by nephron reduction and excessive anticoagulation

An acute increase in international normalized ratio (INR) to >3.0 in patients with chronic kidney disease (CKD) can associate with an unexplained acute increase in serum creatinine and accelerated progression of CKD. A subset of these patients have renal tubular obstruction by casts of red blood cells, presumably the dominant mechanism of the acute kidney injury described as warfarin-related nephropathy. Here, we developed an animal model of this acute kidney injury that is based on the 5/6-nephrectomy model to aid future investigation of the pathogenesis of this condition. We found that acute excessive anticoagulation with brodifacoum ("superwarfarin") increased serum creatinine levels and hematuria in 5/6-nephrectomized rats but not in controls. In addition, morphologic findings in 5/6-nephrectomized rats included glomerular hemorrhage, occlusive red blood cell casts, and acute tubular injury, similar to the biopsy findings among affected patients. Furthermore, in the rat model, we observed an increase in apoptosis of glomerular endothelial cells. In summary, the 5/6-nephrectomy model combined with excessive anticoagulation may be a useful tool to study the pathogenesis of warfarin-related nephropathy.

Proliferative glomerulonephritis with monoclonal IgG deposits recurs or may develop de novo in kidney allografts

Proliferative glomerulonephritis with monoclonal immunoglobulin G (IgG) deposits (PGNMIGD) is a recently recognized glomerular disease. Light microscopy usually resembles membranoproliferative glomerulonephritis. Glomerular deposits are mostly IgG3 κ; however, unlike in the usual forms of monoclonal immunoglobulin deposition disease, extraglomerular deposits are absent. If PGNMIGD is secondary to the glomerular deposition of circulating monoclonal IgG, it is expected to recur in kidney allografts with the same pattern of monoclonal IgG deposition. We reviewed our kidney biopsy files between January 1, 2003, and January 4, 2010, and identified 21 biopsy specimens with PGNMIGD, mostly with glomerular IgG3 κ deposits. Of the 21 biopsy specimens, 4 were from kidney allografts; 2 were recurrent and the other 2 were de novo diseases. Recurrent PGNMIGD develops rapidly, causing proteinuria. This rapid recurrence of PGNMIGD in kidney allografts provides further proof that PGNMIGD is secondary to the glomerular deposition of circulating monoclonal IgG.

The relevance of periglomerular fibrosis in the evaluation of routine needle core renal biopsies

CONTEXT

Renal interstitial fibrosis and, to a lesser extent, sclerotic glomeruli correlate with poor renal function. However, not all nonfunctional glomeruli are sclerotic. Many or most glomeruli with periglomerular fibrosis, while retaining blood flow, probably do not filter; therefore, they may not contribute to renal function.

OBJECTIVE

To examine the relationship of periglomerular fibrosis and the sum of globally sclerotic glomeruli and glomeruli with periglomerular fibrosis (GSG+PF) with interstitial fibrosis and renal function.

DESIGN

Native kidney biopsies from 177 patients with chronic renal injury were assessed for interstitial fibrosis, glomerular sclerosis, and GSG+PF. Renal biopsies with active or acute lesions were not included. The percentage of globally sclerotic glomeruli and GSG+PF was correlated with the degree of interstitial fibrosis and serum creatinine levels.

RESULTS

The percentage of GSG+PF correlates better with the degree of interstitial fibrosis and renal function than does the percentage of globally sclerotic glomeruli alone. This appears particularly true in chronic renal diseases of patients without diabetes. The number of globally sclerotic glomeruli correlates better with interstitial fibrosis and renal function than does the sum of globally and segmentally sclerotic glomeruli.

CONCLUSIONS

The percentage of GSG+PF in a renal biopsy specimen provides a better estimate of chronic renal injury than does the percentage of sclerotic glomeruli alone, probably because many or most glomeruli with periglomerular fibrosis are nonfunctional. Therefore, we recommend that the number of glomeruli with periglomerular fibrosis also be provided in the renal biopsy report.

When one plus one equals more than two--a novel stain for renal biopsies is a combination of two classical stains

Histologic evaluation of renal biopsies includes multiple ancillary stains, including Periodic acid-Schiff's (PAS) and Masson's trichrome (Trichrome). Herein we report an innovative double-stain, derived from two standard stains (PAS and Trichrome). This novel stain not only has advantages of both ancestor stains, but became more distinguishable and colorful, when basement membranes stain dark-violet, whereas the interstitial collagen remains blue. This allows the pathologist immediate estimation of the amount of collagen, tubular atrophy and the degree of interstitial fibrosis in one section. Using computer-based analysis, we confirmed that our innovative double-stain highlights interstitial collagen better than Trichrome stain alone. We strongly recommend renal pathologists to try this innovative stain in their practice.

Warfarin therapy that results in an International Normalization Ratio above the therapeutic range is associated with accelerated progression of chronic kidney disease

BACKGROUND/AIMS

We had previously reported that acute kidney injury (AKI) in warfarin-treated chronic kidney disease (CKD) patients may occur shortly after an acute increase in the International Normalization Ratio (INR) >3.0 with formation of occlusive red blood casts. Recovery from this warfarin-associated AKI is poor. Here we investigated whether excessive warfarin therapy could accelerate the progression of CKD.

METHODS

We analyzed serum creatinine (SC) and INR in 103 consecutive CKD patients on warfarin therapy in our Nephrology program from 2005 to the present.

RESULTS

Forty-nine patients experienced at least 1 episode of INR >3.0. Of these, 18 patients (37%, Group 1) developed an unexplained increase in SC > or =0.3 mg/dl coincident with INR >3.0 (mean SC increase 0.61 +/- 0.44 mg/dl); 31 patients (63%, Group 2) showed stable SC (mean SC change 0.04 +/- 0.19 mg/dl). Subsequent CKD progression was accelerated in Group 1, but not in Group 2. The 2 groups were not different with respect to demographics, comorbidities, blood pressure, or therapies. However, African Americans were overrepresented in Group 1 (p = 0.035).

CONCLUSIONS

Overanticoagulation is associated with faster progression of CKD in a high percentage of patients. Our results indicate the need for prospective trials. Nevertheless, we suggest that our findings are sufficiently compelling at this point to justify extra caution in warfarin-treated CKD patients to avoid overanticoagulation.

Acute kidney injury during warfarin therapy associated with obstructive tubular red blood cell casts: a report of 9 cases

Acute kidney injury (AKI) during warfarin therapy usually is hemodynamic secondary to massive blood loss. Here, we report pathological findings in kidney biopsy specimens from 9 patients with warfarin overdose, hematuria, and AKI. Kidney biopsy specimens from patients on warfarin therapy with AKI were identified in our database within a 5-year period. Each kidney biopsy specimen was evaluated by using semiquantitative morphometric techniques, and medical history was reviewed for conditions explaining AKI. Biopsy specimens with morphological findings of active glomerulonephritis and active inflammatory lesions were excluded from the study. Biopsy specimens from 9 patients were selected. At presentation with AKI, each patient had an abnormal international normalized ratio (mean 4.4 +/- 0.7 IU) and increased serum creatinine level (mean, 4.3 +/- 0.8 mg/dL). Morphologically, each biopsy specimen showed evidence of acute tubular injury and glomerular hemorrhage: red blood cells (RBCs) in Bowman space and numerous occlusive RBC casts in tubules. Each biopsy specimen showed chronic kidney injury. Six of 9 patients did not recover from AKI. These data suggest that warfarin therapy can result in AKI by causing glomerular hemorrhage and renal tubular obstruction by RBC casts. Our experience suggests that this may be a potentially serious complication of warfarin therapy, especially in older patients with underlying chronic kidney injury.

Critical role of effector macrophages in mediating CD4-dependent alloimmune injury of transplanted liver parenchymal cells

Despite the recognition that humoral rejection is an important cause of allograft injury, the mechanism of Ab-mediated injury to allograft parenchyma is not well understood. We used a well-characterized murine hepatocellular allograft model to determine the mechanism of Ab-mediated destruction of transplanted liver parenchymal cells. In this model, allogeneic hepatocytes are transplanted into CD8-deficient hosts to focus on CD4-dependent, alloantibody-mediated rejection. Host serum alloantibody levels correlated with in vivo allospecific cytotoxic activity in CD8 knockout hepatocyte rejector mice. Host macrophage depletion, but not CD4(+) T cell, NK cell, neutrophil, or complement depletion, inhibited in vivo allocytotoxicity. Recipient macrophage deficiency delayed CD4-dependent hepatocyte rejection and inhibited in vivo allocytotoxicity without influencing alloantibody production. Furthermore, hepatocyte coincubation with alloantibody and macrophages resulted in Ab-dependent hepatocellular cytotoxicity in vitro. These studies are consistent with a paradigm of acute humoral rejection in which CD4(+) T cell-dependent alloantibody production results in the targeting of transplanted allogeneic parenchymal cells for macrophage-mediated cytotoxic immune damage. Consequently, strategies to eliminate recipient macrophages during CD4-dependent rejection pathway may prolong allograft survival.

Biomarkers of lupus nephritis determined by serial urine proteomics

Lupus nephritis is a frequent and serious complication of systemic lupus erythematosus (SLE), the treatment of which often requires the use of immunosuppressives that can have severe side effects. Here we determined the low-molecular weight proteome of serial lupus urine samples to uncover novel and predictive biomarkers of SLE renal flare. Urine from 25 flare cycles of 19 patients with WHO Class III, IV, and V SLE nephritis were obtained at baseline, pre-flare, flare and post-flare. Each sample was first fractionated to remove proteins larger than 30 kDa, then applied onto weak cation exchanger protein chips for analysis by SELDI-TOF mass spectrometry. We found 176 protein ions of which 27 were differentially expressed between specific flare intervals. On-chip peptide sequencing by integrated tandem mass spectrometry positively identified the 20 and 25 amino-acid isoforms of hepcidin, as well as fragments of alpha1-antitrypsin and albumin among the selected differentially expressed protein ions. Hepcidin 20 increased 4 months before renal flare and returned to baseline at renal flare, whereas hepcidin 25 decreased at renal flare and returned to baseline 4 months after the flare. These studies provide a beginning proteomic analysis aimed at predicting impending renal relapse, relapse severity, and the potential for recovery after SLE nephritis flare.

An experimental model of acute humoral rejection of renal allografts associated with concomitant cellular rejection

Acute humoral rejection (AHR), which occurs in up to 8% of kidney transplant recipients, is a significant cause of renal allograft dysfunction and loss. More efficacious treatment modalities are needed to eliminate or curtail alloantibody production and its deleterious effects on the kidney. The availability of animal models mimicking human AHR is essential to understand its pathophysiology and develop new treatment strategies. Using a mouse kidney transplant model, we demonstrate that presensitization of recipients with donor skin grafts results in rejection of subsequent renal allografts. All presensitized mice developed renal failure 8.6 +/- 4.3 days after engraftment, with serum creatinine values near 100 micromol/dl. Graft histology revealed mild, diffuse, interstitial, mononuclear cell infiltrates; prominent peritubular capillary inflammatory cell margination; patchy interstitial hemorrhage; interstitial edema; and focal glomerular fibrin deposition. Complement (C3d) deposition was diffuse and prominent in peritubular capillaries. Serum analysis demonstrated high levels of circulating alloantibodies with broad cross-reactivity to many MHC haplotypes. The clinical setting and histological findings of our model strongly resemble AHR, which is frequently associated with cellular rejection, a situation commonly encountered in human renal allograft recipients. This animal model provides a valuable tool to study the pathogenesis of AHR, its relationship to cellular alloimmunity, its contribution to graft injury, and the effects of various potential therapeutic interventions.

Acute humoral rejection of renal allografts in CCR5(-/-) recipients

Increasing detection of acute humoral rejection (AHR) of renal allografts has generated the need for appropriate animal models to investigate underlying mechanisms. Murine recipients lacking the chemokine receptor CCR5 reject cardiac allografts with marked C3d deposition in the parenchymal capillaries and high serum donor-reactive antibody titers, features consistent with AHR. The rejection of MHC-mismatched renal allografts from A/J (H-2(a)) donors by B6.CCR5(-/-) (H-2(b)) recipients was investigated. A/J renal allografts survived longer than 100 days in wild-type C57BL/6 recipients with normal blood creatinine levels (28 +/- 7 micromol/L). All CCR5(-/-) recipients rejected renal allografts within 21 days posttransplant (mean 13.3 +/- 4 days) with elevated creatinine (90 +/- 31 micromol/L). The rejected allografts had neutrophil and macrophage margination and diffuse C3d deposition in peritubular capillaries, interstitial hemorrhage and edema, and glomerular fibrin deposition. Circulating donor-reactive antibody titers were 40-fold higher in B6.CCR5(-/-) versus wild-type recipients. Depletion of recipient CD8 T cells did not circumvent rejection of the renal allografts by CCR5-deficient recipients. In contrast, microMT(-/-)/CCR5(-/-) recipients, incapable of producing antibody, did not reject most renal allografts. Collectively, these results indicate the rapid rejection of renal allografts in CCR5(-/-) recipients with many histopathologic features observed during AHR of human renal allografts.

StaphylococcusInfection-Associated Glomerulonephritis Mimicking IgA Nephropathy

The association of methicillin-resistant Staphylococcus aureus (MRSA) infection with glomerulonephritis (GN) has been well documented in Japan but not in North America. Recently, eight renal biopsies with IgA-predominant or -codominant GN from eight patients with underlying staphylococcal infection, but without endocarditis, were observed at a single institution in a 12-mo period. Renal biopsies were worked up by routinely used methodologies. Eight cases of primary IgA nephropathy were used as controls. Five patients had MRSA infection, one had methicillin-resistant S. epidermidis (MRSE) infection, and two had methicillin-sensitive S. aureus infection. Four patients became infected after surgery; two patients were diabetic and had infected leg ulcers. All patients developed acute renal failure, with active urine sediment and severe proteinuria. Most renal biopsies showed only mild glomerular hypercellularity. Two biopsies had prominent mesangial and intracapillary hypercellularity; one of them (the MRSE-associated case) had large glomerular hyalin thrombi. This patient also had a positive cryoglobulin test. Rare glomerular hyalin thrombi were noted in two other cases. Immunofluorescence showed IgA pre- or codominance in all biopsies. Electron microscopy revealed mesangial deposits in all cases. Five biopsies had rare glomerular capillary deposits as well. In the MRSE-associated GN, large subendothelial electron-dense deposits were present. These cases demonstrate that staphylococcal (especially MRSA) infection-associated GN occurs in the US as well, and a rising incidence is possible. It is important to differentiate a Staphylococcus infection-associated GN from primary IgA nephropathy to avoid erroneous treatment with immunosuppressive medications.

Acute Renal Failure Following Kidney Transplantation Associated with Myoglobinuria in Patients Treated with Rapamycin

BACKGROUND

Since using an immunosuppression regimen that includes rapamycin, we have occasionally encountered renal transplant patients who develop unexpected severe acute renal dysfunction. Biopsies obtained in these recipients demonstrate acute tubular necrosis (ATN) occasionally associated with tubular casts giving the classic appearance of myoglobin casts.

METHODS

We retrospectively reviewed all biopsies from consecutively transplanted kidneys engrafted between April 9, 2002 and June 29, 2004 to determine the incidence of ATN, ATN with intratubular casts, and casts with the classic myoglobin appearance. The clinical setting, treatment, and outcomes of those patients with classic myoglobin-appearing casts are reviewed.

RESULTS

Histological ATN as the principal finding in at least one biopsy occurred in 10.5% (57/543) of patients. About half of these patients (30/57) had tubular casts present in at least one biopsy and in 14 of these the casts had a classic appearance of myoglobin casts. These myoglobin-appearing casts were only noted in patients receiving rapamycin. A review of 28 ATN biopsies from an earlier prerapamycin era did not demonstrate similar myoglobin-appearing casts. Immunostaining for myoglobin was positive in all 14 recipient biopsies. This was confirmed by western blot analyses in three of five patient biopsies tested. Three of three recipients tested had elevated serum creatine phosphokinase levels and detectable serum myoglobin. All 14 patients slowly resolved their acute renal dysfunction and no grafts were lost.

CONCLUSION

We conclude that myoglobinuria with myoglobin cast formation can occur following rapamycin administration, and may be a causative factor in the development of unexpected severe acute renal dysfunction.

Proposed pathogenesis of idiopathic loin pain-hematuria syndrome

BACKGROUND

To study loin pain-hematuria syndrome (LPHS) pathogenesis, we evaluated 43 consecutive patients for whom urological evaluation failed to disclose the cause of their recurrent flank pain and hematuria. Each underwent percutaneous kidney biopsy. In 9 patients, the biopsy specimen showed immunoglobulin A nephritis, an established cause of LPHS. We suggest these cases be designated secondary LPHS. They are not included in this analysis. The remaining patients (N = 34) are designated idiopathic (primary) LPHS. They are the basis of this report.

METHODS

Demographics of patients with primary LPHS are mean age of 30.8 +/- 10.3 years; 74% women; 94% white; and history of kidney stones, 47%, although none was obstructing.

RESULTS

Primary LPHS kidney biopsy specimens showed red blood cells (RBCs) in multiple tubules, consistent with glomerular hematuria. Glomeruli were normal by means of light and immunofluorescent microscopy; however, more than 50% of biopsy specimens showed unusually thin or thick glomerular basement membranes. To assess whether the biopsy itself caused RBCs in tubules, we compared RBCs in renal tubular cross-sections from primary LPHS biopsies with those of normal kidneys (donors, n = 10). The mean percentage of tubular cross-sections containing RBCs was greater in primary LPHS than normal specimens (7.2% +/- 6.5% versus 1.6% +/- 1.0% [SD]; P < 0.0001), confirming glomerular hematuria in patients with primary LPHS.

CONCLUSION

Primary LPHS pathogenesis includes glomerular hematuria, apparently from structurally abnormal glomerular basement membrane. Primary LPHS pain may be initiated by obstructing RBC casts and perhaps microcrystals in those with a history of urolithiasis. Nevertheless, other factors are needed to explain the severe pain in patients with primary LPHS.

Plasma, urine, and renal expression of adiponectin in human systemic lupus erythematosus

BACKGROUND

Adiponectin is an adipocyte-derived cytokine that has anti-inflammatory properties. A preliminary proteomic evaluation of urine for biomarkers of systemic lupus erythematosus (SLE) nephritis demonstrated high levels of adiponectin in SLE urine. This prompted investigation of adiponectin expression in human SLE.

METHODS

Adiponectin was measured by enzyme-linked immunosorbent assay (ELISA) in the urine and plasma of a clinically well-characterized SLE cohort, with renal and nonrenal SLE being followed in a prospective longitudinal study to identify risk factors for SLE flare. Renal adiponectin expression was assessed by immunohistochemical analysis of kidney biopsies from SLE nephritis patients.

RESULTS

Cross-sectional testing showed that plasma adiponectin levels were higher in patients with renal SLE flare than normal controls or patients with nonrenal SLE flare, after accounting for race and body mass index. Urine adiponectin levels increased significantly with renal flare, but not nonrenal SLE flare. Longitudinal testing revealed that the urine adiponectin increase began in the 2 months prior to renal flare. Urine adiponectin correlated with plasma levels and magnitude of proteinuria, and to a lesser extent serum creatinine. Plasma adiponectin levels were independent of renal function and proteinuria. In kidney biopsies, adiponectin was found on endothelial surfaces in normal and SLE kidneys, and on podocytes and in the tubules of SLE kidneys.

CONCLUSION

Plasma adiponectin levels are increased in patients with renal SLE compared to healthy controls and patients with nonrenal SLE. During renal but not nonrenal SLE flare, urine adiponectin levels increase significantly. Urine adiponectin may be a biomarker of renal SLE flare.

Prostate cancer: three-dimensional sonoelastography for in vitro detection

PURPOSE

To prospectively evaluate the accuracy of three-dimensional (3D) sonoelastographic imaging, relative to that of gray-scale ultrasonography (US), in the in vitro detection of prostate cancer.

MATERIALS AND METHODS

The study was approved by the institutional review board and was HIPAA compliant. Informed consent was obtained from all patients. Nineteen prostatectomy specimens from patients aged 46-70 years with biopsy-proved prostate cancer were scanned in three dimensions by using conventional B-mode US and sonoelastography with vibrations of more than 100 Hz. Step-sectioned whole-mount histologic specimens were used to create a 3D volume of the prostate and the tumors within it. B-mode US scans and regions of low vibration on the sonoelastographic images (hard regions) were formatted in three dimensions. The lesions in the 19 cases were classified into two groups, as follows: G1 lesions were pathologically confirmed tumors with a volume of at least 1.0 cm3, and G2 lesions were pathologically confirmed tumors smaller than 1.0 cm3. G1 lesions were evaluated with B-mode US and sonoelastography and classified as true-positive, false-positive, true-negative, or false-negative; G2 lesions were evaluated only with sonoelastography. Findings at histologic examination were used as the reference standard. True-positive findings necessitated 3D lesion correlation between pathologic and imaging data. Conventional definitions of accuracy and sensitivity were used for statistical analysis.

RESULTS

For G1 lesions (seven lesions with a volume of at least 1.0 cm3), sonoelastography had an accuracy of 55% and a sensitivity of 71% and B-mode US had an accuracy of 17% and a sensitivity of 29%. The mean tumor volume was 3.1 cm3 +/- 2.1 (standard deviation). For G2 lesions (22 lesions with a volume of less than 1.0 cm3), the mean tumor volume was 0.32 cm3 +/- 0.21. Sonoelastography had an accuracy of 34% and a sensitivity of 41%; there were six false-positive findings.

CONCLUSION

Sonoelastography performed considerably better than did gray-scale US in the depiction of prostate cancer for tumors with volumes of more than 1 cm3.

Mycophenolate therapy of SLE membranous nephropathy

BACKGROUND

The immunosuppressant mycophenolic acid (MMF) has been used successfully to manage proliferative forms of systemic lupus erythematosus (SLE) glomerulonephritis (GN) World Health Organization (WHO) Classes III and IV. Less is known about MMF treatment of membranous SLE GN (WHO Class V, SLE MN).

METHODS

We report our experience with MMF therapy in 13 consecutive SLE MN patients participating in a prospective study of risk factors for SLE flare.

RESULTS

Baseline characteristics were: mean age 33 +/- 14 SD years, female/male ratio 11/2, Caucasians 7, African Americans 5, Oriental 1, serum creatinine 1.02 +/- 0.41, and mean 24-hour urine protein (P)/creatinine (C), ratio 5.1 +/- 4.1. Initial therapy was prednisone mean dose 31 +/- 17 mg/day, and MMF mean dose 1173 +/- 746 mg/day. Therapy also featured interventions to achieve renoprotection and proteinuria reduction. At 6 months of therapy, complete or partial remission was achieved in 10 of 13 patients. At most recent follow-up visit (mean follow-up 16 +/- 8 months), 9 of 13 patients were in complete remission, and in 11 of 13 patients, urine P/C ratio was < 0.8. During follow-up, serum creatinine either stabilized or was improved. The only serious complication during 208 patient months of follow-up was histoplasma pneumonia in 1 patient.

CONCLUSION

These promising results suggest that moderate dose MMF in combination with renoprotective/antiproteinuria therapy warrants further study in the management of SLE MN.

Three-dimensional registration of prostate images from histology and ultrasound

A whole mount histology protocol for 3-D tissue reconstruction to compare the size and spatial location of tumors (and other components) identified in histology data with that from 3-D ultrasound (US) images is presented. Prostate specimens are imaged in 3-D using B-mode (US) and sonoelastography. The prostate surface is outlined in each B-mode image and a 3-D surface reconstruction is made. The specimen is then prepared for whole mount histology and the histology slides are digitally reconstructed to make a 3-D surface. These two surfaces are then aligned using a 3-D correlation algorithm, and the tumor boundary determined by the pathologist is compared with that using sonoelastography. 3-D images showing the overlapping histology and sonoelastography of prostate surface reconstructions for one prostate are presented to illustrate the technique; results for four prostates yielded an accuracy of 92% +/- 3%.