Renal biopsy in systemic infections: expect the unexpected.

Infection-related glomerulonephritis is well recognized in patients with ongoing infections. It can be missed, however, if the infection is unusual or undetected. We present three cases where the renal biopsy findings prompted the identification or treatment of systemic infections.Case 1: A 84-year-old male presented with acute kidney injury (AKI) and IgA vasculitis on skin biopsy. A renal biopsy showed active glomerulonephritis with abundant neutrophils and predominantly mesangial immune complex deposits containing IgA. The findings prompted an infectious workup which was positive for COVID-19, suggesting exacerbation of IgA nephropathy by recent COVID-19 infection. Case 2: A 31-year-old female status post kidney transplant for granulomatosis with polyangiitis (GPA) had recent pregnancy with preterm delivery, disseminated herpes simplex virus (HSV) infection with HSV hepatitis, E. coli on urine culture, and AKI. A renal biopsy showed proliferative glomerulonephritis with subendothelial and mesangial immune complex deposits containing IgG and C3. The findings were most consistent with infection-related immune complex glomerulonephritis, most likely HSV-related. Case 3: A 78-year-old female presented with AKI, proteinuria, hematuria, and positive p-ANCA. Clinically, ANCA vasculitis was suspected, and renal biopsy did show focal, segmental, necrotizing glomerulonephritis. However, immunofluorescence and electron microscopy showed IgM-rich deposits in the mesangium. The unusual presentation prompted an infectious workup including a Bartonella antibody panel which showed very high titers, suggesting Bartonella endocarditis.Infection-related glomerulonephritis has a wide variety of presentations histologically and clinically. The three cases we present here emphasize the importance of recognizing these entities to help guide treatment and improve patient care.

Clinical Features and Outcomes of Immune Checkpoint Inhibitor-Associated AKI: A Multicenter Study.

BACKGROUND: Despite increasing recognition of the importance of immune checkpoint inhibitor-associated AKI, data on this complication of immunotherapy are sparse. METHODS: We conducted a multicenter study of 138 patients with immune checkpoint inhibitor-associated AKI, defined as a ≥2-fold increase in serum creatinine or new dialysis requirement directly attributed to an immune checkpoint inhibitor. We also collected data on 276 control patients who received these drugs but did not develop AKI. RESULTS: Lower baseline eGFR, proton pump inhibitor use, and combination immune checkpoint inhibitor therapy were each independently associated with an increased risk of immune checkpoint inhibitor-associated AKI. Median (interquartile range) time from immune checkpoint inhibitor initiation to AKI was 14 (6-37) weeks. Most patients had subnephrotic proteinuria, and approximately half had pyuria. Extrarenal immune-related adverse events occurred in 43% of patients; 69% were concurrently receiving a potential tubulointerstitial nephritis-causing medication. Tubulointerstitial nephritis was the dominant lesion in 93% of the 60 patients biopsied. Most patients (86%) were treated with steroids. Complete, partial, or no kidney recovery occurred in 40%, 45%, and 15% of patients, respectively. Concomitant extrarenal immune-related adverse events were associated with worse renal prognosis, whereas concomitant tubulointerstitial nephritis-causing medications and treatment with steroids were each associated with improved renal prognosis. Failure to achieve kidney recovery after immune checkpoint inhibitor-associated AKI was independently associated with higher mortality. Immune checkpoint inhibitor rechallenge occurred in 22% of patients, of whom 23% developed recurrent associated AKI. CONCLUSIONS: This multicenter study identifies insights into the risk factors, clinical features, histopathologic findings, and renal and overall outcomes in patients with immune checkpoint inhibitor-associated AKI.

Angiotensin converting enzyme 2 and the kidney.

PURPOSE OF REVIEW: Angiotensin-converting enzyme 2 (ACE2) is a monocarboxypeptidase that metabolizes angiotensin II (AngII). AngII levels can be modulated by ACE2 in tissues where the enzyme is highly expressed, such as the kidney. In the kidney, ACE2 has the potential to regulate the intrarenal renin-angiotensin system (RAS), which can impact blood pressure and renal injury. Thus, in disease states where the RAS is often upregulated, the function of ACE2 plays a particularly important role. This review highlights the results of recent studies that demonstrate the interplay between ACE2 and the kidney under normal and pathological conditions. RECENT FINDINGS: ACE2 has been reported to play a key role in renal and cardiovascular function. Recent studies have implicated shedding of the membrane-bound ectodomain of ACE2 as one way in which the enzyme can be regulated and enzymatic activity altered. This posttranslational modification releases a fragment which retains enzymatic activity, and thus provides a novel mechanism by which the RAS can be altered in response to physiological stimuli. Decreased ACE2 activity is associated with increased blood pressure, diabetes, and oxidative stress, whereas, increased levels of ACE2 appear to be renoprotective. SUMMARY: A growing body of evidence, involving both experimental and human studies, points out the crucial role that ACE2 plays on the modulation of renal injury. Thus, therapeutic targets aiming to increase ACE2 activity and the ACE2-Ang(1-7)-MasR axis could potentially become clinically relevant, especially in disease states where the renal RAS is upregulated.

Special deLIVERy: podocyte injury promotes renal angiotensin II generation from liver-derived angiotensinogen.

The role of the circulating renin-angiotensin system (RAS) in regulating systemic blood pressure and sodium balance is well established. More recently, researchers have turned their focus to the local generation of angiotensin II (Ang II) in specific tissues. Matsusaka et al. revisit the renal RAS and provide evidence that liver-derived angiotensinogen (AGT) is a major determinant of renal Ang II levels in a model of podocyte injury.

Paraneoplastic Cast Nephropathy Associated With Pancreatic Acinar Cell Carcinoma: A Kidney Biopsy Teaching Case.

Paraneoplastic cast nephropathy, a rare cause of acute kidney injury, is most commonly observed in cases of multiple myeloma and is characterized by the formation of intratubular casts composed of monoclonal light chains. Nonmonoclonal paraneoplastic cast nephropathy has also been reported in patients with pancreatic acinar cell carcinoma or prolactinoma. In this case report, we present a case of polyclonal cast nephropathy in a patient with metastatic acinar cell carcinoma. We aim to emphasize the significance of recognizing this uncommon complication in patients with solid tumors and to discuss the diagnostic challenges and potential pathophysiology of this unique condition.

Role of vaptans in the management of hyponatremia.

Hyponatremia, the most commonly encountered electrolyte abnormality, affects as many as 30% of hospitalized patients. It is a powerful predictor of poor outcomes, especially in patients with congestive heart failure or cirrhosis. The failure to excrete electrolyte-free water that results from persistent secretion of antidiuretic hormone despite low serum osmolality usually underlies the development of hyponatremia. Treatment depends on several factors, including the cause, overall volume status of the patient, severity of hyponatremic symptoms, and duration of hyponatremia at presentation. This review focuses on the role of the vasopressin receptor antagonists, or vaptans, in the treatment of hyponatremia. These recently introduced agents have the unique ability to induce an aquaresis, the excretion of electrolyte-free water without accompanying solutes. After a brief historical perspective and discussion of pharmacologic characteristics of vaptans, we review the accumulated experience with vaptans for the treatment of hyponatremia. Vaptans have been shown to increase serum sodium concentrations in patients with euvolemic or hypervolemic hyponatremia in a reproducible manner, but their safe use requires full understanding of their indications and contraindications.

Advanced chronic kidney disease; A comparison between nephroureterectomy and nephron-sparing surgery for upper tract urothelial carcinoma.

PURPOSE: Renal function outcomes between radical nephroureterectomy (RNU) and nephron-sparing surgery (NSS) for upper tract urothelial carcinoma (UTUC) patients are not well established. We sought to compare the incidence and factors associated with development of advanced chronic kidney disease (CKD) between RNU and NSS and examine the role of acute kidney injury (AKI) on renal function outcomes. METHODS: We retrospectively analyzed an institutional database for patients who underwent either RNU or NSS for UTUC. Cumulative incidence of postoperative advanced CKD, defined as eGFR < 30 ml/min/1.73 m2, was compared between groups. Fine-Gray competing risk regression was used to identify predictors of advanced CKD. Locally weight scatterplot smoothing was used to assess postoperative eGFR trends. AKI events were counted, staged, and assessed for influence of progression to advanced CKD. RESULTS: Four hundred and twenty-six patients were included in analysis, with a median follow up of 6.68 years (IQR 3.4-12.2). Median preoperative eGFR was similar between the groups (NSS: 68 ml/min/1.73 m2, RNU: 65 ml/min/1.73 m2,P = 0.220). Cumulative incidence of advanced CKD was significantly lower in the NSS cohort (P = 0.009). Factors associated with advanced CKD included age, diabetes, recurrent AKI and RNU. Percent of patients with an AKI event differed between the groups (51.5% NSS, 72.7% RNU, P = <0.001), there was no between group difference in percentage of patients with recurrent AKI (25.6% NSS, 25.9% RNU, P =1). CONCLUSION: NSS provides a renal function benefit in UTUC. AKI is common among UTUC patients and recurrent AKI is a risk factor for development of advanced CKD.

The Latino Health Project: pilot testing a culturally adapted behavioral weight loss intervention in obese and overweight Latino adults.

OBJECTIVE: To pilot test a culturally adapted behavioral weight loss intervention in obese and overweight Latino adults. DESIGN: Pilot study. SETTING: Latino community organization in Durham, North Carolina. PARTICIPANTS: Overweight and obese, self-identified Latinos > or =18 years old. INTERVENTION: Intervention consisted of 20 weekly group sessions (90-120 minutes each) incorporating motivational interviewing techniques. The intervention goal was weight loss by adopting the Dietary Approach to Stop Hypertension (DASH) dietary pattern, increasing physical activity, and reducing caloric intake. The cultural adaptation included foods and physical activities commonly used in the Latino culture, using a Spanish-speaking interventionist, and conducting the intervention at a local Latino community organization. MAIN OUTCOME MEASURES: Weight, body mass index (BMI), blood pressure, dietary pattern, and physical activity were measured at baseline and at 20 weeks. RESULTS: A total of 56 participants are included in the final analysis. The average weight loss was 5.1 lbs (95% CI -8.7 to -1.5; P = .006); and there was a reduction in BMI of 1.3 kg/m2 (95% CI -2.2 to -0.5; P =.002) at 20 weeks. Systolic blood pressure decreased by 2.6 mm Hg (95% CI -4.7 to -0.6; P = .013). CONCLUSION: A culturally adapted behavioral intervention for the treatment of overweight and obesity is potentially effective in a diverse group of Latino adults.

Oncosurgery-Related Acute Kidney Injury.

Oncosurgery is a surgical specialty that focuses on the diagnosis, staging, and management of cancer and cancer-related complications. Acute kidney injury is a common and important complication related to oncologic surgery, associated with longer hospital length of stay, greater costs, increased risk of incident or progressive chronic kidney disease (CKD), and higher mortality. The pathogenesis of oncosurgery-related acute kidney injury is multifactorial and determined by different variables, including patient characteristics (comorbidities, volume status, age, pre-existing CKD), specific cancer type or location, surgical procedure involved, as well as intrinsic neuroendocrine and hemodynamic responses to anesthesia and/or surgery. Early nephrology evaluation may be helpful to assist with preservation of kidney function and prevention of further kidney injury.

Soluble ACE2 Is Filtered into the Urine.

Background: ACE2 is a key enzyme in the renin-angiotensin system (RAS) capable of balancing the RAS by metabolizing angiotensin II (AngII). First described in cardiac tissue, abundance of ACE2 is highest in the kidney, and it is also expressed in several extrarenal tissues. Previously, we reported an association between enhanced susceptibility to hypertension and elevated renal AngII levels in global ACE2-knockout mice. Methods: To examine the effect of ACE2 expressed in the kidney, relative to extrarenal expression, on the development of hypertension, we used a kidney crosstransplantation strategy with ACE2-KO and WT mice. In this model, both native kidneys are removed and renal function is provided entirely by the transplanted kidney, such that four experimental groups with restricted ACE2 expression are generated: WT→WT (WT), KO→WT (KidneyKO), WT→KO (SystemicKO), and KO→KO (TotalKO). Additionally, we used nanoscale mass spectrometry-based proteomics to identify ACE2 fragments in early glomerular filtrate of mice. Results: Although significant differences in BP were not detected, a major finding of our study is that shed or soluble ACE2 (sACE2) was present in urine of KidneyKO mice that lack renal ACE2 expression. Detection of sACE2 in the urine of KidneyKO mice during AngII-mediated hypertension suggests that sACE2 originating from extrarenal tissues can reach the kidney and be excreted in urine. To confirm glomerular filtration of ACE2, we used micropuncture and nanoscale proteomics to detect peptides derived from ACE2 in the Bowman's space. Conclusions: Our findings suggest that both systemic and renal tissues may contribute to sACE2 in urine, identifying the kidney as a major site for ACE2 actions. Moreover, filtration of sACE2 into the lumen of the nephron may contribute to the pathophysiology of kidney diseases characterized by disruption of the glomerular filtration barrier.

Shorter versus longer corticosteroid duration and recurrent immune checkpoint inhibitor-associated AKI.

BACKGROUND: Corticosteroids are the mainstay of treatment for immune checkpoint inhibitor-associated acute kidney injury (ICPi-AKI), but the optimal duration of therapy has not been established. Prolonged use of corticosteroids can cause numerous adverse effects and may decrease progression-free survival among patients treated with ICPis. We sought to determine whether a shorter duration of corticosteroids was equally efficacious and safe as compared with a longer duration. METHODS: We used data from an international multicenter cohort study of patients diagnosed with ICPi-AKI from 29 centers across nine countries. We examined whether a shorter duration of corticosteroids (28 days or less) was associated with a higher rate of recurrent ICPi-AKI or death within 30 days following completion of corticosteroid treatment as compared with a longer duration (29-84 days). RESULTS: Of 165 patients treated with corticosteroids, 56 (34%) received a shorter duration of treatment and 109 (66%) received a longer duration. Patients in the shorter versus longer duration groups were similar with respect to baseline and ICPi-AKI characteristics. Five of 56 patients (8.9%) in the shorter duration group and 12 of 109 (11%) in the longer duration group developed recurrent ICPi-AKI or died (p=0.90). Nadir serum creatinine in the first 14, 28, and 90 days following completion of corticosteroid treatment was similar between groups (p=0.40, p=0.56, and p=0.89, respectively). CONCLUSION: A shorter duration of corticosteroids (28 days or less) may be safe for patients with ICPi-AKI. However, the findings may be susceptible to unmeasured confounding and further research from randomized clinical trials is needed.

Acute kidney injury in patients treated with immune checkpoint inhibitors.

BACKGROUND: Immune checkpoint inhibitor-associated acute kidney injury (ICPi-AKI) has emerged as an important toxicity among patients with cancer. METHODS: We collected data on 429 patients with ICPi-AKI and 429 control patients who received ICPis contemporaneously but who did not develop ICPi-AKI from 30 sites in 10 countries. Multivariable logistic regression was used to identify predictors of ICPi-AKI and its recovery. A multivariable Cox model was used to estimate the effect of ICPi rechallenge versus no rechallenge on survival following ICPi-AKI. RESULTS: ICPi-AKI occurred at a median of 16 weeks (IQR 8-32) following ICPi initiation. Lower baseline estimated glomerular filtration rate, proton pump inhibitor (PPI) use, and extrarenal immune-related adverse events (irAEs) were each associated with a higher risk of ICPi-AKI. Acute tubulointerstitial nephritis was the most common lesion on kidney biopsy (125/151 biopsied patients [82.7%]). Renal recovery occurred in 276 patients (64.3%) at a median of 7 weeks (IQR 3-10) following ICPi-AKI. Treatment with corticosteroids within 14 days following ICPi-AKI diagnosis was associated with higher odds of renal recovery (adjusted OR 2.64; 95% CI 1.58 to 4.41). Among patients treated with corticosteroids, early initiation of corticosteroids (within 3 days of ICPi-AKI) was associated with a higher odds of renal recovery compared with later initiation (more than 3 days following ICPi-AKI) (adjusted OR 2.09; 95% CI 1.16 to 3.79). Of 121 patients rechallenged, 20 (16.5%) developed recurrent ICPi-AKI. There was no difference in survival among patients rechallenged versus those not rechallenged following ICPi-AKI. CONCLUSIONS: Patients who developed ICPi-AKI were more likely to have impaired renal function at baseline, use a PPI, and have extrarenal irAEs. Two-thirds of patients had renal recovery following ICPi-AKI. Treatment with corticosteroids was associated with improved renal recovery.

ACE2 deficiency increases NADPH-mediated oxidative stress in the kidney.

Abstract Angiotensin-converting enzyme 2 (ACE2) is highly expressed in the kidney and hydrolyzes angiotensin II (Ang II) to Ang(1-7). Since Ang II is a strong activator of oxidative stress, we reasoned that ACE2 could be involved in the regulation of renal oxidative stress by governing the levels of Ang II. We, therefore, assessed levels of oxidative stress in kidney cortex of ACE2 knockout and wild-type littermate mice under baseline conditions. We found multiple markers of increased oxidative stress in ACE2KO mice. NADPH oxidase activity was increased in kidney cortex from ACE2KO mice as compared to WT (227 ± 24% vs.100 ± 19%, P < 0.001). However, kidney catalase and superoxide dismutase activities were not different between groups. Exogenous Ang II was degraded less efficiently by kidneys from ACE2KO mice than WT mice, and administration of an AT1R blocker (losartan 30 mg/kg/day) resulted in normalization of NADPH oxidase activity in the ACE2KO. These findings suggest that an AT1R-dependent mechanism contributes to increased ROS observed in the ACE2KO. This study demonstrates that genetic deficiency of ACE2 activity in mice fosters oxidative stress in the kidney in the absence of overt hypertension and is associated with reduced kidney capacity to hydrolyze Ang II. ACE2KO mice serve as a novel in vivo model to examine the role of overactivity of NADPH oxidase in kidney function.