Hemolysis-associated hemoglobin cast nephropathy results from a range of clinicopathologic disorders

Investigating an appropriate indicator of acute kidney injury for patient prognosis following lung transplantation

OBJECTIVE

The purpose of this study was to investigate the correlation between different subtypes of acute kidney injury (AKI) and clinical outcomes following lung transplantation (LTx) and to identify a reliable indicator for predicting poor prognosis in the LTx population.

METHODS

We retrospectively analyzed the clinical data of 279 LTx patients from August 2016 to March 2023. The AKI subtypes included AKI, persistent AKI on Day 7 (P7-AKI) and Day 14 (P14-AKI) after LTx, and AKI stages. The correlations of these factors with respiratory outcomes, mortality at 90 days, mortality at 1 year and data finalization were assessed, and the risk factors for the selected AKI subtypes were evaluated.

RESULTS

AKI occurred in 215 patients (77.1%), with 129 (46.2%) experiencing P7-AKI and 95 (34.1%) experiencing P14-AKI. P7-AKI was associated with more respiratory and mortality outcomes than were AKI and AKI stages, and P7-AKI surpassed P14-AKI in terms of a shorter diagnostic time. After adjusting for age, sex, BMI, type of transplant, transplant diagnosis and comorbidities, P7-AKI independently correlated with increased mortality risk at 90 days [HR 12.312 (95% CI: 2.839-53.402)], 1 year [HR 3.847 (95% CI: 1.840-8.044)], and data finalization [HR 2.010 (95% CI: 1.331-3.033)]. Five variables were identified as independent predictors for P7-AKI, including preoperative body mass index, prothrombin activity, hemoglobin and serum creatinine, and intraoperative colloid administration.

CONCLUSION

P7-AKI has been identified as a reliable indicator for predicting adverse outcomes in LTx patients, which may assist healthcare professionals in identifying high-risk individuals.

Acute kidney injury requiring dialysis after endovascular intervention for acute deep venous thrombosis: A case report and literature review

Key Clinical Message

Percutaneous precutaneous mechanical thrombectomy has been used for clot dissolution and removal in selected cases of iliofemoral deep vein thrombosis. Intravascular Hemolysis and hemoglobinuria caused by pharmachomechanical chather directed thrombolysis (PCDT) devices like the Angiojet is associated with an increased risk of acute kidney injury (AKI). Acute tubular necrosis that is severe enough to require hemodialysis can occur. Clinicians should be aware of this potential risk to ensure early recognition and timely referral to the nephrologist, and a clear explanation of the risk of AKI should be given to the patients undergoing this procedure.

Abstract

Lower extremity deep vein thrombosis (DVT) is a frequently encountered medical condition, and one that can lead to death or major disability if not promptly treated. Anticoagulation alone may not always be enough for complete treatment. It has been reported that early thrombus removal can rapidly relieve symptoms and prevent disease progression in some selected cases. Percutaneous pharmacomechanical thrombectomy has been used for clot dissolution and removal in such cases. AngioJet is an increasingly used method of percutaneous mechanical thrombectomy for DVT that can cause intravascular hemolysis and potentially acute kidney injury (AKI). We report here a case of a 39 years old lady who developed severe AKI (illustrated by creatinine level of 664 μmol/L (7.5 mg/dL), bicarb of 13 mmol/L and being anuric), requiring hemodialysis secondary to intravascular hemolysis and hemoglobinuria that occurred immediately after the use of AngioJet pharmacomechanical catheter-directed technique to treat an extensive iliofemoral DVT.

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 Mechanical Circulatory Support in Complex High-Risk and Indicated Percutaneous Coronary Intervention: Current Indications, Device Options, and Potential Complications

Improved expertise and technological advancements have enabled the safe and effective performance of complex and high-risk-indicated percutaneous coronary intervention (CHIP) in patients previously considered inoperable or high-risk. Mechanical circulatory support (MCS) devices play a crucial role in stabilizing hemodynamics during percutaneous coronary intervention (PCI) -related ischemia, thereby reducing the risk of major adverse events and achieving a more complete revascularization. However, the use of MCS devices in protected PCI is not without risks, including peri-procedural myocardial infarction (MI), bleeding, and access-related complications. Despite numerous observational studies, there is a significant lack of randomized clinical trials comparing different MCS devices in various CHIP scenarios and evaluating their long-term safety and efficacy profiles. This review aims to summarize the current evidence regarding the benefits of MCS devices during CHIPs, offer a practical guide for selecting appropriate devices based on clinical scenarios, and highlight the unanswered questions that future trials need to address.

Preexisting Hyperuricemia Before High-Altitude Ascent is Associated with a Slower Recovery of Estimated Glomerular Filtration Rate Following Descent

Zhao, Linggong, Yujie Huang, and Xiaoling Tan. Preexisting hyperuricemia before high-altitude ascent is associated with a slower recovery of estimated glomerular filtration rate following descent. High Alt Med Biol. 00:00-00, 2024. Objectives: Hypoxia at high altitudes results in elevated uric acid (UA) and reduced estimated glomerular filtration rate (eGFR). However, the impact of a prolonged high-altitude sojourn on UA levels and renal function in patients with preexisting hyperuricemia warrants further exploration. The study was to investigate the eGFR and related factors in patients with preexisting hyperuricemia following exposure to high altitude. Methods: The study included 345 participants, who worked at a high altitude for 1 year. Anthropometric and laboratory indices were collected before ascent (i.e., baseline), as well as 20 and 80 days after descent. The participants were categorized into individuals with hyperuricemia (HUA) or normal uric acid (NUA) group based on the presence or absence of hyperuricemia at baseline. Results: No difference in baseline eGFR was observed between the two groups before ascend or on day 20 after descent (p > 0.05). However, on day 80, eGFR of the HUA group was lower compared with the NUA group (p < 0.05). Correlations existed between post-descent eGFR levels and variables, including sampling time, UA levels, total and direct bilirubin, and baseline grouping. Conclusions: After high-altitude exposure, the recovery of eGFR was delayed in participants with preexisting hyperuricemia. Preexisting hyperuricemia and high-altitude hypoxia jointly contribute to renal impairment.

Megalin-related mechanism of hemolysis-induced acute kidney injury and the therapeutic strategy

Hemolysis-induced acute kidney injury (AKI) is attributed to heme-mediated proximal tubule epithelial cell (PTEC) injury and tubular cast formation due to intratubular protein condensation. Megalin is a multiligand endocytic receptor for proteins, peptides, and drugs in PTECs and mediates the uptake of free hemoglobin and the heme-scavenging protein α1-microglobulin. However, understanding of how megalin is involved in the development of hemolysis-induced AKI remains elusive. Here, we investigated the megalin-related pathogenesis of hemolysis-induced AKI and a therapeutic strategy using cilastatin, a megalin blocker. A phenylhydrazine-induced hemolysis model developed in kidney-specific mosaic megalin knockout (MegKO) mice confirmed megalin-dependent PTEC injury revealed by the co-expression of kidney injury molecule-1 (KIM-1). In the hemolysis model in kidney-specific conditional MegKO mice, the uptake of hemoglobin and α1-microglobulin as well as KIM-1 expression in PTECs was suppressed, but tubular cast formation was augmented, likely due to the nonselective inhibition of protein reabsorption in PTECs. Quartz crystal microbalance analysis revealed that cilastatin suppressed the binding of megalin with hemoglobin and α1-microglobulin. Cilastatin also inhibited the specific uptake of fluorescent hemoglobin by megalin-expressing rat yolk sac tumor-derived L2 cells. In a mouse model of hemolysis-induced AKI, repeated cilastatin administration suppressed PTEC injury by inhibiting the uptake of hemoglobin and α1-microglobulin and also prevented cast formation. Hemopexin, another heme-scavenging protein, was also found to be a novel ligand of megalin, and its binding to megalin and uptake by PTECs in the hemolysis model were suppressed by cilastatin. Mass spectrometry-based semiquantitative analysis of urinary proteins in cilastatin-treated C57BL/6J mice indicated that cilastatin suppressed the reabsorption of a limited number of megalin ligands in PTECs, including α1-microglobulin and hemopexin. Collectively, cilastatin-mediated selective megalin blockade is an effective therapeutic strategy to prevent both heme-mediated PTEC injury and cast formation in hemolysis-induced AKI. © 2024 The Pathological Society of Great Britain and Ireland.

A Series of Eight Cases of Pigment Nephropathy: An Obscured Aspect of Acute Kidney Injury

Pigment-induced acute kidney injury (AKI) is an important and preventable complication of rhabdomyolysis or hemolysis. It is characterized by the release of free heme pigment (myoglobin or hemoglobin) in the circulation, leading to direct injury of the proximal tubule and distal tubule obstruction by pigment cast. We are reporting eight cases of pigment-induced AKI, including six cases of myoglobin cast nephropathy and two cases of hemoglobin cast nephropathy. The causes of rhabdomyolysis were strenuous exercise, infection/febrile illness, and drug-induced neuroleptic malignant syndrome. Paroxysmal nocturnal hemoglobinuria and anti-tuberculosis treatment (rifampicin and isoniazid) had led to hemoglobin cast nephropathy each in one case. Seven cases had severe renal failure requiring dialysis. Short-term renal outcome was favorable. However, long-term follow-up is necessary to determine whether pigment-induced AKI has delayed sequelae. Therefore, clinicians should consider rhabdomyolysis or hemolysis as potential hidden causes of AKI in diverse clinical conditions, especially those of non-traumatic origin, to achieve an accurate diagnosis.

Clostridium perfringens-induced massive hemolysis treatment with blood purification to target toxins: a case report

Clostridium perfringens can rarely cause severe systemic infections, usually from an abdominal source, associated with massive hemolysis, which is usually fatal. Hemolytic anemia and acute renal injury resulting from toxin action are critical for the development of multiple organ dysfunction syndrome (MODs), making this condition a real emergency, requiring multispecialty skills and aggressive multimodal therapies. We herein describe a case of septic shock from acute cholecystitis with massive hemolysis caused by C. perfringens in a 55 year-old man that was successfully treated with early blood purification and continuous renal replacement therapy (CRRT) along with antibiotic therapy and surgery. The effect of the enormous amount of toxins produced by Clostridium which elicit a strong cytokine response and the damage caused by the hemolysis products are the main pathogenetic mechanisms of this rare but lethal clinical entity. The main goal of treatment is to remove toxins from plasma, block toxin action, and further production by achieving bacterial killing with antimicrobial agents and controlling the infectious focus, remove waste products and prevent or limit multiorgan damage. Blood purification techniques play an important role due to a strong pathophysiological rationale, as they can remove toxins and cytokines as well as cell-free products from plasma and also replace renal function. Although this condition is rare and robust data are lacking, blood purification techniques for C. perfringens-induced massive hemolysis are promising and should be further explored.

Intravascular Hemolysis and AKI in Children Undergoing Extracorporeal Membrane Oxygenation

Key Points

The incidence of AKI while undergoing ECMO in pediatric patients is high and independently increases mortality. Laboratory markers consistent with intravascular hemolysis increase the hazard of a composite outcome of AKI or RRT while undergoing ECMO. Further research into appropriate monitoring or treatment of ECMO-associated hemolysis may lead to important interventions to prevent AKI.

Background

AKI is common in patients requiring extracorporeal membrane oxygenation (ECMO), with a variety of proposed mechanisms. We sought to describe the effect of laboratory evidence of ECMO-associated intravascular hemolysis on AKI and RRT.

Methods

This retrospective cohort study included patients treated with ECMO at a single center over 10 years. The primary outcome was a composite of time to RRT or AKI (by creatinine-based Kidney Disease Improving Global Outcomes criteria) after ECMO start. Serum creatinine closest to ECMO start time was considered the pre-ECMO baseline and used to determine abnormal kidney function at ECMO start. The patient's subsequent creatinine values were used to identify AKI on ECMO. Multivariable cause-specific Cox proportional hazards models were used to assess the effect of separate markers of intravascular hemolysis on the time to the composite outcome after controlling for confounders.

Results

Five hundred and one children were evaluated with a median age 1.2 years, 56% male. Four separate multivariable models, each with a different marker of hemolysis (plasma-free hemoglobin, lactate dehydrogenase (LDH), minimum platelet count, and minimum daily hemoglobin), were used to examine the effect on the composite outcome of AKI/RRT. An elevated plasma-free hemoglobin, the most specific of these hemolysis markers, demonstrated an almost three-fold higher adjusted hazard for the composite outcome (hazard ratio [HR], 2.9; P value < 0.01; 95% confidence interval [CI], 1.4 to 5.6). Elevated LDH was associated with an adjusted HR of 3.1 (P value < 0.01; 95% CI, 1.7 to 5.5). Effect estimates were also pronounced in a composite outcome of only more severe AKI, stage 2+ AKI/RRT: HR 6.6 (P value < 0.01; 95% CI, 3.3 to 13.2) for plasma-free hemoglobin and 2.8 (P value < 0.01; 95% CI, 1.5 to 5.6) for LDH.

Conclusions

Laboratory findings consistent with intravascular hemolysis on ECMO were independently associated with a higher hazard of a composite outcome of AKI/RRT in children undergoing ECMO.

Risk factors and outcomes regarding the acute kidney injury after AngioJet thrombectomy for acute lower-extremity deep vein thrombosis

OBJECTIVE

To investigate the risk factors and outcomes regarding acute kidney injury (AKI) after AngioJet thrombectomy for acute lower-extremity deep vein thrombosis (DVT).

METHODS

Patients were divided into AKI and non-AKI groups according to whether AKI occurred postoperatively. The demographic data, pre-operative and post-operative laboratory data and surgical differences were compared between the two groups. Logistic regression and Wilcoxon signed-rank test were used to identify the AKI risk factors and outcomes, respectively.

RESULTS

Among the 341 patients who met the inclusion criteria, 45 developed AKI (AKI group) and 296 had normal renal function (non-AKI group) post-surgery. There were significant differences between the two groups in the course (t = 10.885, P = 0.000); preoperative history of a major surgery within 3 months (3M-MS) (odds ratio [OR] = 5.492, P = 0.001); duration of aspiration thrombectomy (Z = -8.803, P = 0.000); volumes of aspiration (Z = -8.215, P = 0.000); contrast volume (Z = -3.204, P = 0.001) and pulmonary thrombectomy (OR = 18.200, P = 0.002); and preoperative complications of hypertension (OR = 4.637, P = 0.002), diabetes (OR = 18.088, P = 0.000), or pulmonary embolism (OR = 0.085, P = 0.011). Wilcoxon signed-rank test showed that the renal function of every patient in the AKI group returned to normal 3 months after the surgery.

CONCLUSIONS

The course, preoperative complications of diabetes or hypertension, 3M-MS, contrast volume, duration and volume of aspiration thrombectomy, and pulmonary thrombectomy are risk factors for post-AngioJet-thrombectomy AKI, which is temporary.

Hemoglobin Casts in Kidney Biopsies: Etiological Spectrum

Intravascular hemolysis, which is the destruction of red blood cells in circulation, can cause acute kidney injury as the hemoglobin released by the lysed cells is toxic to the tubular epithelial cells. We performed a retrospective analysis of 56 cases of hemoglobin cast nephropathy reported at our institution to analyze the etiological spectrum causing this rare disease. The mean patient age was 41.7 (range: 2-72 years), and the male-to-female ratio was 1.8:1. All patients presented with acute kidney injury. The etiologies include rifampicin-induced, snake bite, autoimmune hemolytic anemia, falciparum malarial infection, leptospiral infection, autoimmune hemolytic anemia, sepsis, non-steroidal anti-inflammatory drugs, ingestion of termite oil, heavy metal poisoning, wasp sting, and valvular heart disease with severe mitral regurgitation. We demonstrate a wide spectrum of conditions associated with hemoglobin casts in the kidney biopsy. Hemoglobin immunostain is required to establish the diagnosis.

Device-related complications after Impella mechanical circulatory support implantation: an IMP-IT observational multicentre registry substudy

AIMS

To report the incidence, the predictors and clinical impact of device-related complications (DRCs) in the IMP-IT (IMPella Mechanical Circulatory Support Device in Italy) registry. Impella is percutaneous left ventricular assist devices, which provides mechanical circulatory support both in cardiogenic shock (CS) and high-risk percutaneous coronary intervention (HR-PCI). The IMP-IT registry is a multicentre registry evaluating the trends in use and clinical outcomes of Impella in Italy.

METHODS AND RESULTS

A total of 406 patients have been included in this registry: 56.4% in the setting of CS, while 43.6% patients in the setting of HR-PCI. DRCs were defined as a composite endpoint of access-site bleeding, limb ischaemia, vascular complication requiring treatment, haemolysis, aortic injury, and left ventricular perforation. DRC incidence in the overall population was 25.6%, with significantly higher rate in the CS (37.1%) than in the HR-PCI (10.7%) group. The most frequent complication was haemolysis (11.8%), which occurred almost exclusively in CS population. Access-site bleeding was observed in 9.6% of the overall population, with no significant difference between the two groups. Limb ischaemia was observed in 8.3% of the overall population, with significantly higher rate in the CS group. CS and right ventricular dysfunction appear as the strongest independent predictors of DRC. One-year mortality in patients with DRC appears higher than in patients with no DRC. However, DRC was not confirmed as an independent predictor of 1-year mortality at multivariate analysis.

CONCLUSION

In the IMP-IT registry, the rate of DRC was 25.6%, with CS being the strongest independent predictor. DRC was not found as an independent predictor of 1-year mortality.

Macroscopic hematuria in wasp sting patients: a retrospective study

BACKGROUND

Macroscopic hematuria after wasp sting has been reported in Asia to occur before acute kidney injury (AKI), and is often used by clinicians as a sign indicating the need for intensive care and blood purification therapy. However, there is no study on the clinical characteristics and prognosis of this symptom.

METHODS

The clinical data of 363 patients with wasp sting admitted to Suining Central Hospital from January 2016 to December 2018 were retrospectively analyzed. At admission, the poisoning severity score (PSS) was used as the criterion for severity classification. According to the presence of macroscopic hematuria, the patients were divided into macroscopic hematuria and non-macroscopic hematuria group.

RESULTS

Of the 363 wasp sting patients, 219 were male and 144 were female, with a mean age of 55.9 ± 16.3 years. Fifty-one (14%) had macroscopic hematuria, 39 (10.7%) had AKI, 105 (28.9%) had rhabdomyolysis, 61 (16.8%) had hemolysis, 45 (12.4%) went on to received hemodialysis, and 14 (3.9%) died. The incidence of AKI in macroscopic hematuria group was 70.6%, and oliguric renal failure accounted for 72.2%. Patients with macroscopic hematuria had significantly higher PSS (2.2 ± 0.5 vs. 1.1 ± 0.3, p < .001).

CONCLUSION

Macroscopic hematuria can be regarded as a surrogate marker of deteriorating clinical outcome following wasp stings. In wasp sting patients with symptoms of macroscopic hematuria or serum LDH higher than 463.5 u/L upon admission, the risk of AKI increases significantly, therefore hemodialysis should be considered. The PSS is helpful in early assessment of the severity of wasp sting patients.

An integrative proteomics metabolomics based strategy reveals the mechanisms involved in wasp sting induced acute kidney injury

The pathophysiological mechanisms involved in wasp-sting-induced acute kidney injury (AKI) remain largely unknown. Here, we combined proteomics and metabolomics to investigate the mechanisms behind multiple wasp sting-induced AKI. Interestingly, we found many differentially abundant proteins in the serum of AKI group compared with that of the non-AKI and control groups, involved in several metabolic pathways and the regulation of cellular processes. In addition, we also detected differentially abundant metabolites in the AKI group; among them many were involved in the glycerophospholipid metabolic pathway (the key pathway in the context of AKI): 50 metabolites, all downregulated in the AKI group. Importantly, the convergent analysis of metabolomics and proteomics data revealed that biomarkers of rhabdomyolysis (CA 3, MYL3, and LDH) and hemolysis (ALT and LDH) were integrated into a regulatory network with phospholipid metabolism products in the AKI group, indicating that wasp sting-induced AKI is secondary to rhabdomyolysis and intravascular hemolysis. Of note, such a phenotype suggests the disruption of the membrane of skeletal muscle cells and red blood cells mediated by the phospholipase A1 (PLA1), PLA2, and mastoparan in the wasp venom, via the disruption of membrane glycerophospholipids. Overall, our results highlight a potential new mechanism behind wasp sting-induced AKI and suggest that PLA inhibitors may be potential agents for the treatment of this condition.

Unclogging the effects of the Angiojet® thrombectomy system on kidney function: a case report

Background

AngioJet® is an increasingly used method of percutaneous mechanical thrombectomy for the treatment of patients with arterial and venous thromboses. AngioJet® has been shown to cause intravascular haemoylsis universally. We report the case of a 29 year old patient who underwent AngioJet® thrombectomy and post-procedure developed a stage 3 Acute kidney injury (AKI.) requiring renal replacement therapy (RRT), secondary to intravascular haemolysis. We aim to explore the mechanism and potential risk factors associated with developing AKI in these patients and suggest steps to optimise patient management.

Case presentation

A 29 year old Caucasian male who developed a stage 3 AKI, requiring RRT, following AngioJet® thrombectomy for an occluded femoral vein stent. Urine and laboratory investigations showed evidence of intravascular haemolysis, which was the likely cause of AKI. Following a brief period of RRT he completely recovered renal function.

Conclusions

AKI is an increasingly recognised complication following AngioJet® thrombectomy, but remains underappreciated in clinical practice. AKI results from intravascular haemolysis caused by the device. Up to 13% of patients require RRT, but overall short-term prognosis is good. Pre-procedural risk factors for the development of AKI include recent major surgery. Sodium bicarbonate should be administered to those who develop renal impairment. Renal biopsy is high risk and does not add to management. Increased clinician awareness and vigilance for AKI post-procedure can allow for early recognition and referral to nephrology services for ongoing management.

Acute Kidney Injury Caused by Evans Syndrome with Systemic Lupus Erythematosus and Systemic Sclerosis

A 65-year-old woman with systemic sclerosis and systemic lupus erythematosus developed acute kidney injury (AKI), Coombs-positive autoimmune hemolytic anemia and autoimmune thrombocytopenia; therefore, she was diagnosed with Evans syndrome (ES). Intravascular hemolysis was suggested as the cause of AKI based on the presence of acute tubular injury and trace hemosiderin deposits on the renal biopsy. The renal function, hemolytic anemia and thrombocytopenia were restored by an increased dose of glucocorticoids, hemodialysis, and plasma exchange. Although ES with severe hemolytic anemia is very rare, it is important to detect possible renal dysfunction when encountering patients with severe hemolysis.

Heme Oxygenase 1: A Defensive Mediator in Kidney Diseases

The incidence of kidney disease is rising, constituting a significant burden on the healthcare system and making identification of new therapeutic targets increasingly urgent. The heme oxygenase (HO) system performs an important function in the regulation of oxidative stress and inflammation and, via these mechanisms, is thought to play a role in the prevention of non-specific injuries following acute renal failure or resulting from chronic kidney disease. The expression of HO-1 is strongly inducible by a wide range of stimuli in the kidney, consequent to the kidney's filtration role which means HO-1 is exposed to a wide range of endogenous and exogenous molecules, and it has been shown to be protective in a variety of nephropathological animal models. Interestingly, the positive effect of HO-1 occurs in both hemolysis- and rhabdomyolysis-dominated diseases, where the kidney is extensively exposed to heme (a major HO-1 inducer), as well as in non-heme-dependent diseases such as hypertension, diabetic nephropathy or progression to end-stage renal disease. This highlights the complexity of HO-1's functions, which is also illustrated by the fact that, despite the abundance of preclinical data, no drug targeting HO-1 has so far been translated into clinical use. The objective of this review is to assess current knowledge relating HO-1's role in the kidney and its potential interest as a nephroprotection agent. The potential therapeutic openings will be presented, in particular through the identification of clinical trials targeting this enzyme or its products.

Etiological Spectrum and Histopathological Diagnosis of Rhabdomyolysis Associated Myoglobin Cast Nephropathy in South India

Background and Aims:

Rhabdomyolysis occurs due to injury to skeletal muscle fibers and the release of muscle constituents into the circulation. Myoglobin cast nephropathy leading to acute kidney injury is one of the most severe complications of rhabdomyolysis. This is a retrospective study which aims to analyse the clinicopathological features of myoglobin cast nephropathy.

Methods:

A total of 57 cases of myoglobin cast nephropathy were identified after performing immunohistochemical staining for myoglobin on all renal biopsies with pigment casts. The clinical, laboratory data, histopathological findings and clinical outcome of these cases were evaluated.

Results:

The mean patient age was 34.47 years (range 17-77) and the male to female ratio was 6.1:1. All patients presented with acute kidney injury with mean serum creatinine of 8.4 mg/dl (range: 1.7 to 20.8 mg/dl). Rhabdomyolysis was clinically suspected only in 31 patients. Along with myoglobin casts, acute tubular injury was present in all the biopsies. The most frequent conditions associated with myoglobin cast nephropathy in our study were snake envenomation and unaccustomed physical activities. A few activities that caused rhabdomyolysis in our patients were unique to India.

Conclusion:

Clinicians should be aware of the wide spectrum of causes for rhabdomyolysis. The classical clinical and laboratory findings of rhabdomyolysis may not be present in many of the patients. The pathologist must have a high index of suspicion, and immunohistochemical stain should be used to confirm the diagnosis.

A Case Report of Intravascular Hemolysis and Heme Pigment-Induced Nephropathy Following AngioJet Thrombectomy for Thrombosed DIPS Shunt

RATIONALE

The AngioJet system is a combined mechanical and pharmacological device used for thrombectomy. As a result of the mechanical disruption of clot, intravascular hemolysis is noted to occur. Rarely, intravascular hemolysis can be severe enough to cause heme pigment-induced acute kidney injury (AKI).

PRESENTING CONCERNS OF THE PATIENT

We describe a case of a 45-year-old man with Child-Pugh class B cirrhosis, Budd-Chiari syndrome, and antiphospholipid antibody syndrome who required thrombectomy following a thrombosed direct intrahepatic portosystemic shunt (DIPS). He developed evidence of worsening anemia, dark urine, direct antiglobulin test-negative intravascular hemolysis, and severe AKI within 24 hours of the procedure.

DIAGNOSIS

Based on his severe AKI in association with elevated hemolytic markers, and the temporal association with the AngioJet procedure, the patient was diagnosed with heme pigment-induced AKI secondary to intravascular hemolysis.

INTERVENTIONS

The patient remained anuric and became volume-overloaded after fluid resuscitation. He was started on dialysis 72 hours after the procedure. Five days after thrombectomy, hemolytic markers returned to normal.

OUTCOME

The patient received hemodialysis for approximately 3 weeks, followed by renal recovery and cessation of dialysis treatments. Five weeks after the AngioJet procedure, his renal function returned to normal.

TEACHING POINTS

We present a case of heme pigment-induced AKI following an AngioJet procedure that required initiation of dialysis. Although this rare complication has been reported in the literature, it typically occurs when the procedure is used for larger clot burden (ie, venous thromboembolism). To our knowledge, this is the first case of severe hemolysis with associated AKI following the use of the AngioJet for a thrombosed DIPS. Due to the patient's comorbid conditions, overlapping clinical features, and lack of appreciation of the hemolysis associated with the AngioJet system, the differential diagnosis of the patient's AKI was quite broad. Nephrologists should be aware of this complication when managing patients with AKI to direct therapy early and avoid unnecessary diagnostic and therapeutic interventions.

Acute kidney injury pathology and pathophysiology: a retrospective review

Acute kidney injury (AKI) is the clinical term used for decline or loss of renal function. It is associated with chronic kidney disease (CKD) and high morbidity and mortality. However, not all causes of AKI lead to severe consequences and some are reversible. The underlying pathology can be a guide for treatment and assessment of prognosis. The Kidney Disease: Improving Global Outcomes guidelines recommend that the cause of AKI should be identified if possible. Renal biopsy can distinguish specific AKI entities and assist in patient management. This review aims to show the pathology of AKI, including glomerular and tubular diseases.

Circulating FH Protects Kidneys From Tubular Injury During Systemic Hemolysis

Intravascular hemolysis of any cause can induce acute kidney injury (AKI). Hemolysis-derived product heme activates the innate immune complement system and contributes to renal damage. Therefore, we explored the role of the master complement regulator Factor H (FH) in the kidney's resistance to hemolysis-mediated AKI. Acute systemic hemolysis was induced in mice lacking liver expression of FH (hepatoFH-/-, ~20% residual FH) and in WT controls, by phenylhydrazine injection. The impaired complement regulation in hepatoFH-/- mice resulted in a delayed but aggravated phenotype of hemolysis-related kidney injuries. Plasma urea as well as markers for tubular (NGAL, Kim-1) and vascular aggression peaked at day 1 in WT mice and normalized at day 2, while they increased more in hepatoFH-/- compared to the WT and still persisted at day 4. These were accompanied by exacerbated tubular dilatation and the appearance of tubular casts in the kidneys of hemolytic hepatoFH-/- mice. Complement activation in hemolytic mice occurred in the circulation and C3b/iC3b was deposited in glomeruli in both strains. Both genotypes presented with positive staining of FH in the glomeruli, but hepatoFH-/- mice had reduced staining in the tubular compartment. Despite the clear phenotype of tubular injury, no complement activation was detected in the tubulointerstitium of the phenylhydrazin-injected mice irrespective of the genotype. Nevertheless, phenylhydrazin triggered overexpression of C5aR1 in tubules, predominantly in hepatoFH-/- mice. Moreover, C5b-9 was deposited only in the glomeruli of the hemolytic hepatoFH-/- mice. Therefore, we hypothesize that C5a, generated in the glomeruli, could be filtered into the tubulointerstitium to activate C5aR1 expressed by tubular cells injured by hemolysis-derived products and will aggravate the tissue injury. Plasma-derived FH is critical for the tubular protection, since pre-treatment of the hemolytic hepatoFH-/- mice with purified FH attenuated the tubular injury. Worsening of acute tubular necrosis in the hepatoFH-/- mice was trigger-dependent, as it was also observed in LPS-induced septic AKI model but not in chemotherapy-induced AKI upon cisplatin injection. In conclusion, plasma FH plays a key role in protecting the kidneys, especially the tubules, against hemolysis-mediated injury. Thus, FH-based molecules might be explored as promising therapeutic agents in a context of AKI.

Complement Inhibition Therapy and Dialytic Strategies in Paroxysmal Nocturnal Hemoglobinuria: The Nephrologist's Opinion

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare clonal disease that presents an estimated incidence of 1.3 cases per million per year, with a prevalence of 15.9 cases per million. It is characterized by hemolysis, bone marrow dysfunction with peripheral blood cytopenia, hypercoagulability, thrombosis, renal impairment and arterial and pulmonary hypertension. Hemolysis and subsequent hemosiderin accumulation in tubular epithelium cells induce tubular atrophy and interstitial fibrosis. The origin of PNH is the somatic mutation in the X-linked phosphatidylinositol glycan class A (PIG-A) gene located on Xp22: this condition leads to the production of clonal blood cells with a deficiency in those surface proteins that protect against the lytic action of the activated complement system. Despite the increased knowledge of this syndrome, therapies for PNH were still only experimental and symptomatic, until the introduction of the C5 complement blockade agent Eculizumab. A second generation of anti-complement agents is currently under investigation, representing future promising therapeutic strategies for patients affected by PNH. In the case of chronic hemolysis and renal iron deposition, a multidisciplinary approach should be considered to avoid or treat acute tubular injury or acute kidney injury (AKI). New promising perspectives derive from complement inhibitors and iron chelators, as well as more invasive treatments such as immunoadsorption or the use of dedicated hemodialysis filters in the presence of AKI.

Haptoglobin Therapeutics and Compartmentalization of Cell-Free Hemoglobin Toxicity

Hemolysis and accumulation of cell-free hemoglobin (Hb) in the circulation or in confined tissue compartments such as the subarachnoid space is an important driver of disease. Haptoglobin is the Hb binding and clearance protein in human plasma and an efficient antagonist of Hb toxicity resulting from physiological red blood cell turnover. However, endogenous concentrations of haptoglobin are insufficient to provide protection against Hb-driven disease processes in conditions such as sickle cell anemia, sepsis, transfusion reactions, medical-device associated hemolysis, or after a subarachnoid hemorrhage. As a result, there is increasing interest in developing haptoglobin therapeutics to target 'toxic' cell-free Hb exposures. Here, we discuss key concepts of Hb toxicity and provide a perspective on the use of haptoglobin as a therapeutic protein.

A practical approach to the pathology of renal intratubular casts

The identification and proper characterization of pathologic renal intratubular casts can be an arduous task, especially since they often admixed with non-pathologic casts, obfuscating debris and inflammation. The list of pathologic intratubular casts is long, and they can be easily missed or misdiagnosed without a thorough understanding of their pathophysiology and morphologic variety. Correct characterization of tubular casts is important since each cast type has a unique pathogenic mechanism, with specific treatment and prognostic implications. This review discusses the clinicopathologic characteristics of the six most common pathologic casts: light chain, hemoglobin, myoglobin, red cell, neutrophilic and bile casts. We also discuss hyaline and uromodulin casts, the commonly encountered "benign" cast types that share certain histologic features with pathologic casts. We limit the discussion to proteinaceous and cellular intratubular casts, with crystalline casts discussed in a separate review within the same journal issue. While not exhaustive, this review covers pathogenesis, clinical and prognostic significance, and a practical discussion of the histomorphologic spectrum of each cast type, along with commonly encountered pitfalls.

A guide to crystal-related and nano- or microparticle-related tissue responses

Crystals and nano- and microparticles form inside the human body from intrinsic proteins, minerals, or metabolites or enter the body as particulate matter from occupational and environmental sources. Associated tissue injuries and diseases mostly develop from cellular responses to such crystal deposits and include inflammation, cell necrosis, granuloma formation, tissue fibrosis, and stone-related obstruction of excretory organs. But how do crystals and nano- and microparticles trigger these biological processes? Which pathomechanisms are identical across different particle types, sizes, and shapes? In addition, which mechanisms are specific to the atomic or molecular structure of crystals or to specific sizes or shapes? Do specific cellular or molecular mechanisms qualify as target for therapeutic interventions? Here, we provide a guide to approach this diverse and multidisciplinary research domain. We give an overview about the clinical spectrum of crystallopathies, about shared and specific pathomechanisms as a conceptual overview before digging deeper into the specialty field of interest.

Labile Heme Aggravates Renal Inflammation and Complement Activation After Ischemia Reperfusion Injury

Background: Ischemia reperfusion injury (IRI) plays a major role in solid organ transplantation. The length of warm ischemia time is critical for the extent of tissue damage in renal IRI. In this experimental study we hypothesized that local release of labile heme in renal tissue is triggered by the duration of warm ischemia (15 vs. 45 min IRI) and mediates complement activation, cytokine release, and inflammation. Methods: To induce IRI, renal pedicle clamping was performed in male C57BL/6 mice for short (15 min) or prolonged (45 min) time periods. Two and 24 h after experimental ischemia tissue injury labile heme levels in the kidney were determined with an apo-horseradish peroxidase assay. Moreover, renal injury, cytokines, and C5a and C3a receptor (C5aR, C3aR) expression were determined by histology, immunohistochemistry and qPCR, respectively. In addition, in vitro studies stimulating bone marrow-derived macrophages with LPS and the combination of LPS and heme were performed and cytokine expression was measured. Results: Inflammation and local tissue injury correlated with the duration of warm ischemia time. Labile heme concentrations in renal tissue were significantly higher after prolonged (45 min) as compared to short (15 min) IRI. Notably, expression of the inducible heme-degrading enzyme heme oxygenase-1 (HO-1) was up-regulated in kidneys after prolonged, but not after short IRI. C5aR, the pro-inflammatory cytokines IL-6 and TNF-α as well as pERK were up-regulated after prolonged, but not after short ischemia times. Consecutively, neutrophil infiltration and up-regulation of pro-fibrotic cytokines such as CTGF and PAI were more pronounced in prolonged IRI in comparison to short IRI. In vitro stimulation of macrophages with LPS revealed that IL-6 expression was enhanced in the presence of heme. Finally, administration of the heme scavenger human serum albumin (HSA) reduced the expression of pro-inflammatory cytokines, C3a receptor and improved tubular function indicated by enhanced alpha 1 microglobulin (A1M) absorption after IRI. Conclusions: Our data show that prolonged duration of warm ischemia time increased labile heme levels in the kidney, which correlates with IRI-dependent inflammation and up-regulation of anaphylatoxin receptor expression.

Hemolysis Derived Products Toxicity and Endothelium: Model of the Second Hit

Vascular diseases are multifactorial, often requiring multiple challenges, or ‘hits’, for their initiation. Intra-vascular hemolysis illustrates well the multiple-hit theory where a first event lyses red blood cells, releasing hemolysis-derived products, in particular cell-free heme which is highly toxic for the endothelium. Physiologically, hemolysis derived-products are rapidly neutralized by numerous defense systems, including haptoglobin and hemopexin which scavenge hemoglobin and heme, respectively. Likewise, cellular defense mechanisms are involved, including heme-oxygenase 1 upregulation which metabolizes heme. However, in cases of intra-vascular hemolysis, those systems are overwhelmed. Heme exerts toxic effects by acting as a damage-associated molecular pattern and promoting, together with hemoglobin, nitric oxide scavenging and ROS production. In addition, it activates the complement and the coagulation systems. Together, these processes lead to endothelial cell injury which triggers pro-thrombotic and pro-inflammatory phenotypes. Moreover, among endothelial cells, glomerular ones display a particular susceptibility explained by a weaker capacity to counteract hemolysis injury. In this review, we illustrate the ‘multiple-hit’ theory through the example of intra-vascular hemolysis, with a particular focus on cell-free heme, and we advance hypotheses explaining the glomerular susceptibility observed in hemolytic diseases. Finally, we describe therapeutic options for reducing endothelial injury in hemolytic diseases.