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Acute kidney injury (AKI) in paediatric kidney transplant recipients is common. Infection including urinary tract infection (UTI) and rejection are the most common causes in children. Surgical complications often cause AKI early post-transplant, whereas BK polyomavirus nephropathy rarely occurs in the first month post-transplant. Understanding kidney physiology helps to appreciate the sensitivity of the allograft to AKI, more so than native kidneys. Although the cause of AKI is often multi-factorial, there may be an underlying process that is treatable. Eliciting the aetiology, in this regard, is of paramount importance. Pre-renal and post-renal causes of allograft dysfunction are important to distinguish from intrinsic kidney disease. Clinical information and examination of fluid balance, urine dipstick testing, blood tests, bladder and kidney transplant ultrasound, and kidney transplant biopsy remain vital assessment tools in narrowing the differential diagnosis. A careful prescribed and recreational drug history is always warranted as many drugs including supplements are nephrotoxic. Additional causes such as allograft rejection, recurrent disease, and calcineurin inhibitor toxicity need to be considered in cases of allograft dysfunction, which would not affect the native kidneys. Early detection and assessment of AKI is crucial in promoting recovery. Significant progress has been made in specific pathologies over the last 20 years, which has improved kidney allograft survival rates considerably. Research into identifying AKI biomarkers to assist early diagnosis, before the serum creatinine rises, is ongoing., Competing Interests: Declarations. Competing interest: The authors declare no competing interests., (© 2025. The Author(s).)

Background: The morbidity and mortality from AL amyloidosis has significantly improved with the development of novel treatments. Daratumumab is a highly effective treatment for AL amyloidosis, but end-stage kidney disease is a common complication of this condition. Kidney transplantation is the ideal form of renal replacement therapy but has historically been contraindicated in this group of patients. Methods: Given the improved survival and better treatments of both conditions, we argue that it is time to reconsider transplanting these patients. Results: We report our experience of transplanting four patients with AL amyloidosis who had achieved stable remission through treatment with daratumumab. Conclusions: We highlight the key challenges involved and discuss important clinical issues for patients receiving daratumumab, particularly the difficulties with interpreting the crossmatch in light of daratumumab and immunoglobulin therapy interference. We also discuss the complexities involved in balancing the risks of infection, relapse, rejection, and immunosuppression in such patients.

Background: Dent's disease type 1 (DD1) is a rare X-linked nephropathy caused by CLCN5 mutations, characterized by proximal tubule dysfunction, including low molecular weight proteinuria (LMWP), hypercalciuria, nephrolithiasis-nephrocalcinosis, progressive chronic kidney disease (CKD) and kidney failure (KF). Current management is symptomatic and does not prevent disease progression. Here we describe the contemporary DD1 picture across Europe to highlight its unmet needs., Methods: A physician-based anonymous international e-survey supported by several European nephrology networks/societies was conducted. Questions focused on DD1 clinical features, diagnostic procedure and mutation spectra., Results: A total of 207 DD1 male patients were reported; clinical data were available for 163 with confirmed CLCN5 mutations. Proteinuria was the most common manifestation (49.1%). During follow-up, all patients showed LMWP, 66.4% nephrocalcinosis, 44.4% hypercalciuria and 26.4% nephrolithiasis. After 5.5 years, ≈50% of patients presented with renal dysfunction, 20.7% developed CKD stage ≥3 and 11.1% developed KF. At the last visit, hypercalciuria was more frequent in paediatric patients than in adults (73.4% versus 19.0%). Conversely, nephrolithiasis, nephrocalcinosis and renal dysfunction were more prominent in adults. Furthermore, CKD progressed with age. Despite no clear phenotype/genotype correlation, decreased glomerular filtration rate was more frequent in subjects with CLCN5 mutations affecting the pore or CBS domains compared with those with early-stop mutations., Conclusions: Results from this large DD1 cohort confirm previous findings and provide new insights regarding age and genotype impact on CKD progression. Our data strongly support that DD1 should be considered in male patients with CKD, nephrocalcinosis/hypercalciuria and non-nephrotic proteinuria and provide additional support for new research opportunities., (© The Author(s) 2022. Published by Oxford University Press on behalf of the ERA.)

Introduction: Clinically distinguishing patients with the inherited salt-losing tubulopathies (SLTs), Gitelman or Bartter syndrome (GS or BS) from other causes of hypokalemia (LK) patients is difficult, and genotyping is costly. We decided to identify clinical characteristics that differentiate SLTs from LK., Methods: A total of 66 hypokalemic patients with possible SLTs were recruited to a prospective observational cohort study at the University College London Renal Tubular Clinic, London. All patients were genotyped for pathogenic variants in genes which cause SLTs; 39 patients had pathogenic variants in genes causing SLTs. We obtained similar data sets from cohorts in Taipei and Kobe, as follows: the combined data set comprised 419 patients; 291 had genetically confirmed SLT. London and Taipei data sets were combined to train machine learning (ML) algorithms, which were then tested on the Kobe data set., Results: Single biochemical variables (e.g., plasma renin) were significantly, but inconsistently, different between SLTs and LK in all cohorts. A decision table algorithm using serum bicarbonate and urinary sodium excretion (FE Na ) achieved a classification accuracy of 74%. This was superior to all the single biochemical variables identified previously., Conclusion: ML algorithms can differentiate true SLT in the context of a specialist clinic with some accuracy. However, based on routine biochemistry, the accuracy is insufficient to make genotyping redundant., (© 2022 International Society of Nephrology. Published by Elsevier Inc.)

Background: Small cohort studies have reported high parathyroid hormone (PTH) levels in patients with Bartter syndrome and lower serum phosphate levels have anecdotally been reported in patients with Gitelman syndrome. In this cross-sectional study, we assessed PTH and phosphate homeostasis in a large cohort of patients with salt-losing tubulopathies., Methods: Clinical and laboratory data of 589 patients with Bartter and Gitelman syndrome were provided by members of the European Rare Kidney Diseases Reference Network (ERKNet) and the European Society for Paediatric Nephrology (ESPN)., Results: A total of 285 patients with Bartter syndrome and 304 patients with Gitelman syndrome were included for analysis. Patients with Bartter syndrome type I and II had the highest median PTH level (7.5 pmol/L) and 56% had hyperparathyroidism (PTH >7.0 pmol/L). Serum calcium was slightly lower in Bartter syndrome type I and II patients with hyperparathyroidism (2.42 versus 2.49 mmol/L; P = .038) compared to those with normal PTH levels and correlated inversely with PTH (rs -0.253; P = .009). Serum phosphate and urinary phosphate excretion did not correlate with PTH. Overall, 22% of patients had low serum phosphate levels (phosphate-standard deviation score < -2), with the highest prevalence in patients with Bartter syndrome type III (32%). Serum phosphate correlated with tubular maximum reabsorption of phosphate/glomerular filtration rate (TmP/GFR) (rs 0.699; P < .001), suggesting renal phosphate wasting., Conclusions: Hyperparathyroidism is frequent in patients with Bartter syndrome type I and II. Low serum phosphate is observed in a significant number of patients with Bartter and Gitelman syndrome and appears associated with renal phosphate wasting., (© The Author(s) 2022. Published by Oxford University Press on behalf of ERA.)

A 53 year old female with a background of hypertension, hypothyroidism and Raynaud's was admitted with an acute ischaemic stroke and referred to the renal team after a routine urine dip revealed microscopic haematuria and nephrotic-range proteinuria. Blood tests revealed renal impairment, a monoclonal IgM kappa paraprotein, low complement C4 concentration and a positive rheumatoid factor. Active cryoglobulinaemia was suspected and testing demonstrated type II cryoglobulins secondary to the monoclonal IgM kappa paraprotein. Bone marrow biopsy was normal. Renal biopsy revealed cryoglobulinaemia associated membranoproliferative glomerulonephritis. Treatment with steroids and rituximab improved renal function and proteinuria. This case fits within the evolving spectrum of disorders now termed Monoclonal Gammopathy of Renal Significance and highlights the value of biopsying and treating these patients early.

A 61 year old male presented with a one-week history of abdominal pain and loose stools. He had recently received treatment for cellulitis with flucloxacillin. He was anuric on presentation requiring haemodialysis. His ultrasound scan showed patent vessels with no signs of obstruction. A kidney biopsy revealed tubulointerstitial nephritis, attributed to recent treatment with flucloxacillin. A week later he developed lower limb thromboembolic disease triggering further investigations. A FDG PET-CT scan revealed a large FDG-avid retroperitoneal mass causing non-dilated obstruction of both kidneys. Bilateral retrograde stents were inserted which resulted in a 1.6L diuresis and cessation of haemodialysis. Non-dilated obstruction should be considered in anuric AKI, particularly in the context of malignancy, and may require a therapeutic trial of decompression.

Competing Interests: I have read and understood BMJ policy on declaration of interests and declare no competing interests