A recent Nephrology digest,
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Study Type: Prospective multicentre cohort study

Key Question: How does self-esteem change over 5 years following living kidney donation, and what factors influence this?

Key Findings:

• 98.6% of donors had normal-to-high self-esteem pre-donation; only 2–4% reported low self-esteem (RSES <15) during follow-up.
• Mean self-esteem declined slightly post-donation (<1 point), statistically significant but not clinically meaningful; donors with lower baseline scores (≤20) showed a ~2-point improvement post-donation (P<0.001).
• Higher pre-donation depressive symptoms predicted lower self-esteem at 3 months (P=0.006); increases in self-esteem correlated with concurrent reductions in depression and anxiety symptoms (P<0.001).

Clinical Relevance: Reassures UK transplant teams counselling potential living donors that donation is not associated with clinically significant psychological harm, and highlights depressive symptoms pre-donation as a factor warranting closer psychological follow-up.

Limitations: The study did not assess whether recipient graft failure or death affected donor self-esteem, limiting generalisability to donors facing adverse recipient outcomes.

Study Type: Retrospective single-centre cohort study

Key Question: What factors predict time to prescription increment in incremental PD, and is this approach safe in terms of modality transfer and mortality?

Key Findings:

• Among 527 incident PD patients, 64% (95% CI 60–69%) remained on their starting regimen at 1 year; 36% (95% CI 31–41%) had not incremented by 2 years.
• Shorter time to increment was associated with younger age (HR 0.92 per decade), male sex (HR 1.67), and lower serum albumin (HR 0.96 per unit).
• Haemodialysis transfer was linked to younger age and diabetes; mortality was low (0.11 events/person-year), supporting safety of incremental prescribing.

Clinical Relevance: Provides UK-derived real-world evidence supporting incremental PD as a safe, quality-of-life-preserving strategy, and offers a prototype clinical score to aid shared decision-making in NHS renal units adopting individualised PD prescribing.

Limitations: Single-centre retrospective design limits generalisability, and the proposed clinical score requires external validation before clinical use.

Study Type: Prospective cohort study with proteomics-based mediation analysis and bidirectional two-sample Mendelian randomization

Key Question: Is plasma GDF-15 associated with incident CKD, and is this relationship causal?

Key Findings:

• In 31,965 UK Biobank participants without CKD, highest GDF-15 quartile was associated with markedly increased CKD risk (HR 1.87, 95% CI 1.56–2.26 vs lowest quartile; P-trend <0.001), with similar findings for eGFR-based CKD.
• Mediation/protein-protein interaction analysis implicated TNF receptor signalling, extracellular matrix organisation, and immune cell chemotaxis pathways linking GDF-15 to kidney injury.
• MR analysis showed genetically predicted higher GDF-15 was associated with *higher* eGFR (IVW β=0.003, 95% CI 0.001–0.004), while higher genetically predicted eGFR lowered GDF-15 (IVW β=-1.238, 95% CI -1.591 to -0.886), suggesting GDF-15 elevation may be reactive/compensatory rather than causally nephrotoxic.

Clinical Relevance: GDF-15 shows promise as a prognostic biomarker for CKD risk stratification in UK populations, though genetic evidence suggests it may reflect rather than drive kidney dysfunction, cautioning against its use as a therapeutic target without further mechanistic clarification.

Limitations: Observational associations may be confounded by reverse causation or residual confounding, and MR findings (directionally opposite to observational data) highlight uncertainty regarding true causal pathways.

Study Type: Retrospective matched cohort study

Key Question: Does GLP-1RA use in patients newly starting in-center haemodialysis reduce hospitalisation and mortality risk?

Key Findings:

• Among 2,492 incident ICHD patients prescribed a GLP-1RA within 30 days of dialysis initiation, matched 1:1 to non-users, GLP-1RA use was associated with a 9% lower hospitalisation rate (IRR 0.91, 95% CI 0.87–0.96).
• GLP-1RA use was also associated with a 17% lower mortality rate (IRR 0.83, 95% CI 0.73–0.95).
• GLP-1RA users had higher rates of diabetes (98% vs 73%) and higher BMI (33 vs 30 kg/m²), reflecting confounding by indication despite matching/adjustment.

Clinical Relevance: These findings suggest potential benefit of continuing or initiating GLP-1RAs in incident ESKD/haemodialysis patients, an area with no dedicated RCT evidence (FLOW excluded ESKD), relevant to UK renal units managing increasing numbers of diabetic dialysis patients on GLP-1RAs.

Limitations: Observational design with residual confounding by indication (particularly diabetes prevalence and obesity) limits causal inference despite matching and adjustment.

Study Type: Pooled cohort analysis (CRIC and KNOW-CKD studies)

Key Question: Does urine protein-to-creatinine ratio (UPCR) predict kidney function decline and time to kidney failure in patients with advanced CKD (eGFR 15–45)?

Key Findings:

• Among 2,727 participants (median follow-up 4.9 years), 54% progressed to ≥50% eGFR decline or KRT; risk rose steeply with baseline UPCR, from HR 2.08 (0.5–1.0 g/gCr) to HR 6.32 (≥3.0 g/gCr) versus UPCR <0.5.
• Time-updated UPCR showed stronger associations (HR up to 12.88 for ≥3.0 g/gCr), and eGFR decline accelerated correspondingly (-0.87 to -5.45 mL/min/1.73m²/year).
• Projected time to reach kidney failure threshold (eGFR 10) shortened progressively from 28.7 years (UPCR <0.5) to 3.8 years (UPCR ≥3.0).

Clinical Relevance: UPCR—a cheap, widely available test in NHS primary and secondary care—provides robust risk stratification for CKD progression, supporting its use in prioritising nephrology follow-up, RRT planning, and CKD-modifying therapy initiation (e.g., SGLT2 inhibitors) in advanced CKD.

Limitations: Observational design with proteinuria as a time-updated exposure limits causal inference and may reflect residual confounding by treatment response or unmeasured comorbidities.

Study Type: Prospective multicenter cohort study

Key Question: Does visit-to-visit systolic blood pressure variability (BPV) independently predict ischemic stroke risk in patients on maintenance hemodialysis?

Key Findings:

• In 1,136 hemodialysis patients followed for a median 54 months, 144 developed ischemic stroke; higher systolic BPV (per 10% increase in coefficient of variation) was independently associated with stroke risk (sHR 1.74, 95% CI 1.10–2.76, P=0.02).
• Subtype analysis showed systolic BPV was significantly associated with large artery atherosclerosis stroke, with a weaker, attenuated association for small vessel occlusion after extended adjustment.
• Diastolic BPV showed no significant association after multivariable adjustment.

Clinical Relevance: Pre-dialysis systolic BPV, derived from routinely collected readings, may offer UK renal units a practical, low-cost marker to identify hemodialysis patients at elevated cerebrovascular risk warranting closer monitoring or intervention.

Limitations: Observational design precludes causal inference, and residual confounding (e.g., unmeasured vascular stiffness or medication adherence) may explain part of the association.

Study Type: Preclinical mechanistic study (mouse model, genetic/molecular analysis)

Key Question: Does ciliary ARL13B, via its GEF activity toward ARL3, drive Pkd1-dependent cyst formation in the kidney?

Key Findings:

• Removing ciliary ARL13B (Arl13bV358A) or disrupting its ARL3-GEF activity (Arl13bR79Q) suppressed cyst formation in Pkd1-deficient mice, with reduced kidney size, cystic index, and blood urea nitrogen.
• Both mutations reduced markers of fibrosis (α-smooth muscle actin, picrosirius staining), kidney injury (SOX9), and Wnt pathway activation (β-catenin, cyclin D1).
• Findings localise the cilia-dependent cyst activation (CDCA) pathway mechanism specifically to ciliary ARL13B's GEF function.

Clinical Relevance: Identifies ARL13B's GEF activity as a novel, targetable node in the cilia-dependent cystogenesis pathway underlying ADPKD, the leading inherited cause of kidney failure in UK renal services, potentially informing future disease-modifying therapies beyond tolvaptan.

Limitations: Findings are from a mouse model and require validation in human ADPKD tissue/cell systems before therapeutic translation.

Study Type: Basic/translational research (murine experimental model study)

Key Question: Does renin expression within renin-lineage cells influence their behaviour and disease severity in experimental crescentic glomerulonephritis?

Key Findings:

• Renin-knockout (RenKO) mice showed markedly worse crescentic GN by day 21: 3-fold increase in albuminuria, 50% more crescent formation, and 15% greater podocyte loss versus wild-type.
• Renin-deficient renin-lineage cells showed reduced glomerular migration, decreased mesangial marker colocalisation, and single-cell RNA-seq revealed an interferon-stimulated, anti-migratory transcriptional phenotype.
• Diphtheria toxin-mediated ablation of renin-lineage cells reduced macrophage infiltration but did not significantly alter overall disease severity.

Clinical Relevance: These findings suggest renin itself (not just downstream angiotensin signalling) may have a protective, reparative role in crescentic GN, raising caution about indiscriminate renin-angiotensin system blockade timing in acute severe glomerular injury and highlighting renin-lineage cell plasticity as a potential future therapeutic target.

Limitations: Findings are derived solely from a murine model and require validation in human crescentic GN before clinical translation.