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The glomerular filtration rate (GFR) is a key indicator of kidney function, yet no ideal method exists for its direct measurement. This two-part review examines the development of GFR measurement techniques, focusing on their physiologic basis, performance characteristics, and clinical applications. Part 1 reviews endogenous markers used to estimate GFR (eGFR), including creatinine- and cystatin C-based equations, with emphasis on their derivation, limitations, and clinical use. Part 2 addresses exogenous filtration markers and measured GFR (mGFR) methodologies, highlighting comparative performance and specific uses. Emphasis is placed on innovation in marker development, highlighting the need for continued development and standardization to enhance accuracy and clinical utility.

Measured glomerular filtration rate (mGFR) remains the reference standard for precise assessment of kidney function when estimated approaches are insufficient. This second part of a two-part series reviews exogenous filtration markers used to obtain mGFR, including inulin, iothalamate, iohexol, and radionuclide-based tracers, with emphasis on their physiologic handling, analytic methods, accuracy, and clinical applicability. The review further examines emerging fluorescent and near-infrared tracers coupled with transcutaneous monitoring technologies that enable rapid or continuous assessment of GFR. Together, these approaches illustrate the evolution of mGFR measurement toward methods that are more practical, scalable, and responsive to dynamic changes in kidney function, while maintaining analytical accuracy.

Key Points Baseline kidney function and chronic structural injury strongly predicted both renal recovery and long-term clinical outcomes. Tubulointerstitial nephritis was the predominant lesion in Sjögren syndrome with renal involvement. Early detection and management of renal involvement in Sjögren syndrome are critical to preventing irreversible kidney damage. Background Renal involvement in primary Sjögren syndrome (SS) is uncommon but clinically consequential. Previous studies have been limited by small samples and incomplete biopsy data. We evaluated a large biopsy-confirmed cohort to characterize clinicopathologic features of SS with renal involvement and identify predictors of renal recovery and long-term outcomes. Methods We retrospectively identified adults with SS and kidney biopsy at Mayo Clinic (2012–2025). Clinical, laboratory, and histologic data were extracted. Predictors of complete renal recovery within 6 months, defined as serum creatinine (sCr) returning to within 25% of baseline or <1.4 mg/dl if baseline was unknown, were evaluated using logistic regression. Cox regression assessed long-term risk of a composite end point: newly developed or progressive CKD, ESKD, or all-cause mortality. Results Fifty-six patients were included (median age 57 years; 91% female). Extraglandular manifestations occurred in 76% and baseline CKD in 65%. The median sCr at baseline and biopsy was 1.3 and 1.6 mg/dl, respectively. Anti-Sjogren's syndrome antigen A, often linked with Ro ribonucleoprotein was positive in 80%. Low C3 occurred in 14% and low C4 in 25%. Tubulointerstitial nephritis was the predominant lesion (71%). Moderate/severe interstitial fibrosis/tubular atrophy and arteriosclerosis were present in 36% and 41%, respectively. Immunosuppressive therapy was applied in 84%. Complete recovery occurred in 67%. Over a median 3.9 years (interquartile range, 1.4–7.2), 43% reached the composite end point. Baseline sCr ≥2 mg/dl, 24-hour proteinuria ≥1 g, and presence of segmental glomerulosclerosis were associated with lower odds of recovery (odds ratio=0.16, 0.13 and 0.11, P = 0.02, 0.001 and 0.008, respectively) and higher long-term risk (hazard ratio=4.51, 2.92 and 3.52; P = 0.002, 0.01 and 0.02, respectively). Moderate/severe arteriosclerosis also increased long-term risk (hazard ratio=2.56; P = 0.03). Conclusions In biopsy-confirmed SS-related renal involvement, the severity of kidney dysfunction and the extent of chronic glomerular and vascular injury strongly predict renal prognosis. Early detection and targeted management of high-risk features may improve long-term renal outcomes.

Key Points In autosomal dominant polycystic kidney disease, there is a linear relationship between the log-transformed total kidney volume and eGFR. There is a predictable change in the rate of eGFR decline with reduction in kidney growth rate. This framework can be used to determine treatment effect to support accelerated approval of drugs for polycystic kidney disease. Background Total kidney volume (TKV) is accepted by the US Food and Drug Administration as a surrogate end point that is reasonably likely to predict clinical benefit in autosomal dominant polycystic kidney disease and the most commonly used response biomarker for proof-of-concept intervention trials. However, the magnitude of treatment effect on TKV that would be predictive of a meaningful improvement in a clinical outcome, such as eGFR, is unknown. Inference of this from observational studies has previously been approached by examining interindividual variance in the relationship between TKV and GFR slopes over time. Methods We developed a novel approach to modeling the intraindividual relationship between TKV and eGFR. Patients from the Consortium for Radiologic Imaging Studies of Polycystic Kidney Disease and Halt Progression of Polycystic Kidney Disease Study A dataset were stratified by Mayo Imaging Class (MIC). Linear mixed models were fitted to eGFR with a fixed effect of log(TKV) and random intercepts, and the average slope within each MIC was estimated. Results We found that within each MIC, there is a consistent, linear relationship between log(TKV) and eGFR. The model predicts that within classes 1C–1E, for each 1% point per year reduction in TKV growth rate, the rate of eGFR decline would be reduced by 0.40–0.52 ml/min per 1.73 m 2 per year. Conclusions We have developed a new model that provides a framework for defining the magnitude of treatment effect on TKV that would support accelerated approval of a drug for autosomal dominant polycystic kidney disease. Podcast This article contains a podcast at https://dts.podtrac.com/redirect.mp3/www.asn-online.org/media/podcast/CJASN/2026_05_18_CJASNMay.21.5.51820.mp3

Radiated chronic scalp wounds with exposed bone present a significant reconstructive challenge, particularly when prior attempts have failed or when further surgery is contraindicated due to patient comorbidities or preference. We retrospectively reviewed 10 patients (2014–2024) with radiated chronic scalp wounds with exposed bone who have either failed prior reconstruction, could not medically tolerate anesthesia, or declined surgery. Patients performed daily cleansing with soap and water followed by application of Aquaphor and Silvadene. Treatment duration ranged from 1 to 73 months (mean: 29.4 mo). The area of exposed bone decreased in 6 patients (60%), remained stable in 1 (10%), and increased in 3 (30%). Three of 7 patients with wound improvement (30%) achieved complete healing. Two of 3 patients with wound progression deceased of unrelated causes. To our knowledge, no major complications occurred. These findings support wound care as a safe, and often effective, treatment when larger reconstruction is not feasible.

OBJECTIVE: To evaluate the effect of joint preparation and patient factors on outcomes and complications in patients treated acutely with hindfoot fusion nails for ankle and pilon fractures. METHODS: Design: Retrospective chart review. Setting: Thirteen US trauma centers and 2 UK trauma centers. Patient Selection Criteria: Ankle and pilon fractures (AO-OTA types A-C) from 2010 to 2020 acutely treated definitively with hindfoot fusion nail were reviewed. Patients at least 18 years old and with minimum 6 months follow-up or earlier diagnosis of complication were included. Exclusion criteria included nonambulatory at baseline, prior internal fixation that failed and underwent revision, and prior tibiotalar or subtalar arthrodesis. Outcome Measurements and Comparisons: The primary outcome was final postoperative ambulatory status. Secondary outcomes were infectious and fracture-related complications. RESULTS: One hundred forty-nine patients (75 men; 74 women; age 20–99; median 63 years) were treated for ankle (104) or pilon (45; 8A, 13B, 24C) fractures. Eighty-five patients (44%) had open fractures and 55 (37%) had diabetes. Thirty-six patients (24%) had joint preparation at the time of surgery. Forty-five (30%) were made weight bearing as tolerated postoperatively; the median time to mobilize was 1.5 days (0–210) and to full weight bearing was 35 days (0–1462). Fifty-seven patients (85%) returned to their preinjury ambulatory status, which was not affected by joint preparation (50% vs. 59%, P = 0.327). Joint preparation led to higher articular fusion rates (94% vs. 24%; P = 0.001) and fewer hardware removals (19% vs. 42%, P = 0.013), but trended toward a higher fracture nonunion rate (19% vs. 8%, P = 0.053). Forty-five patients (30%) had infectious complications, 60 (40%) had a fracture-related complication, and 67 (45%) had additional procedures. Open fractures did not lead to any differences in superficial or deep infection. Insulin-dependent diabetes was associated with higher rates of infectious complications (31% vs. 15%, P = 0.028) and amputation (17% vs. 4%, P = 0.029). CONCLUSIONS: Hindfoot fusion nails for acute ankle and pilon injuries had high complication rates. More complications occurred in patients with insulin-dependent diabetes. While 95% regained ambulation, only 57% returned to preoperative status. Joint preparation led to higher rates of articular fusion (94% vs. 24%, P < 0.001) but not fracture union (81% vs. 66%, P = 0.106). LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Background/Objectives: Precocious puberty (PP), defined as the onset of secondary sexual characteristics before 8 years in girls and 9 years in boys, is associated with psychosocial distress, compromised adult height, and long-term metabolic risk. Early identification remains challenging, as current diagnostic approaches are largely reactive and rely on invasive or resource-intensive testing. This narrative review examines how artificial intelligence (AI) can support earlier risk prediction and detection of PP through integration of clinical, hormonal, imaging, lifestyle, and environmental data. Methods: A narrative literature review was conducted using PubMed, Scopus, Embase, Web of Science, and Google Scholar to identify relevant studies published between 2005 and 2025. Eligible studies included original research and high-quality reviews that examined AI-based approaches, such as machine learning and deep learning, in pediatric endocrinology, particularly for the prediction or diagnosis of central or peripheral precocious puberty. Studies incorporating clinical, hormonal, radiological, lifestyle, environmental, or multi-omics data relevant to AI modeling were included. Results: AI models, including XGBoost, random forest, convolutional neural networks, and regression-based approaches, have demonstrated potential utility in predicting central precocious puberty using hormonal, imaging, and growth data. Reported applications include automated bone age assessment, lifestyle and dietary risk stratification, and exploratory use of wearable-derived behavioral data. However, progress is limited by small pediatric datasets, population bias, limited interpretability, and unresolved ethical challenges related to privacy, consent, and equity. Conclusions: Artificial intelligence represents a promising decision-support approach for earlier, non-invasive, and individualized risk assessment in precocious puberty. Future progress will depend on the integration of longitudinal, multimodal data, the development of ethical models, and interdisciplinary collaboration among pediatric endocrinologists, data scientists, and public health stakeholders.