Compensation of contralateral kidney function after living-donor kidney donation is well known, and many predictive factors have been proposed. However, no prediction model has been proposed. This study was performed to establish a tool with which to estimate the degree of compensation of the contralateral kidney after living-donor kidney donation. We retrospectively analyzed 133 living donors for renal transplantation in our institution. We defined a favorable compensation as a post-donation estimated glomerular filtration rate (eGFR) at 1 year (calculated by the Chronic Kidney Disease Epidemiology Collaboration equation) of > 60% of the pre-donation eGFR. We analyzed the living donors’ clinical characteristics and outcomes. The median (range) donor age was 59 (24–79) years, median (range) body mass index was 22.9 (16.8–32.7) kg/m2, and median (range) body surface area was 1.6 (1.3–2.0) m2. All donors were Japanese, and 73% of the donors were biologically related. The median (range) donor pre-donation eGFR was 108.7 (82–144) ml/min/1.73 m2, and the median (range) post-donation eGFR at 1 year was 86.9 (43–143) ml/min/1.73 m2. Eighty-six percent of donors had compensatory hypertrophy. In the univariate analysis, age, female sex, history of hypertension, body surface area, and pre-donation eGFR were significantly associated with hypertrophy (p < 0.05). In the multivariate analysis, age, female sex, history of hypertension, and ratio of the remnant kidney volume to body weight were significantly associated with hypertrophy (p < 0.05). Based on these results, we created a compensation prediction score (CPS). The median (range) CPS was 8.7 (1.1–17.4). Receiver operating characteristic analysis showed strong diagnostic accuracy for predicting favorable compensation (area under the curve, 0.958; 95% confidence interval, 0.925–0.991, p < 0.001). The optimal cut-off value of the CPS was 5.0 (sensitivity, 92.0%; specificity, 89.5%). The CPS had a strong positive correlation with the post-donation eGFR (R = 0.797, p < 0.001). The CPS might be useful tool with which to predict a favorable compensation of the contralateral kidney and remnant kidney function. If the CPS is low, careful management and follow-up might be necessary. Further investigations are needed to validate these findings in larger populations.

Increased water intake is recommended for kidney transplant recipients; however, its efficacy remains controversial. We hypothesized that pre-existing histological findings of the allograft might modulate the impact of water intake. We retrospectively analyzed 167 adults with living-donor kidney transplants (April 2011–May 2020; median observation period, 77 months) whose baseline biopsy data were available. We compared the chronic-change group (n = 38) with the control group (n = 129) to assess the impact of self-reported daily water intake on the estimated glomerular filtration rate (eGFR). The range distribution of water intake was as follows: − 1000 ml (n = 4), 1000–1500 ml (n = 23), 1500–2000 ml (n = 64), 2000–2500 ml (n = 57), 2500–3000 ml (n = 16), and 3000 − ml (n = 3). Donor age was significantly higher in the chronic-change group. In the control group, the ΔeGFR/year increase was correlated with water intake. However, the increase in the water intake of the chronic-change group significantly decreased ΔeGFR/year (1000–1500 ml: + 1.95 ml/min/1.73 m² and > 2000 ml: − 1.92 ml/min/1.73 m², p = 0.014). This study suggested a potential influence of increased water intake on recipients with marginal grafts in living donor kidney transplantation.

TAFRO (Thrombocytopenia, Anasarca, Fever and/or elevated C-reactive protein, Renal dysfunction or Reticulin fibrosis, and Organomegaly) syndrome is a unique systemic inflammatory disease, which has recently been proposed from Japan. We report a case showing TAFRO symptoms, the patient’s condition of which allowed histopathological examinations of several biopsy tissues including the kidney. A 37-year-old man was admitted to our hospital for evaluation of fever of unknown origin, pleural effusion and ascites, renal dysfunction, and lymphadenopathy. Serum IL-6 and VEGF were elevated. Histopathologic findings of the lymph node resembled those of mixed type Castleman disease. The bone marrow biopsy specimen revealed normocellular marrow with a mildly increased number of megakaryocytes, but without obvious fibrosis. The renal biopsy material showed glomerular microangiopathy with double contour of the capillary loops and mesangiolysis. In immunohistochemistry, VEGF was retained in podocytes, whereas IL-6 expression was not limited to the specific sites. Glomerular microangiopathy is regarded as a crucial change in TAFRO syndrome, which should be studied further with regard to VEGF and IL-6.