Renal transplants increase in size and function in keeping with compensatory renal hypertrophy

AIM

To evaluate changes in allograft kidney length in renal transplant recipients and the relationship with estimated glomerular filtration rate (eGFR).

METHODS

This single-centre retrospective study of renal transplant recipients was conducted at Flinders Medical Centre (FMC) from January 2007 to June 2020. Donor and recipient details, renal allograft length from transplant ultrasounds at 0, 1, 3, 6 and 12 months were collected. The association between compensatory renal hypertrophy (CRH) and eGFR and its magnitude was analysed using multivariate multilevel mixed-effects linear regression models.

RESULTS

A total of 183 renal transplant recipients were studied. 100 of 175 recipients (62.9%) demonstrated an increase in renal length defined as any increase in maximal longitudinal diameter on serial ultrasounds. Twenty-three recipients (13.1%) had no change in transplant length and 42 recipients (24%) had a decrease in length. The mean increase in kidney length over the first 12 months was 0.57 cm. Ninety of 156 (57.7%) recipients with a renal ultrasound within a month post-transplant demonstrated a mean increase kidney length of 0.3 cm. Multivariate analysis demonstrated that eGFR increased by 2.5 mL/min/1.73 m2 (95% CI 0.72- 4.4; p = .006) with every 1 cm increase in kidney length. Absolute changes in kidney length did not demonstrate any statistically significant correlation with eGFR in both complete case and multiple imputation analysis.

CONCLUSION

An increase in transplant kidney length is common in renal transplant recipients and is associated with enhanced eGFR. However, further studies need to be performed to study the association of absolute change in kidney length and eGFR.

Combining genotype with height-adjusted kidney length predicts rapid progression of ADPKD

INTRODUCTION

Our main objective was to identify baseline prognostic factors predictive of rapid disease progression in a large unselected clinical ADPKD cohort.

METHODS

A cross-sectional analysis was performed in 618 consecutive ADPKD patients assessed and followed-up for over a decade. 123 patients (19.9%) had reached kidney failure by the study date. Data was available for the following: baseline eGFR (n= 501), genotype (n=549), baseline ultrasound mean kidney length (MKL, n=424), height adjusted baseline MKL (htMKL, n=377). Rapid disease progression was defined as an annualised eGFR decline (∆eGFR) of >2.5ml/min/year by linear regression over 5 years (n=158). Patients were further divided into slow, rapid and very rapid ∆eGFR classes for analysis. Genotyped patients were classified into several categories: PKD1 (T, truncating or NT, non-truncating), PKD2, other genes (non-PKD1 or PKD2), NMD (no mutation detected) or variants of uncertain significance (VUS).

RESULTS

A PKD1-T genotype had the strongest influence on the probability of reduced baseline kidney function by age. A multivariate logistic regression model identified PKD1-T genotype and htMKL (>9.5 cm/m) as independent predictors for rapid disease progression. The combination of both factors increased the positive predictive value (PPV) for rapid disease progression over age 40 years and of reaching kidney failure by age 60 years to 100%. Exploratory analysis in a subgroup with available total kidney volumes (TKV) showed higher PPV (100% v 80%) and NPV (42% v 33%) in predicting rapid disease progression compared to the Mayo Imaging Classification (1C-E).

CONCLUSION

Real-world longitudinal data confirms the importance of genotype and kidney length as independent variables determining ∆eGFR. Individuals with the highest risk of rapid disease progression can be positively selected for treatment based on this combination.

The Clinical Utility of Kidney Cortical Thickness in assessing severity of CKD in Low Income Setting

BACKGROUND

Renal Ultrasound Scan (RUS) is known to have an important role in assessing kidney function in healthy people and people with Chronic Kidney Disease (CKD) with the kidney length (KL) being the most commonly used measure. The Glomerular Filtration Rate (GFR) is the gold standard in kidney function assessment and its strength of correlation with a RUS measure is used in ascertaining the reliability of that RUS measure.

OBJECTIVES

To compare the strength of correlations between the GFR and RUS measures like KL and cortical thickness (CT) in healthy people and people with CKD.

METHODS

One hundred and forty study participants who had kidney ultrasound scan were studied. Creatinine based GFR was determined and linear correlation coefficients (r) were used to determine the relationship between the GFR and RUS measures.

RESULTS

Seventy CKD cohorts with stage 2-4 disease and 70 healthy volunteers (each with 35 males and 35 females) took part. The total mean eGFR, KL and CT for the study participants were 70.5 ± 12.5ml/min, 10.0 ± 3.1cm, and 8.6 ± 2.7mm respectively. There was a progressive decline in eGFR and renal CT as CKD worsened down the stages. The mean eGFR, KL and CT of the CKD cohorts were 44.7 + 3.6 ml/min, 9.1 + 3.3 cm and 7.4 + 2.4 mm respectively. Among the CKD cohorts, the eGFR was highest in CGN and, the KL and CT were highest in obstructive uropathy. The GFR, was positively correlated with KL and CT, the strength of association being more with the CT. The mean age and GFR independently predicted the kidney cortical thickness.

CONCLUSION

Kidney sizes were smaller in females, with aging and with declining kidney function. The CT being more positively correlated with GFR than the KL, is a more reliable RUS measure in assessing kidney function.

Kidney length in healthy members of Balkan endemic nephropathy families

BACKGROUND

Kidney size may differ between healthy members of Balkan endemic nephropathy (BEN) and non-BEN families. The present study was designed to elucidate this, in comparison with values for BEN patients.

METHODS

A total of 71 BEN patients (34 males, 64.4 ± 12.0 years), 74 healthy BEN family members (39 males, 49.1 ± 12.2 years), and 59 non-BEN family members (19 males, 49.2 ± 12.3 years) were involved. We measured the longest craniocaudal length and minimal parenchymal thickness on each kidney of all examined subjects using ultrasound.

RESULTS

No significant difference was found between the kidney length of healthy subjects from BEN (11.0 ± 0.8 cm) and non-BEN families (10.9 ± 0.8 cm), but kidneys were significantly longer than in BEN patients (9.9 ± 1.3 cm). Minimal parenchymal thickness was similar in all three groups. When subjects from each group were divided according to estimated glomerular filtration rate (eGFR), kidney length of the healthy groups was significantly longer than in BEN patients both in stage 1 (p =0.039) and stage 2 (p =0.044) of chronic kidney disease. The parental history of BEN was not associated with kidney dimensions, eGFR, or urinary excretion of albumin and alpha1-microglobulin.

CONCLUSION

Kidneys of BEN patients were significantly shorter than in healthy members of both BEN and non-BEN families, but no difference was found in kidney length and parenchymal thickness between healthy members of BEN and non-BEN families. No significant association was found between parental history of BEN and kidney size and function either in BEN patients or in healthy members from BEN families. Hippokratia 2015; 19 (4): 304-308.

Can renal sonography be a reliable diagnostic tool in the assessment of chronic kidney disease?

OBJECTIVES

Kidney size has been found to be correlated with anthropometric features and kidney function. Therefore, we postulate that if the conventionally measured renal sonographic parameters (pole-to-pole length, width, and parenchymal thickness) are taken according to standardized rules and corrected for body height, their association with kidney function could be strengthened, thus helping validate renal sonographic information for a better assessment of chronic kidney disease (CKD) status.

METHODS

This cross-sectional study included 72 stable adult patients with stage 1 to 4 CKD. Sonographic parameters were obtained from both kidneys and averaged, and the measurements obtained were further corrected for patients' body height. The glomerular filtration rate (GFR) was estimated by the Chronic Kidney Disease Epidemiology Collaboration equation.

RESULTS

Parenchymal thickness and renal length showed the highest correlation level with the GFR. This significant correlation, however, was greatly ameliorated by the correction for patients' body height (r = 0.537; P < .001; r = 0.510; P < .001, respectively). Of note, the product of these two parameters corrected for body height showed the best degree of correlation with the GFR (r = 0.560; P < .001), as confirmed by analysis of variance after subdivision of the population into CKD stage groups according to the GFR. Receiver operating characteristic curve analysis for discrimination of a GFR of less than 60 mL/min indentified the combined parameter as the one with the highest area under the curve (0.78; 95% confidence interval, 0.66-0.89), followed renal length corrected for height (area under the curve, 0.77; 95% confidence interval, 0.66-0.88).

CONCLUSIONS

Correction of renal sonographic parameters for body height strengthens the degree of the correlation of renal sonography with the GFR. The improved correlation with the GFR makes renal sonography a reliable tool for a more complete assessment of patients with CKD.

Need for a nomogram of renal sizes in the Indian population- findings from a single centre sonographic study

BACKGROUND & OBJECTIVES

Renal size is an important parameter used in the diagnosis and follow up of renal diseases. However, while making decisions, clinicians must be aware of the dependence of these dimensions on the ethnicity of the individual, independent of anthropometric indices. There is no established nomogram for renal sizes in the Indian population. The aim of this study was to assess the applicability of oft-quoted ranges of normal renal sizes in our population.

METHODS

Renal dimensions including length, width and parenchymal thickness were sonographically measured in 140 individuals with no renal disease. Analysis was done for differences due to age, gender and laterality. The correlation of renal dimensions with anthropometric parameters like weight, height, body mass index (BMI) and body surface area (BSA) was analyzed.

RESULTS

The means of length, width and parenchymal thickness of all 280 kidneys of 140 patients were 9.65 ± 0.63, 4.5 ± 0.42 and 2.04 ± 0.2 cm, respectively. There was a significant difference in parenchymal thickness between the right and left kidneys, while there was no significant right-left difference in length or width. Gender-wise analysis showed significant differences between male and female renal breadths but not length and parenchymal thickness. Age group-wise analysis showed significant decrease in renal length and parenchymal thickness beyond the seventh decade. There was a moderate positive correlation of bilateral renal length with body weight and BSA, and a weak positive correlation with body height and BMI.

INTERPRETATION & CONCLUSIONS

Renal sizes in our population are in contrast to commonly quoted normal values in literature. Conclusions about renal sizes need to be made with reference to nomograms and should not be based upon data from other populations. We also present formulae whereby to derive renal sizes from anthropometric indices in our population.