European Journal of Cardiovascular Medicine

Chronic Kidney Disease (CKD) is a significant health problem worldwide, with a profound impact on patients' quality of life. The disease burden is substantial, with a high number of individuals affected and considerable medical expenses. Globally, CKD ranks as the 12th leading cause of mortality and the 17th leading cause of disability 1. Patients with CKD are more likely to die from cardiovascular disease than end-stage renal disease (ESRD) 2 . In India, the prevalence of CKD is approximately 800 per million population 3. Diabetic nephropathy is the most common etiology of CKD 4.

CKD is characterized by a progressive loss of kidney structure and function over months, with or without a reduced glomerular filtration rate (GFR). Diagnosis and monitoring of CKD typically involve changes in renal function tests in blood and urine or radiological investigations 5. CKD is detected by albuminuria and a decreased estimated glomerular filtration rate (eGFR) to less than 60 ml/min per 1.73 m² for 3 months or more 6. The most common causes of CKD are diabetes mellitus, hypertension, polycystic kidney disease, and other causes of renal scarring, such as infections 7.

Chronic renal inflammation, often present in renal diseases, can lead to renal failure if not properly managed 8. Most renal disorders can be prevented before progressing to renal failure, where dialysis or kidney transplantation may eventually be needed. CKD and cardiovascular complications are interrelated 9. However, individuals with CKD who develop cardiovascular problems often receive inadequate and improper diagnosis and treatment10. CKD also causes mineral and bone disorders and anemia, contributing to morbidity and shorter life span with increased cardiovascular mortality.

The serum creatinine level is a commonly used endogenous serum marker to estimate GFR (eGFR). CKD is graded according to eGFR, calculated using formulas like the Modification of Diet in Renal Disease (MDRD) equation and CKD-EPI 11. Ultrasound (USG) is a non-invasive, simple, and cost-effective method that can assess various renal parameters, including renal size, renal echogenicity, and cortical thickness 12,13. Renal length is reported to decrease with CKD progression and has been widely used as a predictor of CKD14. Other parameters, such as renal cortical thickness (RCT) and renal echogenicity, are also used in CKD diagnosis. RCT declines, and renal echogenicity increases with disease progression15,16. Changes in RCT correlate well with decreased kidney function in CKD patients 17. Increased cortical echogenicity is a marker of renal disease that correlates with the severity of interstitial histological changes in renal parenchymal disease 17. If renal cortical echogenicity is greater than liver echogenicity, it is considered abnormal and indicates renal disease. Cortical echogenicity can be graded and correlated with eGFR 18. Earlier Reports suggest that it is better than renal length as an indicator of kidney function in chronic kidney disease.19

Despite renal length not being specific, it is still used to assess CKD. In most clinical settings, renal cortical thickness or renal cortical echogenicity is not measured routinely. There is limited evidence comparing renal size, renal cortical thickness, and echogenicity and their correlation with eGFR. Therefore, this study aimed to evaluate the association between renal cortical thickness, renal size, and renal echogenicity with eGFR in CKD patients in our setup.

This observational study was conducted at the Department of General Medicine, Mahatma Gandhi Medical College and Research Institute, Pondicherry, over a period of one year, from January 2024 to December 2024. The study included patients with Chronic Kidney Disease (CKD) stage 1-5, attending the General Medicine OPD, who met the inclusion criteria:- 1.Patients aged above 18 years with CKD stage 1-5 2.Patients with type 2 diabetes mellitus 3.Patients diagnosed with diabetic kidney disease 4. Patients who provided informed consent The exclusion criteria .ere:1.Patients who did not provide consent 2. Patients with adult polycystic kidney disease 3.Patients with unilateral kidney 4. Patients presenting with acute 5.kidney injury (acute on chronic kidney disease) 6.Patients on Renal Replacement Therapy 7.Patients diagnosed with renal tumors 8.Patients diagnosed with amyloidosis 9.Patients with HIV-associated nephropathy 10.Patients diagnosed with fatty liver. The study aimed to: 1.Determine the socio-demographic profiles of the study subjects 2.Investigate the correlation between renal cortical thickness, renal echogenicity, and renal size with estimated glomerular filtration rate (eGFR) as an indicator of renal function in CKD. After obtaining ethical committee clearance, data was collected using a pretested proforma, including: Socio-demographic profiles, Hemoparameters (eGFR, hemoglobin, serum sodium, serum potassium, serum calcium, serum phosphorus, serum creatinine, and blood urea), Renal parameters (renal cortical thickness, renal echogenicity, and renal size).The collected data was analyzed using statistical tools, including: Percentages and proportions,Measures of central tendency and dispersion, Standard error of the mean, Correlation coefficient,Tests of significance etc; The study results were compared with published literature and discussed to draw conclusions and recommendations.

Table 1. Age and Sex-wise Distribution of the Study Subjects

Mean ± SD = 55.45 ± 14.02 = 41 - 69, P < 0.01

It was observed that the burden of the disease was more between 41-60 years of age (66%) with the Mean age 55 years. Also, it was noticed that the morbidity was higher among males (77%) when compared to females (23%) significantly.

Figure1:   Gender Distribution

Table 2 : Distribution of Hemoparameters among the study subjects

With reference to distribution of the complications, it was observed that the mean hemoglobin was 8.87 ± 1.94 g/dl with the range between 5-16 followed by the mean Serum Calcium levels was 7.75 ± 1.04 with the range 6.4 to 12.4, the mean serum phosphorus was 3.89 ± 1.04 with the range between 1.5 to 9.8, the mean Sodium was 134.3 ± 3.14 with the range between 127 to 143,  the mean potassium value was 6.17 ± 13.04 with the range between 2.7 to 8, the mean serum creatinine level was 3.57 2.33 mg/dl with the range between 1.32 mg/dl to 13 mg/dl and the mean Blood urea in the study population was 59.57 ± 23.16 with the range  between with 17 to 107 2 respectively as against the eGFR mean value of 24.92 ± 13.77 with the range between 5 to 56. And mild reduction of hemoparameters were observed  in relation to decreased eGFR in this study.

Figure 2: Grade wise Distribution of Renal Echogenicity

Table 3 : Distribution of Mean of eGFR, Renal size and Renal Cortical Thickness in relation to Renal Echogenicity grade

• It was noticed that, there was significant (P<0.01) reduction of the Mean ± SD values of eGFR (34 ± 76 ), Renal Size Rt (9.08 ± 0.86 ) & Lt (9.35 ± 1.39 ) and Rena Cortical Thickness (7.76 ± 1.29 ) on par with Renal Echogenicity grade among the study subjects.

Table 4 : Distribution of Study Variables in association with eGFR

Correlation is significant at the 0.01 level (2-tailed).

There was significant correlation observed among the CKD patients towards distribution of Renal Cortical Thickness, Renal Echogenicity and Renal Size in relation with eGFR in this study

Our study revealed that the burden of Chronic Kidney Disease (CKD) was higher among individuals aged 41-60 years (66%), with a mean age of 55 years. Males were more affected than females, accounting for 77% of the study population. These findings are consistent with previous studies, such as Verma et al ²⁰, which reported a higher prevalence of CKD among males. The sex disparity in CKD prevalence may be attributed to the modulatory effects of sex hormones on cytokine synthesis, growth factors, and vasoactive chemicals, which influence kidney function ^21,22.

Our study also found significant abnormalities in hemoparameters, including low calcium levels and anemia, which are common complications of CKD. The kidneys' inability to produce sufficient active vitamin D leads to decreased calcium absorption, resulting in low serum calcium levels²³. Anemia in CKD is a multifactorial process involving relative erythropoietin deficiency, uremic-induced inhibitors of erythropoiesis, and disordered iron homeostasis ²⁴.

The mean serum creatinine value and blood urea in our study were 3.57 ± 2.33 mg/dl and 59.57 ± 23.16 mg/dl, respectively, which is consistent with previous studies ²⁵. We used the CKD-EPI formula to calculate the estimated glomerular filtration rate (eGFR) from serum creatinine and found a significant correlation between eGFR and renal echogenicity grading.

The mean renal size of our study participants was 7.75 ± 1.53 mm (right) and 7.81 ± 1.49 mm (left), which is consistent with previous studies ²⁶. In our study, the mean renal size and Glomerular filtration Rate (eGFR) had a moderate correlation with each other and was statistically significant ( P <0.001 ) and similar to the reports of Adibi et al²⁷ and Paleologo et al.   In our study, mean eGFR for Grade 1 was 34 ± 12.76, for grade 2 was 32.10 ± 15.63, for grade 3 was 22.47 ± 11.38, for grade 4 was 18.26 ± 11.20. Majority of the patients belonged to grade 3 and grade 4 stage of Rena Echogenicity. And the mean eGFR among the patients was significant with cortical echogenicity grading (p=0.001). Similar findings were made by Kodarkaran et al²⁸. In our study there was also a statistically significant correlation between mean longitudinal  Renal Size and Renal Cortical Echogenicity (P=<0.001). In our study, the mean cortical thickness was 6.94 ± 1.55mm.The correlation between eGFR and renal cortical thickness (RCT) was positive, weak and statistically significant ( r = 0.342 ) ( P value 0.001 ). Chawla etal²⁹found that the cortical renal thicknesses had a higher correlation coefficient with eGFR than the cortical renal length.  In accordance with a study by Yamashita et al., there was a moderate correlation between eGFR and renal cortical thickness (r = 0.478; p 0.001)³⁰ As the Renal Echogenicity is increased, there is a progressive decrease in renal size and mean cortical thickness. A study done by Beland et al³¹ proved that the cortical thickness when measured by ultrasound had better correlation to GFR than renal length.  In our study, there was also a statistically significant correlation between Renal cortical thickness and Renal echogenicity (P value = 0.004). We found that there was a statistically significant association between eGFR and the grading of renal cortical echogenicity, between renal size and grading of renal echogenicity, cortical thickness and grading of renal echogenicity which was similar to the findings of Reddy et al studyT³² . But our study results conflict with those of Platt et al who conclude that renal echogenicity is not a valid disease predictor³³.Because renal cortical echogenicity, unlike serum creatinine levels, is irreversible, it can be utilized as a marker of renal activity³⁴. There are a few limitations on this study. Since the study was cross-sectional, the measurements were not followed up on, making it difficult to detect the progressive renal cortex thinning brought on by deteriorating glomerular filtration.

In conclusion, our study highlights the importance of renal echogenicity grading in CKD. The correlation between renal echogenicity grading and eGFR, renal size, and cortical thickness suggests that renal echogenicity can be a useful predictor of renal dysfunction in CKD. Further studies are needed to confirm these findings and explore the potential applications of renal echogenicity grading in clinical practice.

LIMITATIONS

The hospital-based design and small sample size may limit the generalizability of the findings to the broader population. The measurements were not followed up on, making it challenging to track the progressive renal cortex thinning caused by deteriorating glomerular filtration over time. Ultrasonography and estimated glomerular filtration rate (eGFR) are unable to identify the precise cause of impaired renal function, which may limit the understanding of the underlying mechanisms.

Our study highlights the need for targeted interventions and preventive strategies to control the incidence and prevalence of Chronic Kidney Disease (CKD) in the community. Given the higher distribution of the disease among males and its proportionate increase with age, it is crucial to focus on these demographics. Implement targeted interventions and preventive strategies among males and older adults to control CKD incidence and prevalence. Effectively implement the National Programme for Prevention and Control of Cancer, Diabetes, Cardiovascular Diseases and Stroke (NPCDCS) strategies to prevent and control diabetes and hypertension, which are the commonest causes of CKD. Regularly monitor hemoparameters and renal ultrasound parameters, such as renal cortical thickness, renal size, and renal echogenicity, to reduce morbidity and prolong the life span of CKD patients. Utilize renal echogenicity grading as a predictor for renal dysfunction, given its strong association with estimated glomerular filtration rate (eGFR).

Early detection and management of CKD can significantly improve patient outcomes. Implementing preventive strategies, such as healthy lifestyle choices and regular monitoring, can help reduce the burden of CKD. Effective implementation of NPCDCS strategies can help control diabetes and hypertension, which are major risk factors for CKD.

Further research is needed to explore the relationship between renal echogenicity grading and CKD progression. Implementing national health policies and strategies for addressing CKD can help improve kidney healthcare globally.

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