Chronic kidney disease (CKD) is a global public health problem due to its increasing prevalence as well as its major risk factors which are hypertension and diabetes. Therefore, it contributes significantly to morbidity and mortality and the reduction in life expectancy. Mortality and morbidity are significant because the most affected patients do not access renal replacement therapy. In 2015, more than one over 10 adults was suffering from CKD and more than 600 million worldwide [1]. In 2013, a study estimated that 956,200 deaths worldwide were directly attributable to CKD, which was an increase of 134.6% from 1990 [2]. However, the data available on CKD in countries with limited resources are patchy and come from a few isolated studies [3]. A recent study in Senegal showed CKD prevalence of 4.9% [4]. This study was carried out with the aim of determining the epidemiological, clinical, paraclinical and therapeutic aspects in patients with CKD.

This was a retrospective and descriptive study carried out over a period of ten years, extending from the first of January 2004 to the 31^st of December 2013 at Principal Hospital in Dakar. Records of any patient aged 18 and over with CKD were included. The CKD was defined according to the 2012 KDIGO (kidney disease improving global outcomes) recommendations [5]. Patients with acute renal failure or any incomplete or inoperable patient records were not included in the study. Sociodemographic, clinical and paraclinical characteristics were studied. Glomerular filtration rate (GFR) was calculated according to the MDRD (Modification of diet in Renal Disease) formula [6]. Data were collected from patient medical records using pre-established forms. The data were entered and analyzed using a questionnaire developed with the Epi info 7 software and analyzed with the SPSS version 18 software.

During our study period, 8873 records were collected, among which 462 presented a CKD, for a hospital prevalence of 5.2%. There were 285 men and 177 women, for a sex ratio of 1.61. The mean age of the patients was 58.37 ± 19.97 years (Table 1). There were 348 (75.32%) patients who were aged 50 years and older (Figure 1). Twenty-seven patients (5.85%) had a history of herbal medicine use. The reasons for consultation were mainly represented by edema of the lower limbs (25.10%), vomiting (13.63%) and dyspnea (22.29%) (Table 2). Three hundred and eighteen patients (68.83%) had systolic hypertension. Two hundred and seventy patients (58.44%) had diastolic hypertension. The mean blood urea level was 1.18 g/L ± 0.95. The mean serum creatinine was 49.14 mg/L ± 56.83. The mean GFR was 27.47 ± 19.86 ml/min/1.73 m². Chronic renal failure was diagnosed in 92% of patients, including 34.9% in the end-stage of the renal disease (ESRD) (Figure 2). There were 82.8% of our patients who had anemia. Hypocalcaemia was observed in 51.62% of patients. Hyperphosphatemia was present in 48.37% of

eGFR = estimated glomerular filtration rate according to 4-variables MDRD equation; HDL = Hight density lipoproteins; LDL = Low density lipoproteins.

patients. Hyperkalaemia was present in 47.8% of patients. Hyponatremia was present in 30.39% of patients. Hypercholesterolemia was present in 55.3% of patients. LDL hypercholesterolemia was present in 76.5% of patients. Hypertriglyceridemia was present in 23.96% of patients. HDL dyslipidemia was present in 31.9% of patients. Hyperuricemia was present in 76.44% of patients. The mean proteinuria was 3.07 ± 4.92 g/24 h. Leukocyturia was present in 34.17% of patients. Hematuria was present in 25% of patients. Obesity was found in 33% of the patients. Smoking was noted in 6% of patients. Hypertension and diabetes were the most common causes, found in 283 patients (61.25%) and 166 patients (35.93%), respectively (Table 3). Kidney biopsy was indicated and performed in 23 patients, 10 of whom presented with focal segmental hyalinosis. Hemodialysis was performed in 49 patients. The mean duration of the sessions was 3.83 ± 0.44 hours with extremes of 2 and 4 hours. Peritoneal dialysis was performed in 2 patients. One patient had undergone a kidney transplant.

In the world, the prevalence of CKD is estimated at 10% but there are many variations between countries [7]. In sub-Saharan Africa, the epidemiology of CKD in the general population is difficult to estimate probably due to possible confusion caused by the heterogeneity of the populations studied, design and methods used to define CKD. By comparing our study with the other studies presented in Table 4, we see that the prevalence of CKD varies from one country to another and within the same country [4] [8] - [14]. In our study, the mean patient age was 58.37 ± 19.97 years and more than 70% of our patients were over 50 years old. Our study is consistent with results found in other studies. This could be explained on the one hand by the physiological decline of GFR which is observed in these advanced ages. This is currently even a topic of discussion because it leads some authors to think about redefining CKD in older ages. On the other hand, improvement in life expectancy of the population could also explain this predominance of CKD in subjects over 50 years of age [15].

Hypertension (61.25%) and diabetes (35.93%) were the two major risk factors associated with CKD in our series. Studies done in several countries had also found hypertension to be the leading cause of CKD [16]. This is the case of studies that were done in Cameroon and the United States where hypertension was found in 84.6% [17] and 86.1% [18] respectively. This high frequency of hypertension can be explained by behavioral changes namely smoking, sedentary lifestyle, an unsuitable diet (high in salt and fat) [16]. Hypertension in general is more common in black people due to the genetic predisposition linked to the presence of a polymorphism in the Apol 1 gene which codes for apolipoprotein 1

[19]. Hypertension is a risk factor for progression associated with CKD. And this has been reported in the studies done in Morocco [20], Lebanon [21] and Germany [22]. The kidney, which is often the cause of hypertension, can in turn be a victim of the latter through its repercussions (fibrous endarteritis and arteriosclerosis). As a result, hypertension is a factor in the progression of CKD. When transmitted to the glomerular capillaries, it aggravates intraglomerular hypertension and precipitates the development of CKD. This transmission is facilitated by the almost constant vasodilation of the afferent arteriole. Administration of antihypertensive drugs to animals with nephron reduction and arterial hypertension to a greater or lesser extent decreases glomerular sclerosis and the progression of CKD [23]. In our study, diabetes was found in 35.93% of cases. These results were similar to those found in Morocco (41.5%) and higher than results previously found in Senegal (12.7%) and Nigeria (5.9%) [4] [24]. The increase in the prevalence of diabetes in developing countries seems to be explained by the rapid urbanization which is associated with a more sedentary lifestyle and the prevalence of obesity which is 33.9% in our work.

In our study, patients were diagnosed with CKD late. In fact, 92% of patients were diagnosed with chronic renal failure, including 34.9% with ESRD. The challenge in our countries must be a diagnosis at the early stages, especially in patients at risk, particularly hypertensive and diabetic patients.

This study establishes the relatively high prevalence of CKD and its risk factors including hypertension and diabetes. It also reveals the late diagnosis of chronic kidney disease in our patients. Developing action plans for the prevention of CKD and its early diagnosis would be beneficial for better health of the population. However, these data cannot be extrapolated to the general population as this is a retrospective study limited to one establishment.

All patient information was anonymised and the written consent for publication of the study was obtained from the patients. The research was conducted ethically in accordance with the World Health Association Declaration of Helsinki and was approved by the local ethics committee.

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Mansour Mbengue reviewed the literature and wrote the first draft of the manuscript. All authors reviewed and edited the manuscript and approved the final version of the manuscript.

The retrospective design of our study represents a limitation. Kidney function was not measured 3 months later to ascertain chronicity of the disease and to roll out acute kidney injuries.

The authors have no conflicts of interest to declare.

Mansour, M., Djenaba, B., Ahmed, L.T., Moustapha, C.M. and Abdou, N. (2021) Chronic Kidney Disease in Sub-Saharan Africans: A Study of 462 Patients. Open Journal of Nephrology, 11, 114-122. https://doi.org/10.4236/ojneph.2021.111009