According to Kidney Disease: Improving Global Outcomes (KDIGO), Chronic Kidney Disease (CKD) is defined as abnormalities of kidney structure or function, present for more than 3 months, with implications for health. CKD is classified based on Cause, GFR and Albuminuria category, abbreviated as CGA.
The onset of CKD is usually insidious and it may not cause any symptoms until CKD stage 4. First symptoms are unspecific so that many patients do not consult their doctor and even then, it might not be easy to relate the symptoms to kidney damage. As the kidneys perform a number of tasks, the loss of kidney function leads to a variety of initially unspecific symptoms.
Many patients often produce light-coloured, pale urine and store water in the legs, around the eyes or all over the body – oedema. Foamy urine can be an indication of proteins in the urine. Some patients also excrete discrete amounts of blood in their urine (microhematuria). Elevated high blood pressure (greater than 140/90 mmHg) or high blood pressure increasingly difficult to control is often an early sign of kidney disease. High blood pressure is not only a consequence of kidney failure, but also a cause.
Once established, CKD cannot be cured. This is why the assessment of risk factors and regular kidney check-ups by general practitioners in high-risk patients are so important.
When the kidneys fail, the blood must be cleaned from uremic toxins through dialysis. If left untreated, kidney failure is life threatening. Being dialysis dependent has a major impact on quality of life and life expectancy. If appropriate, kidney transplantation is the optimal form of renal replacement therapy.
Stages of CKD according to KDIGO 2012 Clinical Practice Guideline
Expected remaining lifetimes of the general population and of prevalent dialysis and kidney transplant patients (cohort 2015-2019) by age. Page 34 ERA-EDTA Registry Annual Report 2019
Causes of CKD
The most important and frequent causes of CKD include high blood pressure and diabetes mellitus. Inflammation of the kidney tissue also reduces the filtering capacity. Other causes of CKD and kidney failure are congenital diseases, polycystic kidneys, and calcification of the kidney vessels so called arteriosclerosis. Prolonged obstruction of the urinary tract can also damage the kidneys as can certain medication. Anyone on long-term medication may need to have their kidney function monitored.
Risk Factor Hypertension
A first-ever high blood pressure of over 140/90 mmHg, repeatedly measured, or increasingly difficult to control high blood pressure can be an early sign of kidney disease.
According to a 2021 published overview in the Lancet¹, globally 1/3 of all adult men and women have high blood pressure. High blood pressure is silent. Yet, in 2019, nearly half of the people affected worldwide did not know they had high blood pressure, men more frequently than women. And of those who did know about their condition, only 47% of women and 38% of men received treatment. Less than half achieved normal blood pressure with treatment, so overall only 23% of female patients and 18% of male patients were under adequate blood pressure control.
High blood pressure is responsible for 8.5 million known deaths per year, worldwide, due to vascular and kidney diseases.
Risk Factor Diabetes
According to the International Diabetes Federation (IDF) 463 million adults – one in eleven – were living with diabetes in 2019. The number of people living with diabetes is expected to rise to 578 million by 2030. 232 million adults with diabetes remain undiagnosed. The majority have type 2 diabetes. Not treated in time, they risk strokes, blindness, amputation, heart and/or kidney failure.
Prevention and early detection of type 2 diabetes are therefore of utmost importance.
About one third of people with type 1 (juvenile onset) diabetes and 4 out of 10 with type 2 (adult onset) diabetes eventually will suffer from kidney disease. In a meta-analysis, a 6-fold higher risk of developing kidney failure requiring kidney replacement therapy was observed in people with diabetes than without diabetes.²
In a German study, 89% of individuals with diabetes were diagnosed with CKD stage G2 or higher, but only 2.2% of those with type 1 diabetes and 0.5% with type 2 diabetes had CKD stage G5 or required dialysis.³ Many die during progression of kidney disease from cardiovascular causes. In fact, the combination of diabetes and CKD is strongly associated with cardiovascular complications and higher morbidity and mortality (KDIGO 2012 clinical practice guideline).
¹ NCD Risk Factor Collaboration (NCD-RisC) (2021): Worldwide trends in hypertension prevalence and progress
in treatment and control from 1990 to 2019: a pooled analysis of 1201 population-representative studies with 104 million participants. In: The Lancet 398: 957–80. DOI: https://doi.org/10.1016/S0140-6736(21)01330-1
² Narres, Maria; Claessen, Heiner; Droste, Sigrid; Kvitkina, Tatjana; Koch, Michael; Kuss, Oliver; Icks, Andrea (2016): The Incidence of End-Stage Renal Disease in the Diabetic (Compared to the Non-Diabetic) Population. A Systematic Review. In: PloS one 11 (1), e0147329. DOI: 10.1371/journal.pone.0147329
³ Thomas, Merlin C.; Cooper, Mark E.; Zimmet, Paul (2016): Changing epidemiology of type 2 diabetes mellitus and associated chronic kidney disease. In: Nature Reviews. Nephrology 12 (2), 73–81. DOI: 10.1038/ nrneph.2015.173