Renal Anaemia

What causes renal anaemia

Renal anaemia is secondary to chronic kidney disease (CKD) and it appears early in the course of CKD, worsening as it progresses. CKD is defined as kidney damage with structural and/or functional abnormalities or a glomerular filtration rate (GFR) <60 mL/min/1.73 m², or both, for ≥3 months. CKD is staged as follows¹:

Stage	Description	eGFR (mL/min/1.73 m²)
1	Kidney damage* with normal or increased eGFR	>90
2	Kidney damage with mild decrease in eGFR	60-89
3	Moderate decrease in eGFR	30-59
4	Severe decrease in eGFR	15-29
5	Kidney failure	<15 or dialysis

*Defined by the National Kidney Foundation as ‘pathologic abnormalities or markers of damage, including abnormalities in blood or urine tests or imaging studies’.

CKD can develop from several conditions, including glomerulonephritis, diabetes mellitus, and hypertension^2-6, as a consequence of damage to the nephrons, reducing their capacity for filtration. The three most common causes of end-stage renal disease (ESRD) are diabetes mellitus (35.4%), hypertension (30.3%) and chronic glomerulonephritis (14.2%)⁷. Currently, diabetes affects approximately 180 million people worldwide⁸, and hypertension affects close to 1 billion⁹. The prevalence of both conditions is expected to increase significantly in the next 20 years⁹. Other risk factors for CKD include: polycystic kidney disease, chronic kidney or urinary infections, immune disorders and obstructions (e.g. stones, tumours)¹⁰.

In early-stage disease, renal anaemia is experienced by up to 25% of CKD patients, increasing to 75-95% in late-stage dialysis patients^11,12. CKD leads to renal anaemia primarily by reducing erythropoietin production, leading to abnormally low haemoglobin concentrations¹.

Other mechanisms by which CKD may lead to anaemia include¹³:

Blood loss through dialysis.
Shortened red cell lifespan (approximately 80 days in dialysis patients compared with 120 days in healthy individuals).
Inefficient iron transportation.
Vitamin B12 and folate deficiencies.
Inflammation.

References:
1. KDOQI (United States National Kidney Foundation ‘Kidney Disease Outcomes Quality Initiative’). Available at
http://www.kidney.org/professionals/KDOQI/guidelines_anemia/index.htm. [Accessed July 2008].
2. NAAC (National Anemia Action Council) Anemia monograph. Available at http://anemia.org/professionals/monograph/ [Accessed June 2008].
3. Alebiosu CO, Ayodele OE. The global burden of chronic kidney disease and the way forward. Eth Dis 2005;15:418-23.
4. Barsoum RS. Chronic kidney disease in the developing world. N Engl J Med. 2006;354:997-9.
5. El Nahas M. Chapter 66 "Progression of chronic renal failure" p. 843-844, in Comprehensive Clinical Nephrology, edited by Johnson RJ, Feehally J, Mosby Edinburgh, 2003.
6. National Kidney Foundation. Chronic kidney disease (CKD). Available at:http://www.kidney.org/kidneydisease/ckd/index.cfm.
[Accessed June 2008].
7. Fishbane S, Berns JS. Haemoglobin cycling in hemodialysis patients treated with recombinant human erythropoietin. Kidney Int. 2005;68:1337-43.
8. World Health Organization. Diabetes. Available at: http://www.who.int/mediacentre/factsheets/fs312/en. [Accessed June 2008].
9. Chockalingam A, Campbell NR, Fodor JG. Worldwide epidemic of hypertension. Can J Cardiol. 2006;22:553-5.
10. American Association of Kidney Patients. Kidney beginnings: a patients´ guide to living with reduced kidney function. Available at http://www.aakp.org/library/attachments/ckdbook.pdf. [Accessed June 2008].
11. McClellan W, Aronoff SL, Bolton WK. The prevalence of anaemia in patients with chronic kidney disease. Curr Med Res Opin. 2004;20:1501-1510.
12. Astor BC, Muntner P, Levin A, et al. Association of kidney function with anaemia: the third national health and nutrition examination survey (1988-1992). Arch Intern Med. 2002;162:1401-8.
13. Nurko S. Anaemia in chronic kidney disease: causes, diagnosis, treatment. Cleve Clin J Med. 2006;73:289-97.