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Chronic kidney disease: changes in practice

Karen Jenkins
RN PG dipHE
Consultant Nurse
Department of Renal Medicine
East Kent Hospitals NHS Trust

Chronic kidney disease (CKD) is now recognised as a major health problem. Studies carried out both in the US and the UK to investigate the prevalence, progression and referral rates of CKD in the general adult population, have shown that older age was strongly associated with moderate or severely decreased function as well as diabetes and hypertension.(1,2) Patients may present with CKD symptoms in primary care and the growing prevalence of CKD means that measures need to be taken to accurately measure kidney function, stage kidney disease, devise referral criteria and develop clear management plans.

Measuring kidney function
Traditionally, kidney function was determined by measuring serum creatinine alone. However, serum creatinine alone is not an accurate index of the level of kidney function. The use of serum creatinine as an index of glomerular filtration rate (GFR) to measure kidney function rests on three important assumptions:

  • Creatinine is an ideal filtration marker whose clearance approximates GFR.
  • Creatinine excretion rate is constant among individuals and over time.
  • Measurement of serum creatinine is accurate and reproducible across clinical laboratories.

However, numerous factors can lead to errors in estimation of the level of GFR from the serum creatinine concentration alone, for example:(3)

  • Kidney disease.
  • Reduced muscle mass.
  • Malnutrition.
  • Ingestion of cooked meat.
  • Trimethoprim or cimetidine.
  • Ketoacidosis.

As creatinine is mainly derived from the metabolism of creatine in muscle, and its generation is proportional to the total muscle mass, this leads to differences in serum creatinine concentration according to age, gender and race.
Therefore it is recommended that kidney function should be assessed by an estimation of glomerular filtration rate (eGFR), not creatinine alone. In May 2006, eGFR reporting was introduced across England.This meant that every time a serum creatinine was requested an eGFR was also reported. The level of eGFR can be related to percentage of kidney function. For example, an eGFR 20 ml/min/1.73 m2 = 20% kidney function. Normal eGFR is considered to be > 90 ml/min/1.73 m2, which assists with the explanation of kidney function to patients.

Staging of chronic kidney disease
It is important that a chronic kidney disease diagnosis be established, based on the presence of kidney damage and level of kidney function irrespective of diagnosis.
CKD can be divided into stages of disease based on the level of kidney function related to eGFR according to the K/DOQI CKD classification (see Table 1).(4)

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Definition of CKD
CKD is defined as either kidney damage due to pathological abnormalities, abnormal blood/urine tests or imaging studies or eGFR Other markers of kidney damage include:

  • Persistent microalbuminuria (measured by an albumin:creatinine ratio).
  • Persistent proteinuria (after exclusion of other causes, eg, urological).
  • Persistent haematuria.
  • Structural abnormalities of the kidney.
  • Biopsy proven chronic glomerulonephritis.

Referral criteria
The UK renal association have produced a set of referral guidelines with specific criteria for referral to a Nephrologist.(5) A CKD register has been introduced as part of the Quality Outcomes Framework (QOF) that will aid early recognition in primary care. The number of referrals to renal services has more than doubled since May 2006. Joint working with renal units, primary care trusts and commissioners for specialist services and patient groups is raising awareness of CKD and removing barriers that have previously stood in the way of providing holistic patient care. There are several renal networks across the UK that were set up with the specific purpose of delivering a renal National Service Framework.(6) Membership of the network is multidisciplinary and representative of both primary and secondary care, patient groups and commissioners.

Anaemia of CKD (ACKD)
One of the major complications of CKD is anaemia of chronic disease. The World Health Organization defines anaemia as a haemoglobin (Hb) level An eGFR of less than 60 ml/min/1.73 m2 should trigger investigation into whether CKD is responsible for the patient's anaemia. When the eGFR is > 60 ml/min/1.73 m2, anaemia is more likely to be related to other causes.

The main causes of ACKD:

  • Reduced production of the hormone erythropoietin.
  • Haemolysis.
  • Iron deficiency.
  • Vitamin B12 and folate deficiency.

Lower levels of kidney function are associated with lower haemoglobin levels and a higher prevalence and severity of anaemia.(9) Those with CKD stage three and diabetes have a greater incidence of anaemia, 22% compared with 7.9% in nondiabetics.(10) Anaemia occurs early in the course of diabetic kidney disease and is associated with inappropriately low erythropoietin concentrations.(11)

Treatment of ACKD
Key recommendations from the NICE guideline for the management of anaemia in chronic kidney disease are:

  • Treatment with erythropoiesis-stimulating agents (ESAs) should be offered to people with anaemia of CKD who are likely to benefit in terms of quality of life and physical function.
  • Age alone should not determine treatment of ACKD.
  • Iron deficiency anaemia should be corrected before commencement of ESA therapy.
  • Iron may be required to maintain adequate iron stores to support the use of intravenous ESAs.

In order for this guideline to support a cohesive service across primary and secondary care, it is important to identify various lead professionals to share and implement the work. These may include consultant nephrologists and GPs with a special interest in renal services. Due to the complexity of this guideline, it is also essential to include representation from medicine management committees and primary and secondary care nursing services.
People with ACKD do not necessarily need to receive their treatment within a hospital setting. A service that emphasises the patient's role in self-care, thus promoting independence and empowering patients to take control of their lives, is a key goal of management of ACKD.(8)

Conclusion
CKD is on the increase and measures need to be taken to care for people who are identified as having CKD and require specialist advice and care from experts in the nephrology field. It is essential that primary and secondary care work together to provide a seamless service for this group of people. Specialist education for healthcare professionals and people with CKD is vital in order to improve understanding of the disease itself, causative factors, management of complications, relevant treatments and the management required.

References

  1. Coresh J, Astor BC, Greene T, Eknoyan G, Levey A. Prevalence of chronic kidney disease and decreased kidney function in the adult US population: third national health and nutrition examination survey. Am J Kidney Dis 2003;41:1-12.
  2. John R, Webb M, Young A, Stevens PE. Unreferred chronic kidney disease: a longitudinal study. Am J Kidney Dis 2004;43:825-35.
  3. Levey AS, Coresh J, Balk E, et al. National Kidney Foundation practice guidelines for chronic kidney disease: evaluation, classification and stratification. Ann Intern Med 2003;139:137-47.
  4. National Kidney Foundation. K/DOQI clinical practice guidelines for chronic kidney disease: evaluation, classification, and stratification. Am J Kidney Dis 2002;39:S1-266.
  5. Renal Association.Chronic kidney disease in adults: UK CKD guidelines for identification, management and referral of adults 2005. Available from: http//www.renal.org/CKDguide/ckd.html
  6. Department of Health. National service framework for renal services. Part two: chronic kidney disease, acute renal failure and end of life care. London: DH; 2005.
  7. World Health Organization. Iron deficiency anaemia, assessment, prevention and control: a guide for programme managers. Geneva: WHO; 2001.
  8. National Collaborating Centre for Chronic Conditions. Anaemia management in chronic kidney disease: national clinical guideline for management in adults and children. London: Royal College of Physicians; 2006.
  9. Coresh J, Astor BC, Greene T, et al. Prevalence of chronic kidney disease and decreased kidney function in the adult US population: third national health and nutrition examination Survey. Am J Kidney Dis 2003;41:112.
  10. El Achkar TM, Ohmit SE, McCullough PA, et al. Higher prevalence of anemia with diabetes mellitus in moderate kidney insufficiency: the kidney early evaluation program. Kidney Int 2005;67:1483-8.
  11. Bosman DR, Winkler AS, Marsden JT, et al. Anemia with erythropoietin deficiency occurs early in diabetic nephropathy. Diabetes Care 2001;24:495-9.