Chronic kidney disease stage 3a: what the eGFR means, monitoring and protecting your kidneys

The NHS describes chronic kidney disease as a long-term condition where the kidneys do not work as well as they should, which is common and often associated with getting older. It can affect anyone but is more common in people who are black or of south Asian origin. It says CKD can get worse over time, but many people live long lives with it, and that stage is a number reflecting how severe the damage is, with a higher number indicating more serious CKD.

NICE classifies CKD in adults using both GFR and urine albumin:creatinine ratio (ACR) categories. Its G3a category is a mild to moderate reduction in GFR, 45 to 59 ml/min/1.73 m2. The ACR category adds to the picture: A1 is under 3 mg/mmol, A2 is 3 to 30 mg/mmol and A3 is over 30 mg/mmol. NICE gives an example: an eGFR of 50 with an ACR of 35 mg/mmol is CKD G3aA3. The risk of adverse outcomes is described as moderate for G3a with a normal ACR, high with A2 and very high with A3, which is why two people at stage 3a can be managed differently.

The NHS says there are usually no symptoms of kidney disease in the early stages and it may only be diagnosed if a blood or urine test for another reason shows a possible problem. At a more advanced stage, symptoms can include tiredness, swollen ankles, feet or hands, shortness of breath, feeling sick and blood in the urine. It advises seeing a GP for persistent or worrying symptoms that could be caused by kidney disease.

The NHS says CKD is usually caused by other conditions that strain the kidneys, often a combination. It lists high blood pressure, diabetes, high cholesterol, kidney infections, glomerulonephritis (kidney inflammation), autosomal dominant polycystic kidney disease, blockages in urine flow such as recurrent kidney stones or an enlarged prostate, and long-term regular use of certain medicines such as lithium and non-steroidal anti-inflammatory drugs (NSAIDs).

NICE lists factors associated with CKD progression, including cardiovascular disease, proteinuria, a previous episode of acute kidney injury, hypertension, diabetes, smoking, African, African-Caribbean or Asian family origin, chronic use of NSAIDs and untreated urinary outflow obstruction, and advises working with people who have these risk factors to optimise their health.

The NHS says CKD is diagnosed using blood and urine tests, and that people at high risk, for example with diabetes or high blood pressure, may be advised to have regular tests. NICE says laboratories should report an eGFR whenever creatinine is measured, and advises that eGFR below 60 in an adult not previously tested should be confirmed by repeating the test within 2 weeks. It notes that eGFR may be less reliable in certain situations, such as acute kidney injury, pregnancy, oedema, muscle-wasting conditions, people with high muscle mass or protein supplement use, and amputees, and advises adults not to eat any meat in the 12 hours before a blood test for eGFR.

For urine, NICE advises using the albumin:creatinine ratio (ACR) rather than protein:creatinine ratio to detect proteinuria, confirming a result between 3 and 70 mg/mmol on an early-morning sample, and regarding a confirmed ACR of 3 mg/mmol or more as clinically important proteinuria. It advises measuring ACR in adults with an eGFR below 60.

NICE advises agreeing the frequency of eGFR and ACR monitoring with the person, bearing in mind CKD is not progressive in many people, and gives a table of minimum checks per year. For G3a the minimum is 1 per year when ACR is under 3 mg/mmol, 1 per year when ACR is 3 to 30, and 2 per year when ACR is over 30. It advises tailoring this to the underlying cause, the rate of decline, other risk factors such as heart failure, diabetes and hypertension, treatment changes such as RAAS antagonists, NSAIDs and diuretics, intercurrent illness such as acute kidney injury, and whether the person has chosen conservative management.

The NHS says there is no cure for CKD but treatment can relieve symptoms and stop it getting worse: lifestyle changes, medicine to control associated problems such as high blood pressure and high cholesterol, and medicine that can help the kidneys keep working for longer. It says you can help prevent CKD by healthy lifestyle changes and by ensuring underlying conditions are well controlled.

NICE gives specific aims. In adults with CKD and ACR under 70 mg/mmol it advises a clinic systolic blood pressure below 140 mmHg (target 120 to 139) and diastolic below 90 mmHg. For adults without diabetes and with ACR of 70 mg/mmol or more it advises referral for nephrology assessment and an ARB or ACE inhibitor titrated to the highest licensed tolerated dose. It points to its cardiovascular guideline for statin use, and to technology appraisals for SGLT2 inhibitors as an add-on for some adults. It advises dietary advice about potassium, phosphate, calorie and salt intake appropriate to severity, and advises against low-protein diets in adults with CKD. All medicine decisions belong to the treating clinician.

On pain relief, NICE says chronic NSAID use may be associated with progression and acute use with a reversible decrease in GFR, and advises caution with NSAIDs over prolonged periods. Check with a pharmacist or GP before taking them regularly.

NICE advises referring adults with CKD for specialist assessment, taking account of wishes and other conditions, if they have a 5-year risk of needing kidney replacement therapy above 5% (using the Kidney Failure Risk Equation), an ACR of 70 mg/mmol or more, an ACR over 30 mg/mmol together with blood in the urine, a sustained fall in eGFR of 25% or more with a change in category within 12 months, or a sustained fall of 15 ml/min/1.73 m2 or more per year, hypertension that remains poorly controlled despite at least four medicines, known or suspected rare or genetic causes, or suspected renal artery stenosis. It also advises giving adults information about their 5-year risk.

The NHS says CKD ranges from a mild condition with few symptoms to kidney failure, most people can control it with medicine and regular check-ups, and it progresses to kidney failure in around 2 in 100 people with the condition. Even mild CKD increases the risk of cardiovascular disease, one of the main causes of death in people with kidney disease, though healthy lifestyle changes and medicine can help reduce that risk. Dialysis or transplant may be needed in advanced CKD.