Diabetic nephropathy (diabetic kidney disease): causes, tests and care

The kidneys clean waste from the blood, balance fluid and salt, help control blood pressure and release hormones. NHS Scotland information on diabetes explains that persistent high blood glucose damages the membranes around the small blood vessels of the kidneys, so they do not filter waste as well. That is diabetic kidney disease, or diabetic nephropathy.

Kidney Research UK describes the damage as affecting the delicate filtering units, the glomeruli. If damage is severe the kidneys can eventually lose the ability to filter waste, and a person may need dialysis or a kidney transplant to stay alive. It adds that in older people with type 2 diabetes the kidneys may already have been harmed by high blood pressure or blood vessel disease, so significant kidney problems can arise more quickly.

Diabetic nephropathy is one form of chronic kidney disease (CKD). The NHS describes CKD as a long-term condition in which the kidneys do not work as well as they should, which can get worse over time. Many people with CKD live long lives with it, and the NHS says it progresses to kidney failure in around 2 in 100 people with the condition.

Kidney Research UK says approximately one in three patients with diabetes go on to develop kidney disease. Diabetes is the most common disease affecting the kidneys that results in people needing dialysis, and it is the second leading cause of kidney failure in the UK.

• Poor blood glucose control and high blood pressure.

• A family history of kidney disease or high blood pressure.

• Smoking, and having overweight or obesity.

• Developing diabetes between the ages of 10 and 20, and being male.

• South Asian, Black, African and African Caribbean heritage; the NHS likewise notes CKD is more common in people who are black or of south Asian origin.

• Living in socioeconomic deprivation, which Kidney Research UK says can limit access to healthcare and health education.

• For people who had gestational diabetes, going on to develop type 2 diabetes after pregnancy raises the risk.

The NHS says there are usually no symptoms of kidney disease in the early stages and that 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. The NHS advises seeing a GP for persistent or worrying symptoms.

Kidney Research UK adds that high blood pressure is usually an early sign of diabetic kidney disease, which means a rising blood pressure reading at a diabetes review deserves attention in its own right. Because of the lack of early symptoms, it is the scheduled tests, not how you feel, that catch the problem in time.

Kidney Research UK says two tests for kidney disease should be included in the annual check-ups for people with diabetes: a urine test looking for protein leaking into the urine, called the urine ACR test, and a blood test to check for high levels of waste products. The NHS says CKD can be diagnosed with blood and urine tests, that the results are used to give a stage reflecting how severe the damage is, with a higher number indicating more serious CKD, and that people at high risk, such as those with diabetes, may be advised to have regular tests so the disease is found early.

Your GP or diabetes team will explain what your numbers mean and how often to repeat them. Our guides to the urine ACR test and the kidney function tests explain the measurements in more detail.

The NHS says there is no cure for CKD but treatment can relieve symptoms and stop it getting worse, depending on stage. The main elements are lifestyle changes, medicine to control associated problems such as high blood pressure and cholesterol, medicine that can help the kidneys keep working for longer, and, in advanced disease, dialysis or a kidney transplant.

Lifestyle measures listed by the NHS include stopping smoking, a healthy balanced diet, limiting salt to less than 6g a day, regular exercise (at least 150 minutes a week), staying within the alcohol limit, losing weight if overweight, and avoiding over-the-counter NSAIDs such as ibuprofen unless a medical professional advises them, because they can harm the kidneys in kidney disease.

Blood pressure control is described as vital. The NHS says people with kidney disease should usually aim for below 140/90 mmHg, and below 130/80 mmHg if they also have diabetes, while Kidney Research UK describes a target usually below 140/90 for people with diabetes, or 130 for some people with CKD; the target for you is set by your clinicians. ACE inhibitors are often used, with angiotensin-II receptor blockers as an alternative if side effects are troublesome, and Kidney Research UK says these can reduce or even cure protein leaks and prevent further kidney damage.

Newer diabetes medicines also protect the kidneys. The NHS says SGLT2 inhibitors can keep kidneys working for longer and that one, dapagliflozin, is used to treat CKD, often in people who also have diabetes, but is not suitable for everybody. Kidney Research UK says SGLT2 inhibitors reduce the risk of developing or worsening diabetic kidney disease beyond their effect on glucose, and describes other drug groups (mineralocorticoid receptor antagonists and GLP-1 agonists) as helpful in some circumstances. These are prescription decisions for your specialist team, informed by kidney function and other conditions.

The NHS says that even mild CKD increases the risk of other serious problems, such as cardiovascular disease, and that cardiovascular disease is one of the main causes of death in people with kidney disease, although healthy lifestyle changes and medicine can help reduce the risk. For this reason, cholesterol treatment, often with a statin, is commonly part of care.

Kidney Research UK groups the other complications of diabetes alongside kidney disease: blood vessel damage raising the risk of heart attack and stroke, eye damage (diabetic retinopathy), nerve damage causing numbness and tingling in the feet, and foot problems from reduced blood flow. It says that with earlier diagnosis and improved treatments, fewer people should go on to develop kidney failure.

The NHS adds that advanced CKD can bring swelling, anaemia and bone problems that are treated individually, and that people with CKD may need to avoid potassium supplements and some other medicines that can raise potassium. Tell any prescriber or pharmacist that you have kidney disease.

Screening with urine and blood tests, blood pressure control and first-line medicines are delivered by GP practices and diabetes teams on the NHS, with referral to a kidney specialist (nephrologist) when kidney function falls or protein leakage is high. Dialysis and transplant are NHS-funded services.

Private consultations with a nephrologist or diabetes specialist can offer a second opinion, additional testing or quicker review. Whichever route you use, keep your NHS team informed so that medicine changes, such as stopping ibuprofen, starting a kidney-protective drug or adjusting diabetes treatment, are coordinated and blood tests are monitored after any change.