Kidneys in diabetes and high blood pressure

How are diabetes, blood pressure and the kidneys connected?

NIDDK writes that diabetic kidney disease is the most common cause of kidney disease, and about one in three adults with diabetes develops it. High blood sugar and high blood pressure damage the kidney’s blood vessels, and the damage usually builds up over years. High blood pressure is the second leading cause of kidney failure after diabetes (NIDDK), and the link works both ways: high blood pressure damages the kidney, and a damaged kidney raises blood pressure further. NHS also lists high blood pressure, diabetes and high cholesterol among the causes of chronic kidney disease.

Factors that raise the risk (NIDDK): long-standing diabetes, uncontrolled blood sugar or blood pressure, smoking, a lot of salt, little physical activity, excess weight, heart disease and a family history of kidney failure.

Symptoms

Most people have no symptoms. High blood pressure is usually silent too, and NHS says only measuring it shows it. When the kidneys are seriously damaged, swollen feet and ankles, tiredness, nausea and changes in urine may appear (NIDDK). So having no symptoms is not a reason to skip tests.

Who should be seen?

• Every adult with diabetes. NIDDK recommends a yearly kidney test.
• Anyone with high blood pressure, especially if protein in the urine or a high creatinine has been mentioned.
• Anyone whose blood pressure does not reach the set target even with several medicines.
• Anyone with a family history of kidney failure.
• A patient with new swelling or a change in urine.

How is it assessed?

NIDDK names two tests: a urine test for albumin (the albumin-to-creatinine ratio, ACR) and a blood test for eGFR. NKF says an ACR below 30 mg/g is normal, and a value of 30 or more that is repeated is albuminuria. If albumin is found, the test is repeated one or two more times to be sure (NIDDK).

For follow-up, blood pressure is measured in the clinic and at home. NHS writes that if the clinic reading is high, several days of home measurements or a 24-hour monitor may be requested. For people with diabetes, NIDDK also counts blood sugar and A1C checks as part of follow-up.

What is treatment-resistant blood pressure?

A review article in Clin J Am Soc Nephrol defines it as blood pressure that stays above target, both in and out of the clinic, despite at least three medicines, one of them a water tablet (diuretic), taken at a suitable dose. Before blood pressure is counted as “resistant”, the doctor checks several things: correct measurement technique, following medicines and diet, and use of substances that raise blood pressure. If another cause is strongly suspected, secondary causes of high blood pressure are also checked. The authors say nephrologists see resistant blood pressure often in kidney patients, and because kidney patients were excluded from blood pressure trials in the past, the evidence on the best treatment for them is more limited.

If your blood pressure stays high, do not raise or stop medicines yourself. Bring your blood pressure notebook and a full medicine list to your doctor.

What does treatment look like overall?

NIDDK says lowering blood pressure is the main way to slow kidney damage, and treatment combines medicines and lifestyle changes.

• Medicines. Two groups of medicines (with the endings “-pril” and “-sartan”) slow the disease in a patient with diabetes. Many patients need two or more blood pressure medicines, and sometimes a water tablet too. As kidney function falls, the type or schedule of a medicine may change. NIDDK and NKF name other medicines too that are used for some kidney patients. The choice is for your doctor.
• Blood sugar control. The blood sugar and A1C target is set by your doctor for each person.
• Nutrition. A low-salt diet, with a dietitian’s advice. Plans such as DASH are rich in fruit and vegetables and may not suit a potassium limit, so do not start one on your own.
• Lifestyle. Regular physical activity, reaching a suitable weight, stopping smoking, managing stress and enough sleep (NIDDK).

What you can do

• Measure blood pressure at home correctly: after sitting for at least five minutes, with your back supported and feet on the floor, with the cuff on your bare upper arm, at least twice, one or two minutes apart, and write the numbers down (CDC). See the guide “Blood pressure at home” for more.
• Take medicines as prescribed. Do not stop or change any blood pressure or diabetes medicine on your own.
• Buy from one pharmacy and carry your medicine list (NIDDK).
• Do not take anti-inflammatory painkillers without asking. NIDDK says they are harmful for people with kidney disease, diabetes and high blood pressure.
• Discuss supplements and herbal teas with your doctor.
• Cut down on salt, stay active and give up smoking.
• At every visit, ask how your eGFR and ACR compare with before (NIDDK).

When to get urgent help

• Very high blood pressure with a sudden severe headache, a sudden change in vision, shortness of breath, pain in the chest, abdomen or back, weakness or numbness on one side of the body, or trouble speaking. NHLBI says in this situation not to wait for blood pressure to come down by itself and to call emergency services.
• Very little urine or none, or sudden swelling and shortness of breath.
• Severe weakness or a sudden racing heart.
• Severe vomiting and diarrhoea so that you cannot keep down fluids and medicines.

In Iran, call 115, Iran’s emergency number. See the full list in the guide “When to get urgent help”.