I have diastolic high blood pressure in this half year, I am taking norvasc 5mg this 2 months. eGFR >90 in Dec2021, latest eGFR 76 two days ago. I do not have any alcohol consumption, only 1-2 cups of coffee everyday, have on and off chest pain and SOB on exertion, also have low back pain, wonder what's cause sudden decline in eGFR, any investigation should be checked. I worried a lot, because GP don't think I have any serious problems before.
Decline in eGFR is inversely proportional to the rise in creatinine and is affected by multiple factors apart from kidney failure: a high protein intake, increase in protein breakdown caused by strenuous exercise, or dehydration causing a relatively higher concentration of creatinine. Norvasc / amlodipine, a dihydropyridine calcium channel blocker, is not known to impair the kidney function. Common medications that may affect the kidney function include ACEI / ARB, NSAID painkillers, and diuretics. Are you taking Chinese herbal medicine or any herbs or supplements that contain impurities? If extrinsic factors are excluded, then one should focus on the kidney itself. The differential diagnoses can be classified into three main groups: "pre-renal" such as narrowing or blockage of the kidney blood vessels; "intrarenal" such as inflammation of the kidney tissue due to infection or autoimmune disease or congenital abnormalities; and "post-renal" such as kidney stones or ureteric stones. One should repeat the kidney function to monitor the progress, check urine protein, blood glucose. For more advanced investigations, one would also consider screening for autoimmune bodies (Lupus, other autoimmune disease), imagings (Ultrasound, CT Urogram or MRI kidney), and finally a kidney biopsy if deemed necessary. Coffee should not have a drastic effect on the kidney apart from mild diuresis. If the heart has anything to to do with the kidneys, then one would first consider congestive heart failure leading to low blood supply to the kidneys causing a rise in eGFR. Very rarely, chronic atrial fibrillation patients might have a large atrial thrombus, which gets dislodged and acutely occludes the kidney blood vessels. I have only encountered one patient who had kidney artery embolism from atrial fibrillation, throughout my whole medical career.