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synergy · 1
Many drugs are first processed in the liver and then excreted through the kidneys. Damage to either the liver or the kidney adds to the load on the other, and drugs are more likely to build up in the body. Older adults taking several medicines at once face this risk most.
cofactor · 2
The final step in activating vitamin D is carried out by an enzyme called CYP27B1 in the kidney. As kidney function falls, this step stalls, active vitamin D drops, and calcium and phosphate control goes out of balance; this is one of the starting points of chronic kidney disease–mineral and bone disorder (CKD-MBD).
Gluconeogenesis does not happen only in the liver; the kidneys make glucose too, and during long fasting or starvation their share rises clearly. So the idea that the liver alone manages blood glucose is an outdated simplification, and this is one reason declining kidney function can affect blood glucose control.
regulates · 7
The kidney is also an endocrine organ: it releases erythropoietin (EPO), which directs red blood cell production, converts vitamin D into its active form, and releases renin, which starts the renin-angiotensin-aldosterone system that regulates blood pressure. When kidney function falls, anemia, bone disease and blood pressure problems often appear together.
→Bone
In chronic kidney disease, phosphate cannot be cleared, vitamin D activation falters, parathyroid hormone rises in response, and bone suffers along with them. The whole set of changes is called chronic kidney disease–mineral and bone disorder, and its bone part is called renal osteodystrophy. Once kidney function declines, calcium and phosphate metabolism is a clinical problem that has to be managed.
Most kidney stones are calcium oxalate; others are uric acid, calcium phosphate, infection-related struvite and cystine stones. Low urine volume is one of the most important risks, and the oxalate, calcium, citrate, acidity and purines in urine all play a part. Changing diet is the first line of prevention; people with recurrent stones, stones on both sides or a family history need a full metabolic evaluation.
The heart and kidneys pull on each other (cardiorenal syndrome): a large share of people with chronic kidney disease die of cardiovascular disease, and heart failure often worsens kidney function. The two affect each other through the renin-angiotensin system, fluid volume, chronic inflammation and uremic toxins, so treating one means keeping an eye on the other.
The kidney is phosphorus's main way out of the body: excess phosphate in the blood is filtered and passed into the urine as needed. In chronic kidney disease that exit narrows and blood phosphate tends to rise; together with the kidney's reduced ability to make active vitamin D and a rise in parathyroid hormone, this pulls on both bone and blood vessels (chronic kidney disease–mineral and bone disorder). So for people whose kidney function has already fallen, phosphorus intake is for the doctor to set, and phosphate additives in processed food deserve particular attention.
The blood's acid-base balance is kept by the lungs and kidneys together: the lungs adjust quickly by breathing out carbon dioxide, and the kidneys adjust slowly by keeping or excreting bicarbonate. When chronic obstructive pulmonary disease causes carbon dioxide retention, the kidneys hold on to more bicarbonate to compensate; when kidney failure causes acidosis, breathing becomes deep and rapid (Kussmaul breathing).
Most urinary tract infections happen in the bladder, and the first step is bacteria sticking to its inner lining; in the test tube, the proanthocyanidins in cranberry block that sticking, and pooled trials found cranberry products cut symptomatic urinary tract infections by about 30%. Filtering and concentrating urine in the kidney is a different stretch. A kidney infection with fever and flank pain needs a doctor; drinking more juice will not fix it.
contrast · 1
The idea that protein harms the kidneys is a common misconception: in a meta-analysis of randomized trials, healthy adults on high-protein diets did not see their kidney function decline compared with those on normal protein. The main drivers of kidney damage are poorly controlled diabetes and high blood pressure, overuse of painkillers, and herbal products containing aristolochic acid. People who already have chronic kidney disease should follow their doctor on protein.