Metabolic acidosis may result from decreased capacity to generate enough ammonia from the cells of the proximal tubule. Acidemia affects the function of enzymes and increases excitability of cardiac and neuronal membranes by the promotion of hyperkalemia. Anemia is common and is especially prevalent in those requiring haemodialysis. It is multifactorial in cause, but includes increased inflammation, reduction in erythropoietin, and hyperuricemia leading to bone-marrow suppression. Hypoproliferative anemia occurs due to inadequate production of erythropoietin by the kidneys. In later stages, cachexia may develop, leading to unintentional weight loss, muscle wasting, weakness, and anorexia. Sexual dysfunction is very common in both men and women with CKD. A majority of men have a reduced sex drive, difficulty obtaining an erection, and reaching orgasm, and the problems get worse with age. Most women have trouble with sexual arousal, and painful menstruation and problems with performing and enjoying sex are common. Causes
The three most common causes of CKD in order of frequency as of 2015 are diabetes mellitus, hypertension, and glomerulonephritis. About one of five adults with hypertension and one of three adults with diabetes have CKD. If the cause is unknown, it is called idiopathic. By anatomical location
Vascular disease includes large-vessel disease such as bilateral kidney artery stenosis and small-vessel disease such as ischemic nephropathy, hemolytic-uremic syndrome, and vasculitis.
Glomerular disease comprises a diverse group and is classified into:Primary glomerular disease such as focal segmental glomerulosclerosis and IgA nephropathy (or nephritis)
Secondary glomerular disease such as diabetic nephropathy and lupus nephritis
Tubulointerstitial disease includes drug- and toxin-induced chronic tubulointerstitial nephritis, and reflux nephropathy
Obstructive nephropathy, as exemplified by bilateral kidney stones and benign prostatic hyperplasia of the prostate gland; rarely, pinworms infecting the kidney can cause obstructive nephropathy. Other
Genetic congenital disease such as polycystic kidney disease or 17q12 microdeletion syndrome. Mesoamerican nephropathy, is "a new form of kidney disease that could be called agricultural nephropathy". A high and so-far unexplained number of new cases of CKD, referred to as the Mesoamerican nephropathy, has been noted among male workers in Central America, mainly in sugarcane fields in the lowlands of El Salvador and Nicaragua. Heat stress from long hours of piece-rate work at high average temperatures of about 36 °C (96 °F) is suspected, as are agricultural chemicals

Diagnosis
Diagnosis of CKD is largely based on history, examination, and urine dipstick combined with the measurement of the serum creatinine level (see above). Differentiating CKD from acute kidney injury (AKI) is important because AKI can be reversible. One diagnostic clue that helps differentiate CKD from AKI is a gradual rise in serum creatinine (over several months or years) as opposed to a sudden increase in the serum creatinine (several days to weeks). In many people with CKD, previous kidney disease or other underlying diseases are already known. A significant number present with CKD of unknown cause.