Gout may harms kidney. The statistics show that 20%-25% of patients of gout are suffered from uric acid nephropathy; and the results of autopsy show that almost 100% of patient has nephropathy, including gouty nephropathy, acute obstructive nephropathy and urolithiasis.
Gouty nephropathy: 20% of patients with persistent hyperuricemia have nephropathy clinically, which will incur damage to kidney tubules and glomerulus successively after several years or longer time, and may incur uremia in few cases. The incidence rate of urate nephropathy is next only to the gouty joint damage, and is closely related to the course of disease and treatment. Relevant researches show that urate nephropathy is not related to the severity of gouty arthritis, that is the patient with mild arthritis may have nephropathy, while the patient with serious arthritis is not necessarily accompanied by renal abnormalities. The patient with gout at an early stage may have unilateral or bilateral mild low back pain, and may develop mild edema and moderate elevation of blood pressure hereafter. The urine is acidic, with intermittent or persistent proteinuria, which is generally no more than ++. Almost all of the patients have decreased concentrating function of kidney tubules and the symptoms of enuresis nocturna and dieresis, and the relative density of urine is relatively low. The nephropathy will get worse after about 5-10 years, and develop into uremia hereafter, and about 17%-25% of such patients are died of kidney failure.
Urolithiasis: The urine of patient with gout is acidic, and the uric acid concentration in urine increases consequently; smaller calculi will be excreted through urine without incurring any feeling, fine brown sand can be found in urinary precipitate; larger calculi will block the ureter, resulting in hematuria and renal colic, which will develop into nephropyelitis due to secondary infection caused by bradyuria. Huge calculi will result in deformation of pelvis and kidney calices, hydronephrosis. Simple urine acid calculi will not be showed in the X-ray image, and the calculi will be shown in the X-ray when the sodium urate is combined with calcium salt.
Acute obstructive nephropathy: It is mainly manifested by obvious increase of uric acid in blood and urine, which is resulted by extensive block of kidney tubules by lots of uric acid crystal.
Gout is usually accompanied by high blood pressure, hyperlipidemia, arteriosclerosis, coronary heart disease, and type II diabetes. Among the reasons of death of older patients with gout, the proportion of cardiovascular factors is much higher than that of renal insufficiency. But, there is no direct causal association between gout and cardiovascular disease, but both are related to fat and dietary factors.