Kidney Stones and Gout

Kidney stones
Kidney stones are hard deposits made of minerals and salts that form inside your kidneys. Kidney stones have many causes and can affect any part of your urinary tract — from your kidneys to your bladder. Kidney stones form when your urine contains more crystal-forming substances — such as calcium, oxalate and uric acid — than the fluid in your urine can dilute. At the same time, your urine may lack substances that prevent crystals from sticking together, creating an ideal environment for kidney stones to form.

Kidney stones form due to a combination of genetics and environmental factors. Risk factors include high urine calcium levels, obesity, certain foods, sodium (salt), some medical conditions or medications, calcium supplements, gout, not drinking enough fluids and soft drinks containing phosphoric acid (typically colas).

Gout
Gout occurs when urate crystals accumulate in your joint, causing the inflammation and intense pain of a gout attack. Urate crystals can form when you have high levels of uric acid in your blood.

Gout is a common and complex form of arthritis. It is characterized by sudden, severe attacks of pain, swelling, redness and tenderness in the joints, often the joint at the base of the big toe. The affected joint is hot, swollen and so tender that even the weight of the sheet on it may seem intolerable.

Gout forms due to a combination of genetics and environmental factors. Risk factors include foods rich in purine (steak, organ meats and seafood), alcoholic beverages (especially beer), and drinks sweetened with fruit sugar (fructose).

New research
The underlying etiology of kidney stones is thought to be multifactorial with an environmental (notable dietary), hormonal, and genetic component. The heritability of kidney stones has been estimated at 56%[1].

According to a recent study, the belief that these environmental factors are the primary cause of gout is mostly untrue[2]. Some foods may slightly increase the risk of developing gout (beer, wine, spirits, potatoes and meat), while others (cheese, eggs, peanuts and brown bread) may decrease that risk. However, a comparison of healthy and unhealthy diets shows there is only an 0.3% impact. Adhering to a Mediterranean diet reduced that impact even further to 0.06%. In comparison, the heritability explained by common genetic variants, was estimated to be 23.9%.

This suggests that both kidney stones and gout may share a common etiology.

[1] Halbritter et al: Update on Hereditary Kidney Stone Disease and Introduction of a New Clinical Patient Registry in Germany in Frontiers in Pediatrics - 2018
[2] Major et al: Evaluation of the diet wide contribution to serum urate levels: meta-analysis of population based cohorts in British Medical Journal – 2018. See here.