A doctor can diagnose someone with a kidney stone from across the room, because they are doubled over in pain, trying to find a comfortable position. Decades ago, kidney stones occurred in 1 out of 20 Americans—now they occur in 1 out of 11. The increase in incidence is thought to be due to an increase in animal products in the American diet.

Kidney stones are more apt to occur in men, with a male to female ratio of 2.5 to 1. Eighty-five percent of stones contain calcium, which shows up on x-rays. Many stones also contain oxalate, and uric acid is often present in the center of kidney stones.

 In addition to high intake of animal products, high intake of sodium (salt) contributes to stones, as does inadequate hydration and low urine pH (i.e. urine that is more acidic than normal). The reason animal products cause stones is that amino acids that make up animal proteins contain sulfur, which leads to acidic urine.

Stones form in the kidneys, and usually don’t cause symptoms until they work their way down the left or right ureter—small tubes that lead from each kidney to the bladder. Under the microscope, stones appear as crystals with sharp points and edges, so it’s easy to see how as they move down the ureter, they would cause pain. When a stone is moving down the kidney end of the ureter, pain is usually located in the back on whatever side the stone is on. As the stone moves further down, the pain is located on one side of the upper and then lower abdomen. When the stone reaches the bladder end of the ureter, the pain is in the groin. Once the stone makes it to the bladder, the pain resolves, and its exit from the bladder via the urethra is usually not associated with pain (the diameter of the urethra is greater than that of the ureter). 

When we see a patient with symptoms of a kidney stone, we order a urinalysis, which usually shows microscopic blood. Sometimes imaging is warranted, to confirm the diagnosis and to determine where the stone in the ureter the stone located and how big it is. Especially if the stone is large, it sometimes gets hung up in the ureter, which can lead to complete obstruction and/or infection.

Usually, stones pass within hours to a few days. Patients are asked to strain their urine and bring in the stone when it passes so it can be sent to a special lab that determines what it’s made of. If stones don’t eventually pass, or if they cause complete obstruction or infection, surgical removal or lithotripsy (breaking up the stone with soundwaves) is indicated.

Most kidney stones are related to high acid load to the kidneys. Fish has the highest acid score, followed by pork, then poultry, then cheese. A total plant-based, whole food diet is alkaline, and vegans–and to a lesser extent vegetarians–have a low incidence of kidney stones. Within days of going on a plant-based diet, risk of a kidney stone drops by 93 percent. Kidney stones can even completely resolve by going on a plant-based diet.

Other helpful dietary measures are avoidance of salt, and adequate hydration. The food industry has Americans hooked on salt, sugar and fat. The maximum amount of salt adults should eat is 1500 mg. a day. So, don’t use a salt shaker, and check food labels (bread is the biggest source of salt for adults, and pizza for kids). Drink enough water so that your urine is a light yellow to clear color.

Dr. Greg Feinsinger is a retired family physician who started the non-profit Center For Prevention and Treatment of Disease Through Nutrition. For questions or to schedule a free consultation about nutrition or heart attack prevention contact him at gfmd41@gmail.com or 970-379-5718.