DEAR DR. ROACH: My husband had a kidney stone, and the doctor used shock waves to clear it up. Now the doctor says he needs to take fresh lemon juice twice a day, all his life. None of the other men in the community center with stones have been recommended lemon juice. We would like your opinion. — M.C.

ANSWER: Lemon juice is tart because of its high concentration of citric acid. Citric acid is essentially turned into bicarbonate in the body, and the excess bicarbonate is excreted in the kidney. This raises the pH of the urine and makes it harder for both calcium stones and uric acid stones to form.

Citric acid itself in the urine — what hasn’t been metabolized — binds to oxalate, preventing it from making calcium oxalate stones. The addition of citric acid is particularly helpful in people who have a diet with lower amounts of animal protein, so animal protein should be modest and plant protein emphasized in your husband’s diet.

Potassium citrate tablets are commonly prescribed to people with recurrent kidney stones. However, lemon juice is also proven effective at reducing stone formation. Lime juice, orange juice and melon juice are other good sources of citric acid, but avoid grapefruit and cranberry juice, as they are high in oxalates. The potassium, found in both fruit and the tablet, is synergistic at reducing stone risk. Plenty of water is always important for any person with kidney stones.

I do worry about the teeth in consuming very concentrated acid like lemon juice, so I usually prescribe the tablet, but 4 ounces of juice daily is certainly a reasonable option.

DEAR DR. ROACH: I am a 71-year-old woman who’s physically active and of normal weight. I’m currently on 20 mg of simvastatin and have started taking aspirin, 81 mg three times a week. I have white coat hypertension with home blood pressure measurements around 125-130/80. I have no diabetes, and my cholesterol is 194 with HDL of 92 and LDL of 92. An incidental finding on a recent X-ray notes calcium on my aorta. Is further testing, such as a CT angiogram, warranted? — M.P.

ANSWER: The aorta is the largest blood vessel in the body, and calcium, which blocks X-rays, can be seen in large blood vessels. People with calcium in blood vessels are more likely to have plaque and blockages in those blood vessels. Healthy cholesterol levels do not rule out the possibility of coronary artery blockages.

For a person with no symptoms but who is suspected to have blockages in the aorta or coronary vessels, the doctor generally has two options: do further diagnostic testing to increase the certainty of the diagnosis, or treat the patient medically as though she has coronary artery disease. That would mean prescribing a statin drug — more commonly a higher-potency drug like atorvastatin or rosuvastatin nowadays — and aspirin. Beta blockers and ACE inhibitors are also commonly used, but your blood pressure is nearly optimal as it is now. Still, many cardiologists would still use a low dose of a beta blocker like metoprolol.

Since more aggressive therapies like surgery or angioplasty and stent placement are unlikely to have a beneficial effect on your life expectancy, proceeding with treatment as though you already had coronary disease makes a great deal of sense to me.

Nonetheless, a CT angiogram is an excellent test to make the diagnosis of coronary artery blockages. It has the disadvantages of cost, radiation exposure, and dye load (which might damage your kidneys), but the advantage of providing more certainty about the diagnosis.

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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or send mail to 628 Virginia Dr., Orlando, FL 32803.