Hello again, dear readers, and welcome to the oh-yes-it’s-summer edition of our monthly letters column. To date, it seems no part of the nation has escaped the unique misery of a heat wave. Please be careful when temperatures spike, and take all local heat advisories seriously. It’s easy to underestimate the effects of extreme heat and humidity and to overestimate our ability to withstand it. Limit outdoor or strenuous activities, particularly during the peak hours of 10 a.m. to 4 p.m. Use air conditioners or fans if you have them; if not, take refuge in an air-conditioned mall or a cooling center. Drink plenty of water and avoid alcohol. Check in with children and the aged, who are particularly susceptible to heat exhaustion and heat stroke.

And now, your letters. We recently answered questions about a study that found the sustained scent of a tempting food had the unexpected effect of actually easing the craving for a snack. Several of you wrote to say you’ve experienced this phenomenon, including a reader from Grand Island, Nebraska. After two years of working in an ice cream shop, she developed an aversion to the sweet treats she was working with. “Now, 40 years later, I finally like small servings of ice cream occasionally, but no gooey toppings -- ever!” she wrote. “I would joke that the perfect diet would require me to work full time for two years each for a bakery, a pizza parlor, a steakhouse, etc. Aversion therapy does work! Ice cream may not have much aroma, but the sensory overload did the trick!”

A column about the fairly new idea of creating an advanced care directive specific to a dementia diagnosis rang true for many of you, who said it prompted important conversations and even some decision-making. We heard from a paramedic in Terre Haute, Indiana, who asked families and caregivers to honor the advanced care directives of their loved ones. “Too many times I have been called on a respiratory/cardiac arrest, and when I ask if the patient has a DNR (do not resuscitate) or advanced directive, there is one person who says, ‘Yes, she has a DNR, but I'm revoking it. Save her!’“ he wrote. “I understand that sudden death can cause people to act contrary to people’s wishes. However, if a person has taken the time to have their wishes properly documented, family members and caregivers need to understand that this is what the patient wants.”

We continue to hear from older readers about their pets and the companionship, joy and sense of purpose they bring. An 87-year-old reader in Simi Valley, California, says her two small dogs get her out of the house for a walk several times a day. “The exercise keeps my legs moving so I don’t end up in a wheelchair,” she wrote.

Thank you, as ever, for taking the time to write to us. We look forward to hearing from you, and will see you back here next month.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: My husband was in agony recently, and it turned out he was passing a kidney stone. Why does that hurt so much, and what can he do to keep it from happening again?

Dear Reader: It can be shocking, after passing a kidney stone, to see the relatively small size of the object that caused so much pain.

As the name suggests, kidney stones are hard, pebblelike objects formed from the minerals and salts found within the kidney. They can range in size from a grain of sand to a large marble. When stones leave the kidney, they pass into the ureter, which is the duct that carries urine to the bladder. The ureter can’t stretch to accommodate a foreign object, which makes the passage of larger stones difficult -- or even impossible. Pain from kidney stones often comes in waves because the ureter goes into spasm to try to force out the stone. When a stone reaches the junction where the ureter meets the bladder, it can cause a sharp, sometimes burning pain during urination.

When a kidney stone blocks the ureter, it causes a backup of urine into the kidney. The resulting pressure causes widespread pain and discomfort, including in the back, belly and groin. The blockage can also lead to infection, which adds fever and chills to the daunting list of symptoms. Nausea, vomiting, cloudy urine, smelly urine, blood in the urine and urinary urgency are also common symptoms. Treatment ranges from hydration and pain meds to make patients more comfortable while passing smaller stones to using shock wave therapy to break larger stones into particles small enough to pass to surgical options for difficult cases.

If you’ve had kidney stones, you can take steps to lessen the odds of a recurrence. First, drink plenty of water throughout the day. Hydrating dilutes your urine, inhibiting the growth of salts and minerals that may aggregate into stones. Also, avoid the use of a sauna, hot tub or steam bath; intensive and extensive workouts; a hot yoga class; and even relaxing on a hot summer day, which can result in sweating and loss of water that, in turn, leads to a drop in urine production. As you drink water during the day, you can add a generous squeeze of lime or lemon, both of which are high in natural citrate, a substance that helps prevent stone formation.

Be aware of your diet. The most common type of kidney stones are calcium stones, which are usually made up of calcium and oxalate, a chemical found in most foods. Foods high in oxalate include beets, spinach, peanuts, sweet potatoes, tea and chocolate.

Red meat, organ meats and shellfish are high in purines, which lead to a higher production of uric acid. This is tied to the formation of uric acid stones, another common type of kidney stone. Fructose, phosphate, salt and alcohol also play a role in kidney stone production. If this all sounds a bit overwhelming, consider asking your doctor to help you create a lifestyle plan to reduce your risk of getting kidney stones.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Our summer is filling up with pool and beach activities, and though it’s great that our kids will get exercise and have fun, I’m also worried. The older boys are decent swimmers, but the youngest, who just turned 4, is still learning. How do we keep them all safe?

Dear Reader: Thank you for bringing up an important topic. With the hot (and hotter) weather and carefree summer vibe, water safety may not be the first thing on everyone’s minds. But according to statistics compiled by the Centers for Disease Control and Prevention, drowning is the leading cause of accidental death among children age 4 and younger. It’s the third-most-common cause of accidental death among children and adolescents between the ages of 5 and 19.

It’s great that your older kids can swim and that you’re making sure your youngest is learning. However, swimming skills alone aren’t enough to keep a child safe. As anyone who has spent time around kids at play knows, it’s basically chaos. That makes ensuring their safety around open water a daunting task. But the good news is that the basics of water safety fall into three manageable categories -- barriers, surveillance and education.

The American Academy of Pediatrics recommends -- and some local and state laws require -- that swimming pools be enclosed by a four-sided fence at least 4 feet high, with self-closing and self-locking gates with alarms. When swim time is over, doors facing the pool should remain locked. Let kids swim only in pools with clear water with good visibility, particularly near the dangerous area of the pool drain. At the ocean or a lake, set non-negotiable boundaries for where children can range. This includes not only water depth, but the width of the play area. That lets you create a manageable zone to watch them. An adult who can swim should always stay within arm’s length of any child with poor swim skills.

Vigilant surveillance is crucial. Even in areas with lifeguards, a designated adult should continually monitor kids in the water. No cellphones, no chatting, no daydreaming. As any parent whose child has gotten into trouble in the water can attest, the unthinkable happens in mere seconds. If you’re with other capable adults, break surveillance into shifts. When alone, give kids timed swim sessions. Regularly bring them onto dry land for snacks and sunscreen, and everyone gets a needed rest. Restate the physical limits of their play area each time they return to the water. If someone breaks the rules, the penalty is a non-negotiable return to dry land.

Education includes swimming and water competency lessons, which can begin as early as age 1. Learning CPR makes everyone safer. Studies show that kids as young as 9 can learn and use this vital skill. And learn the signs of drowning, which is actually a quiet event. Speech is secondary to breathing, and a drowning person may only have the ability to gasp for breath and try to stay afloat, and thus can’t cry for help. For information on water safety, visit poolsafely.gov.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)