Dear Doctor: Our 92-year-old mother, who’s still sharp as a tack, was perfectly fine one moment and then suddenly became weak and extremely disoriented. It was like she had dementia. We expected to hear that she had suffered a stroke, but hospital tests showed she had a UTI. Why would that affect her mind? And why didn’t she ever have any other symptoms?

Dear Reader: A urinary tract infection, or UTI, often presents differently in the elderly than in younger individuals. The typical symptoms we’re familiar with -- which include a burning sensation during urination; scant urinary output despite a frequent urge to go; urine that is cloudy, dark or that smells strange; and pressure or pain in the abdomen -- frequently do not show up. Instead, the first sign that an elderly person has contracted a UTI can often be what you have described -- a sudden change to their well-being and demeanor. These infections can lead to serious problems, such as kidney damage or even sepsis, so “silent” UTIs present a real health threat to the elderly.

A UTI occurs when any part of the urinary system, which includes the urethra, bladder, ureters and kidneys, becomes infected with bacteria. The urethra is the duct through which urine flows from the bladder and out of the body. The ureters are the ducts that convey urine from the kidneys to the bladder. Because the urethra is shorter in women than in men, and because it is located so close to the rectum, a potential source of bacteria, UTIs tend to be more common in women than in men.

It’s possible that the reason older adults often fail to produce noticeable symptoms is that the physical changes that signal a UTI are the result of the immune system fighting off the infection. As we age, our immune systems tend to slow down, so an infection can be more advanced by the time any symptoms show up.

The first symptom that some older adults will notice is lower back pain, which happens when the infection has reached the kidneys. In post-menopausal women, changes to the urinary tract can make them more vulnerable to infection. In men, prostate issues can result in incomplete emptying of the bladder, which leaves them vulnerable to infection. As for why UTIs are associated with altered mental status in the elderly, the reasons aren’t completely clear. One theory is that the surge in inflammation, which can affect the neurotransmitters that help nerve cells to communicate, interferes with normal brain function.

A urinalysis can reveal the presence of certain compounds in the urine that suggest a UTI. A urine culture will pinpoint the specific bacterial culprit. The good news is that UTIs respond well to antibiotics. As with all antibiotic therapies, it’s vital to take the entire course that has been prescribed. In patients whose UTI had no symptoms, we also think it’s a good idea to consider a follow-up urine culture a few days after the antibiotic therapy is complete. This will confirm that the UTI has cleared up completely.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Hello again, dear readers! It's been a busy month for letters, so we'll get right to it.

-- Regarding a column about post-operative cognitive dysfunction (POCD), in which elderly patients experience mental disruptions following surgery, we heard from an anesthesiologist in Florida. In our column, we explored the link the condition has to general anesthesia. However, he points out that the stress of surgery in and of itself can lead to POCD, and that a more accurate definition is an "impairment to the mental functions of an individual following surgery."

His concern is that isolating general anesthesia as the cause "will create unnecessary fear for elderly patients scheduled for general anesthesia, as there are no definitive studies showing that one form of anesthesia is better than another in preventing POCD. Patients may request a less-than-optimal form of anesthesia in the misguided belief that it would prevent POCD."

-- We recently wrote about a fascinating study in which researchers found that a wound sustained during the day heals twice as fast as one sustained at night. A reader from Louisville, Ohio, wondered whether this applies to the operating room as well.

"What about surgery, since that is a type of wound, and since many doctors like to do surgery early in the morning, is there any evidence about faster healing for surgery done at any special time of day?"

The answer is yes, the time at which surgical cuts are made affects their healing rate as well. The study tied the speed of wound healing to the body's circadian clock, the rhythms of which are keyed to daylight and darkness. The incisions from an emergency surgery performed at night healed more slowly than similar daytime incisions. Although the study didn't go into differences in healing rates between early-morning wounds and afternoon or early-evening wounds, we'd love to see that data.

-- Regarding nighttime leg cramps, many of you offered home remedies.

A reader in Pennsylvania wrote that "when attacked by leg cramps in the middle of the night, I manage to make it into the kitchen and put a rice bag in the microwave for a minute or so. The heat from that, or even a hand towel run under very hot water and wrung out, is very effective when applied to the cramp."

A reader from Simi Valley, California, says that standing tall and then slowly bending forward, aiming for the floor ("if your knees hurt, as mine now do at 74, I bend them a bit") delivers a thigh and calf stretch that helps banish cramps.

One more, from a reader who drinks "1/2 to 1 teaspoon of baking soda in a glass of water (and no, it is not the water by itself that does it, I've tried). The cramp will be gone within a minute or two. Gone are even the agonizing cramps in my groin that drove me crazy. I keep baking soda by my sink in my bathroom so it's handy whenever I need relief."

Thank you, as always, for your thoughts, corrections, thanks and encouragement. It's a pleasure to hear from you.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Between my sister and me, we have three kids with serious allergies (two peanut and one bee sting), and each of their schools requires us to provide them with an EpiPen for emergencies. Now there's a shortage and we can't find even one EpiPen, let alone three. What's going on? Are there any other options for us?

Dear Reader: As anyone with a serious allergy knows, an EpiPen can save your life. Whether the trigger is a food, a drug, an insect sting or bite, or another kind of allergen, the result can range from serious discomfort all the way to anaphylaxis, a severe and potentially life-threatening reaction that requires immediate treatment. Injecting the contents of an EpiPen into the thigh releases a calibrated dose of epinephrine, a chemical that eases the symptoms of an allergic reaction by narrowing blood vessels and opening the airways of the lungs. Although the relief from symptoms is swift, it's not prolonged. That's why, after an allergic reaction that requires the use of an EpiPen, it's important to immediately seek medical care.

Since last spring, there has been a national shortage of EpiPens available. According to Mylan, the company that markets the EpiPen, this is due to a variety of production and delivery issues. At the same time, with millions of kids headed back to school in late August and early September, pharmacies have seen a marked spike in demand. As you noted in your letter, schools require parents to provide one -- and often two -- EpiPens for children with known allergies. Add in sports teams and after-school programs, as well as the ones needed at home, and the demand is far outstripping the supply.

Parents are reporting that despite calls to pharmacies throughout their areas, they are unable to fill their prescriptions. According to data collected by patient advocacy groups, up to 80 percent of parents in 43 states have been either unable to fill their EpiPen prescriptions or were able to purchase only part of what they needed. A generic (and less expensive) version of the EpiPen, manufactured by Mylan, is also in short supply. Meanwhile, another generic ephedrine auto-injector, to be produced by the Israeli company Teva Pharmaceuticals, is not yet available.

The EpiPen shortage has resulted in action from the U.S. Food and Drug Administration. In late August, the agency extended the expiration dates of specific lots of EpiPens by four months. Although EpiPen is by far the best-selling epinephrine auto-injector on the market at this time, there are several other FDA-approved brands available, including Adrenaclick and Auvi-Q. Each requires its own prescription, so a visit to the family doctor or a clinic is necessary. However, these alternative versions may not be covered by insurance.

For information on pharmacies that still have a stock of EpiPens available, Mylan has asked patients to call its customer relations department at 1-800-796-9526. For more information about the alternative FDA-approved ephedrine auto-injectors, visit the agency's website at (sorry, they don't make it easy) www.fda.gov/downloads/Drugs/InformationOnDrugs/UCM520800.pdf.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)