By Randy Dotinga

The persistent bruise on the back of President Donald Trump's right hand was again clearly visible this week, setting off another round of speculation about his health.

The bruise may be nothing more than senile purpura, a normal sign of aging, said physicians. But it could be a sign of something more serious like undisclosed anticoagulant use or even congestive heart failure, although those possibilities seem unlikely, they said.

The high visibility of the bruise, which is often reportedly covered with makeup, comes as Trump, 79, has been facing a high level of scrutiny over his health. He was diagnosed last month with chronic venous insufficiency, according to the White House, and a pair of media reports in the last few days have highlighted an apparent bruise on his other hand and "wobbly walking."

Here's a closer look at several possible explanations for the bruise, listed roughly from the ones considered most likely to least likely:

Senile Purpura

If José López, MD, a hematologist at the University of Washington in Seattle, was presented with the case of a 79-year-old man with a similar bruising pattern, he said his first thought would be senile purpura, also known as actinic purpura and solar purpura.

Senile purpura, which causes bruises that appear on sun-damaged skin, is due to "subcutaneous bleeding that occurs because of small vessel rupture caused by a weak connection between the skin and the underlying tissue," López said. It's a common condition in elderly people.

A cross-sectional study from South Korea found that 14% of 193 older adults surveyed reported current senile purpura, and another 15.5% had a history of it. Among those with the condition, lower arms and hands were the most common locations (96.5%), and more than 50% blamed minor trauma.

Those with the condition versus those without were much more likely to have cardiac disease (26.3% vs 9.6%, P=0.003) or dyslipidemia (42.1% vs 25%, P=0.018), and to be taking anticoagulation drugs (44.2% vs 17.3%, P<0.001).

Sex, body mass index, hypertension, and diabetes weren't risk factors. Only 19.3% of those with the condition said it lasted more than 3 weeks.

Samuel Durso, MD, MBA, a geriatrician at Johns Hopkins Medicine in Baltimore, agreed with López's assessment. "Bruising on the back of the hand of an older adult is common, especially if that person, a golfer, has solar skin damage and takes aspirin," Durso explained.

As for prognosis, López noted that "these bruises take notoriously long to resolve and are often recurrent. If it does recur, it can lead to chronic discoloration from the deposition of hemosiderin, an iron-containing pigment produced by the degradation of red cells. This would usually be copper-colored or brown rather than purple."

Aspirin Use

White House physician Sean Barbabella, DO, wrote in a July memo that the hand bruising is "consistent with soft tissue irritation from frequent hand shaking and use of aspirin, which is taken as part of a standard cardiovascular prevention regimen."

However, guidelines recommend against the use of low-dose aspirin in people over 70 due to the risk of bleeding.

"Aspirin can increase the risk of bruising on the back of the hand," particularly when combined with sun-damaged skin, Durso said.

Michael Roizen, MD, chief wellness officer emeritus with the Cleveland Clinic, said the bruising could be related to Trump's golfing habit and aspirin use. "I've seen pictures of him getting a club out of a bag. You can hit your hand as you're pulling the club out because the clubs are packed relatively tightly. Your hand and lower arm get bruised. And once you're taking baby aspirin, it's easy to get bruised."

Handshaking

In addition to Barbabella's statement putting blame on handshaking, Trump himself attributed his bruising to "shaking hands with thousands of people," in an interview with Time magazine.

However, photos of Trump shaking hands don't show pressure being put on the back of his right hand.

Physicians are skeptical of the handshaking explanation. Durso acknowledged that "any light trauma to solar-damaged skin may lead to bruising," but suggested this would be more likely to come from age-related skin changes.

Blood Draws/Infusions

The top of the hand is sometimes used for intravenous therapy or blood draws when veins can't be accessed. The procedure is not ideal since it's especially painful.

Observers speculated that a bruise on the top of Queen Elizabeth II's right hand, seen shortly before her death, could be due to a blood draw or IV access.

However, "a bruise on the back of the hand due to phlebotomy would be expected to resolve after a couple weeks," said hematologist Adam Cuker, MD, of the University of Pennsylvania in Philadelphia. Trump's bruise has been apparent in public appearances on and off for months.

Also, Trump is right-handed, and he or his medical staff would have likely chosen to have blood drawn or an IV inserted via the back of his non-dominant hand.

Serious Disease

According to López, use of anticoagulants for a variety of conditions -- such as deep vein thrombosis (DVT) or atrial fibrillation -- could explain the bruising. "I would also investigate acquired bleeding disorders and the possibility that other drugs are interfering with the coagulation system or platelets," he said.

The president's case of chronic venous insufficiency could be connected to the bruising if it reflects a high risk for clotting or is the result of DVT, López noted.

Congestive heart failure could explain the president's swollen ankles, he added, although it's less likely to explain his bruising, "unless it entails anticoagulation or other drugs." However, "he doesn't seem short of breath when he is confabulating."

Of note, many people with congestive heart failure take diuretics, which lead to frequent urination to rid the body of excess fluid. This week, Trump held a marathon 3-hour-and-15-minute cabinet meeting, apparently without any breaks.

However, Roizen said that oral or IV diuretics can be timed to avoid excessive urination during certain periods of the day.

The July memo from the White House, which was mainly devoted to the president's "benign" case of chronic venous insufficiency, said tests showed "no evidence" of DVT or arterial disease and "no signs of heart failure, renal impairment, or systemic illness."

You can read the White House's April report on Trump's health, including various lab results, here. In addition to aspirin, he is reported to be taking two cholesterol drugs.

Is the White House Telling Us Everything?

Following in the tradition of presidents from Grover Cleveland to Franklin D. Roosevelt and John F. Kennedy, Trump and those around him have been cagey about his health.

In 2015, his doctor proclaimed in a letteropens in a new tab or window that Trump would be "the healthiest individual ever elected to the presidency." The physician, who has since died, later said Trump "dictated that whole letter."

White House claims about Trump's weight have spawned a skeptical "girther" movement, and it was reported that his 2020 case of COVID-19 was "more severe than the White House acknowledged at the time."

On the other hand, Trump hasn't suffered from significant visible health problems during his presidencies other than his COVID case.

For much of his first presidency, in fact, Trump stood out among his older White House peers for not experiencing any major health problems or physical mishaps in office.

Over the past 125 years, presidents have had heart attacks and undergone prostate, colon, hemorrhoid, tendon, root canal, bowel obstruction, and gallbladder procedures in office. While serving, they've suffered from public vomiting, private fainting, atrial fibrillation, stroke, depression, obesity, Addison's disease, and possibly even Alzheimer's disease.

One president needed stitches after being elbowed during a basketball game. And two -- Roosevelt and Warren Harding -- dropped dead of natural causes while in office.