It was, he says, one of the best decisions he ever made.
Smith's eagle-eyed examination spotted a critical clue that had been overlooked for years, culminating in a diagnosis that the 15 physicians who treated Lopez apparently never considered.
"At first I didn't believe David's theory," recalled Lopez, now 44. "I had been burned a lot of times."
In December 2010, Lopez was visiting an airplane hangar with his employer, who owned a Cessna. While walking around the plane, Lopez, blinded by the glare of the late afternoon sun, smacked forehead first - hard - into the low-slung wing.
"I fell to the ground, but didn't black out," he remembered. Lopez got to his feet and insisted he was fine. "I was more embarrassed than anything."
A week later, he began feeling "hung over." Returning from his daily five-mile run, Lopez started trembling and felt so weak he had to lie on the bathroom floor. His wife brought him a glass of orange juice. Within minutes, he seemed to have recovered.
But a few weeks afterward Lopez suddenly became dizzy and extremely nauseated while drinking a beer. He stopped drinking alcohol, but the hung-over feeling persisted, accompanied by a headache, shakiness, vomiting and diarrhea.
His primary care doctor at the time, Lopez said, was dismissive, telling him he was "anxious" and "working too hard." It was an explanation he would hear from other doctors.
During the next six months, Lopez consulted an ear, nose and throat specialist in Albuquerque, New Mexico, who ruled out labyrinthitis, an infection of the inner ear that causes vertigo and nausea. An ENT expert in Los Angeles suggested he might have chronic fatigue syndrome.
At the recommendation of his internist stepfather, Lopez underwent a brain MRI. A neurologist told Lopez he had an acoustic neuroma, a benign brain tumor, then abruptly changed her mind and said the scan showed nothing.
Visits to gastroenterologists led nowhere. One New Mexico specialist, for reasons that remain inexplicable, suggested that Lopez's wife might be intentionally poisoning him, but the specialist did not order toxicology tests.
Lopez remembers feeling flabbergasted by the speculation. His wife, Lorena, had been unfailingly supportive in every possible way.
His stepfather, whom Lopez called "my medical rock," was aghast.
" 'That is absurd,' " Lopez remembers him saying. "I can't believe these people.' "
In 2014, a third gastroenterologist recommended removal of Lopez's gallbladder, citing his 45-pound weight loss, coupled with the results of a scan that seemed to indicate biliary dyskinesia, a disorder in which bile drainage is impaired. The operation was a failure and left him feeling sicker.
A fourth gastroenterologist diagnosed postcholecystectomy syndrome, a complication of gallbladder surgery that causes severe nausea and diarrhea. She referred him to a prominent out-of-state medical center for a comprehensive GI work-up.
Lopez spent a week there in 2015. Doctors weren't sure what was wrong, but they told him he appeared to be unusually sensitive to certain foods. Lopez noted that although he craved salt, he became violently ill after eating salty foods such as popcorn. Doctors prescribed a diet sometimes recommended for irritable bowel syndrome as well as a drug to slow digestion; neither helped.
In 2016, Lopez decided to stop seeing doctors for a while. He had exhausted every option he could think of. Too sick to attend his children's school events or eat dinner with his family most nights, he routinely came home from work and fell into bed.
"At times, I thought I was going to have to close my practice," he recalled. "Losing my work would have been the final nail in the coffin."
In July 2017, a seemingly promising new explanation emerged after Lopez and his wife traveled to a major teaching hospital in California.
Several tests, including a spinal MRI, showed a possible chronic leak of cerebrospinal fluid from the dura, the outer membrane that surrounds the brain and spinal cord. Experts told Lopez they believed the leaks were the result of his 2010 collision with the Cessna, but couldn't pinpoint their location. They recommended a series of epidural blood patches, in which a small amount of blood is injected into the epidural space in the spine to plug the leak.
Days after the October procedure, Lopez said he vividly remembers recovering in a hotel room "lying flat on my back and my wife feeding me cereal." He was told to temporarily boost his consumption of caffeine and salt to increase the production of spinal fluid. For weeks afterward he was violently ill.
"I got very depressed," Lopez recalled. During an emotional conversation with his wife, he confided that while he never felt suicidal, he wasn't sure how he could continue living in his current condition.
The meeting with Smith occurred a few weeks later.
As he paged through Lopez's records, Smith was struck by the absence of a positional headache, pain that improves when lying flat. It is one of the most common symptoms of a spinal fluid leak. And when he looked at the MRI, the neurologist did not see a leak.
Lopez told Smith, as he had the doctors he had seen, that his symptoms started after he hit his head. "He said he was fine until then," Smith said. "To me it seemed logical to start there."
Lopez mentioned that he had recently told his internist that he was getting up six or more times each night to urinate. Smith suspected the cause might not be his prostate, the most common origin of such a problem, but rather dehydration which can result from an electrolyte problem.
Reviewing his lab tests, Smith spotted a slightly but persistently elevated sodium count in the years after the accident - but not before. He calculated Lopez's serum osmolality, which measures the concentration of sodium ions and other substances in the blood. The specialized test is sometimes ordered to check for an electrolyte imbalance but had never been ordered. Smith's calculations showed that it, too, was elevated.
Smith suspected that the blow to Lopez's head might have damaged his pituitary, the pea-size gland at the base of the brain, which serves as the body's metabolic control center. A traumatic brain injury can cause hypopituitarism, a condition in which a hormone deficiency impairs normal function. One of the hormones released by the pituitary is antidiuretic hormone (ADH), which regulates fluid balance.
The neurologist theorized that Lopez's damaged pituitary had caused central diabetes insipidus, a rare disorder in which the kidneys remove too much fluid. (The condition is unrelated to the far more common diabetes mellitus, which involves blood sugar.)
Lopez initially was skeptical.
"I remember feeling kind of irritated when David said I didn't have a CSF leak and shouldn't get another patch," he recalled. "I had already pursued a lot of dead ends."
But Lopez was desperate. "I remember thinking, 'I don't even care if I get well, I just want an answer.' "
Smith urged Lopez to ask his primary care doctor to order osmolality and urine tests. Lopez said his new internist balked, telling him, "You don't have diabetes insipidus, it's so rare." After Lopez insisted, the internist ordered the tests, followed by a second round. All were abnormal, but the doctor remained unconvinced.
Lopez pushed for a referral to an endocrinologist. He, too, was skeptical but ordered additional tests that yielded the same result, along with a scan that ruled out a pituitary tumor.
Now there could be no doubt. Smith's meticulous analysis had led to the diagnosis of diabetes insipidus that essentially had been hiding in plain sight.
Lopez began taking a form of vasopressin, the replacement hormone he will need for the rest of his life. Slowly but steadily, he began to improve. His nighttime urination stopped once he started taking the medication.
"I feel 80 to 90% better," Lopez said recently. He carefully monitors his salt intake to prevent sodium overload, must avoid becoming overheated - he no longer runs - and cannot consume alcohol or caffeine, which are too dehydrating. He also takes expensive medication to treat the consequences of his unnecessary gallbladder surgery.
Lopez is trying to make up for the years he lost with his children, who are now 5, 12 and 14. He deeply regrets that his stepfather, who he said was consumed by trying to help him, did not live to see the outcome. He died in 2015.
Lopez thinks his work as a malpractice lawyer "actually set me back. There were too many chefs in the kitchen," he said. "I think the fact that I had so many connections, it put me on the wrong course."
"I also think that but for me doing this work, I would never have met the person who diagnosed it," he added. He said he worries about others who are suffering and lack support or resources. "I represent people like that all the time," he added.
Smith, who has been in practice for 18 years, has a different perspective.
"I felt there was a lot of tunnel vision," he said, adding that he believes time constraints may have played a role. "There are a lot of practices that run like an assembly line."
In the neurologist's view, the most glaring error may have been the failure to take a complete and careful history - the cornerstone of the diagnostic process - and to listen carefully to what Lopez was reporting.
Smith said he remains surprised by the resistance that Lopez, a medically knowledgeable patient, encountered when he pursued a possible diagnosis of diabetes insipidus.
"Some arrogant physicians" are offended by an outside doctor's suggestion, Smith said. "It wounds egos."
