A Boy Name Wally

Note: Although this is my contribution to Take It and Run Thursday on the topic of Hydration, you might not learn anything that would teach you how or what to drink on your runs. If that is what you’re looking for, I suggest you check out all of the other posts that are not only educational, but well worth reading. Instead, what you will find here is some complicated human physiology, a story about me, and a boy name Wally.

Everything I know about hydration and water balance I learned because of Wally. I first met Wally (not his real name, of course) when I was a first year house officer, or intern as we’re known in the medical community, rotating through the pediatric emergency room. Even on our first encounter, Wally made it quite clear that he would not soon be forgotten. “Hi, Wally, what brings you here today?” “I’m fine. I’m here to teach you everything about MY condition.” “Really? And what condition is that?” “I have DI.” And with those infamous words, spoken with the same tone was if he was introducing me to his best friend, I was introduced into Wally’s world.

DI, or diabetes insipidus, is a disorder of water balance, whereby the body loses the ability to regulate the loss of free water from the body. In the majority of cases, it is caused by a deficiency of the anti-diuretic hormone (ADH) that is normally produced from the posterior pituitary gland in response to dehydration. Rarely, it can also can be caused by electrolyte imbalances, medications, or kidney disease. The role of ADH is to bind to receptors in the kidney and reclaim some of the water that would otherwise be lost in the urine. So in a normal person who is dehydrated, ADH levels are high, allowing more water to be reabsorbed by the kidney to be returned back to the blood, and causing the urine to be very concentrated. (Anyone still here?) People who have DI, like Wally, lack this hormone. As a result, they cannot reclaim any water from their kidneys and become severely polyuric (meaning they produce massive amounts of urine) polydipsic (meaning they have to drink massive quantities of water to keep up with their frequent urination) and is at high risk for severe dehydration. Fortunately, the ADH hormone can be replaced pharmacologically. However, the medication, called DDAVP or vasopressin, must be given at the right dose and at the right time to maintain the water level in the body at a safe and stable level.

By the time I met him, Wally was 12 years old and has had DI for 3 years. For the first 1.5 of those years, no one knew why Wally had DI. But then, someone found a small speckle of something on his brain MRI. Two lumbar punctures and a few lab tests later, it was confirmed that Wally had a brain tumor called a germinoma. Because germinomas are exquisitely sensitive to chemotherapy, Wally was started immediately on a regimen with three different chemotherapeutic agents. Although most cancer patients nowadays often receive chemo as outpatients, because of his DI, Wally always received his chemo in the hospital.

Over the next six years, Wally and I got to know each other very well because of his frequent admissions for chemo, and he taught me many things about fluid management that I would not have learned otherwise. For example, he taught me early on, that unregulated water input leads to hyponatremia, which can be just as dangerous as unregulated water loss leading to dehydration. He taught me that the most sensitive indicator of the body’s water status is the sensation of thirst. He also taught me that carbonated drinks, especially the caffeinated ones, actually cause you to be more dehydrated an hour later than you were before you drank it. For a kid so young, he actually knew quite a lot about himself and his condition. But just like any kid, Wally had a wild side too. At times, when he was frustrated with how a particular doctor was not nice to him, he would purposely not drink or drink too much just before his daily blood draw so that his labs would be all out of wack, and cause his doctor to freak. My favorite was when he would correct medical students during rounds when they were forced to give a synopsis of his condition. “I only drank 100cc yesterday, not 120. I gave the other 20 to the kid next to me when he wanted a sip of my orange juice…” Ah, he was something.

Sometime last year, during my second to last month of fellowship training, Wally passed away. The tumor in his brain, which had initially responded to his first course of chemotherapy, had recurred and eventually became resistant to all other treatments. I remember one of the last conversations I had with Wally was when I asked him who’d teach me what to do the next time someone came in with DI and I couldn’t figure out what fluids to give him. “Don’t worry about it, Doc.” He said, with his usual candor and honesty. “Just ask yourself. What would Wally do? You’ll figure it out.”

I have figured it out, thanks to you, Wally.