March is National Kidney Month, and I thought it would be a good time to discuss kidney stones. Those of you who have passed a kidney stone know what I mean when I say that it can be the worst pain that you have ever experienced! You understand that you would not want to be “up here wishing you were down there” when you got an attack.
For a short anatomy review, the kidneys are bean-shaped organs that lie in the abdomen on each side of your spine below the bottom of your rib cage and extend to just above your hip bones. Each kidney has a network of “collecting systems,” an upper, middle, and lower. These empty into the renal (another name for kidney) pelvis, a larger area of the kidney where the upper, middle, and lower collecting systems join. The pelvis leads into the ureters, which are tubes that carry urine from the kidneys to the bladder.
Renal stones, referred to as “calculi,” can be found in the upper, middle, and lower collecting system, the renal pelvis, the ureters, or the bladder. The stones can be as small as one to two millimeters all the way up to the size of a golf ball! The stone itself is usually not smooth but is pointed and sharp, which contributes to the pain when it passes. Stones occur when the material they are made of becomes saturated in the urine as the kidney absorbs the nutrients that the body is saving. This can occur when there isn’t adequate fluid intake (so always drink lots of water!). Some people have metabolic actions that just over produce the substances that predispose them to stone formation. The most common mineral that makes up a stone is calcium, but uric acid, the acid that causes the symptoms of gout, is also a culprit.
The pain part of a kidney stone, known as renal colic in urology-speak, occurs when the stone begins to pass through the ureter and scrapes and stretches the delicate inner lining. The pain may be subtle when it first becomes noticeable, but gets more severe over a short period of time. It may come and go as the stone moves and stops, but getting comfortable by changing positions, lying down, walking, or standing is virtually impossible. The pain can be so severe that strong narcotic medications are required to relieve it.
When someone presents with an acute kidney stone attack, the emergency department physician (and believe me, most patients with a kidney stone will present to the ER as an emergency) will order a CT scan to determine the size and location of the stone. There also will be an order for blood and urine tests to determine if there is something metabolic going on that is causing the stone development.
The doctor will treat the patient passing a stone with pain medications and ask them to drink plenty of water. They will give them a “strainer” and ask them to strain all urine in an attempt to catch the stone. That way they can analyze the stone to determine what it is made of in order to better treat the condition.
Sometimes the stone is just too large to pass. The urologist can perform a procedure called a shock wave lithotripsy that uses directed sonar-type waves to break the stone into small pieces so it can be passed. Another procedure involves passing a small “basket” up the ureter from the bladder in an attempt to snare the stone and remove it from the ureter. In the severe cases of large or unusually shaped stones called staghorn stones that resemble pieces of coral, surgery may be required to remove the stone. In cases where the stone has traveled as far as it can down the ureter and becomes lodged along the way, blocking the flow of urine into the bladder, surgical intervention may also be required. Most of the time, though, it’s just a waiting game to see if the stone passes.
An airman who passes a kidney stone the first time no longer requires a special issuance, but there should be a note from the treating physician and a report of an X-ray study that demonstrates that there are no remaining stones.
In the past several months, the FAA has removed the special issuance requirement for airmen with retained stones. This is one of the conditions AMEs can issue a medical certificate for without requiring the applicant to go through the special issuance process. Retained kidney stones are those that are seen on an imaging study that may never pass because of the size and location of the stone in the kidney. Just like with a single kidney stone, the airman should have the treating physician write up a status note that addresses the items on the CACI worksheet. If there have been no changes, the AME is permitted to issue the airman an unrestricted medical certificate. An airman who has a history of more than one episode of kidney stones will still require review by the FAA and may be placed on an annual special issuance for continued certification.