Originally published in The Ottawa Citizen July 29, 2003
Original Title: The Stones Wrong Address Part III; Sand and water are more fun on the beach
During my residency at the Jewish General Hospital in Montreal, I watched a groaning patient in tremendous pain hobble into the emergency room, clutching his lower back and side.
The ER staff physician, his back to the ER entrance and writing his notes, said without the slightest hesitation: “Kidney stones. That groan is unmistakable.”
Passing a kidney stone ranks as one of the most painful events in a person’s life. Twelve per cent of white men and five per cent of white women will experience this by the time they’re 70.
Younger adults are more prone to stones than the elderly. Whites are more likely to develop stones than Asians and blacks. Kidney stones occur more frequently in hot, dry regions of the world.
Although many assume the kidneys are located in the lower back area, their true location is behind and below the rib cage in the middle back.
Millions of microscopic tubes within the kidney collect and filter blood and create urine. These tubes drain into larger collecting areas, the calyces, which lead to a large central region called the renal pelvis. Urine flows through from the renal pelvis into the ureter, the tube connecting the kidney to the bladder.
The anatomy of the kidney lends itself to the process of stone formation. Greater than normal concentrations of certain substances in the urine will crystallize and adhere to the collecting system of the kidney. These microcrystals gradually increase in size, forming stones ranging from the size of a grain of sand to as large as a golf ball.
Stone fragments can travel down the urinary system, either passing completely through or lodging within the ureter and obstructing the urinary flow.
Dietary habits pose a significant risk factor. Eighty per cent of stones contain calcium compounds, primarily calcium oxalate (and calcium phosphate to a lesser extent). Oxalate-containing foods include spinach, rhubarb, beets, strawberries, wheat bran, nuts and nut butters.
Bowel surgery, chronic diarrhea and short-bowel syndrome are among the medical conditions that increase the absorption of oxalate from the bowel. Dehydration will concentrate the urine, increasing the risk of stone formation.
Drinking a litre a week of soft drinks acidified with phosphoric acid can mildly increase the risk of stones.
Uric acid, a breakdown product of protein metabolism, is responsible for gout and can cause kidney stones. Eating red meat and drinking alcoholic beverages can increase blood uric acid levels.
Certain bacterial strains found in urinary tract infections can directly influence the production of struvite stones (magnesium ammonium phosphate).
People with high blood pressure have twice the risk of developing stones. There’s also a higher risk if you have a family member with a history of having stones. The chance of forming another stone after one year is 15 per cent, 35 to 40 per cent at five years and about 80 per cent at ten years.
The pain associated with renal colic, from hardly noticeable to excruciating, depends on how far the stone travels within the ureter. Spasms of severe pain can last 20 to 60 minutes. A stone found in the upper ureter/pelvis will cause flank pain in the area between the ribs and the hip. As the stone descends, the pain intensifies, radiating to the lower front part of the abdomen and groin.
Nausea and vomiting may accompany the attack. Some people may have painful urination and feel an urgent need to urinate. Blood in the urine is a common sign. Grains of sand or gravel may be present. Others may have less typical symptoms such as vague or sudden abdominal pain or penile or testicular pain.
Major complications include obstruction of the ureter and severe infections. The urine backflow due to complete obstruction can lead to damage of the delicate filtering structures within the kidney.
The diagnoses of a kidney stone are based on symptoms, urine tests, X-ray with special dye, ultrasound and CT scan imaging. Many people, unaware they have kidney stones, do not have symptoms. Discovering the stone commonly occurs when an X-ray or ultrasound of the abdomen is performed in the course of investigating a different medical condition.
For some, the treatment consists of pain control while waiting for the stone to come out. Stones greater than seven millimetres may need sound shock waves (extracorporeal shock wave lithotripsy) to shatter them into smaller pieces. Others may require a small fibre-optic tube with a snare at its end inserted through the urethra into the bladder and ureter to grab the stone.
People who have had one stone should increase their fluid intake to three litres per day. This will increase urine flow and help prevent the formation of microcrystals within the kidney.
Calcium restriction is not a requirement because oxalate is the main culprit. Restrict oxalate-containing foods instead. Avoid megadoses of vitamins C and D and reduce red meat if you have uric acid stones.
© Dr. Barry Dworkin 2003