Understanding Kidney Stones, Types and Treatments
By Eva Briggs, M.D.
A friend recently observed that he’d jinxed himself when he remarked that he hadn’t had a kidney stone in 24 years and then — boom — he was promptly brought to his knees by a kidney stone.
Kidney stones are also called renal calculi, nephrolithiasis or urolithiasis. They are hard deposits of salts and minerals that form within the kidneys.
There are four main types of kidney stones.
• Calcium oxalate stones form from the combination of calcium and oxalate in the urine.
• Uric acid stones can form from an excess dietary intake of purines. Purines are a natural substance found in high levels in shellfish and organ meats. The tendency to form uric acid stones can run in families.
• Struvite stones are rare and related to urinary tract infections. They were named by a German chemist who identified struvite crystals in a medieval midden in Hamburg, Germany. He named the substance after a geologist Heinrich Christian Gottfried von Struve.
• Cystine stones are caused by an accumulation of the amino acid cystine in the urine due to an inherited disorder called cystinuria.
Small kidney stones may cause no symptoms. But as stones enlarge, they can block urine flow. This distends the kidney or the tubes that collect the urine, leading to pain called renal colic. The pain may start as a dull ache in the flank. But as the blockage causes more distension of upstream structures the pain becomes sharp and severe. The pain can be incapacitating. Kidney stone pain often causes patients to writhe around, unable to find a comfortable position. Patients may vomit.
The pain often starts in the back, wrapping around the flank, when a stone becomes hung up in the renal pelvis. That’s the junction where the kidney tubules meet up with the ureter (tube from the kidney to bladder.) Sometimes a kidney stone may move into the ureter only to become caught where the ureter meets the bladder. The pain then migrates to the lower abdomen. If the stone makes it into the bladder, it may become caught in the urethra, the tube from the bladder to the outside. This pain then moves to the urethra, felt by men at the tip of the penis.
Initial treatment consists of pain medication and antiemetics (nausea medicine). CT scan is used to delineate the stone’s size and location and to help exclude alternate diagnoses. If the stone can’t pass on its own, a urologist might have to retrieve it by a scope, insert a stent to keep the ureter open, or sometimes insert a tube to drain from the kidney to the outside (nephrostomy tube).
Another treatment is lithotripsy, bombarding the stone with sound waves to break it into smaller pieces that can be passed.
It’s important to strain the urine to determine the type of stone involved. This enables the patient’s doctor to determine what type of dietary recommendations or medicine is needed to prevent recurrences.
Drinking plenty of fluid decreases the concentration of offending substances in the urine, reducing the likelihood of stone formation.