Q:Although most of your articles are interesting and informative, I have found that the subject that concerns me kidney stones has received little attention, apart from one brief paragraph on the dangers of ultrasonic treatment. Maybe kidney stones
A:I'm sure they interest many people, as it is an increasingly common problem, particularly among men.
Kidney stones are, in 90 per cent of cases, calcium and oxalate, a salt derived from oxalic acid, which binds calcium together. Medicine believes that they are caused by a flaw in the intestines, leading to increased absorption of calcium. Another cause is hypercalciuria (too much calcium in the urea) caused by excess resorption of bone (tearing down of old bone). Otherwise, the problem may stem from the kidney itself in its ability to reabsorb calcium.
In the other 10 per cent of cases, the stone is made up of amino acids cystine, xanthine, a protein byproduct, uric acid a consequence of hyperuricemia (high levels of uric acid in the blood) or gout, a form of arthritis where crystals of uric acid salts cluster near joints causing periodic inflammation.
Anyone who has passed a kidney stone knows that the pain, which rushes from abdomen to groin, can be excruciating, accompanied by blood in the urine.
Increasingly, medicine has discovered that a number of prescribed drugs may be a major cause of stone formation. Stones have now been linked to carbonic anhydrase inhibitors (acetazolamide or methazolamide), used to treat glaucoma (J of Urology, May 1991); to furosemide in infants, used for congenital heart failure (J of Pediatrics, July 1994); some antiepileptic drugs (J Assoc Phys India, November 1993); triameterene for hypertension (J of Urology, December 1990); trisilicate containing antacids, used for gastric discomfort and heartburn (Scand J of Urology & Nephr, 1993;27(2): 267-9); ceftriaxone, to prevent the body from rejecting transplants (Nephro, Dialysis, Transpl, 1990; 5(11): 974-6) and even thiazide diuretics, combined with restriction of calcium in patients with high blood pressure (Acta Urolog Belg, June 1994).
Numerous studies have made the connection between kidney stones and use of sulphasalazine, particularly in AIDS patients given long-term use of drugs like Septrin as just-in-case measures against pneumocystis carinii pneumonia (J of Urology, June 1994). Laxative abuse can also bring on kidney stones.
In the past decade, a high-tech invention with the unwieldy name of "extracorporeal shockwave lithotripsy" (ESWL) has revolutionized the medical management of kidney stones. In ESWL, the lithotriptor creates shockwaves, which, guided by x-rays, are aimed at the stone, causing it to disintegrate. By use of sound, the lithotripter is theoretically able to distinguish between the body's own tissues and those of kidney stones.
Urologists all over the world rushed in to embrace lithotripsy (it is now recommended for three-quarters of all stone problems) without subjecting it to proper clinical trials because it seemed, on the face of it, an improvement over surgery, the conventional method of handling stones. Initial reports didn't demonstrate any short or long-term damage to the kidney and its surrounding tissues.
Or so medicine originally thought. A number of the studies that are only now being done cast a few shadows over these rosy assumptions. It now seems evident that lithotripsy definitely causes damage to the kidney in a good percentage of cases. Most patients experience internal bleeding, ranging from tiny hemorrhage to major bleeding requiring transfusion.
This bleeding also seems to change the dynamics of the blood in the kidney, causing kidney hypertension, in up to 8 per cent of patients (Robert H Heptinstall, Pathology of the Kidney, 1992: 1592). Other studies show irreversible kidney failure (Nephron,1 1993; 63 (2):242-3). One study of 17 patients showed that 5 had a 22 per cent reduction in the kidney filtration rate (J of Endourology, 1994; 8 (1): 15-9). In another French study of 45 patients who'd undergone ESWL, 15 per cent had blood in the urine, 11 per cent pain in the lower back, and 4 per cent bleeding inside the kidney.
Two years later, a computed tomography (CT) scan performed on 20 of the patients showed that 40 per cent had a recurrence of stones and a quarter had scarring, and 1 of the 43 had developed hypertension (Nephrologie, 1993; 14 (6): 305-7).
Other studies confirm that lithotripsy can raise blood pressure (J of Urol, December 1993) and heartbeat (Pol Arch Med Wewnet, May 1993). Rarely, it can even rupture the kidney (Br J of Urol, December 1991). The extent of damage appears dependent upon the dose of shock waves used. In one study, nearly a fifth of patients had sustained damage (Jap J of Clin Radiology, September 1990)
Of 105 patients with CT studies done after ESWL, 31 per cent had kidney edema (water retention) or bleeding in or outside the kidney. Three of the 23 patients who'd been followed after three years had chronic kidney changes, and 10 had new stones (Rof Fort Geb Ront Neuen Bild Verfahr, February 1993).
ESWL can also cause septic shock (Act Urol Japonica, December 1993), and the bacteria within the stones, released upon fragmentation, cause inflammation (Acta Urolog Japon, September 1992).
Aside from the damage to the kidney, there are suggestions that lithotripsy can cause hearing loss, although these suggestions may be unfounded (Br J of Urology, 1994, 73(2): 129-35). Nevetheless, there is evidence that shock waves can structually damage both sperm and the testes. Studies on human semen and rat testes showed that after five weeks, the treated rat testes appeared to have atrophied, with an absence of sperm cells. In the human cells, sperm movement and the percentage of viable sperm decreased, while abnormal sperm correspondingly increased (Urol Internation, 1993, 51 (3): 152-7). Hemorrhage has also been noted in the scrotum (J of Urology, August 1993).
These problems are not only caused by the fragmentation of the stones but also cavitation (bubbling), which can cause physical damage and generate free radicals. One study in rats found that vitamin E, which acts as a free radical "scavenger", could offer "moderate" protection from their release (Ultrasonics, July 1994). Rarely, it also seems to cause the generation of antibodies to the kidney's own tissue (Urolog Intern, 1994; 52 (2): 106-8).
For more complicated stone problems, percutaneous nephrolithotomy (a surgical technique), is the procedure of choice. However, this technique is associated with a 29 per cent reduction in kidney function (J of Endourology, 1994; 8 (1): 15-9) and also scarring (J of Endourology, Dec 1993).
Urologists have found that giving patients certain drugs before the procedure may minimize ESWL damage. Studies have shown that calcium antagonist nifedipine may limit kidney tubular dysfunction, and angina drug verapamil also protect patients (European Urology, 1994; 25 (2): 99-104; J of Urology, July 1993).
Besides shock waves, a number of drugs have been used to dissolve stones or prevent the formation of new ones. Glycosamionglycan pentosan polysulphate and chlorhexidine have been used to successfully break down stones, although in the case of the former, half the patients in one study had new stones re-form (World J of Urology, 1994, 12 (1): 52-4). Medicine has even tried non-steroidal anti-inflammatory drug diclofenac sodium (Urolog Internation, 1992, 48 (4): 404-8).
Mineral salts have also been used to break up or prevent stones. Sodium bicarbonate sometimes works, although in one study, some patients only partially responded to therapy, necessitating surgery as a last minute salvage operation (Urolog Internation, 1992; 48 (1): 81-6). Sodium lactate solution has been used without apparent side effects, according to one Russian study (Vrachebnoe Delo, June 1992). Potassium citrate given with a large quantities of water has been shown to break up and stop future formation of stones in nearly three-quarters of patients (Biomed and Pharmaco, 1993 (47 (1): 25-8), although it is not as effective as potassium magnesium citrate combination (J of Bone & Mineral Res, March 1992). And of course with this approach, you've got to take these salts for the rest of your life.
But all these procedures do not address the reasons the body is making stones in the first place. In fact, many, including ESWL, may even increase the rate of new stone formation (Hepinstall).