396 CHAPTER 8 Stone disease
Treatment options for ureteric stones
-ESWL: in situ; after push-back into the kidney (i.e., into the renal pelvis or calyces); or after JJ stent insertion
-Ureteroscopy
-PCNL
-Open ureterolithotomy
-Laparoscopic ureterolithotomy
Basketing of stones (blind or under radiographic control) are historical treatments (the potential for serious ureteric injury is significant).
The ureter can be divided into two halves (proximal and distal to the iliac vessels) or in thirds (upper third from the UPJ to the upper edge of the sacrum; middle third from the upper to the lower edge of the sacrum; lower third from the lower edge of the sacrum to the VUJ).
AUA guidelines panel recommendations1
These guidelines should be interpreted in light of the following:
-Recent (within the last 5 years or so) improvements in ureteroscope design
-Local facilities and expertise
Smaller ureteroscopes with improved optics and larger instrument channels and the advent of holmium laser lithotripsy have improved the efficacy of ureteroscopic stone fragmentation (to ~95% stone clearance) and reduced its morbidity. As a consequence, many surgeons and patients will opt for ureteroscopy, with its potential for a one-off treatment, over ESWL, which requires more than one treatment and post-treatment imaging is needed to confirm stone clearance (with ureteroscopy you can directly see that the stone has gone).
Most urology departments do not have unlimited access to ESWL and patients may therefore opt for ureteroscopic stone extraction.
The stone clearance rates for ESWL are stone-size dependent. ESWL is more efficient for stones <1 cm in diameter than for those >1 cm in size. Conversely, the outcome of ureteroscopy is somewhat less dependent on stone size.
Recommendations
Proximal ureteric stones
-<1 cm diameter: ESWL (in situ, push-back)
->1 cm diameter: ESWL, ureteroscopy, PCNL
JJ stent insertion does not increase stone-free rates and is therefore not required in routine cases. It is indicated for pain relief, relief of obstruction, and in those with solitary kidneys.
Distal ureteric stones
-Both ESWL and ureteroscopy are acceptable options.
-Stone-free rate <1 cm: 80–90% for both ESWL and ureteroscopy; >1 cm: 75% for both ESWL and ureteroscopy.
1 Segura JW, Preminger GM, Assimos DG, et al. (1997) Ureteral stones clinical guidelines panel summary report on the management of ureteral calculi. J Urol 158:1915–1921.
TREATMENT OPTIONS FOR URETERIC STONES 397
Failed initial ESWL is associated with a low success rate for subsequent ESWL. Therefore, if ESWL has no effect after one or two treatments, change tactics.2
Open ureterolithotomy and laparoscopic ureterolithotomy are used when ESWL or ureteroscopy have been tried and failed or were not feasible.
2 Pace KT. et al. (2000). Low success rate of repeat shock wave lithotripsy for uretal stones after failed initial treatment. J Urol 164:1905–1907.
398 CHAPTER 8 Stone disease
Prevention of calcium oxalate stone formation
A series of landmark papers from Harvard Medical School1 and other groups help us to give rational advice on reducing the risk of future stone formation in those who have formed one or more stones. The Harvard studies stratified risk of stone formation on the basis of intake of calcium and other nutrients (Nurses Health Study, n = 81,000 women; equivalent male study, n = 45,000).
Low fluid intake
Low fluid intake may be the single most important risk factor for recurrent stone formation. High fluid intake is protective,1 by reducing urinary saturation of calcium, oxalate, and urate.
Time to recurrent stone formation is prolonged from 2 to 3 years in previous stone formers randomized to high fluid vs. low fluid intake (averaging about 2.5 vs. 1 L/day) and over 5 years, risk of recurrent stones was 27% in low-volume controls compared with 12% in high-volume patients.2
Dietary calcium
Conventional teaching was that high calcium intake increases the risk of calcium oxalate stone disease. The Harvard Medical School studies have shown that low calcium intake is, paradoxically, associated with an increased risk of forming kidney stones, in both men and women (relative risk of stone formation for the highest quintile of dietary calcium intake vs. the lowest quintile = 0.65; 95% confidence intervals 0.5 to 0.83—i.e., high calcium intake was associated with a low risk of stone formation).
Calcium supplements
In the Harvard studies,3 the relative risk of stone formation in women on supplemental calcium compared with those not on calcium was 1.2 (95% confidence intervals 1.02–1.4). In 67% of women on supplements, the calcium was either not consumed with a meal or was consumed with a meal with low oxalate content. It is possible that consuming calcium supplements with a meal or with oxalate-containing foods could reduce this small risk of inducing kidney stones.
Other dietary risk factors related to stone formation
Increased risk of stone formation (relative risk of stone formation shown in brackets for highest to lowest quintiles of intake of particular dietary factor):
-Sucrose [1.5]
-Sodium [1.3]: high sodium intake (leading to natriuresis) causes hypercalciuria
-Potassium [0.65]
1 Curhan GC, et al. (1993). A prospective study of dietary calcium and other nutrients and the risk of symptomatic kidney stones. N Engl J Med 328:833–38.
2 Borghi L, et al. (1996). Urinary volume, water and recurrences in idiopathic calcium nephrolithiasis: A 5-year randomized prospective study. J Urol 155:839–843.
3 Curhan G, et al. (1997). Comparison of dietary calcium with supplemental calcium and other nutrients as factors affecting the risk for kidney stones in women. Ann Intern Med 126:497–504.
PREVENTION OF CALCIUM OXALATE STONE FORMATION 399
Animal proteins
High intake of animal proteins causes increased urinary excretion of calcium, reduced pH, high urinary uric acid, and reduced urinary citrate, all of which predispose to stone formation.4
Alcohol
Curhan’s studies from Harvard5 suggest small quantities of wine decrease risk of stones.
Vegetarian diet
Vegetable proteins contain less of the amino acids phenylalanine, tyrosine, and tryptophan that increase the endogenous production of oxalate. A vegetarian diet may protect against the risk of stone formation.6,7
Dietary oxalate
A small increase in urinary oxalate concentration increases calcium oxalate supersaturation much more than an increase in urinary calcium concentration. Mild hyperoxaluria is one of the main factors leading to calcium stone formation.8
4 Kok DJ (1990). The effects of dietary excesses in animal protein and in sodium on the composition and crystallization kinetics of calcium oxalate monohydrate in urines of healthy men. J Clin Endocrinol Metab 71:861–867.
5 Curhan G, et al. (1998). Beverage use and risk for kidney stones in women. Ann Intern Med 128:534–540.
6 Robertson WG, et al. (1982). Prevalence of urinary stone disease in vegetarians. Eur Urol 8:334–339. 7 Borghi, L (2002). Comparison of two diets for prevention of recurrent stones in idiopathic hypercalciuria. N Engl J Med 346:77–84.
8 Robertson WG, Peacock M, Ouimet D, et al. (1981). The main risk for calcium oxalate stone disease in man: hypercalciuria or mild hyperoxaluria? In Smith LH, Robertson WG, Finlayson B (Eds.), Urolithiasis: Clinical and Basic Research. New York: Plenum Press, pp. 3–12.