370 CHAPTER 8 Stone disease

Kidney stone treatment options: watchful waiting

The traditional indications for intervention are pain, infection, and obstruction. Hematuria caused by a stone is only very rarely severe or frequent enough to be the only reason to warrant treatment.

Before embarking on treatment of a stone that you think is the cause of the patient’s pain or infections, warn the patient that though you may be able to remove the stone successfully, their pain or infections may persist (i.e., the stone may be coincidental to their pain or infections, which may be due to something else).

Remember, UTIs are common in women, as are stones, and it is not therefore surprising that the two may coexist in the same patient but be otherwise unrelated.

Options for stone treatment are watchful waiting, extracorporeal shock wave (ESWL), flexible ureteroscopy, percutaneous nephrolithotomy (PCNL), open surgery, and medical dissolution therapy.

When to watch and wait—and when not to

It is not necessary to treat every kidney stone. As a rule of thumb, the younger the patient, the larger the stone, and the more symptoms it is causing, the more inclined we are to recommend treatment.

Thus, one would probably do nothing about a 1 cm asymptomatic stone in the kidney of a 95-year-old patient. On the other hand, a 1 cm stone in an asymptomatic 20-year-old runs the risk over the remaining (many) years of the patient’s life of causing problems. It could drop into the ureter, causing ureteric colic, or it could increase in size and affect kidney function or cause pain.

Asymptomatic stones followed over a 3-year period are more likely to require intervention (surgery or ESWL) or to increase in size or cause pain if they are >4 mm in diameter and if they are located in a middle or lower pole calyx.1 The approximate risks, over 3 years of follow-up, of requiring intervention, of developing pain, or of increase in stone size, relative to stone size, is shown in Table 8.3.

Another factor determining the need for treatment is the patient’s job. Airline pilots are not allowed to fly if they have kidney stones, for fear that the stones could drop into the ureter at 30,000 ft, with disastrous consequences.

Some stones are definitely not suitable for watchful waiting. Untreated struvite (i.e., infection related) staghorn calculi will eventually destroy the kidney if untreated and are a significant risk to the patient’s life. Watchful waiting is therefore NOT recommended for staghorn calculi unless patient comorbidity is such that surgery would be a higher risk than watchful waiting.

1 Burgher A, et al. (2004). Progression of nephrolithiasis: long-term outcomes with observation of asymptomatic calculi. J Endourol 18:534–539.

KIDNEY STONE TREATMENT OPTIONS: WATCHFUL WAITING 371

Table 8.3 Approximate 3-year risk of intervention, pain, or increase in stone size

			Stone size
	<5 mm	5–10 mm	11–15 mm	>15 mm
% Requiring	20%	25%	40%	30%
intervention
% Causing pain	40%	40%	40%	60%
% Increasing	50%	55%	60%	70%
in size

Historical series suggest that ~30% of patients with staghorn calculi who did not undergo surgical removal died of renal-related causes—renal failure and urosepsis (septicemia, pyonephrosis, perinephric abscess).2,3 A combination of a neurogenic bladder and staghorn calculus seems to be particularly associated with a poor outcome.4

2 Blandy JP, Singh M (1976). The case for a more aggressive approach to staghorn stones. J Urol 115:505–506.

3 Rous SN, Turner WR (1977). Retrospective study of 95 patients with staghorn calculus disease. J Urol 118:902.

4 Teichmann J (1995). Long-term renal fate and prognosis after staghorn calculus management. J Urol 153:1403–1407.

372 CHAPTER 8 Stone disease

Stone fragmentation techniques: extracorporeal lithotripsy (ESWL)

The technique of focusing externally generated shock waves at a target (the stone) was first used in humans in 1980. The first commercial lithotriptor, the Dornier HM3, became available in 1983.1 ESWL revolutionized kidney and ureteric stone treatment.

Three methods of shock wave generation are commercially available— electrohydraulic, electromagnetic, and piezoelectric.

Electrohydraulic

Application of a high-voltage electrical current between 2 electrodes about 1 mm apart under water causes discharge of a spark. Water around the tip of the electrode is vaporized by the high temperature, resulting in a rapidly expanding gas bubble. The rapid expansion and then rapid collapse of this bubble generates a shock wave that is focused by a metal reflector shaped as a hemi-ellipsoid.

This method was used in the original Dornier HM3 lithotriptor.

Electromagnetic

Two electrically conducting cylindrical plates are separated by a thin membrane of insulating material. Passage of an electrical current through the plates generates a strong magnetic field between them, the subsequent movement of which generates a shock wave. An acoustic lens is used to focus the shock wave.

Piezoelectric

A spherical dish is covered with about 3000 small ceramic elements, each of which expands rapidly when a high voltage is applied across them. This rapid expansion generates a shock wave. X-ray, ultrasound, or combinations of both are used to locate the stone on which the shock waves are focused.

Older machines required general or regional anesthesia because the shock waves were powerful and caused severe pain.

Newer lithotriptors generate less powerful shock waves, allowing ESWL with oral or parenteral analgesia in many cases, but they are less efficient at stone fragmentation.

Efficacy of ESWL

The likelihood of fragmentation with ESWL depends on stone size and location, anatomy of renal collecting system, degree of obesity, and stone composition. ESWL is most effective for stones <2 cm in diameter, in favorable anatomical locations. It is less effective for stones >2 cm diameter, in lower-pole stones in a calyceal diverticulum (poor drainage), and those composed of cystine or calcium oxalate monohydrate (very hard).

Stone-free rates for solitary kidney stones are 80% for stones <1 cm in diameter, 60% for those between 1 and 2 cm, and 50% for those >2 cm in diameter. Lower stone-free rates as compared with open surgery or PCNL are accepted because of the minimal morbidity of ESWL.

1 Chaussy CG, Brendel W, Schmidt E (1980). Extracorporeal induced destruction of kidney stones by shock waves. Lancet 2:1265–1268.

STONE FRAGMENTATION TECHNIQUES: ESWL 373

There have been no randomized studies comparing stone-free rates between different lithotriptors. In nonrandomized studies, rather surprisingly, when it comes to efficacy of stone fragmentation, older (the original Dornier HM3 machine) is better (but with higher requirement for analgesia and sedation or general anesthesia). Less powerful (modern) lithotriptors have lower stone-free rates and higher retreatment rates.

Side effects of ESWL

ESWL causes a certain amount of structural and functional renal damage (found more frequently the harder you look). Hematuria (microscopic, macroscopic) and edema are common, perirenal hematomas less so (0.5% detected on ultrasound with modern machines, although reported in as many as 30% with the Dornier HM3).

Effective renal plasma flow (measured by renography) has been reported to fall in ~30% of treated kidneys. There are data suggesting that ESWL may increase the likelihood of development of hypertension.

Acute renal injury may be more likely to occur in patients with preexisting hypertension, prolonged coagulation time, coexisting coronary heart disease, or diabetes and in those with solitary kidneys.

Contraindications to ESWL

Absolute contraindications are pregnancy and uncorrected blood clotting disorders (including anticoagulation).

Procedure-specific consent form: potential complications after ESWL

Common

-Bleeding on passing urine for short period after procedure

-Pain in the kidney as small fragments of stone pass after fragmentation

-UTI from bacteria released from the stone, needing antibiotic treatment.

Occasional

-Stone will not break as too hard, requiring an alternative treatment

-Repeated ESWL treatments may be required

-Recurrence of stones

Rare

-Kidney damage (bruising) or infection, needing further treatment

-Stone fragments occasionally get stuck in the tube (ureter) between the kidney and the bladder, requiring hospital admission and sometimes surgery to remove the stone fragment

-Severe infection requiring intravenous antibiotics and sometimes drainage of the kidney by a small drain placed through the back into the kidney.

Alternative therapy

Endoscopic surgery, open surgery, or observation can be used to allow spontaneous passage.