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Practical Urology: EssEntial PrinciPlEs and PracticE

Percutaneous surgery has a higher success

are thought to have an influence in stone-free

rate for simple stones than ESWL, but is obvi-

rates.14

ously more invasive; nevertheless, PCNL has

The Lower Pole Study Group15 reported a

been shown to be both effective and safe13 with

multicentre randomized trial of ESWL versus

the inherent advantage of removal of a large

PCNL for lower pole stones less than 3 cm in

stone burden obviating the need for the patient

size. It was found that overall stone-free rate was

to pass the fragments generated by other

far superior for PCNL compared to lithotripsy

techniques.

(95% vs. 37%) and for stones greater than 1 cm

With flexible ureterorenoscopy, a successful

the stone-free rate for ESWL was only 21%. This

outcome of over 80% can be expected rising to

group analyzed the various features of lower

around 90% for repeat sessions when stones are

pole anatomy, but did not find it to be of rele-

treated with the combination of flexible uret-

vance in the stone-free rate after ESWL. The

eroscopy and laser given favorable anatomy and

advent of flexible ureterorenoscopy has added a

a modest stone burden.

further option to the endourologist’s armamen-

The following categories of stone require

tarium, but there does remain a role for primary

endoscopic surgery: Larger stones (>2 cm),

lithotripsy stones of 1 cm or less as shown by a

staghorn calculi, adverse anatomy (larger lower

randomized prospective trial of ESWL versus

pole stones, associated pelviureteric obstruc-

ureteroscopy with results showing equivalent

tion), certain stone compositions (cystine or

success rates.16

calcium oxalate monohydrate).To this list should

be added ESWL failures and certain patient fac-

Horseshoe Kidneys and Stones

tors including where ESWL is contraindicated

or not feasible (e.g., morbid obesity, bleeding

The association between horseshoe kidneys and

diatheses).

stones is well recognized. ESWL may be unsuc-

Staghorn Calculi

cessful because of failure to target the stones

with the kidney lying more anteriorly than usual

Guidelines indicate that these complex stones

and there may be concern about drainage issues.

Endoscopic surgery especially PCNL usually

should be treated by PCNL as ESWL monother-

presents little difficulty although the skin to

apy gives poor stone clearance.13 Careful plan-

stone depth can be significantly larger than nor-

ning of the approach enhanced in the modern

mal. CT is particularly useful in planning the

era by 3D CT reconstruction is helpful and mul-

approach.

tiple tracts may be required. An upper pole

approach can improve the chances of stone

Calyceal Diverticula Stones

clearance with predominantly lower pole stag-

horn calculi which involve parallel calyces. The

Stones in calyceal diverticula are very unlikely

increased complication rate has been discussed

to be cleared by ESWL, but there is anecdotal

elsewhere. Supplementary ESWL for unreach-

evidence of resolution of symptoms. A percuta-

able fragments needs to be considered with

neous approach requires a precise placement of

sandwich therapy (PCNL, ESWL, PCNL) and

the tract into the diverticulum. Although this

second look nephroscopy as further options.

can be a challenge, stone removal is straightfor-

Refinements in PCNL techniques have however

ward when access is achieved. Attempts are then

further reduced the role of supplementary

made to gain access via the diverticulum into

ESWL.13

the main collecting system to improve later

drainage. Balloon dilatation has been proposed

Lower Pole Stones

to accomplish this17 and fulguration of the diver-

ticulum has also been suggested to reduce the

Lower pole anatomy has been thought to be rel-

chances of recurrence.

evant to the success or otherwise of ESWL for

The alternative is to use the flexible uretero-

lower pole stones. Such parameters as infundib-

scope and the holmium laser.Finding the ostium

ulo-pelvic angle, infundibular width and length

to the diverticulum can be difficult but is greatly

412

Practical Urology: EssEntial PrinciPlEs and PracticE

Intervention for Ureteric Stones

the ureter when ultrasound may be able to

assist targeting. For giant ureteric stones there

Absolute reasons for intervention include

may be a role for laparoscopic surgery. The pos-

pyonephrosis, persistent symptoms, bilateral

sibility of utilizing percutaneous antegrade

ureteric stones causing obstruction,and ureteric

access particularly if there upper ureteric dila-

stones causing obstruction to a solitary kidney.

tation down to a large impacted stone also war-

Relative indications include failure of progre-

rants consideration.

ssion and larger stone size.

Pyonephrosis is an emergency situation and

Stones in Pregnancy

immediate drainage is required. There are advo-

cates of emergency stenting, but this requires

The combination of stone disease and preg-

anesthesia and there may be concerns about the

nancy presents a challenge in both diagnosis

reliability of stent giving adequate decompres-

and management. There are issues about expo-

sion in all cases. Percutaneous nephrostomy

sure to x-rays and imaging will be with ultra-

drainage has the advantage of avoiding anes-

sound or MRI will be required. The latter will

thetics and consequent decompression of the

not identify a stone but will indicate the level of

system can still lead to spontaneous stone pas-

any obstruction. The former will help in the

sage when coaptation of the ureter is restored.

detection of renal stones but may miss ureteric

As there is access to the kidney the facility is

calculi. If present hydronephrosis will be appar-

there for contrast studies in follow-up. A recent

ent, but this may be related to the pregnancy

consensus report confirmed agreement in both

rather than any primary urological problem. In

urological and radiological circles that percuta-

terms of management of proven stones, ESWL is

neous drainage was preferable unless the patient

contraindicated. Ureteroscopy may be consid-

had clotting problems.23

ered, but this will be without the safety of radio-

Regarding definitive treatment of the stone,

logical screening. Temporizing measures such

ESWL or ureteroscopy can be theoretically

as nephrostomy drainage or stenting can be

applied to calculi at any site particularly with

considered until the pregnancy reaches term.

the proliferation of flexible ureteroscopy. Patient

There are disadvantages with both.Percutaneous

or stone factors will determine which modality

drains are uncomfortable and require a collec-

is most suitable for a given stone scenario. There

tion bag. They will need to be changed at

is no evidence that stenting a patient with a ure-

3-month intervals. Stents will accentuate blad-

teric stone improves the outcome of ESWL.

der problems and will require regular changes

Previous guidelines suggest that ESWL is con-

too and therefore the need for endoscopy and

sidered the optimal treatment for upper ureteric

anesthesia.

stones less than 1 cm in size,18 whereas in the

lower ureter, stone-free rates of ESWL and URS

are equal and approach 100%.18,24 There is no

Morbid Obesity

evidence that stenting a patient with a ureteric

stone improves the outcome of ESWL. Overall, a

Patients in this category can present challenges

recent meta-analysis showed that the stone-free

in both radiological diagnosis and management.

rate was higher, but with a higher complication

Ultrasound is difficult in the obese and patients

rate and longer hospital stay for URS compared

may be too large to fit on the CT scanner. In

to ESWL.25 There is however undoubtedly a role

terms of treatment, ESWL may not be possible

for ureteroscopy when ESWL does not work

because the patient may be too heavy for the

after a maximum of two treatments.26,27

table and the depth of the stone from the skin

Stone size is a further issue with larger ure-

may preclude targeting. The skin to stone dis-

teric stones (>1 cm) being better treated endo-

tance can make a percutaneous approach impos-

scopically.18 Flexible ureteroscopy can be

sible too or may require the use of longer

invaluable in the upper ureter particularly if

instruments. A patient’s obesity is less of an

the ureter is dilated or tortuous. When stones

issue when approaching a stone endoscopically,

are radiolucent, there is no place for ESWL

but the patient’s fitness for anesthesia and

unless the stone is at the very top or bottom of

comorbidities may be an issue.