Nonstaghorn Calculi

8/11/2019 Nonstaghorn Calculi

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Nonstaghorn Calculi. In examining the efficacy of SWL in the treatment of patients

with renal calculi, passage of stone debris rather than fragmentation of the stone is the primary

limiting

factor (Renner et al, 1999). There is general agreement that stone free is the most rigorous

definition of successful outcome of any stone removal procedure and that complete stone

clearance should be the preferred goal of any intervention (Psihramis et al, 1992). However,

because SWL outcome is dependent on spontaneous stone clearance, treatment results are often

reported in terms of success rates, which may be defined as patients who are either stone free

or who have asymptomatic, small, residual fragments. Various cutoff points between 2 and 5

mm are used in the literature to define the size of these fragments, making study comparisons

difficult. In many cases, failure of SWL is not due to a failure of stone fragmentation but rather a

failure to clear the resulting stone fragments. Failure to clear stone fragments is a concern,

because it results in a higher re-treatment rate as well as a higher number of ancillary procedures.

Clayman and associates (1989) suggested that in comparing the results of SWL and PNL or in

comparing different lithotripters, the parameters of stone-free rate, re-treatment rate, and number

of auxiliary procedures should be combined into an effectiveness quotient that may better

express treatment results and allow one to compare different treatment modalities:

% stone free

100% + re treatment + % auxillary procedures

For example, Netto and associates (1991), in a study comparing PNL and SWL for

patients with lower pole calculi, reported overall stone-free rates of 93.6% and 79.2% for PNL

and SWL, respectively; these values were not significantly different. However, the effectiveness

quotients of 93.7% and 55.9% for PNL and SWL did differ significantly because this calculation

incorporated the 41% re-treatment rate for the SWL group.

The negative effect of an increasing stone burden (size and number) on the results of

SWL has been describedby a number of groups, dating from the initial reportsof SWL to

the present generation of lithotripters(Drach et al, 1986; Lingeman et al, 1986a; El-Assmy et

al, 2006a; Tan et al, 2006). A now-axiomatic principle of SWL is that as stone burden

increases, the stone-free rate declines and the need for ancillary procedures and re-

treatment rises.Importantly, stone burden is not defined solely on the basis of the largest stone

present in the kidney but also it takes into account the overall number of stones present.


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Furthermore, larger stone burdens are associated with a higher rate of residual stones, a point of

particular concern in the treatment of patients with struvite calculi (Preminger et al, 2005).

Figure 483illustrates the effect of the size of solitary renal stones on the results of SWL.

PNL, although more invasive and often associated with higher morbidity, achieves better stone-

free rates than does SWL and is not affected by stone size (Lingeman et al, 1987a).

Ureteroscopy, an alternative treatment for patients with renal calculi, is also negatively affected

by increasing stone burden, although to a lesser degree than is SWL, because stone fragments are

often removed or vaporized. Thus, as stone burden increases, PNL becomes more efficient than

either SWL or ureteroscopy.

Importantly, 50% to 60% of all solitary renal calculi are less than 10 mm in

diameter(Cass, 1995; Renner and Rassweiler, 1999; Logarakis et al, 2000). Treatment results

of SWL for this substantial group of patients are generallysatisfactoryand independent of

stone location or composition. Although better results can be achieved with PNL or ureteroscopy

for patients with stones smaller than 10 mm, these procedures are more invasive, are associated

with greater morbidity, and may be reserved for special circumstances (e.g., anatomic

malformation causing obstruction, SWL failure).

Patients with calculi between 10 and 20 mm are oftentreated with SWL as first-line

management.However, stone location and composition can meaningfully affect the results of


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91%, which is comparable to PNL results. However, the 6-month follow-up data, which were

available for 25 patients, demonstrated that only 60% of patients were stone free, whereas 24%

had small lower pole debris and 16% had new stone growth. As surgical techniques and

technology have evolved, ureteroscopy has been applied to patients with progressively larger

stone burdens with acceptable results and morbidity (Mariani, 2007; Ricchiuti et al, 2007; Breda

et al, 2008). In general, these treatment approaches have relied on a staged approach to achieve a

successful outcome.

In summary, for patients harboring nonstaghornstones smaller than 10 mm, SWL

is usually the primaryapproach. For patients with stones between 10 and20 mm, SWL can

still be considered a first-line treatment unless factors of stone composition, location, or

renal anatomy suggest that a more optimal outcome may beachieved with a more invasive

treatment modality (PNL or ureteroscopy). Patients with stones larger than 20 mm should

primarily be treated by PNL unless specific indications for ureteroscopy are present

(e.g.,bleeding diathesis, obesity).

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Nonstaghorn Calculi