Initial Choice of Therapy in the Stone Patient

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Initial Choice of Therapy in the Stone Patient

Peter L. Steinberg¹ & David M. Hoenig²

¹ Beth Israel Deaconess Medical Center, Boston, MA, USA

² The Arthur Smith Institute for Urology, Zucker School of Medicine at Hofstra/Northwell, Lake Success, NY, USA

Introduction

Urolithiasis is a prevalent condition, afflicting nearly 10% of the US population [1]. Cost estimates for stone management range from US$2 billion to $10 billion annually in the American healthcare system [1, 2]. As the front line in managing stone disease, the urologist is armed with numerous tools to manage a patient presenting with a urinary stone. This chapter will focus on adult patients with “normal” renal anatomy, as stones in aberrant urinary systems are discussed in Chapters 67–71. Since the focus is elective stone management, patients presenting with sepsis, renal failure, or intractable pain are not discussed, as these situations dictate urgent urinary tract decompression with either ureteral stenting or percutaneous nephrostomy and are described in Chapter 66. The prime modalities discussed are shock‐wave lithotripsy (SWL), ureteroscopy/ureterorenoscopy (URS), percutaneous nephrolithotomy (PCNL), medical expulsive therapy (MET), and observation.

Overall approach

Most urologists confront ureteral stones acutely and renal stones in a less urgent fashion. As such, the primary issue facing the urologist treating a patient with a ureteral stone, after insuring appropriate pain management, renal function, and that systemic inflammatory response syndrome (SIRS)/sepsis is not an issue, is to determine if spontaneous passage is likely or not. When faced with a renal stone, decision‐making is often less pressed and selecting the optimal surgical approach is paramount to assure the best chance of success.

A recent New England Journal of Medicine article by Smith‐Bindman et al. provided some insight into the rate of urgent intervention needed when patients present to the emergency department with renal colic [3]. Nearly 10% of patients seen initially for renal colic require hospital admission for pain management and/or surgical intervention. In the month following initial evaluation, another 10–15% will present back to the emergency department and one‐third of these patients will require hospital admission [3]. This highlights that although some patients need urgent intervention, many will semi‐electively end up seeing a urologist where a plan for observation or intervention will be created.

Ureteral stones

Although some data have come to light questioning the efficacy of MET [4], the general paradigm for managing ureteral stones involves observation with or without MET for most stones and if that fails proceeding to a URS or SWL. Rarely will an antegrade/percutaneous or laparoscopic/robotic/open approach be needed for these stones.

Distal ureteral stones

Stones in the distal ureter are among those with the highest rate of spontaneous passage [5, 6]. The ureterovesical junction (UVJ) remains a common site for stones to become lodged, as it is the narrowest part of the ureter (Figure 64.1a). Generally speaking, smaller stones that are further along the ureter have a greater chance of spontaneous passage than larger stones in a more proximal location. Although it is difficult to tell the exact fate of any given stone, there is ample evidence that the majority of stones under 4–5 mm often pass [5, 6]. Additionally, stones that have not passed within 4–6 weeks seldom do so [5].

Image described by caption. — **Figure 64.1** (a) Computed tomography (CT) of right distal ureteral calculus at the UVJ (demarcated by lines). (b) Fluoroscopy of right distal ureteral stone localized at the F2 focal point for shock‐wave lithotripsy.

A trial of MET is warranted in nearly all patients with an uncomplicated distal stones under 1 cm. Two meta‐analyses support the role of both alpha‐antagonists and calcium channel blockers (CCBs) to increase the number of stones passed and to hasten the speed of stone passage [7, 8]. A review from Hollingsworth et al. suggests a 65% increased rate of stone expulsion with either agent, and the number needed to treat to lead to one additional stone expulsion was four [7]. A study from the emergency medicine literature, pooling data from 16 alpha‐blocker studies and nine CCB studies, shows a 59% greater rate of passage with alpha‐blockers and a 50% greater rate of passage with CCBs [8]. The number needed to treat in this study for alpha‐blockers was 3.3 and for CCBs it was 3.9 [8]. Based upon their own analysis of the data, the American Urological Association (AUA) suggests alpha‐blockers are the preferred agent for MET, primarily due to their lower rate of side effects than CCBs [6].

Recently, a well‐powered study from the United Kingdom suggested that MET with either alpha‐blockers or CCBs provides minimal benefit over observation [4]. This study randomized over 1100 patients to placebo, nifedipine, or tamsulosin and showed that 80% of patients in each arm did not require surgical intervention. Interestingly, this trial accrued patients with stones in all ureteral locations while prior work has focused on the distal ureter, and had only one‐third of enrolled patients with stones >5 mm in size [4]. This high‐quality trial is the best‐powered study to date on MET; however, there are some legitimate criticisms of the study design. Given the familiarity urologists have with alpha‐blockers and their excellent safety profile, it seems a trial that is both well powered and with a patient population similar to the prior studies with equivalent percentages of distal stones >5 mm may be needed to curtail the practice of MET.

Two sets of AUA guidelines on the surgical management of stones have clearly demonstrated that URS is the most efficacious means of managing a distal ureteral stone [5, 6]. Success rates for URS are well over 90% in most series and SWL has a clearance rate much lower, often in the 60–70% range: this is clearly dependent on a number of factors including the lithotripter used. Overall, a patient undergoing a SWL for a distal stone will require 1.3 procedures for clearance, as compared to a patient undergoing a URS [5, 6]. Both procedures are relatively safe, with URS associated with a <5% risk of several ureteral injury in modern series [6]; however, the common use of ureteral stents after URS is a continuing source of morbidity and often dreaded by patients who are recurrent stone formers.

Given this information, it seems apparent that a trial of MET is appropriate in many patients with uncomplicated distal ureteral stones. If MET fails, the choice of URS or SWL for a distal ureteral stone lies with the available expertise and equipment, and with the patient after an informed discussion of the risks and benefits of each modality. Armed with the knowledge that both modalities lead to high rates of stone clearance, additional factors such as the potential need for stenting, type of anesthetic used, and complication profile of each procedure can be used to guide the choice of therapy.

Proximal and mid‐ureteral stones

Optimal management of these stones depends heavily upon the size and density of the calculus in question [9]. As described above, larger and more proximal stones are associated with a lower rate and longer time to spontaneous passage than smaller and more distal stones [5, 6]. Management of mid‐ and proximal ureteral stones is slightly different from that of distal stones, with the largest difference being the lack of evidence for MET in mid‐ and proximal ureteral stones as it has not been thoroughly tested. A study by Pickard et al. would suggest there is no role for MET in these stones, although it also suggested no role for MET in distal stones [4]. Operative intervention consists primarily of SWL or URS, although there is a select role for antegrade approaches to large and complex proximal calculi.

Once again, pooled data from multiple studies are provided by the 2007 and 2016 AUA guidelines delineating outcomes in the management of proximal and mid‐ureteral stones [5, 6]. Overall, URS is associated with improved stone‐free rates in both locations, with nearly 90% success in many studies, while SWL again has a lower stone‐free rate in the 70–85% range [5, 6]. This relationship holds until stones get over 1 cm in size and then outcomes begin to converge, with roughly 80% stone‐free rates for both modalities [5, 6]. The rate of secondary procedures is higher when SWL is used for stones under 1 cm, as in the distal ureter [5, 6].

One unique issue with SWL in the mid ureter involves the bony pelvis interfering with visualization and treatment of the stone (Figure 64.2). In some lithotripters, a prone position must be used to ensure the stone is in the ideal position for treatment, and localization of the stone may be challenging due to the bony structures.

An additional consideration to aid in selecting optimal initial therapy for proximal ureteral stones focuses on the costs incurred with treatment. A cost analysis from Lotan et al. shows that URS is less costly than SWL for proximal stones when performed primarily [10]. When considering the higher rate of adjunctive procedures for SWL compared with URS, the cost differential is even greater and is something to potentially consider when deciding how to approach the patient with such a stone [10].

In select cases of very large stones in the proximal ureter, or stones which are heavily impacted and do not permit retrograde access, a patient can be offered an antegrade procedure for clearance [11]. Both rigid and flexible nephroscopy can be used to approach the ureteropelvic junction and proximal ureter. In addition, following treatment of the stone, fragments can be removed via the percutaneous tract, obviating the need for passage.