and Mikolaj Przydacz1
(1)
Department of Urology, Jewish General Hospital, McGill University, Montreal, QC, Canada
Keywords
StonesShockwave lithotripsyUreteroscopyPercutaneous nephrolithotomyMetabolic evaluationIntroduction
Urolithiasis is a well-documented complication of neurogenic bladder with significant morbidity and even mortality. Underlying neurological disorder can often make the clinical diagnosis and treatment of this condition more challenging than in non-neurogenic patients. Therefore, evaluation and medical management of stone disease in neurogenic patients should be personalized. Identifying the risk factors for the development of urolithiasis and introduction of the precautionary measures may help to minimize recurrence and improve these patients’ prognosis and future quality of life.
Epidemiology
The incidence and prevalence of urolithiasis among patients with neurogenic lower urinary tract dysfunction vary, depending on the underlying neurological disorder and developed risk factors. The risk of urinary tract stone disease in patients with neurogenic bladder is significantly higher than in the general population. The lifetime risk for urolithiasis in the general population is estimated at 12% for men and 6% for women with age standardized annual incidence rates from 0.36 to 1.22/1000 person-years [1]. The prevalence of urolithiasis in patients with spinal cord injury (SCI) has been reported to be as high as 38% and the risk of stone formation appears to increase over time [2–4]. The annual risk for forming bladder stones in SCI patients has been calculated as 4% [5]. It has been estimated that up to 20% of SCI individuals will develop struvite stones within 10 years of injury and up to 7% of them will complain of renal stones [6, 7]. Interestingly, the incidence of renal calculi appears to peak during the period immediately after SCI (3–6 months) [2, 4, 6]. This early risk of stone formation is hypothesized to be a result of a significantly increased calcium excretion because of immobilization and loss of calcium from the lower extremity skeleton [8]. In myelomeningocele patients, the incidence of renal calculi may be greater [9]. The annual risk of forming bladder stones in individuals who have already formed one stone is 16% [5]. Once a kidney stone develops, there is a 34% chance of a second renal stone developing within the next 5 years [4]. The frequency of recurrences may be even higher, with reported episodes up to 64 and 72% [10, 11]. Patients with SCI also have a high incidence of bilateral stones (23–74%) [12–14].
Risk Factors
The main risk factors for stone development in neurogenic patients are [8, 11, 15–20]:
Recurrent urinary tract infections (UTIs), in particular with urea-splitting organisms (Proteus, Pseudomonas, Klebsiella, Staphylococcus, Mycoplasma)
Bacteriuria
Indwelling catheterization (both suprapubic and urethral)
Urine stasis (may be seen either in patients with an indwelling catheter that does not drain well or in those who catheterize infrequently or who fail to empty fully)
Vesicoureteral reflux
Hydronephrosis
Renal scarring
Lower urinary tract reconstruction (in particular with surgical interposition of bowel segments)
Bladder diverticula (may predispose to incomplete emptying and thus stone formation in the diverticulum)
Foreign bodies (e.g., hair introduced during clean intermittent catheterization)
Previous history of urolithiasis and persistent stone fragments and residual fragments left after previous treatment
High spinal cord lesions
Complete spinal cord lesions
Paraplegic and quadriplegic dysfunctions
Chronic immobilization
Metabolic abnormalities
hypercalciuria (resulting from immobilization and demineralization of bone)
hypocitraturia (resulting from a reduced filtered load of citrate)
dehydration (resulting from hyperhidrosis, reduced fluid intake in order to reduce the number of catheterizations or postural oliguria from autonomic disturbances)
Increased urinary pH (resulting from bacterial infection)
Young and old age
Specific geographic variations and environmental risk factors (may exert a greater magnitude of risk than they do in the general population)
Stone Composition
The majority of urolithiasis in the SCI population is either apatite (calcium phosphate) or struvite (magnesium ammonium phosphate) in composition [17]. Whereas the first type occurs as a result of the alkaline pH of infected urine, the latter is the direct result of urinary infection with urease-producing bacteria (Proteus, Klebsiella, Pseudomonas) [14]. In the past decades, >90% of stones in patients after SCI were reported to be struvite [23, 24]. However, contemporary studies have suggested that the proportion of struvite stones has decreased and that stones of a metabolic origin now predominate in patients with SCI [8]. A study of individuals with musculoskeletal anomalies found struvite stones in only 18% of patients [14]. The most common stone type was calcium apatite (50%), which is an uncommon stone in the general population. It has been proposed that the shift from an infectious to a metabolic etiology may represent reduced risk of UTIs among patients with SCI because of dedicated SCI units, commonness of clean intermittent catheterization, better bladder augmentation techniques, and more precise urodynamic assessment [8, 25]. Therefore, when a metabolically derived stone is identified, the patient should be offered metabolic evaluation with medical and dietary therapy [26].
Diagnosis and Treatment
Comprehensive guidelines for diagnosis and treatment of urolithiasis have been developed and they can be applied in the management of patients with neurogenic bladder. This includes Guidelines of the European Association of Urology (EAU) [27], the American Urological Association (AUA) [28], and the Canadian Urological Association (CUA) [29]. Importantly, the proposed guidelines also highlight and support management of metabolically derived stones. Nevertheless, some differences in diagnosis and treatment of urolithiasis in neurogenic individuals have to be stressed.
Diagnosis
Ureteral stones can cause acute unilateral flank pain radiating to the groin, often accompanied by nausea, vomiting, and urinary symptoms [30]. The diagnosis of urolithiasis in neurologically impaired patients may be more difficult because of atypical presentation and non-specific symptoms, including feeling unwell, abdominal discomfort, sweating, increased spasms, and autonomic dysreflexia [15]. Depending on the level of neurologic dysfunction, many patients do not experience flank pain [8]. Urolithiasis may also be demonstrated by storage symptoms (urgency, frequency, incontinence), hematuria, difficulties in self-catheterization, recurrent catheter blockages, and recurrent UTIs or even sepsis. Relapsing infection within the urinary tract is considered the most common presentation in individuals with neurogenic lower urinary tract dysfunction that leads to a stone diagnosis [10].
With the exception of pregnant women, the imaging modality of choice for diagnosis in the general population is computed tomography of the kidneys, ureters, and bladder, characterized by a sensitivity of 95–96% and specificity of 98% (Fig. 11.1) [31, 32]. While ultrasound is free of radiation, it has a relatively low sensitivity and specificity of 45 and 94%, respectively (Fig. 11.2) [33–35]. A plain frontal supine radiograph of the abdomen can support the diagnosis of stone disease (Fig. 11.3) [36]. However, in neurogenic patients, the final diagnosis of urinary stones is often made using endoscopy [37, 38]. The National Institute for Health and Care Excellence recommends referring neurogenic patients with symptoms that suggest the presence of bladder stones for cystoscopy (Figs. 11.4 and 11.5) [39–41].
Fig. 11.1
Urinary stones in different patients. Noncontrast sagittal reformatted CT (a) shows a single stone (arrow) in the ureter, which is dilated proximal to the stone. (b, c) Multiple stones in the right ureter (arrows) with hydronephrosis (arrowhead) and stones in lower pole calyces (arrow). (d) Coronal reformatted image shows large staghorn stone in the left kidney with hydronephrosis. The calyces distal to the stone are dilated and fluid filled (arrow). (e) Sagittal reformatted image shows stone (arrow) along with stent and hydroureter. (f) Postcontrast coronal reformatted image shows a stone (arrowhead) with stent (white arrow) at ureteropelvic junction causing hydronephrosis. Axial CT (g) shows a jackstone urinary bladder. Axial CT shows (h) a stone (arrowhead) in Hutch diverticulum (white arrow) and a small stone within the bladder (black arrow). (i) Stone at ureterovesical junction with surrounding soft tissue (arrow) of the bladder wall (with permission from Agarwala [32])
Fig. 11.2
(a) Renal stones in the upper and lower poles. Both stones are echogenic (long arrows) with posterior acoustic shadowing (arrow heads). (b) Bladder stone. Similar to the renal stones, the bladder stone is echogenic and demonstrates clear posterior acoustic shadowing (with permission from Ching et al. [35])
Fig. 11.3
Partially obstructing right distal ureter stone (arrow) on plain film (a) and as a filling defect on intravenous pyelogram (b) (with permission from Ünsal and Karaman [36])
Treatment
Shockwave lithotripsy (SWL) , ureteroscopy (URS) , and percutaneous nephrolithotomy (PCNL) are commonly used treatment modalities of stone disease. Whereas open surgery is currently rarely used in the general population, it still remains a valuable treatment option in neurogenic patients [42].
Preoperative Considerations in Neurogenic Patients Suffering from Urolithiasis
Bacterial Colonization
Colonization of urine occurs in the majority of patients with neurogenic lower urinary tract dysfunction (see Chap. 10, “Urinary Tract Infections”). Bacterial strains resistant to multiple antibiotics are not uncommon and contribute to polymicrobial colonization of the urinary tract. This increases the risk of sepsis as a result of treatment of the stone [43]. Preoperative treatment with appropriate antibiotics is necessary, as untreated bacteriuria can lead to serious complications [44]. Postoperative urosepsis has been reported in the literature in up to 14% of operated patients [12, 45]. Furthermore, it has been shown that the retreatment and complication rates are higher in neurogenic patients, primarily because of bacterial colonization and recurrent UTIs with infected stones [12, 17]. Preoperative treatment should always be based on a recent urine culture at least 7 days prior to stone treatment [17]. In individuals colonized by multi-resistant strains of bacteria, intravenous antibiotics may be necessary. Once treatment is initiated, all catheters should be changed. In patients performing intermittent catheterization, more frequent and complete emptying is required. Appropriate prophylactic antibiotic therapy during the procedure is recommended in order to minimize the chances of urosepsis during urinary tract manipulation and stone fragmentation [17]. Further proposals include re-culturing the urine and obtaining sensitivities immediately following the procedure, as bacteria released from fragmented stones may differ from the pre-operative urinary tract flora [17]. Additional perioperative urine cultures should always be obtained when indicated by the clinical scenario.
Orthopedic Factors
Scoliosis, limb contractures, skeletal deformities, and spinal hardware may hamper positioning of patients and obtaining retrograde access for URS or good visualization of the upper urinary tract with fluoroscopy for PCNL [44–46]. Poor visualization and complicated anatomy may contribute to an increase in complications. Careful assessment of extremity and trunk mobility and range of movement should be performed before any procedure to ensure that the patient can be positioned properly during the operation. To overcome orthopedic issues, different positions such as modified flank or flank and biplanar fluoroscopy with more dynamic visualization can be used to achieve treatment success [44]. In those patients in whom retrograde access cannot be achieved, a percutaneous approach may be useful to perform antegrade flexible ureteroscopy and lithotripsy [8]. Regardless of the chosen treatment, patients should be protected from pressure ulcers during the procedure by appropriate padding of all pressure points.
Patients After Reconstructive Surgery within the Urinary Tract
Although it has been demonstrated that retrograde endourologic techniques are feasible and safe (with success rates of 75%) in patients with urinary diversion [47], altered anatomic relations of the urinary tract after reconstructive surgery can make retrograde access to the ureter challenging and lead to additional complications and lower clearance rates. Preoperative surgical history should carefully document any prior procedures within the urinary tract . The patient’s medical documentation may be of value in choosing a proper treatment.
Hydronephrosis or Suspicion of Upper Tract Obstruction
In cases of preoperative hydronephrosis , some experts recommend appropriate drainage with a stent or a nephrostomy tube prior to any procedure [44]. Hydronephrosis in neurogenic patients may indicate pyonephrosis, even with negative urine cultures. Thus, if hydronephrosis is not appropriately drained and diagnosed preoperatively, postoperative urosepsis may lead to serious life-threatening complications.
Autonomic Dysreflexia
In patients with high-level SCI, surgery may trigger autonomic dysreflexia (see Chap. 14, “Autonomic Dysreflexia”). Bladder overdistension is the most common trigger of this disorder, characterized by high blood pressure, bradycardia, headache, flushing, and sweating. Treatment consists of draining the bladder and placing the patient in the upright position if he or she is awake. If this fails, a fast-acting antihypertensive should be administered [48]. Standard anesthesia monitoring (including blood pressure control) is therefore required for all patients during any procedure of stone treatment.
Treatment Options
Management of urolithiasis in individuals with neurogenic bladder is similar to that in non-neurogenic patients and is described in reliable guidelines but some important issues need to be acknowledged:
General anesthesia may sometimes be necessary because of the impossibility of using spinal anesthesia due to spinal deformities or injuries.
The length of hospital stay in a population of neurogenic patients may be longer than that for the general population [49]. Prolonged hospitalization may result from surgical complications as well as issues with management of other medical comorbidities.
Chosen treatment should aim to completely remove all stone particles, regardless of size. SWL may be effective at breaking a stone, but neurogenic patients may be unable to clear the pieces due to impaired voiding, reduced mobility, and often large stone burden [8]. Small residual fragments may contribute to rapid stone recurrence and relapsing infections [50, 51]. In SCI patients, success rates and stone-free rates of SWL vary from 50 to over 70% [52]. Therefore, URS or PCNL may represent a better treatment modality to ensure complete stone-free status postoperatively [53]. On the other hand, SWL is feasible without additional anesthesia in most patients, and the rates of intra-operative complications, including autonomic dysreflexia , are low [52]. SWL may be a good option for treating patients who are anesthetic risks or prone to autonomic dysreflexia. Quadriplegics with high-level cord injuries requiring cardiac pacemakers and those with baclofen pumps have safely undergone SWL without complications [54, 55]. To sum up, SWL in patients with neurogenic lower urinary tract dysfunction may be considered as part of a multimodality strategy in stone management, rather than a standalone treatment.
Flexible URS may be of value in achieving stone-free status postoperatively, particularly in patients after reconstructive surgery within the urinary tract or those with orthopedic issues hindering proper patient positioning. Moreover, fibrosis and thickening of the bladder wall, often seen in neurogenic bladders, alter the ureteral orifice anatomy and make ureteral access challenging [56]. When retrograde URS fails to clear the stones, alternative approaches (SWL or antegrade flexible URS following percutaneous renal access and tract dilation) should be considered [17, 44]. However, there is a paucity of data to support clinicians with reliable recommendations on treating neurogenic patients with URS.Related posts:
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