Description of the condition
Urolithiasis or stone disease is a condition where crystalline mineral deposits are formed in the urinary tract. Metabolic and anatomical factors, iatrogenic and idiopathic causes all contribute to stone formation. In children infection is an important contributor to stone development.
Formation of the urinary stones is positively influenced by increased concentrations of uric acid, calcium, oxalate and cystine molecules. Crystallisation inhibitors such as citrate, magnesium, glycosaminoglycans and pyrophosphate play an important role as inhibitors in the formation of the urinary stones and their depletion may be the main cause of the stone formation.
The composition of the stones, their location in the urinary tract and prevalence of the disease varies around the world. The prevalence rate in low- to middle-income countries such as Pakistan and Turkey is 5% to 15% (Shah 1991) compared with 1% to 5% in high-income countries (Elsobky 2000; Yoshida 1990). Boys are affected more than girls with a male-to-female ratio of 3:1 (Rizvi 2002).
Urinary stones can be located in any part of the urinary tract. Many stones found in children born in low- to middle-income countries are located within the urinary bladder (Rizvi 2002; Rizvi 2003). There is some evidence to suggest that the predominant location of urinary stones has shifted from the bladder to the upper urinary tract over a 13-year period from 1987 to 2000 (Rizvi 2002). Of these, 75% to 80% have upper urinary tract stones and 5% are caused by infection (Ozokutan 2000).
The manifestation and clinical presentation of urinary stones in children differs from the adult population and can vary with age. Fifty per cent of children will present with abdominal pain, 33% with haematuria and 11% with infection. Children under the age of five years most commonly present with haematuria, while pain is a more common finding in older children. In children the localisation of pain is not as typical as in adults and flank pain radiating to the groin is rare (Santos-Victoriano 1998). Pain in children with stones can have a distribution such as appendicitis or gastroenteritis. In infants, the only presenting sign of stone disease might be urinary tract infection.
Diagnosis is confirmed by radiological evaluation which is also used to assess the size of the stone, its location, and the degree of possible urinary obstruction.
Description of the intervention
The most suitable management strategy depends on a number of factors, principally the size, location and composition of the stone. Other factors influencing management include the availability of different treatment options and local expertise, as well as anatomical variations in children with congenital abnormalities of the urinary tract.
Extracorporeal shock wave lithotripsy (ESWL) is a commonly used therapy for children with smaller upper urinary tract stones. This technique is typically used for small to moderate stones between 4 mm to 10 mm but depends on there being adequate drainage of the urinary system below the level of the stone. ESWL can be also used for treatment of ureteric stones. Success rates and complications are significantly affected by location of the stone and can depend on the type of machine used.
In children with larger and more complex stone disease percutaneous nephrolithotomy (PCNL) is widely used. This technique is considered in children with large upper tract stones (1.5 cm or larger). Until recently this technique was limited by the availability of appropriately sized instruments; however paediatric size instruments are now available (Desai 2005).
Children with stones within the ureter or collecting system may be treated by ureterorenoscopy, although in smaller children the size of the ureteric orifice may be insufficient to accommodate an ureterorenoscope. Different lithotripsy techniques such as laser, ultrasound, and pneumatic lithotripsy can be utilised with ureterorenoscopy. This technique is being used in children with stone size from 4 mm where visualization during ESWL failed or cannot be done.
The last surgical technique used for stone removal is open stone surgery. This technique is most commonly employed in very young children with large stones or in children with a large stone which would require multiple endoscopic procedures. It is also indicated in children with a stone in the presence of congenital anomalies of the urinary system or orthopaedic anomalies where operative positioning is impossible. Open surgery is rarely indicated as first-line treatment in children. It has the advantage of very high primary stone clearance rates but this radical approach has obvious disadvantages.
A conservative method of stone removal is medical expulsion therapy. The concept of medical expulsion therapy is administration of medications to accelerate and facilitate the spontaneous passage of ureteric stones. Corticosteroids, hormones, nonsteroidal anti-inflammatory agents, calcium-channel blockers and alpha-adrenergic blockers are used in conservative management of stone disease.
The success of the intervention is measured by the stone-free rate. There is currently no stone-free rate consensus regarding the size of the stone. A child's capacity to pass a stone has been shown to be greater than in adults. This is likely due to higher tissue compliance. Kidney stones less than 3 mm are likely to pass spontaneously and the chance of passing a ureteric stone less than 5 mm is approximately 70%. The passage rate in stones greater than 5 mm does not depend on age in children older than one year (Pietrow 2002).
How the intervention might work
ESWL is deemed to be safe and effective. This technique is not thought to adversely affect kidney function or linear growth of the kidneys. There is also no risk of scarring and hypertension (Jayanthi 1999). The reported stone-free rates following treatment depend on the location and size of the stone. There is a strong positive correlation between the increasing size of the stone and ineffective stone clearance. The disadvantages of ESWL include the need for potential fluoroscopic localization of some stones and the inability to adequately focus the energy in smaller children, as the machines in use are designed for older patients. The equipment is bulky and cumbersome and difficult to move; in children the technique is typically performed under general anaesthesia, and many patients with kidney stones have significant comorbidities making this a significant consideration when multiple attempts at stone clearance may be required. Complications following ESWL are relatively commonplace and include urosepsis, haematuria, flank pain and ‘steinstrasse’. All of these complications are less common with second generation lithotripters (Kroovand 1987). The stone-free range for ESWL reported by most centres for moderate size stones is between 70% and 80% (Picramenos 1996; Van Horn 1995). ESWL is the least invasive procedure for the management of most types of stones in children.
PCNL in the children was performed first time by Woodside 1985 almost 30 years ago. Initial results were excellent with a reported stone-free rate of 100% with no complications. Subsequent publications have demonstrated a number of potential complications of PCNL include renal scarring (Wilson 1993) bleeding, postoperative infection and persistent urinary leakage.
Use of ureteroscopic techniques is similar to those in adults. Complete stone clearance rates of up to 90% have been reported with the use of a semi-rigid ureteroscope (Dogan 2011). The incidence of vesicoureteric reflux disease after ureteroscopy is very low (Thomas 1993).
Alpha-1 adrenergic receptors are located throughout the human ureter. The physiologic response to antagonism of these receptors is decreased contraction, decreased peristaltic frequency, and increased fluid bolus volume transported down the ureter. Alpha-blockers (specifically alpha-1 antagonists) increase the expulsion rate of distal ureteric stones, hence reducing the time to stone passage. The rate of spontaneous passage with no medical intervention for a stone of less than 5 mm located in the proximal ureter is 29% to 98% and 71% to 98% in the distal ureter (Segura 1997).
Why it is important to do this review
There is a lot of evidence providing information on management of stone disease in adults, but significantly less for children. Urinary stones are less prevalent in children than in adults, but are associated with significant morbidity. There is also evidence that the incidence is increasing (Clayton 2011). Once the diagnosis of stone disease in a child has been made and the child treated, the reoccurrence rate is high.