Table 12: Critical values for renal excretion in children: when to start therapy

 

	mmol/kg*d-^1
Calcium	>0.1
Oxalate	> 0.0063
Uric acid	> 0.063
Citrate*	< 0.01
Cystine	heterocygotous 0.0058-0.0117
	homocygotous > 0.024
Magnesium	< 0.045
Phosphate	> 0.483

Tlease note the presence of citrate splitting bacteria in the urine sample

TREATMENT

The first-line treatment of paediatric nephrolithiasis in the absence of obstructive uropathy is extracorporeal shock wave lithotripsy (ESWL). When planning interventional stone therapy in children the necessity of general anaesthesia must be taken into account for percutaneous litholapaxy (PNL), ureterorenoscopy (URS) and, depending on the child's age, for ESWL. For this reason, the treatment option with the highest probability of success in a single or at most two sessions should be chosen. In a few cases, this can only be achieved by open surgery, which, generally, is indicated if obstruction of the urinary tract requires correction in the same session.

Several factors affect interventional stone treatment in children: size, localization and composition of the calculus, and urinary tract configuration. With larger stones, the probability of a single ESWL session for complete clearance decreases. Disintegration is particularly difficult in cystine calculi. The size of the stone must be viewed in relation to the size of the kidney and the draining system. A stone or a fragment may lead to

serious complications in children because of the narrow ureteral lumen. On the other hand, a relatively large stone may pass more easily than in adults.

Indications and complications of interventional stone therapy in children are similar to those in adults. Even problems with Steinstrasse are much less frequent in children. The ESWL treatment of children less than 100 cm in height was initially thought to be impossible. That has changed with special positioning techniques (e.g. protecting the lungs with polystyrene) and lithotriptors with a more confined shock wave focus. Detrimen­tal long-term effects on renal function and growth have been ruled out in recent studies.

In small children, general anaesthesia is mandatory. Percutaneous endoscopic procedures can be performed safely in children beyond their fourth year of life. Ureteroscopy is also an option in the treatment of nephrolithiasis in children.

Conservative treatment

Conservative stone treatment of paediatric nephrolithiasis follows the same rules as in adult patients (e.g. medical dissolution of uric acid stones, antibiotic agents for infection stones).

Metaphylaxis of paediatric nephrolithiasis

Metaphylaxis of paediatric nephrolithiasis follows the principles detailed in the AWMF guidelines. (2) Dosage of metaphylactic drugs, however, requires appropriate adaptation. Examples of adapted dosages are given below.

Table 13: Metaphylaxis in paediatric nephrolithiasis: corrected dosages

 

Urinary excretion	30-40 ml_/kg*d-^1
Sodium/potassium citrate	0.9-2.0 mEq/kg*d"^1
Allopurinol	4 mg/kg*d^1
Magnesium	5.7 mg/kg*d^1
Ammonium chloride test	100 mg/kg*d"^1

Metaphylaxis of paediatric nephrolithiasis also includes a high fluid intake, nutritional and dietetic aspects. In patients with metabolic disease (e.g. cystinuria, renal tubular acidosis, hypercalciuria, rare cases of enzymatic defects [uric acid]), only a medical metaphylaxis should be considered.

REFERENCES

Brandle E, Hautmann R.

Leitlinie zum Harnsteinleiden bei Kindern. http://www.dgu.de/lei/5_98.htm.

Brandle E, Hautmann R.

Leitlinie zur Metaphylaxe des Harnsteinleidens: http://www.rz.uni-duesseldorf.de/www/AWMF/ll/urol-026.htm (Arbeidsgemeinschaft der Wissenschaftlichen Medischen Fachgesellschaften).

3. al Busaidy SS, Prem AR, Medhat M, Giriraj D, Gopakumar P, Bhat HS.

Paediatric ureteric calculi: efficacy of primary in situ extracorporeal shock wave lithotripsy. Br J Urol 1998; 82: 90-96.

4. Carvajal Busslinger Ml, Gygi C, Ackermann D, Kaiser G, Bianchetti M.
Urolithiasis in childhood: when to do what? Eur J Pediatr Surg 1994; 4: 199-200.