group 5, renal anatomical abnormality with calculi in the same kidney. Demographics, stone profile, procedure and outcome indicators were analysed for each group. RESULTSIn all, 188 consecutive PCNLs in 169 children were included (mean age 3.3-10.3 years, mean stone burden 19.1-33.3 mm in the five groups). The mean duration of PCNL was 69-115 min. Stone clearance was satisfactory with single tract access in 90-100% of patients. Transient postoperative fever was the commonest complication (12.5-51%) followed by hyponatraemia and hypokalaemia. Blood transfusion was required in 0-7.7%. The mean stone clearance rates were 47-90% in the five groups; additional extracorporeal shockwave lithotripsy increased the cumulative clearance rates to 90-100%. CONCLUSIONPCNL is safe for treating renal stones, with excellent results and minimal complications. Comparable results are achieved in the very young child, children with anatomically abnormal kidneys, children with impaired renal function and children with bilateral renal stones undergoing simultaneous bilateral PCNL. Hence none of these factors should be considered as relative contraindications.

RESULTSThere were 30 renal units in 29 children (median age 3.8 years, range 1.4-5). Because of poor growth the mean ( SD ) body weight of the children was only 12.2 (2.8) kg, which is near the 50th percentile for children of mean age 3.5 years. The median (range) stone burden was 2.35 (1.3-6) cm; 60% of the patients had single stones while 28% had more than five. There were five staghorn stones. All PCNL was primary and with one puncture, using a 17 F angled nephroscope; stones were fragmented using a pneumatic lithoclast. After PCNL stones were completely cleared in 60% of the renal units, which increased to 100% after combining it with extracorporeal shockwave lithotripsy. The median (range) follow-up was 24.9 (4-51) months; the overall complication rate was 6%. In the long follow-up hypertension was not detected in any child and isotopic renograms in 17 kidneys detected no new scarring or loss of renal function. CONCLUSIONPCNL is a safe and effective for treating renal stones in very young children. KEYWORDS PCNL, renal stones, pre-school children OBJECTIVETo review our experience of percutaneous nephrolithotomy (PCNL) in children before school age, and determine its efficacy and safety in this age group. PATIENTS AND METHODSThe records of children aged £ 5 years undergoing PCNL were reviewed. Variables assessed included stone number, size, location and type. The PCNL puncture site and number were also recorded. We reviewed stone clearance with PCNL, ancillary procedures used, complication rates and follow-up status of the children.

The amino acid sequence of a recently isolated camel milk protein rich in half-cystine has been determined by peptide analyses. The 11 7-residue protein has 16 half-cystine residues, concluded to correspond to disulfide bridges and suggesting a tight conformation of the molecule.Comparisons of the structure with those of other proteins reveal several interesting relationships. The camel protein is clearly homologous with a previously reported rat whey phosphoprotein of possible importance for mammary gland growth regulation, and with a mouse protein of probable relationship to neurophysins. The camel, rat and mouse proteins may represent species variants from a rapidly evolving gene. Residue identities in pairwise comparisons are 40% for the camel/rat proteins and 33% for the camel/mouse proteins, with 38 positions conserved in all three forms. The camel protein also reveals an internal repeat pattern similar to that for the other two proteins.The homology between the three milk whey proteins has wide implications for further relationships. Thus, previously noticed similarities, involving either of the milk proteins, include limited similarities to casein phosphorylation sites for the camel protein, to neurophysins in repeat and half-cystine patterns for the mouse and rat proteins, and to an antiprotease for the rat protein. These similarities are reinforced by the camel protein structure and the recognition of the three whey proteins as related. Finally a few superficial similarities with the insulin family of peptides and with some other peptides of biological importance are noticed. Combined, the results relate the camel protein in a family of whey proteins, and extend suggestions of relationships with some binding proteins.

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