Identification of 12 novel mutations in the SLC3A1 gene in Swedish cystinuria patients.

Cystinuria is an autosomal recessive disorder that affects luminal transport of cystine and dibasic amino acids in the kidneys and the small intestine. Three subtypes of cystinuria can be defined biochemically, and the classical form (type I) has been associated with mutations in the amino acid transporter gene SLC3A1. The mutations detected in SLC3A1 tend to be population specific and have not been previously investigated in Sweden. We have screened the entire coding sequence and the intron/exon boundaries of the SLC3A1 gene in 53 cystinuria patients by means of single strand conformation polymorphism (SSCP) and DNA sequencing. We identified 12 novel mutations (a 2 bp deletion, one splice site mutation, and 10 missense mutations) and detected another three mutations that were previously reported. Five polymorphisms were also identified, four of which were formerly described. The most frequent mutation in this study was the previously reported M467T and it was also detected in the normal population with an allelic frequency of 0.5%. Thirty-seven patients were homozygous for mutations in the SLC3A1 gene and another seven were heterozygous which implies that other genes may be involved in cystinuria. Future investigation of the non-type I cystinuria gene SLC7A9 may complement our results but recent studies also suggest the presence of other potential disease genes.

Biochemical risk factors in patients with renal staghorn stone disease.

Thirty-three patients operated on for renal staghorn calculous disease were studied retrospectively with respect to urine and stone composition, bacteriuria, and abnormalities of the urinary tract. Calcium phosphate was the most common stone constituent, present in 30 of 31 concrements. Twenty-one of these stones also contained magnesium ammonium phosphate, despite the fact that only 10 patients had presented evidence of urinary tract infection during the initial period of the disease. Twenty-four-hour urine composition was normal in only 3 patients. In 59 per cent an increased CaOx risk index was observed suggesting that CaOx risk factors might contribute to the development of staghorn concrements. A metabolic evaluation of staghorn stone formers appears to be of importance for design of the postoperative treatment.

An improved method for the routine biochemical evaluation of patients with recurrent calcium oxalate stone disease.

By means of a computerized calculation program, a simplified estimate of the ion-activity product of calcium oxalate was derived (AP(CaOx)-index), based on the 24-h urinary excretion of calcium (Ca), oxalate (Ox), magnesium (Mg), citrate (Cit) and the urine volume (V): (formula: see text) With urinary electrolyte values within the normal range, there was a good correlation between the AP(CaOx)-index and the more laboriously obtained ion-activity product (r = 0.997). To express the biochemical risk of CaOx stone formation a CaOx-risk index was designed, which also includes the inhibition of calcium oxalate crystal growth (I) and with all variables related to urinary creatinine (Cr): (formula: see text) The mean CaOx-risk index (+/-SEM) in urine from 100 normal men and 156 male stone formers were 648 +/- 27 and 1019 +/- 38 respectively (p less than 0.001). A risk index without inhibition index, had the corresponding values 366 +/- 14 and 527 +/- 17 (p less than 0.001).

A routine method for determination of glycine and taurine distribution in bile acids.

A procedure is described in which the content of glycine and taurine in bile acids is determined. Following an alkaline hydrolysis, the amino acids are separated on a column of Dowex 50-X8 and quantitatively estimated by a ninhydrin colorimetric method. The taurine/taurine + glycine ratios in a series of samples were determined by this method and by an enzymatic bile acid analysis and a good accordance between the two methods was obtained.

A method for quantitative wet chemical analysis of urinary calculi.

We describe a simple method for quantitative chemical analysis of urinary calculi requiring no specialized equipment. Pulverized calculi are dried over silica gel at room temperature and dissolved in nitric acid, which was the only effective agent for complete dissolution. Calcium, magnesium, ammonium, and phosphate are then determined by conventional methods. Oxalate is determined by a method based on the quenching action of oxalate on the fluorescence of a zirconium-flavonol complex. Uric acid, when treated with nitric acid, is stoichiometrically converted to alloxan, which is determined fluorimetrically with 1,2-phenylenediamine. Similarly, cystine is oxidized by nitric acid to sulfate, which is determined turbidimetrically as barium sulfate. Protein is determined spectrophotometrically as xanthoprotein. The total mass recovery of authentic calculi was 92.2 +/- 6.7 (SD) per cent. The method permits analysis of calculi as small as 1.0 mg. Internal quality control is performed with specially designed control samples.

Effects of postmenopausal ethinylestradiol treatment on gallbladder bile.

Bile composition was studied in three postmenopausal women without evidence of gallstone disease during administration of 50 micrograms of ethinylestradiol daily. The treatment resulted in an increased fraction of cholesterol in gallbladder bile and a shift in the bile acid composition with decreased relative concentration of chenodeoxycholate and increased fraction of cholate. These changes in bile lipid composition might explain the higher incidence of gallstones in women treated with estrogens.

PIP: Because of previously reported associations between raised incidence of bile composition changes associated with oral contraceptive intake, this study, which the editors note is very small and perhaps is merely indicative, determined the bile composition of 3 women volunteers, all of postmenopausal status, who had been given 50 mcg of ethinylestradiol (EE) daily for 3 weeks followed by 1 therapy-free week. The women had no indications of gallbladder problems and all were suffering from postmenopausal vasomotor symptoms. Gallbladder bile was collected with a duodenal tube after administration of 80 U of cholecystokinin intravenously before treatment and at the end of the third or fourth cycle of treatment. Results showed that the molar fraction of cholesterol in the gallbladder bile increased in all subjects during treatment with EE. A change in the distribution of bile acids also occurred. In addition, the relative concentration of cholate increased whereas the relative concentration of chenodeoxycholate decreased. Deoxycholate decreased in 2 and increased in 1 subjects. It is suggested that these bile composition changes may explain the higher incidence of gallstones encountered in women treated with estrogens.

Clinical significance of phosphate in calcium oxalate renal stones.

We analysed calcium, magnesium, oxalate, citrate, urate and creatinine in urine and calculated risk factors in patients who had formed stones composed of calcium oxalate, and calcium phosphate, alone or as a mixture. Patients producing pure calcium oxalate stones (less than 0.1% phosphate) had a higher oxalate, and lower calcium excretion than stone-free subjects and patients forming other stone types. In contrast, patients producing calcium oxalate stones containing phosphate, even in trace amounts (greater than 0.1%) had no increase in oxalate excretion, but a higher calcium excretion than stone-free subjects. We could not correlate any computed variable (e.g. AP(CaOx) index) to stone composition. We conclude that pure CaOx stones may be the result of a high oxalate excretion, and that other calcium containing stones may have another and probably more complex aetiology, including primary precipitation of calcium phosphates.

Technical tip: simple concept for minimizing problems with double-J stents with distal end at high level in ureter.

A procedure is described to avoid problems with stents that either have been inserted too far in the ureter or have migrated to a level above the bladder and to solve this problem easily if it nevertheless occurs. A knot is tied on the pulling thread at the end of the stent to create a loop of approximately 2 cm. With such a pre-caution, the loop usually remains in the bladder in case of limited stent retraction. For stents that retract to a higher level in the ureter, a special extraction device was constructed from a standard ureteral catheter. These two procedures have so far made it possible to easily remove or adjust the position of 13 of those 15 stents (87%) in 225 patients in whom the distal end became positioned proximal to the ureteral orifice. The procedure was in all cases undertaken without regional or general anesthesia and without the need for ureteroscopy.

Anesthesia-free extracorporeal shock wave lithotripsy of distal ureteral stones without a ureteral catheter.

The therapeutic results of extracorporeal shock wave lithotripsy (SWL) for distal ureteral stones were compared between 70 patients treated without a ureteral catheter (Group 0) and 142 patients treated during a period when attempts always were made to pass the stone with a catheter before the treatment (Group UC). All SWL procedures were carried out with an unmodified Dornier HM3 lithotripter and with only analgosedation with pethidine (meperidine) and diazepam. One shock wave session was sufficient in 76% of the patients in Group 0 and in 77% of those in Group UC. There were no differences between the groups in terms of need for retreatment and the mean numbers of sessions were 1.37 +/- 0.79 (SD) in Group 0 and 1.28 +/- 0.61 in Group UC (P > 0.05). The stone-free rate after 4 weeks was 96% and 97%, respectively. This result was achieved without ureteral manipulations after SWL in 89% of the patients in Group 0 and in 95% of the patients in Group UC (P > 0.05). The number of shock waves and the energy index were lower in Group 0 than in Group UC (P < 0.001). Patients with distal ureteral stones apparently can be treated with SWL without a ureteral catheter with approximately the same success rate as with a catheter. The use of a catheter might, however, be of value for easy localization of scarcely radiopaque stones and possibly in some cases of seriously impacted stones, as well as for treatment of children, who regularly require general anesthesia.