Lars Grenabo

Urease-Induced Crystallization in Synthetic Urine

The urease-induced crystallization of magnesium ammonium phosphate and calcium phosphate was studied at different alkalinization degrees by incubating synthetic urine with increasing Jack Bean urease concentrations. The crystallization was studied as precipitation on glass rods immersed in synthetic urine. The calcium phosphate precipitation on the glass rods occurred when the pH reached 6.8. Magnesium ammonium phosphate precipitation occurred when the pH reached 7.0. The maximal crystallization occurred at a pH between 7.5 and 8.0; at higher pHs the precipitation was considerably lower. The possible mechanisms and clinical implications behind this narrow pH optimum for urease-induced crystallization, which also have important implications for future experimental studies, are discussed.

Adherence of urease-induced crystals to rat bladder epithelium.

SummaryApart from urine supersaturation with respect to struvite and calcium phosphate caused by urease-producing microorganisms, retention of formed crystals in the urinary tract is necessary for the formation of infection stones. This study was performed to investigate the role of the mucous coat lining the urothelium in the adhesion of urease-induced crystals. Removal of this glycosaminoglycan-containing layer from rat bladders increased the adherence of struvite and calcium phosphate crystals 5–6 times compared to that in intact rat bladders. Heparin completely restored the anti-adherence capacity while chondroitin sulphate had a very weak restorative effect and human urine had no restorative effect. These findings support the view that the mucous coat is of importance in preventing retention of urease-induced crystals.

The Inhibitory Effect of Human Urine on Urease-Induced Crystallization in Vitro

To study whether human urine contains inhibitors against urease-induced crystallization, Jackbean urease and human urine, in amounts small enough (0.5 to 10 per cent) not to influence the ion concentration, buffering capacity or pH, were added to synthetic urine. The ammonia production and alkalinization that followed were independent of the amounts of human urine added. The addition of human urine gave a dose-related decrease in the amount of calcium phosphate and struvite precipitated on glass rods immersed in the synthetic urine, however. Addition of only 0.5 per cent human urine gave a reproducible decrease and when 10 per cent human urine was added to the synthetic urine the precipitation of calcium phosphate was reduced by 50 per cent and that of struvite by 75 per cent. The results thus indicate that human urine contains components with the ability to reduce the urease-induced crystallization.

Ureaplasma Ureal Yticum-Induced Crystallization of Magnesium Ammonium Phosphate and Calcium Phosphates in Synthetic Urine

Crystallization of struvite and calcium phosphates was studied in vitro as encrustations on glass rods immersed in synthetic urine, to evaluate the crystallization capacity of Ureaplasma urealyticum and compare it with that of known urease and non-urease-producing bacteria. Inoculation of the synthetic urine with Ureaplasma urealyticum resulted in alkalinization of the synthetic urine and crystallization of struvite and brushite. Inoculation with Proteus mirabilis caused a faster and more pronounced alkalinization as well as crystallization of struvite and apatite. The alkalinization and crystallization caused by Ureaplasma urealyticum and Proteus mirabilis was completely prevented by acetohydroxamic acid, a potent urease inhibitor, linking the crystallization to the urease activity of the microorganisms. When the synthetic urine was inoculated with urease-negative Escherichia coli no alkalinization and no crystallization were seen.

The effects of urease in undiluted human urine.

Undiluted human urine and synthetic urine were inoculated with urease. No inhibitory activity against urease enzymatic activity could be detected in human urine. The urease-induced crystallization of both calcium phosphate and magnesium ammonium phosphate differed markedly, however, between the individuals studied, and it was less pronounced in human urine than in synthetic urine. This supports the observation made in experiments using diluted urine that human urine possesses an inhibitory activity against urease-induced crystallization and suggests that it has a large interindividual variation.

Citrate and urease-induced crystallization in synthetic and human urine

SummaryThe effects of citrate on the different phases of urease-induced crystallization were studied using Coulter counter techniques and optical microscopy. Citrate increased urine pH and markedly delayed the initiation of the crystallization (nucleation) in both human and synthetic urine. In synthetic urine, particle aggregation and espicially particle growth were delayed and inhibited by citrate. In human urine, aggregation was distinctly inhibited by citrate. It appears that the susceptibility of urine to form crystals in the precense of urease activity is influenced by its citrate concentration.

Analysis of Stone Fragility in Vitro and in Vivo With Piezoelectric Shock Waves Using the Edap LT-01

A total of 100 whole stones was fragmented in vitro at 3-minute intervals with piezoelectric shock waves using the EDAP LT-01 device until all fragments were less than 2 mm. Larger stones and stones with a high computerized tomography attenuation needed longer treatments for fragmentation. Smoothly bulging stones with an even structure according to plain x-ray films were also more resistant to the shock wave treatment. Calcium oxalate monohydrate stones were not more difficult to break than other types of calculi. Stone fragments from 100 patients after extracorporeal shock wave lithotripsy were also analyzed. The average size of the fragments collected was less than 1 mm. Larger stones produced larger fragments and required more treatment sessions.

Adherence of Urease-Induced Crystals to Rat Bladder Epithelium Following Acute Infection with Different Uropathogenic Microorganisms

Apart from urine supersaturation with respect to struvite and calcium phosphate, crystal retention is considered to be necessary for the formation of infection stones. This study was performed to investigate the role of the mucous coat in rat bladders in the adhesion of sterile urease-induced crystals and to determine to what extent the adhesion was influenced by infection. Elimination of the mucous coat with 0.1 M HCl increased the adherence of crystals six times compared to that in bladders with an intact mucous coat. Infection with Proteus mirabilis, Escherichia coli, enterococci and Ureaplasma urealyticum increased the adherence six, five, four and two times, respectively. Injury to the mucous coat may thus be one mechanism by which microorganisms can contribute to the formation of infection stones in the urinary tract.

Indomethacin as Prophylaxis Against Recurrent Ureteral Colic

In a prospective, randomized study, the prophylactic effect of indomethacin (150 mg daily) in regard to recurrence of ureteral colic was investigated in 78 patients. Severe recurrent attacks were experienced in 78 patients. Severe recurrent attacks were experienced by 4 of 37 patients in the test group and by 16 of the 41 controls without indomethacin. The mean duration of recurrent pain including the severe attacks was 5.6 +/- 1.1 hour/patient/week in the test group and 12.5 +/- 2.9 in the control group. Passage of stone within 7 days was not influenced by indomethacin (22/37 and 25/41 cases). Indomethacin administration for 7 days after an acute attack of ureteral colic thus reduced the frequency of severe attacks and the total duration of recurrent pain, without influencing the stone passage.

Immediate versus deferred radiological investigation after acute renal colic : A prospective randomized study

Objective. The timing of radiological assessment after acute renal colic is controversial. The aim of this study was to investigate the value of immediate versus deferred radiological imaging and to compare morbidity rates after an attack of acute renal colic. Material and methods. Between September 2001 and December 2002 all 686 patients with acute renal colic attending our university hospital were registered. Of these, 172 patients rendered pain-free after analgesic injection were randomized to either immediate or deferred radiological investigation. All patients received a questionnaire encompassing questions on consumption of analgesics, impact of symptoms on normal daily activity (including working ability), need for additional emergency department visits and hospitalization. Stone treatments were registered. Results. The incidence of renal colic was 0.9/1000 inhabitants per year. In total, 74% of all patients became pain-free after analgesic injection. Morbidity was low among the randomized patients, and did not differ between the immediate or deferred radiological investigation groups. In both groups, the duration of impairment of normal daily activities and analgesic consumption was a median of 2 days. In the immediate group, 14% needed another emergency visit and 4% were hospitalized. Corresponding figures for the deferred group were 15% and 7%. In the immediate group, 17% had stone treatment, compared with 8% in the deferred group. Conclusion. For most patients with acute renal colic, parenteral analgesia resulted in complete symptom resolution. When initial medical treatment was successful, patient morbidity was low. In these patients, immediate radiological imaging did not lead to reduced morbidity compared with radiological imaging after 2–3 weeks.