[Infection-induced urinary stones]

A case report of a giant bladder stone (12 × 8 cm, 610 g)

Bladder lithiasis is common in developing countries. It has become rare in industrialized countries and exceptional in the absence of associated lower tract pathology. usually caused by urinary tract infections, urethral obstruction or the presence of intravesical foreign bodies. Open cystolithotomy was performed on a 45-year-old patient with lower abdominal pain, moderate dysuria, pollakiuria, nocturia, and hematuria for a long time. A stone of 12 × 8cm in size and approximately 620 grams in weight was removed. The cystoscopy was performed without any infravesical obstruction during the operation. The stone analysis showed 21% struvite and 79% carbonate apatite. Bladder lithiasis is common in Morocco. However, giant lithiasis is rare and is the consequence of neglected voiding disorders. Open cystolithotomy remains the most treatment in the management of giant stones.

Intravesical Infection Stones Caused by Magnetic Beads

The presence of an intravesical foreign body is a rare condition concerning the diseases of the urinary system. Intravesical foreign bodies may cause hematuria and bladder perforation, which are difficult to diagnose and treat. There are various types of foreign bodies in the bladder; however, magnetic beads are rare. Multiple beads may be inserted into the urethra. A few small magnetic beads may be removed from the urethra, but an open removal is an option for many or large beads because of calculus adherence. This case reports the successful open removal of 57 magnetic beads with calculus adherence.

In vivo assessment of biodegradable magnesium alloy ureteral stents in a pig model

Today, ureteral stent technology is making progress towards the reduction of complications and patient discomfort. Therefore, magnesium alloys have become excellent candidate materials for manufacturing ureteral stents due to their biodegradability and antibacterial activity. Built on our previous work on biodegradable magnesium alloys, this article reports a semisolid rheo-formed magnesium implant that displays degradability and biocompatibility in vivo, and feasibility as ureteral stents in a pig model. Refined non-dendritic microstructure was observed in the rheo-formed alloy, whose grain size and shape factor were ca. 25.2 μm and ca. 1.56 respectively. Neither post-interventional inflammation nor pathological changes were observed in the urinary system during the implantation period of 14 weeks, and the degradation profile (14 weeks) meets the common requirement for the indwelling time of ureteral stents (8 to 16 weeks). Furthermore, histopathological observation and urinalysis results confirmed that the alloy had significantly higher antibacterial activity than the medical-grade stainless steel control. To our knowledge, this is the first in vivo study of biodegradable magnesium alloy as urinary implants in large animal models. Our results demonstrate that magnesium alloys may be a reasonable option for manufacturing biodegradable ureteral stents.

Giant bladder stone: A case report and review of the literature

Bladder stones comprise 5% of urinary tract stones. Generally, they occur in the presence of bladder neck obstruction, urinary tract infections associated with neurogenic bladder and foreign objects. They are more common among men than women. Infection stones comprise approximately 15% of urinary tract stones. A giant bladder stone is a rare finding in contemporary urological practice. The general clinical setting is recurrent urinary tract infections, hematuria and urinary retention. We performed an open cystolithotomy on a mentally impaired patient who had a giant bladder stone. The stone removed weighed 465 grams. There was no evidence of any infravesical obstruction on the cystoscopy performed before the operation or during the operation. The stone consisted of 75% carbonate apatite and 25% struvite. Given that such a stone was found in a mentally impaired patient indicates that infection stones can form without infravesical obstruction.

Bacteria can promote calcium oxalate crystal growth and aggregation

Our previous report showed that uropathogenic bacteria, e.g., Escherichia coli, are commonly found inside the nidus of calcium oxalate (CaOx) kidney stones and may play pivotal roles in stone genesis. The present study aimed to prove this new hypothesis by direct examining CaOx lithogenic activities of both Gram-negative and Gram-positive bacteria. CaOx was crystallized in the absence (blank control) or presence of 10(5) CFU/ml E. coli, Klebsiella pneumoniae, Staphylococcus aureus, or Streptococcus pneumoniae. Fragmented red blood cell membranes and intact red blood cells were used as positive and negative controls, respectively. The crystal area and the number of aggregates were measured to initially screen for effects of bacteria on CaOx crystal growth and aggregation. The data revealed that all the bacteria tested dramatically increased the crystal area and number of crystal aggregates. Validation assays (spectrophotometric oxalate-depletion assay and an aggregation-sedimentation study) confirmed their promoting effects on both growth (20.17 ± 3.42, 17.55 ± 2.27, 16.37 ± 1.38, and 21.87 ± 0.85 % increase, respectively) and aggregation (57.45 ± 2.08, 51.06 ± 5.51, 55.32 ± 2.08, and 46.81 ± 3.61 % increase, respectively) of CaOx crystals. Also, these bacteria significantly enlarged CaOx aggregates, with the diameter greater than the luminal size of distal tubules, implying that tubular occlusion might occur. Moreover, these bacterial effects were dose-dependent and specific to intact viable bacteria, not intact dead or fragmented bacteria. In summary, intact viable E. coli, K. pneumoniae, S. aureus, and S. pneumoniae had significant promoting effects on CaOx crystal growth and aggregation. This functional evidence supported the hypothesis that various types of bacteria can induce or aggravate metabolic stone disease, particularly the CaOx type.

[Urinary tract infections and Urolithiasis]

The classic "infection stone" struvite is formed as a result of metabolic activity of urease-positive bacteria from alkaline urine with pH-values above 7.5. Due to improved infection diagnostics and antibiotic therapy, the occurrence of infection-related urinary stones in the western industrialized world decreases, despite the generally increasing prevalence rates of urolithiasis in these societies. Struvite is often associated with other mineral phases. These accessory mineral phases could indicate other, non-infection-related causes of urinary stone formation. Thus, mineral analysis is always recommended. Struvite stones as well as struvite encrustations on urinary tract implants are characterized by rapid growth. The rapid growth-related embedding of urease-positive bacteria in the crystalline material makes the urinary stone a persistent source of recurrent urinary tract infections. According to the German Society of Urology guidelines on urolithiasis, a patient with the diagnosis "infection stone" should be assigned to the "high-risk" patient group. Complete stone and debris removal, as well as a special metaphylaxis strategy are required to initiate successful stone therapy.