Urine Biomarker for Stone Recurrence
Condition: Urolithiasis
MeSH terms: Urolithiasis; Urinary Calculi
Study type: Observational

Summary: 
      Despite the advent of treating stones with Extracorporeal Shock Wave Lithotripsy (ESWL) and
      Percutaneous nephrolithotomy (PCNL), the recurrence rate for renal stones remains high and
      this may be due to poor compliance of patients with dietary and fluid advice, age, metabolic
      abnormalities, medicines and the formation of "new stones" from clinically insignificant
      residual fragments (CIRF).

      Though some patients become stone-free after ESWL/PCNL or open surgeries, the majority
      develop "new stones" and it is difficult to predict when these stones will recur until either
      they have imaging perform or they developed symptoms. However, the use of regular imaging for
      monitoring will be costly and involve radiation exposure. Therefore, a diagnostic tool is
      needed to enable the clinician and/or patient to monitor for stone recurrence.

      In the previous studies, some urine markers were identified that are related to stone
      formation. The relationship of these urine markers with the recurrence of renal stone will be
      further explore in this study. Also, potential markers that could predict stone recurrence
      will be identified, and hence earlier intervention could be offered to patients.
    

Detailed description: 
      Stone recurrences remain a major challenge in the management of renal stone patients, despite
      the emergence of ESWL as an internationally accepted method for the minimally invasive
      treatment of most renal stones . Depending on the location and size of a stone, the success
      rates for ESWL can be greater than 80% for successful disintegration (fragmentation) of the
      stone, and the rate at which patients remain stone-free after 3 months ranges from 40%-80%.
      The rates of stone recurrence, defined as symptomatic episodes and/or interventions due to
      residual fragments, after ESWL, PCNL and URETS range from 10%-60% and depend upon the
      duration of the prospective follow-up study. In long-term follow-up studies after ESWL, the
      recurrence rates have been shown to increase annually. This recurrence could be due to poor
      patient compliance with dietary and fluid-intake advice, patient age, metabolic
      abnormalities, the side-effects of medicines or the formation of new stones from the CIRFs
      that result from ESWL.

      The fragments of clinically insignificant or significant stones that remain after
      ESWL/PCNL/URETS can pose a long-term risk for patients by serving as a nidus for new stone
      formation. Patients are declared 'stone-free' after ESWL only if no fragments are detected on
      radiographs, ultrasound scans or intravenous pyelograms with tomography and spiral computed
      tomography (CT) scans. Fragments smaller than 5 mm are considered capable of spontaneous
      passage, and such fragments are regarded as CIRF. Despite prophylactic measures to reduce
      stone formation, the recurrence rate remains high. There is also a paucity of information
      concerning the biochemical or metabolic evaluations of patients who have been tracked in the
      long-term studies described above. Some specific biological effects from ESWL are well known;
      for example, the urinary enzyme levels are known to increase. Although the enzyme levels
      commonly return to normal in the short-term, the levels of these enzymes, and other
      biomarkers such as glycosaminoglycans and cytokines, have not been tracked over longer
      periods of time.

      The urinary levels of both cytokines and mediators of inflammation are becoming increasingly
      recognised as important markers for urologic diseases. In a study of the urinary levels of
      IL-6, IL-1β and 1α in patients with stone disease, patients without bacterial cystitis showed
      significant elevations of IL-6 but did not have marked increases in either IL-1β or 1α
      relative to control subjects. The patients with bacterial cystitis showed elevations in all
      three cytokines. Studies have also examined the injury to cells from oxalate toxicity and
      calcium oxalate crystal exposure, using tests on tissue cultures and rat models [20-22]. Such
      types of cellular damage have also been shown to attract crystal binding, which can lead to
      crystal growth and aggregation. An inflammatory response has also been seen in experimental
      nephrolithiatic rats, whereby crystals were shown to form in the tubular lumen and eventually
      to move into the interstitium, causing inflammation and attracting macrophages or other
      inflammatory cells. Recent advances in translational medicine have also identified new
      molecules such as urinary kidney injury molecule-1 (uKIM-1). The levels of the uKIM-1
      molecule have been found to be increased following lithotripsy, suggesting it might be a good
      candidate for an acute kidney injury (AKI) molecule. Hence, studying the levels of cytokines
      and the mediators of inflammation could help in understanding the pathogenesis of
      urolithiasis. Such studies could also identify a reliable marker for the early diagnosis,
      treatment and prevention of stone recurrence.

      Small fragments (<5 mm) that have not passed spontaneously and are retained undetected in the
      urinary tract can develop into new stones in the ensuing months or years. The investigators
      hypothesise that such retained fragments are most likely to be attached to the urothelium,
      thereby injuring the cells and the underlying tissue. The investigators also hypothesise that
      depending on the growth rate of a fragment, this injury can invoke an inflammatory response
      that begins as sub-clinical (i.e., asymptomatic). This kind of injury is akin to
      stone-formation causing mechanical stimulation (i.e., irritation) of the epithelial cells,
      which results in the production of cytokines and mediators of inflammation. These by-products
      eventually become a 'plaque', similar to a Randall's plaque. These hypotheses have been
      recently reviewed and have been suggested to indicate a likely pathway to calcium stone
      formation.

      In previous studies on the separation of urinary glycosaminoglycans (GAGs), the investigators
      have reported the electrophoretic separation of urinary GAGs into their sub-classes on a
      preparative scale. Chondroitin sulphates (CS) and HAs were cleanly separated from the heparan
      sulphates (HS). On further analysis by high-performance liquid chromatography, HAs were
      identified as the major contributors to the crystallisation-promoting properties observed in
      the early electrophoretic fractions of stone-formers. The involvement of HAs in urolithiasis
      was further supported from studies involving their extraction and identification in
      calcium-containing stones. The investigators also confirmed that the in vivo role of HAs was
      more likely to be a secondary effect rather than a cause of stone formation, although the
      release and increase of HAs from injured tissues could accelerate the growth and deposition
      of calcium and oxalate (e.g., on the CIRF).

      In previous preliminary case-controlled study, the investigators had looked into a multitude
      of potential biomarkers and inflammatory cytokines. The molecular candidates were from both
      urine and serum samples, and six patient groups were assessed including active stone-formers
      with and without infection and before and after the removal of stones. Also, normal controls
      with and without urinary tract infections were assessed.

      The most well-studied and characterised markers, which are also easily available, were
      selected for the study. The markers included: (1) the inflammatory markers IL-1α, IL-6 and
      IL-8, (2) the mediator macrophage inflammatory protein-1α (MIP-1α) and (3) the urinary
      biochemical markers N-acetyl-β-D-glucosaminidase (NAG), neutrophil gelatinase-associated
      lipocalin (NGAL) and HA. In addition, the metabolic biochemical parameters were also
      investigated. These parameters included levels of sodium, potassium, calcium, magnesium,
      ammonia, phosphate, sulphate, oxalate, citrate, urate, chloride and creatinine.The pH and
      osmolality were also investigated.

      The preliminary results have confirmed that urinary HA is a reliable indicator of active or
      silent stones. The investigators reported this earlier in the initial findings of the
      presence of urinary HA. The proportion of excreted HA was significantly high. This finding
      was reported at the October 2018 meeting of the Société Internationale d'Urologie held in
      Seoul, Korea. HA is a ubiquitously distributed component of the extracellular matrix. In its
      native form, it exists as a high-molecular weight polymer, and lower-molecular weight forms
      of HA species accumulate at sites of inflammation and tissue injury. Previous studies concur
      that urinary HA is composed predominantly of lower-molecular weight (~10 kDa) species , which
      suggests a role for these species as mediators of inflammation.

      Of the inflammatory and urinary biochemical markers, IL-6 and IL-8 were predictably higher,
      and NGAL was also significantly increased compared to controls and patients who had stones
      removed. It is also interesting to note that the stone-former cohorts had lower citrate and
      higher oxalate excretion, although just at the trend level. However, the medians differed
      clearly from those of the control group, suggesting that the measurement of citrate and
      oxalate is still a useful indicator of the risk of stone formation.

      Therefore in this follow-up study, the investigators would like to investigate the time
      points at which recurrent stone-formers should be monitored over the longitudinal study
      period proposed herein.
    

Observational model: Case-Control
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Patients with history of radio-opaque urinary calculi with treatment performed (including
        spontaneous passage) and now stone free.
      
Biospecimen description: 
      about 100 cc urine will be collected for the measurement of Biomarkers