Mohd Nazli Kamarulzaman

Re: Agrawal et al. Ultra-mini-percutaneous nephrolithotomy: A minimally-invasive option for percutaneous stone removal. Indian J Urol 2016;32:132-6

The authors demonstrate a successful reduction in size from 30F for conventional PCNL to 11F in ultra-mini-PCNL. This reduction will reduce tissue trauma and bleeding.[1] Further, they did not routinely use a nephrostomy or stent which will possibly allow us to categorize ultra-mini-PCNL as less invasive than conventional PCNL. However, the question which is not solved from this study was regarding the specific indication for this procedure. In this study, the authors used this procedure to treat renal stone (pelvis, upper calyx, middle calyx, and lower calyx) and upper ureteric stone size between 8 and 20 mm. The other methods of treatment were well established their specific indication. For example, in the European Association of Urology guideline, PCNL is recommended therapy to treat large renal stone (>20 mm) and smaller stones (10–20 mm) of the lower renal calyx when unfavorable factors for shockwave lithotripsy (SWL) exist.[2] Retrograde intrarenal surgery (RIRS) was recommended in treating lower pole renal stone <20 mm.[2]

Comment on: Laparoscopic transperitoneal ureterolithotomy for large ureteric stone

Sir, A recent publication on urinary pH, melamine, and kidney stone formation is very interesting.[1] Lu et al. reported “an association of gender and urinary pH with melamine-associated kidney stone formation risk”.[1] This can be useful epidemiological information. However, some facts of medical biochemistry should be discussed. The reported pH in this publication is not clear. Only a value of < and ≥6.5 can be read. Indeed, the correlation can be directly assessed by the correlation study between the exact urine pH value and solubility. Based on chemical structure, melamine is a base and increases solubility in acidic conditions (very good if pH is lower than 4).[2] However, it is a fact that the range of human urine pH is not wide (4.5–8); hence, the solubility of melamine might be affected slightly.