A 51-year-old man Sonu with a history of passing stones in urine, presents to the emergency room with excruciating flank pain and blood in the urine. Imaging of kidneys and ureters revealed stag-horn calculi occupying the right renal pelvis. This patient is likely to have which of the following underlying disorders?

Magnesium ammonium phosphate stones ("triple phosphate" stones/"struvite" stones) are formed largely after infections by urea-splitting bacteria (e.g., Proteus and some staphylococci) that conve urea to ammonia. The resultant alkaline urine causes the precipitation of magnesium ammonium phosphate salts. These form some of the largest stones, as the amount of urea excreted normally is very large. Stag-horn calculi occupying large poions of the renal pelvis are frequently a consequence of infection.