A 26 years boy c/o pain in between epigastrium and umbilicus, pin point, not relieved by anti-spamodic tabs. TLC, RFT, LFT are normal. Only usg shows Ballooning of Lt kidney but no pain over anterior and posterior renal area, only mild heaviness on Lt side in comparison to rt .,but by face he looks in distress.

No stone in ureter visible. Usg done at lab of High repute. What is the cause of ballooning?