title: Is infundibuloureteropelvic angle (IUPA) a significant risk factor in formation of inferior calyceal calculi?
abstract: BACKGROUND
  Many studies confirm the fact that radiographic anatomy of inferior calyx has a significant role in the clearance of a stone lodged in it [Br. J. Urol. 50 (1978) 449; Invest. Urol. 18 (2) (1980) 167; BJU Int. 83 (Suppl) (1999) 24; J. Urol. 132 (1984) 1085]. Acutely angled and narrow infundibular neck of a inferior calyx has a poorer stone clearance in comparison to that with a less acute angled and wider infundibular neck [Br. J. Urol. 50 (1978) 449; Invest. Urol. 18 (2) (1980) 167; Br. J. Urol. 82 (1998) 12; BJU Int. 83 (Suppl) (1999) 24]. Incidence of bilateral stones in clinical practice is significantly less than unilateral stones. This study was taken up to define the significance of radiographic anatomy of the inferior calyx as a risk factor predisposing to stone formation in a patient and compared the anatomy of inferior calyx of the stone forming and contralateral kidney. The fact that inspite of the similar known etiological factors (intrinsic and extrinsic) of stone formation, why stone forms unilaterally?
  
  
  METHODS
  100 consecutive cases of non-obstructed unilateral inferior calyceal calculus with non-metabolically active stones were studied. The infundibuloureteropelvic angle (IUPA) and infundibular width of the stone forming and non-stone forming contralateral side were compared.
  
  
  RESULTS
  IUPA of stone forming side was more acute than the non-stone forming side, in 74% of the cases, more obtuse in 18% of the cases, and same in 8% of the cases. The difference in the IUPA of the stone forming and that of non-stone forming contralateral side was statistically significant (p<0.0002). The infundibular width of the stone forming side ranged from 1 to 16 mm and that of non-stone forming side from 2 to 11 mm. There was no statistically significant difference between the infundibular width of both the sides. Exactly, how and more importantly under what influences the macromolecules in the urine transforms into a calculus in the pelvicalyceal system is still not known till date but from our observations we conclude that IUPA is a significant risk factor which predisposes to calculus formation in inferior calyx.
  
  
  CONCLUSIONS
  IUPA is a significant risk factor, which predisposes to urolithiasis in inferior calyx.
authors.affiliation: Department of Urology, All India Institute of Medical Sciences, New Delhi 29, India. nabeegholam@hotmail.com
authors.forename: G
authors.initials: G
authors.lastname: Nabi
authors.forename: N P
authors.initials: NP
authors.lastname: Gupta
authors.forename: Subhasis
authors.initials: S
authors.lastname: Mandal
authors.forename: A K
authors.initials: AK
authors.lastname: Hemal
authors.forename: P N
authors.initials: PN
authors.lastname: Dogra
authors.forename: M S
authors.initials: MS
authors.lastname: Ansari
mesh_terms: D006801:Humans; D007669:Kidney Calculi / Q000209:etiology*; D007670:Kidney Calices; D007682:Kidney Pelvis / Q000033:anatomy & histology*; D012307:Risk Factors; D014513:Ureter / Q000033:anatomy & histology*