Nomogram to predict the risk of endoscopic removal failure with forceps/baskets for treating submandibular stones

Table 1 Clinical features of the enrolled stones

Variables
Sex
Male	99 (46.9%)
Female	112 (53.1%)
Age of the patient
< 44 yr	123 (58.3%)
≥ 44 yr	88 (41.7%)
Intraductal stone treatment history
Yes	34 (16.1%)
No	177 (83.9%)
Involved side
Left	100 (47.4%)
Right	111 (52.6%)
Amounts of stones
Single	180 (85.3%)
Multiple	31 (14.7%)
Palpation
Positive	134 (63.6%)
Negative	77 (36.4%)
Location/cm
Range	0.42-5.69
Mean	3.48 ± 1.51
TD/mm
Range	1.23-12.00
Mean	5.17 ± 2.01
LD/mm
Range	0.57-9.26
Mean	4.97 ± 1.48
Surgical methods
Endoscopic removal	89 (42.2%)
ERF	122 (57.8%)

TD: Transverse diameter; LD: Longitudinal diameter; ERF: Endoscopic removal failure.