Ultrasonographic Measurement of the Diameter of Internal Inguinal Ring and Prediction of Bilaterality in Pediatric Inguinal Hernia

ABSTRACT

BACKGROUND: It has been reported that bilateral pediatric inguinal hernias (PIH) are around 10% and that a late contralateral herniorrhapy is needed in up to 34% of ipsilateral operations. However, clinical prediction of the contralateral patent processus vaginalis (PPV) is difficult. The aims of this study were to measure the mean diameter of the internal inguinal ring (IIR) of the PIH at rest and during straining and to define the diagnostic criterion for positive contralateral PIH (or PPV) by using ultrasonography (USG). METHODS: The diameters of both ipsilateral and contralateral IIRs at rest and during straining were measured preoperatively by USG in 104 consecutive pediatric patients (75 male, 29 female; mean age of 3 years) who had undergone an ipsilateral herniorrhaphy with contralateral exploration from March 1997 to December 1997. Fifty-seven right inguinal hernias (RIH), 43 left inguinal hernias (LIH), and 4 bilateral inguinal hernias were enrolled. The contralateral PPV was defined as a sac greater than 3 mm in diameter and longer than 2 cm in length measured intraoperatively. Statistical analysis was performed by using the t-test and the chi-square test. RESULTS: Contralateral exploration showed positive PPV in 44% of RIH and 47% of LIH (p>0.05). In RIH, the mean diameter of right IIR (RIIR) was wider than that of left IIR (LIIR) (5.02+/-0.27 mm vs 2.94+/-0.12 mm at rest and 7.50+/-0.52 mm vs. 3.82+/-0.23 mm during straining, p<0.01), and the difference in diameters between straining and rest were also significant (2.38+/-0.37 mm in RIIR and 0.76+/-0.14 mm in LIIR, p<0.01). In LIH, the mean diameter of LIIR was wider than that of RIIR (4.59+/-0.27 mm vs. 3.13+/-0.19 mm at rest, 6.82+/-0.43 mm vs. 3.61+/-0.26 mm during straining, p<0.01). The diameter difference between straining and rest of LIIR and RIIR were also significant (2.17+/-0.28 mm in LIIR, 0.60+/-0.12 mm in RIIR, p<0.01). Cases of positive contralateral PPVs in RIH had significantly wider LIIRs than those of negative PPV (3.5+/-0.16 mm vs. 2.5+/-0.14 mm at rest and 4.70+/-0.32 mm vs. 2.97+/-0.20 mm during straining, p<0.01). The difference of diameter between strainingand rest of positive and negative PPVs were significant (1.16+/-0.25 mm and 0.38+/-0.09 mm, respectively, p<0.01). Cases of positive contralateral PPVs in LIH had wider RIIRs than those of negative PPV significantly (3.83+/-0.27 mm vs. 2.52+/-0.18 mm at rest and 4.58+/-0.38 mm vs. 2.68+/-0.19 mm during straining, p<0.01). The diameter difference between straining and rest of positive and negative PPVs was significant (0.93+/-0.21 mm and 0.3+/- 0.09 mm, respectively, p<0.05). CONCLUSION: In most negative PPVs, the diameter of the IIR did not exceed 3.0 mm. Therefore, contralateral IIR with diameters wider than 3.0 mm and diameters of difference more than 1.0 mm between straining and rest, as determined by using USG need to be explored.