A diagnostic model for histologic damage in undescended testes based on testis rigidity measurement: an experimental study with a novel device.

Background: We aimed to test whether testis rigidity (hardness) measured using a newly-designed device we previously introduced would offer more reliable assessment of histologic damage in undescended testes than conventional methods (consistency feel at palpation, volume measurement).
Materials and Methods: Forty-five 18-d-old Lewis rats underwent surgical inhibition of descent of left testes and were followed to 40 (n = 16), 63 (n = 14), or 90 days (n = 15). Another 45 18-d-old Lewis rats were sham operated (left side) and followed likewise (n = 14, n = 15, and n = 16). At the designated time points, testes were exposed bilaterally, rigidity was measured, and consistency at palpation was scored; testes were removed and subjected to length, width, weight measurements, volume calculation, and histomorphometry (mean Johnsen score [MJS], mean tubular diameter [MTD], and mean capsule width [MCW]). Testes of experimental group were compared with ipsilateral testes of sham-operated rats.
Results: At all time points, undescended testes had decreased rigidity, MJS, and MTD, increased MCW, decreased volume and weight; contralateral testes remained unaffected. Rigidity was associated only with MJS and MTD, and most strongly with MJS (multiple stepwise linear regression, F = 694.44, P < 0.0005). MJS could be precisely predicted from rigidity: MJS = 0.699 × testis rigidity (F = 1358.82, P < 0.0005). This model showed good fit between predicted and actual MJS values (R(2) = 0.94), low error, nonsignificant bias, sensitivity 75% and specificity 90%. Model validation showed low prediction error and nonsignificant bias, indicating generalizability. Testis volume and palpation proved imprecise MJS predictors.
Conclusions: Testis rigidity is an effective predictor of histologic damage in rat undescended testes, with diagnostic value superior to testis palpation scoring and volume measurement.
(Copyright © 2014 Elsevier Inc. All rights reserved.)