Diagnostic performance of ultrasound in nonpalpable cryptorchidism: a systematic review and meta-analysis

Abstract

Context: Ultrasound is frequently obtained during the presurgical evaluation of boys with nonpalpable undescended testes, but its clinical utility is uncertain.

Objective: To determine the diagnostic performance of ultrasound in localizing nonpalpable testes in pediatric patients.

Methods: English-language articles were identified by searching Medline, Embase, and the Cochrane Library. We included studies of subjects younger than 18 years who had preoperative ultrasound evaluation for nonpalpable testes and whose testis position was determined by surgery. Data on testis location determined by ultrasound and surgery were extracted by 2 independent reviewers, from which ultrasound performance characteristics (true-positives, false-positives, false-negatives, and true-negatives) were derived. Meta-analysis of 12 studies (591 testes) was performed by using a random-effects regression model; composite estimates of sensitivity, specificity, and likelihood ratios were calculated.

Results: Ultrasound has a sensitivity of 45% (95% confidence interval [CI]: 29-61) and a specificity of 78% (95% CI: 43-94). The positive and negative likelihood ratios are 1.48 (95% CI: 0.54-4.03) and 0.79 (95% CI: 0.46-1.35), respectively. A positive ultrasound result increases and negative ultrasound result decreases the probability that a nonpalpable testis is located within the abdomen from 55% to 64% and 49%, respectively. Significant heterogeneity limited the precision of these estimates, which was attributable to variability in the reporting of selection criteria, ultrasound methodology, and differences in the proportion of intraabdominal testes.

Conclusions: Ultrasound does not reliably localize nonpalpable testes and does not rule out an intraabdominal testis. Eliminating the use of ultrasound will not change management of nonpalpable cryptorchidism but will decrease health care expenditures.

FIGURE 1

Selection process for study inclusion.

FIGURE 2

Forest plot of positive (A) and negative (B) likelihood ratios. The dot refers to the point estimate for the likelihood ratio, and the lines represent the 95% CLs. Box size is proportional to the weight given to the study and is based on the study sample size and variance. The vertical line denotes the summary likelihood ratio, and the diamond represents the associated 95% CLs. Note that weights are from random-effects analysis.

FIGURE 3

Effect of ultrasound on the probability of testis location. The pretest probability that a nonpalpable testis is within the abdomen is 55%. Using the positive likelihood-ratio point estimate (solid red line) and upper CL (dashed red line), an ultrasound that localizes a nonpalpable testis within the abdomen increases the probability that the testis is truly in the abdomen to 64% and 83%, respectively. Using the negative likelihood-ratio point estimate (solid blue line) and lower CL (dashed blue line), an ultrasound that does not visualize a nonpalpable testis decreases the probability that the testis is truly in the abdomen to 49% and 36%, respectively.