PEDIATRICS Vol. 105 No. 3 March 2000, pp. 604-607

An Analysis of Clinical Outcomes Using Color Doppler Testicular Ultrasound for Testicular Torsion

Linda A. Baker, MD^*, David Sigman, MD, Ranjiv I. Mathews, MD^*, Jane Benson, MD^§, and Steven G. Docimo, MD^*

From the ^* Division of Pediatric Urology, Brady Urological Institute, Johns Hopkins Hospital, Baltimore, Maryland; the  Division of Urology, Department of Surgery, University of Maryland, Baltimore, Maryland; and the ^§ Department of Radiology, Johns Hopkins Hospital, Baltimore, Maryland.

	ABSTRACT

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Objectives.  To delineate the clinical outcomes of color Doppler ultrasound (US) in the equivocal torsion patient.

Methods.  From 1992 to 1997, 130 patients (<23 years old) from 2 institutions underwent US imaging using a 7.5-mHz linear transducer to evaluate an acute scrotum equivocal, or of low suspicion, for torsion. The US reports and hospital charts of these patients were retrospectively reviewed.

Results.  After clinical and radiologic evaluation, torsion was excluded in 110 patients without surgical exploration. In 3 patients, intermittent testicular torsion was diagnosed and in 17 patients, emergent exploration was performed for US diagnosis of testicular torsion. Twenty-five patients (22.7%) were subsequently lost to follow-up. Follow-up of 85 patients with US negative for torsion (mean length of follow-up = 466.9 days) revealed no testicular atrophy in 83. Two patients underwent delayed orchiectomy/contralateral orchiopexy for missed testicular torsion. Of 17 patients with US positive for torsion, 9 underwent orchiectomy for a necrotic torsed testis, 7 viable torsed testes were found, and 1 torsed appendix testis was found. Therefore, color Doppler US for the equivocal acute scrotum yielded a 1% false-positive rate, sensitivity of 88.9%, and specificity of 98.8%.

Conclusion.  When faced with ruling out testicular torsion, it is necessary to integrate the multiple pieces of patient data, knowing that each piece of data may have inaccuracies. With this in mind, this analysis of outcomes verifies that color Doppler US is an excellent adjunctive study in the clinically real situation in which the clinical evaluation is equivocal or low suspicion.  Key words:  testicular torsion, color Doppler sonography, acute scrotum.

The acute scrotum presents a diagnostic challenge for the urologist and the radiologist, as no singular or combined examination or test provides definitive diagnosis with 100% accuracy, short of surgical exploration. The need for an expedient diagnosis and therapy further complicates this situation, for radiologic testing delays diagnosis although unnecessary surgical exploration is undesirable.

Most urologists would agree that if the clinical history and examination are highly suspicious for torsion, immediate surgical exploration is indicated, without radiologic evaluation. However, up to 70% of cases with an acute scrotum have pathology that does not require surgery.^1-3 Therefore, a rapid, accurate, noninvasive, widely available radiologic test for testicular torsion would find great utility. One such modality which meets many of these criteria is color Doppler ultrasound (US). However, the urologic literature has multiple isolated case reports demonstrating instances of missed testicular torsion by color Doppler US imaging (US) raising justified concerns over its use.^4-9 Despite these isolated cases, color Doppler US is commonly used during the evaluation of the acute scrotum.

Most reports concerning color Doppler US in the acute scrotum incorporated patients whose history, physical examination, and laboratory evaluation warranted direct surgical exploration for torsion without radiologic investigation.^4,6,810-13 Such data are required to validate the use of this US modality, but it is difficult to conclude how the quoted sensitivity and specificity rates are applicable to current practice patterns, in which only patients with clinical presentation suggesting equivocal or low probability of torsion are imaged. To address this issue, a retrospective review was performed from 2 academic institutions of patients <23 years old with an acute scrotum whose clinical presentation was equivocal for testicular torsion. Therefore, all the patients in this study were imaged by color Doppler US to further rule out testicular torsion. The patients whose clinical presentation was consistent with testicular torsion were not included in this study, because they immediately were surgically explored.

	METHODS

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The scrotal US records and hospital charts from 2 institutions (A and B) were retrospectively reviewed to identify patients <23 years old who presented from September 1992 to April 1997 with either scrotal/testicular pain or scrotal swelling with/without paina possible acute scrotum. Patients whose history and physical examination warranted direct surgical exploration for suspected testicular torsion were not included in this study because they did not have radiologic evaluation. Therefore, the study population consisted of patients with clinical findings that were equivocal or of low suspicion for testicular torsion. By these inclusion criteria, 130 patients, 93 from institution A and 37 from institution B (93A:37B), were identified with the mean age at US study of 11.83 years (range, 2 days to 23 years). At both institutions, emergent evaluation included a routine history, physical examination, laboratory analysis, and color Doppler and conventional B mode US.

In the supine position, patients were scanned on an Acuson XP-10 unit (Acuson, Mountain View, CA) using a 7-MHz-linear-array transducer. In general, the image quality was maximized on the normal side, and then the transducer was moved to the abnormal side without changing the parameters. Parameters included: power, 0 dB; preprocessing, 0; postprocessing, 4; persistence, 3; gain, 4; wall filter, low; and log compression, 60 dB. Transverse and longitudinal images were scrutinized for testicular and epididymal size, flow, echotexture and configuration, presence of an enlarged appendix testis, scrotal wall thickening, and hydrocele. Color Doppler flow was assessed within the testis and epididymis in each case at low-flow settings. Point spectral analysis was also used in some cases to verify arterial waveforms. Whereas the results of the gray-scale images were noted, the diagnosis of testicular torsion was made ultrasonographically if the color Doppler imaging revealed absent or significantly reduced flow in the symptomatic side when compared with the asymptomatic testis. At institution A, the US study was performed exclusively by a pediatric radiologist while at institution B, the study was performed by a radiology resident and/or a radiology attending. Based on the urologic and radiologic evaluations, a clinical diagnosis was made by multiple observers including urology residents and urology attendings.

Clinical follow-up after the US was performed by either the attending urologist, urology residents, or by the patient's pediatrician. When a follow-up examination could not be documented from 1 of these sources, the patient was contacted by telephone or if was not reached, was considered lost to follow-up.

	RESULTS

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The most common urologic clinical diagnoses made at the time of the emergency visit were epididymitis (n = 50, 38.5%) and testicular torsion(n = 18, 13.8%) (Table 1). Based on this clinical diagnosis, the 130 patients were categorized into 3 groups: 1) 110 patients (77 patients in institution A, 33 in institution B) in whom torsion was excluded without surgical exploration, 2) 3 patients (2 in institution A, 1 in institution B) diagnosed with intermittent testicular torsion based on clinical history and negative US, and 3) 17 patients (14 in institution A, 3 in institution B) emergently explored for US diagnosis of testicular torsion (Fig 1).

View larger version (19K): [in this window] [in a new window]   Fig. 1.   Clinical diagnosis after color Doppler ultrasound and clinical outcomes of 130 patients with an acute scrotum. This study group does not include patients whose history and physical examination were of high suspicion for testicular torsion who underwent direct surgical exploration without radiologic evaluation.

Of the patients in group 1, 25 patients (21 in institutions A, 4 in institution B; 22.7%) were subsequently lost to follow-up. Follow-up of the remaining 85 patients (56 in institution A, 29 in institution B; mean length = 466.9 days) revealed no testicular atrophy in any of the 56 patients seen at institution A. Two of the 29 patients seen in follow-up at institution B demonstrated testicular atrophy. These 2 patients underwent delayed orchiectomy/contralateral orchiopexy for missed testicular torsion.

Of the 3 patients in group 2, 2 patients, 1 from each institution, were lost to follow-up. The remaining patient underwent elective bilateral orchiopexy.

Of the 17 patients in group 3, 9 (7 in institution A, 2 in institution B) underwent orchiectomy for a necrotic torsed testis at the time of presentation. Seven testes (6in institution A, 1 in institution B) seemed to have torsed but were considered viable at the time of exploration and underwent bilateral orchiopexy. One patient at institution A was found to have a torsed appendix testis at the time of emergent scrotal exploration, yielding a false-positive rate of 1% (1 false-positive scan out of 103 scans with known outcome concerning presence or absence of torsion).

Overall, testicular color Doppler US, when used to evaluate the equivocal acute scrotum, demonstrated sensitivity of 88.9% and specificity of 98.8%.

	DISCUSSION

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Despite the fact that the urologic literature contains multiple isolated cases of missed testicular torsion by color Doppler US imaging,^4-9 it is still a widely used diagnostic modality. Previously, color Doppler US was validated by imaging all patients with an acute scrotum, including patients with blatant testicular torsion, by history and physical examination. However, the greater test of the sensitivity, specificity, and accuracy of US is to limit the patient population to patients with equivocal or low probability for testicular torsion. Therefore, the goal of this investigation was to delineate how often a false-positive or false-negative US occurs, especially in the setting of an equivocal clinical diagnosis of torsion. By analyzing the outcomes of the set of patients with an equivocal clinical diagnosis, this study provides statistics which more closely approximate clinical reality of practice patterns, because the equivocal patients are imaged and the high likelihood for torsion patients are surgically explored.

In our population of 130 patients with equivocal or low probability for testicular torsion, color Doppler US demonstrated 88.9% sensitivity and 98.8% specificity. Unfortunately, 22.7% were lost to follow-up, likely because of the patient population consisting primarily of inner city children.

There is no one history, physical, laboratory, or radiologic finding diagnostic of testicular torsion. The clinical diagnosis therefore requires an integration of all sources of patient data. A history and physical suggestive of torsion should lead to surgical exploration without delay for testicular US. When US is obtained, meticulous attention to the performance and interpretation of the US is required. The nature of testicular torsion introduces diagnostic errors; in cases of intermittent testicular torsion or lesser degrees of severity and duration of torsion Doppler blood flow may be maintained.^14,15 Therefore, a negative US in the face of a suggestive history and physical examination must be interpreted with caution. In addition, Ingram and Hollman¹⁶ noted that 38% of normal boys aged 10 weeks to 13 years had no flow detectable with color Doppler US. Therefore, normal prepubertal testes are a source of false-negative flow results. Recent reports examining the use of power Doppler US in prepubertal testes have reported equal or slightly improved sensitivity when compared with conventional color Doppler US in detecting normal prepubertal testicular flow.^17,18 Power Doppler US, which displays the integrated power of a Doppler signal rather than its mean frequency shift as seen in color Doppler US, is more sensitive to low flow but is also more sensitive to motion artifacts. Performing both power and color Doppler US can improve the detection of flow in 14% of cases.¹⁷ In an experimental rabbit model of testicular torsion, unenhanced or contrast-enhanced power Doppler was no more accurate than color Doppler.¹⁹ This modality was not used in this study and its utility in diagnosing human testicular torsion awaits further study. However, refinements in technology will not replace the close interaction which is necessary between the pediatricians, urologists, and the radiologists to make the accurate diagnosis.

	CONCLUSIONS

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When faced with ruling out testicular torsion, it is necessary to integrate multiple pieces of patient data, knowing that each piece of data may have inaccuracies. With this in mind, this analysis of outcomes verifies that color Doppler US is an excellent adjunctive study in the situation in which the clinical evaluation suggests equivocal or low suspicion for testicular torsion.

	FOOTNOTES

Received for publication Feb 16, 1999; accepted Jun 15, 1999.

Reprint requests to (S.G.D.) Division of Pediatric Urology, Brady Urological Institute, Marburg 148, 600 N Wolfe St, Johns Hopkins Hospital, Baltimore, MD 21287-2101. E-mail: sdocimo{at}jhmi.edu

	ABBREVIATIONS

US, ultrasound.

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