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Acute segmental testicular infarction is an uncommon clinical situation. The etiologic mechanism is largely considered idiopathic, but cases have been associated with hypercoagulability disorders, vasculitis, torsion, trauma, infection [1], and iatrogenic vascular injury [2–4]. Segmental testicular infarction usually presents with acute scrotal pain and may resemble epididymoorchitis or torsion. Although surgery once was recommended, imaging has improved and increases confidence in assessment in many cases. If a firm diagnosis of segmental testicular infarction is reached on the basis of imaging features and negative tumor marker results, follow-up is advocated [1, 5]. Orchiectomy is not performed if symptoms subside and the lesion remains stable or shrinks.

The appearance of acute segmental testicular infarction at gray-scale and color Doppler ultrasound may be variable but often helps establish the benign nature of the lesion and guide diagnosis. According to Bilagi et al. [1], a typical segmental testicular infarct appears as a solitary solid wedge-shaped or round area in the testis. It is hypoechoic or has mixed echogenicity and has markedly diminished or no vascularity. Differential diagnosis from a tumor less vascularized than the surrounding testicular parenchyma can be difficult if the lesion is rounded and when vascularity is not completely absent at color Doppler examination [6, 7]. Although the presence of pain argues against tumor, patients with testicular cancer may have acute symptoms [8].

Contrast-enhanced MRI has been considered the best imaging modality for obtaining a firm diagnosis of segmental testicular infarction [5, 9–11]. The lesion is not enhancing after gadolinium administration, and an enhancing perilesional rim can be seen. MRI, however, cannot be used without the collaboration of the patient, is expensive, and is not widely available in emergency departments. Moreover, patients with pacemakers cannot undergo MRI, and patients with renal failure may be at risk of nephrogenic systemic fibrosis.

The use of contrast-enhanced ultrasound is opening perspective on the evaluation of intratesticular flow [12–15]. In 2005, Cochlin [14] presented the case of a patient with segmental testicular infarction evaluated with contrast-enhanced ultrasound, suggesting that microbubble contrast agents would be useful for differentiating this lesion from a hypovascular tumor. To the best of our knowledge, however, no systematic studies have been performed on this topic. In this retrospective study, the gray-scale, color Doppler, and contrast-enhanced ultrasound features in 20 cases of acute segmental testicular infarction were reviewed. The lesions were evaluated soon after the onset of symptoms and during follow-up with the purpose of investigating whether microbubble contrast injection improves characterization of the lesions and prevents unnecessary orchiectomy.

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We reviewed the gray-scale, color Doppler, and contrast-enhanced ultrasound images of 20 men (age range, 18–85 years; mean, 46 ± 16 [SD] years; median, 43 years) with acute segmental testicular infarction examined from March 2004 to November 2009. All patients presented with acute scrotal pain. The right testis was involved in four patients and the left in 16. No lesion was palpable. Testicular infarction was considered idiopathic in 12 of the 20 patients: 11 without other remarkable pathologic conditions and one who had undergone orchiopexy at an early age and had ipsilateral testicular atrophy. Two of the other eight patients had scrotal trauma; one patient had Schönlein-Henoch purpura; two patients had undergone ipsilateral inguinal hernia repair that was complicated by inguinal hematoma compressing the spermatic cord; one patient had epididymoorchitis; one patient was at high risk of thromboembolism because of chronic atrial fibrillation, valvular heart disease, and anticoagulation therapy; and one had abdominal and bilateral enlarged inguinal lymph nodes associated with a mixed germinal testicular tumor. In this last patient, contrast-enhanced ultrasound depicted both a segmental infarct and a nonpalpable tumor in the same testis (Table 1). Tumor marker results were negative in all but in the patient with an associated testicular tumor. Institutional review board approval and informed consent from each patient were obtained before contrast ultrasound examination.

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TABLE 1: Characteristics of Patients With Acute Segmental Testicular Infarction

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The features of acute segmental testicular infarction at gray-scale, color Doppler, and contrast-enhanced ultrasound are summarized in Tables 2 and 3. The lesion was located in the upper pole of the testis in 13 patients, in the lower pole in two patients, and in the middle portion in three patients. In one patient the infarction involved the middle and upper portions, and in another patient it affected the middle and lower portions. Infarction was significantly more frequent on the left side and in the upper pole of the testis (chi-square test, p < 0.01). The lesion characteristics differed over time, depending on whether the ultrasound examination was performed soon after the onset of symptoms or during short- or long-term follow-up.

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TABLE 2: Findings at Gray-Scale and Color Doppler Ultrasound Evaluation of Segmental Testicular Infarction

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TABLE 3: Findings at Contrast-Enhanced Ultrasound Evaluation of Segmental Testicular Infarction at Different Times From Onset of Testicular Pain

Early Findings

Within 24 hours after the onset of symptoms, eight of 16 lesions were nearly isoechoic to the testis, barely visible at gray-scale ultrasound owing to slightly inhomogeneous echotexture (Figs. 1A, 1B, 1C, 2A, 2B, 2C, 2D, and 2E). Six lesions were hypoechoic to testis, and two had mixed echogenicity with hypoechoic and hyperechoic portions. Fourteen lesions were oval, and two were wedge shaped. All but two lesions had ill-defined borders. The average lesion size ranged from 1.1 to 3 cm (mean, 2.0 ± 0.6 [SD] cm). At color Doppler examination, 12 of 16 lesions evaluated within 24 hours after the onset of symptoms were avascular (Figs. 1A, 1B, 1C, 2A, 2B, 2C, 2D, and 2E). The other four lesions were hypovascular compared with adjacent parenchyma. Increased perilesional flow was appreciated in eight of 16 patients.

Thirteen patients underwent contrast-enhanced ultrasound within 24 hours after the onset of scrotal pain. A single avascular portion of parenchyma was identified in six of the 13 patients (Figs. 1A, 1B, and 1C). Seven lesions were formed by adjacent avascular parenchymal regions separated by patent centripetal arteries, consistent with ischemic lobules with intervening parenchymal vessels (Figs. 2A, 2B, 2C, 2D, and 2E). Contrast-enhanced ultrasound showed that all four hypovascular lesions and three avascular lesions found with color Doppler ultrasound consisted of more than one lobule. Perilesional rim enhancement was identified at contrast-enhanced ultrasound in one of 13 patients (8%).

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Fig. 1A —51-year-old man with right acute testicular pain for less than 24 hours. Gray-scale ultrasound image shows inhomogeneous area (arrowheads) in upper pole of testis.

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Fig. 1B —51-year-old man with right acute testicular pain for less than 24 hours. Power Doppler ultrasound image shows avascular area (asterisk) surrounded by parenchyma with subjectively increased vascularization.

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Fig. 1C —51-year-old man with right acute testicular pain for less than 24 hours. Contrast-enhanced ultrasound image shows ischemic lobule (asterisk) without perilesional enhancement consistent with acute segmental infarction.

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The key factor that allows differential diagnosis between segmental testicular infarction and tumor is recognition that the lesion is formed by one or more ischemic testicular lobules. Identification of the lobular morphologic features and the ischemic nature is straightforward in cases of wedge-shaped hypoechoic lesions that are avascular at color Doppler examination. Segmental testicular infarction, however, can be round and appear not completely avascular at color Doppler examination [1, 6]. When intralesional color spots are present, infarction cannot be safely differentiated from a hypovascular tumor. Moreover, increased perilesional parenchymal flow signal may be present in segmental infarction that is difficult to differentiate from peripheral vascularization, especially in small lesions [14], or from the hypervascular rim often visible in testicular abscesses. In addition, small testicular tumors may appear avascular at color Doppler examination [7]. In these situations, differentiation of infarction from hypovascular tumor can be difficult or even impossible [1, 9].

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Fig. 2A —45-year-old man with left acute testicular pain for 24 hours. Gray-scale ultrasound image shows inhomogeneous area (arrowheads) in lower pole of testis.

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Fig. 2B —45-year-old man with left acute testicular pain for 24 hours. Color Doppler ultrasound image shows avascular area (asterisk) surrounded by parenchyma with subjectively increased vascularization.

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Fig. 2C —45-year-old man with left acute testicular pain for 24 hours. Contrast-enhanced ultrasound image shows multiple ischemic lobules without perilesional enhancement separated by normal centripetal vessels (arrowheads) arising from capsular vessels (arrows).

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Fig. 2D —45-year-old man with left acute testicular pain for 24 hours. Color Doppler ultrasound image obtained 9 days after A–C shows hypoechoic wedge-shaped hypovascular lesion (asterisk). Vascularization of surrounding parenchyma is subjectively increased.

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Fig. 2E —45-year-old man with left acute testicular pain for 24 hours. Contrast-enhanced ultrasound image obtained 9 days after A–C shows ischemic lobules with intervening areas of viable parenchyma (arrows). Perilesional rim (arrowheads) of enhancement is evident.

Results during careful color Doppler investigation may suggest the correct diagnosis of segmental testicular infarction in many cases, but in clinical practice, diagnosis is often made after orchiectomy for a suspected tumor. In our series contrast-enhanced ultrasound improved characterization of acute testicular segmental infarction, showing the morphologic features of this lesion, which are different from those of hypovascular tumors. Infarction presents as one or more avascular areas separated by normal vessels, consistent with ischemic testicular lobules. Unlike color Doppler ultrasound, contrast-enhanced ultrasound shows vessels for a long time after injection of microbubbles, and differentiation between normal centripetal testicular arteries originating from the capsular arteries and tumor neovascularization is straightforward.

We found gray-scale and color Doppler features of segmental testicular infarction similar to those described in other studies [1, 5, 9, 11, 14–17]. The spectrum of findings differed depending on the time between the onset of testicular pain and the ultrasound examination. Lesions identified earlier were more often rounded and nearly isoechoic to testis and had ill-defined margins. They became more conspicuous and smaller over time and hypoechoic to testis and often were wedge shaped.

As it was in the study by Bilagi et al. [1], in our series segmental infarction was more frequent in the upper pole of the testis (chisquare test, p < 0.01). Predisposition to partial infarction in the upper hemisphere of the testis can result from impairment of arterial flow due to vascular abnormalities [9]. Unlike other authors [1, 5, 9], we found segmental infarction had a statistically significant predilection for the left testis (chisquare test, p < 0.01). The explanation for this difference is not clear; it may be related to differences in patient populations. Anatomic factors also may explain our finding. The left-sided prevalence of varicocele is well known owing to differences in testicular venous drainage on the two sides. This condition may be associated with decreased testicular blood flow [18]. Slightly compromised left venous drainage associated with reduction in arterial flow may also be present in patients without varicocele, increasing the likelihood of finding infarcts in our series.

In eight of 16 patients in our series, slightly increased perilesional parenchymal flow was appreciable at color Doppler examination within 24 hours after the onset of pain; in 10 of 14 patients, this finding was made at examinations performed 2–17 days after pain onset. Perilesional hyperemia faded in chronic segmental infarction. This feature was described by Gianfrilli et al. [17] and may be due to perilesional inflammatory changes around the infarcted areas. According to Bilagi et al. [1], this finding can be interpreted as a mass effect due to intralesional edema in the infarcted area that displaces the surrounding testicular tissue and causes bundling of the perilesional parenchymal vessels.

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Fig. 3A —41-year-old man examined 3 days (A and B) and 1 year (C and D) after onset of left acute testicular pain. Color Doppler ultrasound image shows avascular oval hypoechoic lesion (asterisk). Vascularization of surrounding parenchyma is subjectively increased.

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Fig. 3B —41-year-old man examined 3 days (A and B) and 1 year (C and D) after onset of left acute testicular pain. Contrast-enhanced ultrasound image shows oval avascular lesion (asterisk) with perilesional enhancing rim (arrowheads).

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Fig. 3C —41-year-old man examined 3 days (A and B) and 1 year (C and D) after onset of left acute testicular pain. Follow-up color Doppler ultrasound image shows hypoechoic avascular oval area (asterisk) in upper pole of testis markedly reduced in size compared with size in A.

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Fig. 3D —41-year-old man examined 3 days (A and B) and 1 year (C and D) after onset of left acute testicular pain. Follow-up contrast-enhanced ultrasound image shows hypovascular lesion (asterisk) with no perilesional rim of enhancement and few intralesional vascular spots.

Acute testicular segmental infarction presenting as a round lesion with perilesional hyperemia must be differentiated from testicular abscess [19, 20], which is usually anechoic or markedly hypoechoic and has irregular wall and low-level internal echoes and increased through transmission. Moreover, an abscess does not conform to lobular distribution [16]. We have found that the perilesional hyperemia observed in segmental testicular infarction usually is more pronounced than the hypervascular rim of an abscess.

As in gray-scale and color Doppler ultrasound, after microbubble injection we found the spectrum of findings depended on the time between the onset of testicular pain and the contrast-enhanced ultrasound examination. Unlike perilesional hyperemia at color Doppler examination, which is identified within 24 hours from the onset of pain in 50% of patients, perilesional rim enhancement was observed early at contrast-enhanced ultrasound in only one of 13 (8%) patients. It was prevalent (6/7, 86%), however, in examinations performed 2–17 days after the onset of pain. No patient examined longer from the episode of acute scrotal pain presented with perilesional rim enhancement. This temporal evolution suggests a different pathologic basis. Because radiologic-pathologic correlation was not performed in our series, we can only speculate on the anatomic basis of perilesional rim enhancement. Histologic studies of the heart have shown that vessels bordering an infarcted area actively proliferate to form new channels under the influence of several hypoxia-inducible peptides, such as vascular endothelial growth factor [21]. Other experimental studies have shown that vascular endothelial growth factor also mediates angiogenesis in ischemic testis [22]. It is conceivable that the perilesional rim enhancement observed at contrast-enhanced ultrasound represents histologic evidence of granulation tissue, including inflammatory cells, fibroblasts, and neovasculature, in response to ischemia, which is not present either during the early phase or in old infarcts [23, 24]. If this interpretation is correct, perilesional rim enhancement at contrast-enhanced ultrasound may be a sign of subacute segmental testicular infarction.

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Fig. 4A —39-year-old man with 2-day history of left acute testicular pain. Color Doppler ultrasound image shows avascular inhomogeneously hypoechoic lesion (asterisk). Vascularization of surrounding parenchyma is subjectively increased.

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Fig. 4B —39-year-old man with 2-day history of left acute testicular pain. Contrast-enhanced ultrasound image shows ischemic lobules with intervening viable parenchyma (arrow). Perilesional rim of enhancement is present.

Intralesional vascular spots were identified at contrast-enhanced ultrasound in 12 of 14 patients with segmental testicular infarction examined 1 month or more after the onset of symptoms. Differential diagnosis between chronic segmental infarction and hypovascular testicular tumor based on imaging findings alone can be difficult in the care of these patients, especially if the lesion is rounded [7]. The diagnosis of chronic segmental infarction, however, is possible on the basis of the combination of a history of testicular pain, imaging features, and changes in shape, size, and characteristics from previous ultrasound examinations. A possible explanation for the presence of intralesional vessels in chronic segmental infarction is found in heart studies showing that scar is living, dynamic tissue with a neovasculature [25].

This study had several limitations. First, the number of patients with segmental testicular infarction evaluated was relatively low, reflecting the rarity of this pathologic condition. Second, in our series, segmental testicular infarction was first suspected at conventional sonography and then studied with contrast-enhanced ultrasound, limiting false-positive and false-negative results. Moreover, no other pathologic conditions that present with similar findings, hypovascular and infarcted tumors in particular, were considered. Therefore, our data cannot be used to extrapolate into clinical practice the importance of contrast-enhanced ultrasound in the characterization of testicular lesions in the general population of patients. Third, histologic correlation was not obtained in most of the cases. Orchiectomy, however, is not currently indicated in the management of segmental testicular infarction if a firm diagnosis is reached with clinical and imaging findings [1, 5]. Fourth, color Doppler and contrast-enhanced ultrasound were the only imaging modalities available in this series because MRI was not performed. Although according to Bilagi et al. [1], MRI is not needed to characterize segmental testicular infarction [1], other authors [5, 9–11, 26] suggest that this technique is excellent for establishing the diagnosis in equivocal cases.

We conclude that acute segmental testicular infarction often presents with typical features at ultrasound, but differentiation from tumors can be difficult. Moreover, approximately one half of infarcts are nearly isoechoic to testis within 24 hours after the onset of pain and are identified mainly as a hypovascular region at color Doppler examination. In our series, contrast-enhanced ultrasound improved lesion conspicuity and depicted the anatomic characteristics. As in gray-scale and color Doppler examinations, lesion changes over time are important for confirming a diagnosis with contrast-enhanced ultrasound. In particular, perilesional rim enhancement is evident within 2–17 days after the onset of symptoms. Later in follow-up, the appearance of the lesion is not characteristic because the perilesional enhancing rim disappears, and intralesional vascular signal often is identified. Comparison with results of previous examinations, however, shows a reduction in lesion size and changes in vascular features that lead to a firm diagnosis of segmental testicular infarction that prevents unnecessary orchiectomy.