Teaching Case

A 35-year-old male patient presented to the emergency department after sustaining a self-inflicted clamping injury to the right hemiscrotum. Clinical examination revealed localised oedema and skin erythema. Scrotal ultrasound was requested to evaluate the scrotal contents.

Ultrasound identified enlargement, heterogeneity and low reflectivity of the right testis and epididymis, compared to the left. Only the lower pole of the right testis showed normal echotexture. (Fig. 1A,B) On colour Doppler imaging minimal flow was identified in the lower pole of the right testis and no Doppler signals could be seen within the hypoechoic upper part of the testis. (Fig. 1C) There was also thickening and hyperaemia of the right hemiscrotum soft tissues.(Fig. 1D) The left testis appeared normal. (Fig. 1E) Two hours later a contrast-enhanced ultrasound (CEUS) was requested for further evaluation. After intravenous administration of 4.8 mL of microbubbles, no enhancement could be seen in the upper and mid aspects of the right testis, which had appeared hypoechoic and avascular on conventional ultrasound. The lower pole which appeared normal on the first examination showed minimal and delayed enhancement on CEUS. The left testis enhanced normally.(Fig. 2)

Testicular infarcts are characterized as global when affecting the entire testis or segmental when affecting only part of it [1, 2]. Segmental testicular infarction (STI) is usually idiopathic but has been associated with conditions like epididymoorchitis, trauma, sickle cell disease and recent surgery [2, 3]. It is rare, with a prevalence of only 0.3% in testicular sonographic examinations [4]. Although classic testicular infarction caused by torsion affects young patients, STI is more frequent in patients older than 30 [5].
STI typically causes scrotal pain and swelling with ultrasound being the first-line imaging modality. It characteristically appears as a peripherally located, rounded or wedge-shaped hypoechoic intratesticular lesion which shows no or minimal blood flow on colour Doppler. It usually presents as a single lesion with possibly geographic distribution but multiple infarcts may also occur [2, 6]. Sometimes, there may be increased vascularity peripheral to the lesion. In the acute phase, an STI may be ill-defined but as it becomes chronic, it gradually appears more discrete and hypoechoic. A decrease in size over time is considered characteristic for the follow-up of a STI [2, 5, 7]. The wedge shape of STI, although not always present, is considered suggestive and is created by the lobular morphology of the infarcted area [7]. All STI imaging findings reflect histological features like haemorrhage, oedema, inflammation and hyalinised interstitial fibrosis [2]. As a definitive diagnosis is not always possible with conventional ultrasound, CEUS or contrast-enhanced Magnetic Resonance imaging can be used to further characterize the lesion. The use of more elaborate techniques is driven by the need for differential diagnosis between a true STI and a malignant tumour, since an orchiectomy would be unnecessary in STI [2, 5]. Unfortunately, in some cases a definitive diagnosis still needs to be made based on histology after orchiectomy [2]. On CEUS, the appearances of STI depend on their age. Acute STI appear as areas with no internal or peripheral enhancement. Normal blood vessels can be seen between infarcted areas. In the subacute phase microbubbles may outline a peripheral rim of enhancement, while in the chronic phase there may be evidence of limited vascular foci within the lesion [5-8]. In a recent study with scrotal emergency patients, it was concluded that CEUS is more sensitive and specific and reaches the diagnosis in more cases compared with conventional ultrasound [9]. In patients with a confident diagnosis, negative tumour markers and a lesion stable or decreasing in size on follow-up, there is no need for surgery [7, 10].