Written by Martin Necas, Waikato Hospital
Ultrasound is the imaging test of choice for patients with scrotal trauma. Ultrasound is fast, safe and readily available. Most patients can be examined with high-frequency linear transducers up to 20MHz in frequency offering spectacular axial resolution down to 0.1mm. For instance, the GE ML6-15 or Philips eL18-4 represent some of the widely available instruments of choice, but most transducers above 10MHz are adequate. Both B-mode and colour Doppler (sometimes with spectral Doppler) are important because colour can demonstrate vascular anatomical distortion, areas of tissue viability or infarction, and can help in differentiating trauma from other pathologies.
Because significant testicular injury represents a urological emergency, patients require imaging as soon as possible. While some patients present with a clear mechanism of injury and obvious clinical features of scrotal trauma, others present with less convincing mechanisms and vague symptoms. The wide spectrum of scrotal trauma mechanisms and degrees of injury results in a variety of imaging appearances, including the frequent discovery of incidental or unexpected findings. Let’s have a look at what ultrasound finding that can be encountered. First, let’s consider the patients with a clear mechanism of injury:
Testicular rupture
Testicular rupture pertains to a tear of the tunica allowing for testicular parenchyma to herniate through the defect. This is a urological emergency.
Figure 1: Testicular fracture, characterised by a tear of the tunica. In this case, the tunica has been displaced into the testis (arrows) with associated haematoma (H) filling the defect.
Figure 2: Testicular fracture, with large areas of tissue necrosis and only sparse viable testicular tissue (arrows) as shown on power Doppler imaging.
Figure 3: Testicular rupture of the lower pole (arrows) associated with a crescent-shaped haematoma (H) surrounding the testis.
Testicular fracture
Testicular fracture and rupture are sometimes used synonymously. A fracture more specifically pertains to internal sheer injury with an intact tunica. Good case examples are rare. Some authors describe the appearance of an intratesticular cleft, but one has to be careful not to confuse the transmediastinal artery variant has a fracture.
Figure 4: Two areas of well-demarcated cleft in the testicle, representing normal transmediastinal artery variant as evidenced by colour Doppler
Segmental infarction
Segmental infarcts can sometimes be found in the context of testicular pain or injury. Infacts can be idiopathic or related to infection or trauma. They appear hypoechoic and are usually lentiform or wedge-shaped. The absence of any vascularity within the infarcts helps in distinguishing these from testicular tumours.
Figure 5: Small idiopathic segmental infarcts (left image) with complete spontaneous resolution on subsequent examination (right image).
Figure 6: Large infarct involving approximately 40% of the testicle in the upper pole.
Figure 7: Small hypoechoic but vascularised lesions. These are not segmental infarcts, but intratesticular tumours. In this case, multifocal seminoma.
Intratesticular haematoma
Intratesticular haematomas with or without overt rupture can occur. They are typically hypoechoic.
Figure 8: Intratesticular haematoma
It is important not to confuse age-related testicular change in older men with a presence of testicular injury on B-mode ultrasound alone. Colour Doppler or contrast-enhanced ultrasound may be required for definitive characterisation.
Figure 9: Normal age-related changes (marbled echotexture on B-mode), can mimic testicular injury such as contusion, haematoma or segmental infarction.
Haematocoele
Any bleeding into the scrotal sac will result to form a haematocoele, the evolution of which is comparable to haemorrhage at other anatomical sites. In the acute stage, low-level homogenous particulate echoes are seen. These tend to form fibrin strands and discrete clots with evolution.
Figure 10: Gravity-dependent haematocoele containing low-level homogeneous echoes.
Figure 11: Fibrin strands within a haematocoele
Figure 12: Organising haematocoele with blood of varying echtextures, fluid-level (arrow), fibrin and clots (C).
Scrotal wall trauma
Scrotal wall trauma can affect any layer(s) of the scrotal wall from skin to the parietal layer of the tunica vaginalis. Ultrasound offers excellent spatial resolution to determine which layer is affected.
Figure 13: Rupture of the parietal layer of the tunica vaginalis with associated haematocoele and clot, but without testicular injury.
Scrotal wall haematoma
Scrotal wall trauma makes clinical examination of the underlying testis difficult. Ultrasound can readily distinguish isolated scrotal wall trauma from underlying testicular trauma.
Figure 14: Contained infected scrotal wall haematoma (H) causing scrotal wall swelling but without associated testicular (T) injury in a multi-trauma patient.
In contrast to patients without a clear mechanism of injury, the story in patients with vague (or sometimes imagined) trauma is quite different. Men often attribute all testicular pain to some mechanical agitation and offer speculative history such as: “I must have sat on it”, “I must have knocked it”, “I must have slept in an awkward position”. Rather than trauma, underlying infection is a far more plausible cause for testicular pain in these patients. It’s interesting that in my ultrasound career of nearly 30 years, I have never encountered a male patient who openly suspected infection (or sexually transmitted infection) as the cause of their scrotal pain. So it follows that a high proportion of patients referred for ultrasound with a vague history of trauma harbour epididymitis or epididymo-orchitis. It should also be acknowledged that testicular pain can also signal the presence of other unexpected problems including idiopathic segmental infarction, intermittent tortion, post-acute tortion (with a necrotic testicle) or underlying tumour.
Figure 15: A patient with persistent pain following a kick to the scrotum during soccer demonstrates a normal testicle, but swollen hyperaemic epididymis with a central abscess.
Figure 16: Incidental discovery of a testicular tumour in a patient reporting aching after being kicked in the scrotum. Fortunately for the patient, this proved to be a benign Leydig cell tumour.
In conclusion, ultrasound is the most powerful tool to assist the clinician in the identification and correct classification of scrotal trauma. However, ultrasound users should be mindful of misleading or inaccurate clinical history, various trauma mimics and the frequent discovery of pathology not related to trauma.
References:
Nicola R, Carson N, Dogra VS. Imaging of traumatic injuries to the scrotum and penis. AJR Am J Roentgenol. 2014 Jun;202(6):W512-520.
Rao MS, Arjun K. Sonography of scrotal trauma. Indian J Radiol Imaging. 2012;22(4):293–7.
Yusuf GT, Sidhu PS. A review of ultrasound imaging in scrotal emergencies. J Ultrasound. 2013 Sep 4;16(4):171–8.
Adlan T, Freeman S. Can ultrasound help to manage patients with scrotal trauma? Ultrasound. 2014 Nov;22(4):205–12.