Ultrasound is a safe, painless, and non-invasive procedure. The procedure uses high frequency sound waves to produce images of organs inside your body. Ultrasound provides excellent anatomic detail and plays a vital role in current clinical practice; with accurate diagnosis ultrasound significantly improves the management of numerous medical conditions (Kane, 2003). The availability, non-invasiveness, no known side effects, minimal patient preparation, cost effectiveness renders ultrasound an imaging modality of choice compared to other radiological investigations (Prasad Hari et al, 2007).
Common Clinical indication for Thyroid Ultrasound
Evaluating the thyroid gland consists of two hypoechoic lobes joined by isthmus and surrounded by a thin capsule. Normal parathyroid glands have similar appearance but being small are difficult to visualize on ultrasound.
The use of ultrasound in the clinical evaluation of patients with thyroid lesions has expanded from the detection of non-palpable thyroid nodules to include the delineation of benign and malignant thyroid lesions, the examination of lymph node basins for staging purposes and treatment planning, fine-needle aspiration (FNA) guidance for thyroid nodules or suspicious appearing lymph nodes, intraoperative localization of thyroid lesions and/or lymph nodes, and postoperative surveillance for recurrent thyroid cancer (Appendix 1) (Milas et al., 2005). The ultimate aim of ultrasound is to identify a malignant nodule against a background nodular goitre (Wong, 2005).
Clinic ultrasound can be a valuable extension of the clinical examination as this modality can image thyroid lesions and provide additional information in real time with greater clarity (Kouvaraki et al., 2003).
Thyroid ultrasound may changes management in 60% of patients who have been referred for a solitary thyroid nodule. Ultrasound-guided FNA of suspicious thyroid nodules can be performed with a low sampling error rate. Ultrasound also helps in the detection of cervical nodal metastases (Marqusee et al., 2000).
Elastography utilizes ultrasound to analyse the stiffness of a nodule, this results in excellent correlation and subsequent pathology determined by biopsy (Levine Robert,2008).
Ultrasound may also identify coexisting thyroid and lymph node disease that may influence the extent of the intended thyroid operation (Solorzano, 2004). Recently, ultrasound was used to preoperatively stage patients with well-differentiated thyroid cancer and to determine the extent of surgical resection (Park et al., 2009).
Ultrasound of thyroid nodules
Thyroid nodules are clinically important because they require further evaluation to exclude the underlying possibility of thyroid cancer (Hegedus, 2004).
Thyroid ultrasound is used to evaluate index nodule size, location, characteristics, and the number and presence of additional thyroid nodules (e.g., contralateral lobe), and for the detection of suspicious-appearing lymph nodes (Davies and Welch, 2006).
Nodule size has been shown to not be predictive of malignancy. Patients with multiple thyroid nodules also have the same risk for malignancy as those with solitary nodules, and it is recommended that all patients with nodular thyroid glands undergo ultrasound evaluation (Marqusee, 2000).
Recent evidence suggests that preoperative ultrasound may alter the planned surgical procedure in cases where newly discovered multifocal thyroid cancer with regional metastasis may alert the surgeon to perform a total thyroidectomy with extended neck dissection (Milas et al., 2005).
Characteristics of Thyroid Nodules
A variety of ultrasound characteristics are thought to differentiate benign from malignant thyroid nodules (Kim et al., 2002 and Jabieve et al., 2009).
These ultrasound features include echogenicity, internal echo pattern, margins, calcifications, shape/dimension ratio, acoustic phenomenon, compressibility, and vascularity. Whereas the well-defined and smooth margins of a thyroid nodule may signify benignity, irregular or ill defined lesions suggest malignancy. Although benign nodules are more likely to be entirely cystic in nature, many malignant lesions are solid and appear hypoechoic relative to adjacent thyroid tissue. Furthermore, thyroid nodules with a spongiform appearance comprised of 50%> multiple micro-cystic components are most likely benign (Bonavita et al., 2009). A thyroid nodule defined as being greater in its anteroposterior than its transverse dimension (i.e., taller greater than wider) has been described as more likely to be malignant than benign (Kim et al, 2002).
Thyroid nodules with microcalcifications are more strongly associated with malignancy than those with no calcifications. Central vascularity is more likely to be characteristic of malignant thyroid nodules, whereas peripheral vascularity is associated with benign lesions. Apart from the index nodule, the presence of suspicious-appearing lymph nodes is also associated with thyroid malignancy (Papini et al., 2002 and Kim et al 2002).
Common Clinical indication for Testicular (Scrotum) Ultrasound
Ultrasound plays an important role in the diagnostic workup of scrotal diseases (Akin, 2004). A testicle ultrasound is a test used to obtain images of the testicles and the surrounding area in the scrotum. Both testes should be scanned on the same image for comparison. Longitudinal and transverse views demonstrate homogenous testes and epididymis. Ultrasound is considered the most sensitive, non-invasive investigation of scrotal pathology; a scrotal ultrasound is a safe and painless test that uses sound waves to make images of the scrotum (Lau et al, 1999) (Appendix 2, 3).
Ultrasound can differentiate a testicular mass from an extra testicular mass and determine whether the mass is cystic, solid, or complex. The scan appearances may be suggestive of a cause for the swelling, sometimes the ultrasound is used to guide a biopsy of a swelling or lump (Akin, 2004). In painful conditions of the testicle, the main aim is to determine whether the blood supply to the testis is normal. Increased blood flow is suggestive of epididymitis, while decreased blood flow would be much more serious and may indicate a testicular torsion (Akin, 2004).
In the acute scrotum, acute epididymitis / epididymo-orchitis can be distinguished from testicular torsion in the most cases. Following scrotal trauma, surgery is needed to salvage the testis if there is testicular disruption and ultrasound can help with this diagnostic dilemma (Akin, 2004).
Ultrasound allows evaluation of the underlying testis and epididymis in case of the present of large hydrocele, it can detect varicoceles, especially in the infertile male (Akin, 2004).
In patients at risk for a testicular tumour (cryptorchid testis, testicular microlithiasis), ultrasound is the best imaging modality for follow-up. CT, MRI, and nuclear medicine scanning may be necessary for further evaluation (Akin, 2004).
A hydrocele is the most common cause of scrotal swelling. Acquired hydroceles are associated with infection, tumours, trauma, torsion, and radiation therapy. Hematoceles and pyoceles are complex hydroceles. Sonographically, a simple hydrocele is seen as an anechoic dark fluid collection surrounding the testicle, whereas a complex hydrocele may contain internal echoes with septations and loculations. A chronic hydrocele may also demonstrate internal echoes from cholesterol crystal formation (Blaivas , 2004 and Blaivas, 2001).
A varicocele is a collection of tortuous and dilated veins within the pampiniform plexus of the spermatic cord. Sonographically, they appear as multiple anechoic serpiginous tubular or curvilinear structures of varying sizes in the region of the epididymis. Power Doppler should be used to confirm flow in the varicocele (Akin, 2004 and Blaivas, 2004 and Blaivas, 2001).
Torsion Sonographic findings can be variable depending on the duration of torsion and extent of vascular compromise. The testicle can appear enlarged and hypoechoic and the parenchyma of the testicle will become less homogenous when compared with the unaffected testicle (Akin, 2004 and Blaivas, 2004).
Unfortunately ultrasound findings may be subtle early in the course. Colour Doppler or power Doppler may be helpful to identify flow patterns in the acutely tender testicle. When blood flow is absent in the affected testicle, the diagnosis of testicular torsion is clear (Stavros et al, 2008).
Occasionally decreased blood flow seen in early torsion can be erroneously diagnosed as normal. Thus, comparison to the contralateral side is crucial. Colour Doppler alone will not assure both venous and arterial flow in the testicle. Spectral Doppler tracings should also be obtained to confirm both arterial and venous flow. The absence of a venous pattern by spectral Doppler on the affected side suggests early torsion. If the diagnosis is in doubt due to torsion-detorsion, repeat colour Doppler imaging along with spectral examination in one hour is recommended (Blaivas, 2004 and Blaivas, 2001).
Differential diagnosis of acute scrotal pain includes epididymitis, orchitis, testicular torsion, torsion of the testicular appendage, testicular trauma, and herniation of abdominal contents into the scrotum. Ultrasonography of the acute scrotum has high utility for emergency physicians (Adhikari, 2009).
Testicular neoplasms presenting with/without pain may be clinically misdiagnosed as epididymitis and ultrasound imaging is performed in cases of persistent swelling despite conservative treatment (Adhikari, 2009).
Epididymitis is the most common cause of acute scrotal pain in post-pubertal males. Classically, patients present with a painful tender scrotum, dysuria, and fever. Gray-scale findings of acute epididymitis include an enlarged epididymis with decreased echogenicity. Often, a reactive hydrocele is noted as well. A chronically inflamed epididymis becomes thickened and has focal echogenicity with areas of calcification. With Doppler sonography increased blood flow secondary to epididymal inflammation is noted (Blaivas, 2004 and Blaivas, 2001).
Orchitis is an acute infection of the testicle usually following epididymitis. Orchitis often presents with a tender and inflamed testicle. On gray-scale ultrasound, orchitis is seen as an enlarged testicle with heterogeneous echogenicity. This appearance is nonspecific and can be seen in many other conditions such as tumors, metastasis, infarct and torsion. Standard B-mode is not a reliable method to differentiate between orchitis and testicular torsion. For both orchitis and torsion, inflammation and edema can lead to enlargement and heterogeneous echogenicity of the testis. Color Doppler is helpful to differentiate between orchitis and torsion (Blaivas, 2004 and Blaivas, 2001).
Trauma Blunt trauma to the scrotum can lead to damage of the testicle and adjacent structures. Injuries to scrotum include laceration, haemorrhage, or contusion of the testicle. Sonographic findings suggestive of testicular injury include irregular outline and an inhomogeneous echotexture from haemorrhage or infarction (Blaivas, 2004). A discrete fracture line is seen by ultrasound in only 17 % of ruptures. A significant haematocele is an indirect finding for possible testicular rupture. Haemorrhage within the testicle changes its appearance depending on the age of the haemorrhage. Colour Doppler helps to differentiate hematomas from tumours. Tumours are usually vascular, whereas hematomas will not reveal any blood flow (Adhikari, 2009).
The theoretical risks of ultrasound including heat and cavitation resulting in tissue damage remain, despite extensive research showing diagnostic ultrasound is safe in humans. Guidelines for safety include ALARA (As low as reasonably achievable-BMUS, 2008) Counseling about abnormal findings is and important communication skill. Professionalism must be maintained at all times. The patient’s dignity and privacy in the presence of an unrelated chaperone must be observed during the examination. The ultrasound must be performed in a skillful, gentle way being alert of any discomfort experienced by the patient. Standard reporting forms with clear department protocols and risk management systems are recommended as they aid clinical audits. Accuracy can be improved by interdisciplinary clinical meetings and reporting audits (Nicol, 2009). Quality assurance tests include regular monitoring, equipment maintenance, and proper training of personnel. A structured quality and safety approach must be maintained to deliver the highest possible standard of care (Selbmann and Geraedts, 1997)
Ultrasound is a vital adjunct to clinical examination in diagnosing scrotal and thyroid disease. Potential applications range from acute emergency to long-term screening as well as cases in which a distinct scrotal or thyroid abnormality may or may not be palpable (Bonavita, 2009). Technology advancements such as the use of multi-frequency transducers, Doppler capabilities, biopsy guide attachments, portability, and high image quality have enhanced diagnosis and management of pathology (Kane, 2003)
Ultrasound availability in clinical practice has produced increasing opportunities for ‘one stop’ clinics to reduce the hospital load, cut down on the healthcare budget and reduce patient waiting times. This kind of practice requires consultants to work closely with primary care providers to develop protocols, and referral guidelines and establish multidisciplinary teams to provide organizational continuity rather than the traditional model of a lone consultant. The use of ultrasound is fast increasing and the most exciting future developments will be in the field of therapeutic ultrasound.