A pyocele or extratesticular scrotal abscess may occur as a complication of trauma, surgery or epididymo-orchitis when the mesothelial lining of the tunica vaginalis is breached and infection ensues. Clinical history and physical examination of a painful scrotum help in making the diagnosis [7].

At ultrasound, a pyocele often appears as a complex heterogeneous extratesticular fluid collection (Fig. 43.2).

In most cases, conservative treatment with antibiotics is sufficient. However, a scrotal abscess complicated by necrotizing infection of the perineum requires prompt surgery [12].

Haematocele is a collection of blood within the tunica vaginalis layers. It appears after a scrotal trauma or surgery but may also occur spontaneously or, more rarely, in association with clotting disorders, vasculitis or other inflammatory conditions. Haematocele has rarely been described as the presenting feature of malignancy [13].

In the absence of a clear history of trauma, however, the exclusion of tumour is difficult and surgical exploration may be required.

Haematocele has a variable appearance on ultrasound, with a temporal change in characteristics on repeat ultrasound. Acutely it is echogenic and becomes more complex and more hypoechoic with age (Fig. 43.3).

An inguinoscrotal hernia occurs when an intestinal loop or part of the omentum passes into the scrotal cavity through an incompletely obliterated processus vaginalis. Inguinoscrotal hernias are most common in preterm neonates, but they may also develop in adults. The diagnosis can be difficult at physical examination. Ultrasound may be indicated to differentiate an inguinoscrotal hernia from other conditions and to investigate contralateral involvement [12].

At ultrasound, intestinal loops within the scrotum appear as a non-homogeneous mass, most commonly hypoechoic due to the fluid content of the bowel. The most useful finding is generally the presence of air bubbles within the cystic-appearing mass (Fig. 43.4a). Peristalsis of bowel loops is possible to detect but the herniated loops are usually filled and without movement. Colour Doppler interrogation may demonstrate vascularity of the intestinal wall. Hernias can also be diagnosed with CT, MR imaging and even plain radiography if the bowel loops contain gas [7] (Fig. 43.4b).

Occasionally, the bladder may herniate into the inguinal and femoral canals, the latter being more frequent in women. A predilection for the right side has been reported. Preoperative recognition is important to avoid complications such as urinary leakage and sepsis [14].

Extratesticular solid masses are malignant in about 3 % of cases [2, 3, 15, 16]. These tumours arise from paratesticular tissue. The paratesticular region is a complex anatomical area which includes the contents of the spermatic cord, testicular tunics, epididymis and vestigial remnants, e.g. the appendices epididymis and testis [17]. Histogenetically, this area is composed of a variety of epithelial, mesothelial and mesenchymal elements. Neoplasms arising from this region therefore form a heterogeneous group of tumours with different behavioural patterns. On rare occasions, tumours from distant sites may metastasize to the paratesticular region [17]. Tumours occurring in the paratesticular region may be clinically indistinguishable from testicular tumours, thus resulting in initial misdiagnosis. Most tumours of this region present as a scrotal mass or swelling, which may or may not be painful and is occasionally accompanied by a hydrocele. The preoperative distinction between the benign and malignant paratesticular tumour is rarely made, as there may be no specific finding, which results in difficulty in diagnosis and management.

The criteria which can help in the differential diagnosis are localization of the lesion and correlation with clinical history and laboratory tests. Most of inflammatory masses, in fact, are associated with acute symptoms and positive laboratory results. Imaging findings are often non-specific and not helpful to differentiate among the different types of lesions.