Sonographic evaluation of inguinal lesions

    Sonographic Evaluation of Inguinal Lesions Hwi Ryong Park, Sung Bin Park, Sun Lee Eun, Hyun Jeong Park PII: DOI: Reference:

S0899-7071(16)30048-1 doi: 10.1016/j.clinimag.2016.04.017 JCT 8054

To appear in:

Journal of Clinical Imaging

Received date: Revised date: Accepted date:

29 September 2015 24 April 2016 29 April 2016

Please cite this article as: Park Hwi Ryong, Park Sung Bin, Eun Sun Lee, Park Hyun Jeong, Sonographic Evaluation of Inguinal Lesions, Journal of Clinical Imaging (2016), doi: 10.1016/j.clinimag.2016.04.017

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Sonographic Evaluation of Inguinal Lesions

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Department of Radiology, Chung-Ang University Hospital, Chung-Ang University College of Medicine, 102, Heukseok-ro, Dongjak-gu, Seoul, 156-755, Korea

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Hwi Ryong Park, MD, Sung Bin Park, MD, Eun Sun Lee, MD, Hyun Jeong Park, MD

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Author correspondence to Sung Bin Park, Department of Radiology, Chung-Ang University Hospital, Chung-Ang University College of Medicine, 102, Heukseok-ro, Dongjak-gu, Seoul, 156-755, Korea e-mail: [email protected] Tel) 82-2-6299-3196 Fax) 82-2-6263-1557

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Abstract

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Abnormalities in the inguinal region are varied. The most common abnormality in the

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inguinal region is the hernia: direct or indirect inguinal hernia and femoral hernia. There are many hernia-mimicking lesions, such as spermatic cord hydrocele, undescended

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testis, hematoma, inflammation, abscess, benign or malignant tumors, metastatic or benign lymph node enlargement, round ligament varicosities or mesothelial cyst, and

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herniated ovary. Ultrasonography is currently the primary imaging modality used in assessing inguinal lesions and helpful for the differential diagnosis of a broad spectrum of these diseases. Familiarity with clinical setting and certain ultrasonography details

Keywords: Groin

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will facilitate prompt and accurate diagnosis and treatment.

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Inguinal Canal

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Hernia, Inguinal Hernia, Femoral

Ultrasonography

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Introduction

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Inguinal lesions can vary widely, from benign to malignant, from cystic to solid, from

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tumorous to nontumorous, and from congenital to acquired [1-5]. Therefore, the differential diagnosis of inguinal lesions is important, although it is challenging because

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the abnormalities have similar clinical appearances, such as tender palpable masses [3]. Ultrasonography (US) is considered the imaging modality of choice for patients with

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suspected inguinal abnormalities [3,4]. Inherent advantages of US include accessibility, quick scan time, low cost, multiplanar capability, and the ability to perform dynamic real-time imaging with contralateral comparison [6]. The modality is accurate for distinguishing between solid and cystic lesions [3,4]. The purpose of this article is to

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describe the broad spectrum and imaging features, especially of US, with regard to these

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Normal Anatomy

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inguinal lesions.

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The inguinal region consists of the inguinal canal and the femoral triangle [1,3]. The normal inguinal canal is a narrow diagonal tunnel lined by the aponeuroses of three abdominal wall muscles (external oblique, internal oblique, and transversus abdominis) [7]. The inguinal canal runs from the deep inguinal ring to the superficial inguinal ring from superiorly posterolateral to inferiorly anteromedial direction [7]. The inguinal ligament, the folded and thickened lower border of the external oblique aponeurosis, attaches at the anterior superior iliac spine and pubic tubercle and medially forms the inferior floor of the inguinal canal [8]. The deep or internal inguinal ring is a gap in the transversalis fascia just superior to the inguinal ligament and posterolateral to the inferior epigastric vessels. The superficial or external inguinal ring is an opening in the

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external oblique aponeurosis just superior and lateral to the pubic tubercle [7].

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The inguinal canal contains vascular and neural structures, and the spermatic cord (in

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men) or round ligament (in women) [2,8]. The Hesselbach triangle is anatomically bounded inferiorly by the inguinal ligament, medially by the lateral margin of the rectus

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abdominis, and superolaterally by the inferior epigastric artery (Figure 1). The inferior epigastric artery originates from the external iliac artery proximal to the inguinal

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ligament, initially passing along the medial boundary of the deep inguinal ring, and eventually anastomoses above the umbilicus with the superior epigastric artery along the rectus abdominis muscle [7,8]. Inguinal hernias are classified as direct and indirect, depending on their relationship to the inferior epigastric artery [3]. In indirect hernias,

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the herniated structures enter the inguinal canal [2] lateral to the inferior epigastric

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artery and superior to the inguinal ligament [5], and extend for a variable distance through the inguinal canal. In direct hernias, the herniation is at the inferior aspect of the

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Hesselbach triangle that originates medial to the inferior epigastric artery [5,7,8] (Figure

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1).

The femoral triangle contains the femoral sheath, which is formed by the deep fascia lata of the thigh and surrounds the femoral artery, femoral vein, and femoral canal, from lateral to medial direction [1,7]. In femoral hernias, the herniation occurs at the femoral canal, which is inferior in relation to the inguinal ligament, typically medial and adjacent to the femoral vessels [8] (Figure 1).

US Technique Because the inguinal region structures are superficial, a linear transducer of 10 MHz or greater is effective; others have reported that a transducer of at least 7 MHz is

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effective [8,9]. Initially, an examination of the inguinal region is done with the patient

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supine. It is essential to ask the patient to strain (increase abdominal pressure, the

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Valsalva maneuver) at each of the US steps to identify transient hernias (Figure 2). The Valsalva maneuver is a critical component of the examination, because in many patients,

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the hernia may be completely reduced at rest [8]. In addition, the characteristic movement of the herniating tissues often clinches the diagnosis [8]. If necessary, the

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patient will be asked to stand up to improve detection of an inguinal hernia [3] (Figure 1). Reexamination with the patient standing is also recommended if the supine evaluation does not reveal a herniation, or particularly in the case of a suspected femoral hernia [8,9]. Because bilateral inguinal hernias may occur, the contralateral unapparent

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asymptomatic side should be also evaluated.

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The split-screen function that is available on most US units can expand the field of view to approximately double the width, or can be used for side-by-side comparisons

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[6]. The extended field-of-view function can display a very large continuous section of

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the anatomy, preserving spatial resolution without distorting structural relationships [6]. Color and power Doppler US features show the degree of vascularity associated with inflammatory processes and solid masses and the viability of the herniated bowel loops [8]. US may also be used as guidance for biopsy or aspiration of inguinal masses or lymph node enlargements [3].

Inguinal Hernia The most common abnormality in the inguinal region is the hernia, which contains bowel loops, omental fat, and peritoneal fluid [3]. A hernia is “the protrusion of a part or structure through the tissues that normally contain it,” either through an opening in the

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tissues or via stretching of the tissue wall [8]. External abdominal hernias are most

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commonly found in the inguinal region, where most are direct and indirect inguinal

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hernias and femoral hernias [7,8]. Indirect inguinal hernias are the most common regardless of sex; femoral hernias are more common in women [7,8]. Hernias may be

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associated with significant morbidity and even mortality [8,10]. The risk of strangulation is lowest for direct inguinal hernias, which can often be monitored and

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managed conservatively. Indirect inguinal hernias are at a moderate risk of strangulation, whereas approximately 40% of femoral hernias manifest with strangulation [7]. Although they are traditionally diagnosed clinically, hernias may be difficult to identify and even more difficult to classify. US is used to evaluate in patients with

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equivocal physical findings and in those with acute inguinoscrotal swelling [3,11]. On

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US, the hernia contents can be hyperechoic because of omental fat, anechoic because of fluid, or of mixed echogenicity with reverberations caused by air in the bowel loops

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[3,5] (Figures 2, 3). US allows for the direct visualization of the bowel loops and

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peristalsis. It is important to evaluate for both reducibility and bowel viability identified by peristalsis or mucosal blood flow [8]. The hernia sac may be hard to discern on US [3]. US may be useful not only in providing the diagnosis but also in identifying the variety of hernia and providing additional information, such as the contents of the hernia and the extent of reducibility of the hernia contents. These observations may affect surgical decision-making and reconstruction [9].

Direct Inguinal Hernia A direct hernia passes medially to the inferior epigastric vessels through a defect in the Hesselbach triangle [7,8] (Figure 2). The lateral crescent sign may be useful in the

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diagnosis of early direct inguinal hernias, as it represents lateral compression and the

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stretching of the inguinal canal fat and contents by the hernia sac on axial CT [7]. This

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hernia is generally acquired and its incidence increases with age, as it results from a

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weakening of the transversalis fascia in the Hesselbach triangle.

Indirect Inguinal Hernia

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An indirect hernia originates at the deep inguinal ring, lateral to the inferior epigastric vessels. It follows the path of the inguinal canal inferomedially [3,8]. An indirect inguinal hernia may reach the pubic tubercle and exit the superficial ring and may enter the scrotum in a male [7,8] (Figure 3). In the female, the indirect hernia follows the

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round ligament into the labia majora [7].

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The indirect hernia is five times more common than the direct hernia [7]. In boys, the indirect inguinal hernia is the result of a congenital defect of a patent processus

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ring [2,7,12].

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vaginalis. In adults, it is acquired due to weakness and dilatation of the internal inguinal

Femoral Hernia

The femoral hernia lies in the femoral canal, inferior to the inguinal ligament and medial to the femoral vein [1,3]. During the Valsalva maneuver, the femoral vein will normally dilate and should be differentiated from a femoral hernia [8]. Because of the narrowness of the femoral ring (the opening that forms the neck of a femoral hernia), it is more likely than an inguinal hernia to become incarcerated and strangulated [1]. The femoral hernia is relatively uncommon, with a prevalence less than one-tenth that of the inguinal hernia. It has a female predominance of 4:1, which is thought to be

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secondary to the dilatation of the femoral ring connective tissue due to the hormonal

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and physical changes of pregnancy. It is twice as common on the right as on the left side

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[7,13].

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Mimickers of Inguinal Hernias

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Spermatic Cord Hydrocele (Cyst of Canal of Nuck)

The processus vaginalis (called the canal of Nuck in the female) is a tubular fold of the parietal peritoneum that invaginates into the inguinal canal anterior to the descending testis, ending in the scrotum [1]. The upper part usually closes at or just

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before birth, and obliteration proceeds gradually in a downward direction. In the male,

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the scrotal section remains patent, forming the tunica vaginalis testis; in the female, the entire processus normally becomes obliterated by 8 months of gestation [1].

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A hydrocele of the spermatic cord is a fluid collection and results from aberrant

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closure of the processus vaginalis [2,14]. Symptoms of hydrocele include inguinal swelling and a fluctuant palpable mass. There are two variations of a spermatic cord hydrocele: the “encysted” type that does not communicate with the peritoneal cavity or tunica vaginalis and the “funicular” type (Figure 4) that communicates with the peritoneal cavity at the internal inguinal ring [2,14].

Undescended Testis Failure of the intra-abdominal testes to descend into the scrotal sac is known as cryptorchidism or undescended testes [3]. The prevalence of this condition is 9.2% to 30% in premature infants and 3.4% to 5.8% in full-term infants [15]. In this condition,

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the testis can be found in any position along its usual line of decent; however, 80% will

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be located in the inguinal region just outside the inguinal canal [2,16]. Later risks

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include infertility and malignancy [2].

An undescended testis appears as an ovoid hypoechoic mass in the course of the

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inguinal canal. On US, it is usually smaller than the normal testis and is revealed as an

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isoechoic or hypoechoic lesion (Figure 5) relative to the normally located testis [17].

Hematoma

A hematoma may occur as a result of warfarin therapy, trauma, surgery, catheter placement, or a neoplasm [18]. Clinically, it manifests as pain and swelling. A

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hematoma usually appears as an anechoic mass on US in the acute phase; however, it

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has mixed echogenicity in the subacute and chronic phases [3,5] (Figure 6). US-guided aspiration can be performed to alleviate pressure from a large hematoma and to exclude

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infection. Serial US can be used for the follow-up of large or worrisome hematomas and

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to confirm the healing and resolution of the lesion [2].

Inflammation and Abscess Inflammation and abscesses may arise in the inguinal region. US appearances are variable and range from hypoechoic fluid to echogenic masses [3]. There is substantial overlap of US findings in hematomas, abscesses, and tumors. Clinical findings include abdominal cramping, inguinal mass, fever, and leukocytosis [2]. When the differentiation between hematomas, inflammation, and tumors is difficult on US, the clinical history can assist in making the correct diagnosis [3].

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Benign Tumors

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Primary tumors may arise from any of the structures within the inguinal region:

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connective tissue, muscle, fat, blood vessels, and lymphoid tissue [1-3]. The most common benign tumor of the inguinal region is a lipoma [1,2]. The lipoma is seen as a

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hyperechoic mass on US (Figure 7), which may be difficult to differentiate from a liposarcoma [1,5]. A lipoma and a hernia containing omentum have the potential to

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appear similar, but the lipoma is generally smaller [3], more homogeneous, and has no connection with retroperitoneal fat [2] (Figure 7), whereas the hernia is an elongated mass that can often be traced back to the internal inguinal ring. Spermatic cord lipoma is lateral or inferior to the spermatic cord, whereas a fat-containing hernia occurs

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anteromedial to the cord [2]. Other benign tumors of the inguinal region include

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leiomyomas, dermoid cysts, epidermoid cysts, and lymphangiomas [2,3].

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Primary Malignant Tumors

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Most malignant tumors in the inguinal region are sarcomas because most of the components of the cord are derived embryologically from mesodermal tissues. The most common sarcoma in the inguinal areas is a liposarcoma [1,2,19], which occurs commonly in adults. A liposarcoma is a bulky yellow tumor, similar to a lipoma, but is generally more complex and contains areas of prominent sclerosis [19]. The US findings of a liposarcoma are variable and nonspecific [19] (Figure 8). Other malignant tumors involving the inguinal region include synovial sarcomas, leiomyosarcomas, malignant fibrous histiocytomas, fibrosarcomas, and undifferentiated sarcomas [1-3].

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Lymph Node Metastasis vs. Hyperplasia

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Inguinal lymph node metastases are most frequently from primary cancers of the

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lower part of the vagina, vulva, and penis (Figure 9), lower part of the rectum, anus, and the lower extremities [3]. They should be distinguishable from benign lymph nodes [3].

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A normal lymph node is usually seen as an ovoid mass with a hypoechoic peripheral zone and an echogenic center [20]. Normal inguinal lymph nodes may have a short-axis

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diameter that measure up to 1.5 cm [9,21]. On US, malignant lymph nodes are usually round and have a normal or an absent hilus and eccentric widening of the cortex on gray scale US and a high resistive index on color Doppler US [20,22] (Figure 9).

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Round Ligament Varicosities

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The round ligament of the uterus is homologous to the male spermatic cord [1]. The round ligament extends from the anterolateral aspect of the fundus of the uterus to the

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pelvic side wall between the folds of the broad ligament. It leaves the abdominal cavity

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through the deep inguinal ring and traverses the inguinal canal to attach to the labium majorus [2,4]. Round ligament lesions are usually misdiagnosed as more common diseases, such as inguinal hernias, femoral hernias, and lipomas on physical examination [23, 24]. Uncomplicated round ligament varicosities can mimic an irreducible inguinal hernia, especially during pregnancy [4,24,25]. Both round ligament varicosities and inguinal hernias can occur in the second trimester of pregnancy; therefore, round ligament varicosities are easily misdiagnosed as an obstructed hernia [24]. The characteristic US features are the change in the shape of the cystic masses during the examination in the supine and upright positions as well as at rest and during straining (Valsalva maneuver)

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and a prominent venous plexus with accompanying dilated draining veins and the

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typical “bag of worms” appearance of smaller varices on the color Doppler US

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[4,24,25] (Figure 10). The change in the shape of the cystic masses during the examination in the supine and upright position as well as at rest and during the Valsalva

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maneuver are also characteristic [4,24].

Usually, nonsurgical treatment leads to spontaneous regression after delivery [24,25].

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However, round ligament varicosities require close monitoring during pregnancy as rupture and thrombosis may occur and result in an intense painful swelling in the groin [24, 26]. Upon imaging, if the veins are non-compressible, no flow signal can be obtained, and/or there is a visible clot within the lumen, complicated round ligament

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varicosities should be suspected and emergency surgical exploration is recommended

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[24, 26].

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Round Ligament Mesothelial Cyst

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Mesothelial cysts of the round ligament are rare and usually occur in the right inguinal region of middle-aged women [4,23]. US findings of a round ligament cyst are peculiar: it is a fusiform-shaped cystic mass without peristalsis and is connected to a stalk-like structure (Figure 11). The location of the mass is medial to that of the usual inguinal hernia [4] (Figure 11).

Herniation of the Ovary An inguinal hernia may have very unusual sac content. Hernias including the vermiform appendix, acute appendicitis, the ovary, the fallopian tube, and the urinary bladder have been rarely reported [1,2,4,7,27,28]. Inguinal hernias containing the

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adnexa are not uncommon in infancy. According to a previous report, the adnexa are

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found in as many as 31% of inguinal hernia sacs in female infants; however, this

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incidence decreases with age, so it is rare in adult women. Another study noted that 82% of incarcerated inguinal hernias in girls contained ovaries [29]. Inguinal hernias

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that contain ovaries are usually seen in children younger than 5 years old [2,28,30]. Herniation of the ovary usually occurs in infants (Figure 12) or girls, and is very rare in

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adults.

The US findings of a herniated ovary vary, according to the cystic components of the ovary [28] (Figure 12). The visualization of ovary-like structures containing peripheral cysts; in other word, solid masses containing small cysts on US were helpful for the

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diagnosis [28]. Early diagnosis is important when the hernia contains an ovary, because

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incarceration of the ovary is common and has been reported in up to 43% of cases [28, 31]. It is necessary to evaluate the torsion of the vascular pedicle [4,28] (Figure 12). US

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findings of ovary torsion are an enlarged, mass-like ovary with heterogeneous

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echogenicity that contains multiple peripheral cysts and no blood flow within the ovary [28, 32]. However, the presence of arterial or venous flow or both dose not exclude the diagnosis of torsion. The sensitivity of color Doppler US is low because flow may be provided through a dual blood supply from both the ovarian and uterine arteries and venous thrombosis may lead to symptoms before arterial occlusion occurs [33,34].

Summary and Conclusion Inguinal lesions can vary widely. The role of the radiologist is to ensure the identification of a broad spectrum of inguinal lesions and possibly to provide a differential diagnosis by either particular imaging or clinical features (Table 1).

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Familiarity with the clinical setting and certain US details will facilitate prompt and

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accurate diagnosis and treatment.

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Acknowledgements

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We would like to express our gratitude to Dr. Sang Youn Kim, Seoul National

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University Hospital, Seoul National University, Seoul, Korea for sharing his case

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images (Fig. 8).

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Shadbolt CL, Heinze SB, Dietrich RB. Imaging of groin masses: inguinal

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[1]

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Table 1. Characterization of Inguinal Lesions Disease

Characteristics

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Inguinal Hernia

Direct Inguinal Hernia

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Through Hesselbach triangle, medial to inferior epigastric artery

Lateral crescent sign on CT

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Can be monitored and managed conservatively Through the inguinal canal, lateral to inferior epigastric artery Extension to the scrotum and labia majora

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Indirect Inguinal Hernia

Moderate risk of strangulation Through the femoral canal, medial to femoral vein Femoral Hernia

Risk for incarceration and strangulation Female predominance (4:1)

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Mimickers of Inguinal Hernias

Aberrant closure of the processus vaginalis

Spermatic Cord Hydrocele

“Encysted” and “Funicular” type

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Cyst of canal of Nuck in female 80% located in the inguinal canal

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Undescended Testis

Hematoma

Inflammation and Abscess

Later risks of infertility and malignancy Ovoid small hypoechoic mass Different features depending on stage Acute - anechoic, subacute, and chronic - mixed echogenicity Serial follow-up US Overlap in hematoma, abscess, and tumor Clinical history correlation Lipoma - most common

Benign Tumors

Smaller, more homogeneous without connection to the peritoneum

Malignant Tumors

Lymph Node Metastasis Lymph Node Hyperplasia

Most are sarcoma; liposarcoma - most common Similar to benign lipoma, but more complex Round, absent hilus and eccentric widening of the cortex High resistive index Ovoid, hypoechoic peripheral zone and echogenic center

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Short-axis diameter: up to 1.5 cm

Cyst

“Bag of worms” appearance Right side, middle-aged woman

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Round Ligament Mesothelial

Pregnant woman

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Round Ligament Varicosities

Fusiform-shaped cystic mass with stalk-like structure Medial to that of usual inguinal hernia

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Younger than 5 years old, rare in adults

Mandatory to evaluate torsion of vascular pedicle

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Herniation of the Ovary

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FIGURE LEGENDS

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Fig. 1. Diagram of man’s right inguinal region from anterior view shows predisposed locations for direct inguinal hernia (1), indirect inguinal hernia (2), and femoral

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hernia (3). Note locations of inguinal ligament (curved arrow), rectus abdominis muscle (R), and the lateral boundary of the Hesselbach triangle (H) defined by the

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inferior epigastric artery (black arrow) and spermatic cord (arrowhead).

Fig.2. A 73-year-old man with right direct inguinal hernia. (A) Color Doppler US shows herniated bowel loop (H), which is located on the

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inferomedial aspect of the inferior epigastric artery (arrow).

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(B, C) Gray scale US after Valsalva maneuver (B) and standing US (C) show

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provocation of the herniated bowel loop (H).

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Fig.3. A 32-year-old man with right indirect inguinal hernia. Gray scale US shows herniated bowel loop (H), which is extended to the scrotum. T; Testis.

Fig.4. An 87-year-old man with right funicular spermatic cord hydrocele. (A, B) Gray scale US on supine (A) and standing (B) show an ovoid cystic lesion in the right spermatic cord, connected to the peritoneum (arrowhead) and increased size on standing position. (C) Coronal reformatted enhanced computed tomography (CT) shows a lobulated cystic lesion (arrow) with connection to the peritoneum (arrowhead) of the right inguinal

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region.

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Fig.5. A 38-year-old man with left undescended testis.

(A) Longitudinal gray scale US of the left testis at the level of the inguinal canal shows

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an ovoid hypoechoic testis.

(B) T2-weighted coronal magnetic resonance (MR) image shows a normal appearing

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contralateral right testis in the scrotum and dystrophic undescended left testis (arrow) in the left inguinal region.

Fig.6. A 49-year-old man with left inguinal hematoma after trauma.

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Color Doppler US using convex probe of the left inguinal region shows a large complex

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cystic mass without increased vascularity. US features as well as clinical history may be

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helpful for the correct diagnosis.

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Fig.7. A 52-year-old man with left inguinal lipoma. Longitudinal gray scale US shows an echogenic mass (arrow) in the left spermatic cord.

Fig.8. A 68-year-old man with right inguinal liposarcoma. (A) Axial gray scale US shows a complex solid and cystic mass with lobulated contour in the right inguinal region. (B) Color Doppler US demonstrates internal vascularity in the solid portion of the mass. (C) T2-weighted axial MR image shows a lobulated heterogeneous mass (arrow) with cystic portion in the right inguinal lesion. (D, E) T1-weighted axial MR images obtained without fat suppression (D) and with fat

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suppression (E) demonstrate fatty components (arrowhead) of the mass with a loss of

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signal on the fat-suppressed image.

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(F) Gadolinium-enhanced axial T1-weighted MR image demonstrates marked enhancement within the solid portion of the mass. Diffusion-weighted MR image (not

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shown) shows that the solid portion of the mass demonstrates restricted diffusion with

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high signal intensity (Courtesy of Dr. Sang Youn Kim).

Fig.9. A 65-year-old man with left inguinal metastatic lymph node enlargement from penile cancer.

(A) Color Doppler US shows a lobulated contoured ovoid hypoechoic mass with

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increased internal blood flow in the left inguinal region.

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(B) T2-weighted coronal MR image shows a well-defined hypointense mass in the left

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inguinal region (arrowhead) and penile mass (arrow).

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Fig.10. A 29-year-old pregnant woman with left round ligament varicosities. (A) Longitudinal gray scale US shows an ovoid multicystic mass in the left pubic area. This location is a typical position for an indirect inguinal hernia. (B) Color Doppler US in the standing position shows an engorged highly vascular mass.

Fig.11. A 28-year-old woman with right round ligament mesothelial cyst. (A) Longitudinal gray scale US shows an elongated cystic mass with some septations. The stalk-like structure (arrows) is shown in the cranial aspect of the mass. (B) Axial enhanced CT shows a lobulated cystic mass with connection to the stalk-like structure (arrow) in the typical location of the round ligament of the right inguinal

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Fig.12. A 1-month-old woman with herniation of right ovary.

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region.

(A) Longitudinal gray scale US shows a hernia sac containing an ovary. The wide defect

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(arrow) is shown in the inguinal canal.

(B) Color Doppler transverse US shows intact vascularity (arrowhead) of the ovarian

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pedicle without evidence of ovarian torsion.

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Fig. 1

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