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Monday, 12 June 2017 18:48

Ultrasound of the Inguinal Canal – Part I

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Pierre Vassallo

Ultrasound has a major role in detecting disease in the inguinal region. A good knowledge of the anatomy and pathologic findings on ultrasound is required to reach a correct diagnosis.

The structure and function of the inguinal canal can only be appreciated when one understands what occurs at this site during the embryonic and fetal periods. The formation of the inguinal canal starts at the 7th week of gestation. In males, it represents the passage through which the testis passes from its intraabdominal location of origin to the scrotum, its normal location at birth. In females, it contains the round ligament of the uterus.

At around 7 weeks of gestation, the gonads (testes and ovaries) develop along with the kidneys from the urogenital ridges. The urogenital ridges are located on either side of the structures that will form the lumbar spine. The more medially located portion of the urogenital ridge forms the gonad and the lateral portion forms the kidney (Fig 1). A ligament called the gubernaculum is attached to the inferior pole of the gonad and extends inferiorly through the abdominal wall into the inguinal region to attach to the labroscrotal fold; the labroscrotal fold forms the scrotum in males and the labia major in females. In female fetuses, the gubernaculum is attached to the uterus in its mid-section. In male fetuses, the gubernaculum shortens and pulls the testis down from its original position near the spine into the scrotum (Fig 2). Due to the attachment of the gubernaculum to the uterus in female fetuses, the migration of the ovary halts near the uterus and the distal gubernaculum forms the round ligament.

All layers of the abdominal wall extend along the gubernaculum, testis and round ligament; they form the scrotal sac in the male (Fig 2). The passage through the different abdominal wall layers represents the inguinal canal, which contains the spermatic cord in the male and the round ligament in the female. An invagination of peritoneum that follows the testis into the scrotum, detaches from the main peritoneal cavity and forms the tunica vaginalis. This peritoneal invagination closes in the female. A persistent peritoneal communication in the male is called a patent processus vaginalis (Fig 3), while in the female, it is called the canal of Nuck. A persistent processus vaginalis predisposes to an indirect inguinal hernia and a communicating hydrocoele.

The inguinal canal is circa 4cm long and extends above the inguinal ligament through the layers of the abdominal wall muscles, starting internally at the internal inguinal ring that lies just lateral to the origin of the inferior epigastric vessels and ending externally above and medial to the pubic tubercle (Fig 4). On ultrasound, the inguinal canal can be traced along its path, starting at the internal inguinal ring and extending to the external inguinal ring (Fig 5).

Inguinal hernias

An indirect inguinal hernia results from the passage of intraabdominal contents into the inguinal canal through the internal inguinal ring. Whereas a direct inguinal hernia passes directly through the abdominal wall layers and does not follow the inguinal canal. An indirect inguinal hernia therefore passes lateral to the inferior epigastric vessels while a direct inguinal hernia courses medial to them (Fig. 6).

Direct and indirect inguinal hernias are usually more evident when the patient increases his/her intraabdominal pressure (e.g. during Valsalva manoeuvre or in the standing position). Consequently, dynamic ultrasound examination at rest, during Valsalva and in the standing position are necessary to detect an inguinal hernia since a hernia may be fully reduced at rest. In addition, dynamic examination will help distinguish reducible from incarcerated hernias, since the latter do not reduce even on compression with the probe (Fig 7).  Thickening of the contents of the hernial sac and associated fluid collections are signs of strangulation of the hernia contents (Fig 8). Strangulation may also be noted through the absence of blood flow on colour Doppler ultrasound examination.

The more common complications of surgical hernia repair include seromas, haematomas and abscesses at the site of repair. These are readily detected by ultrasound (Fig 9). Abscesses tend to appear in the late post-operative period (usually after 30 days) and are accompanied by clinical signs of infection. A further post-operative complication of hernia is repair is hernia recurrence, which is also readily detected by ultrasound.

Figure Legends

Figure 1. The kidney and gonad develop from a common structure, the urogenital ridge, that is located next to the structures that will form the lower spine in the embryo. The inner part of the urogenital ridge forms the gonad that descends into the pelvic/scrotal area, while the lateral part forms the kidney that retains its paraspinal location.

Figure 2. The gubernaculum is attached to the inferior pole of the gonad proximally and into the labroscrotal fold inferiorly. It shortens from the 7th week of gestation onwards and pulls the gonad inferiorly. In males, the testis descends into the scrotum. Due to the attachment of the gubernaculum to the uterus in females, the ovary halts next to the uterus and the distal gubernaculum forms the round ligament. All abdominal wall layers extend along the gubernaculum and around the testis to form the scrotum in males. The path through which the testis and round ligament pass represents the inguinal canal.

Figure 3. Diagram showing a patent processus vaginalis (arrow) communicating the peritoneal cavity with the tunica vaginalis; this is called a communicating hydrocoele.

Figure 4. Anatomy of the inguinal canal (arrows). The anterior wall is formed by the external and internal oblique muscle aponeuroses and the posterior wall is composed of the transversus abdominis aponeurosis and the conjoint tendon; the latter is formed by fusion of the distal rectus abdominis tendon with the proximal adductor longus tendon.

Figure 5. Ultrasound scan parallel to the course of the inguinal canal, showing the internal inguinal ring (arrowheads) and the inguinal canal (arrows) with its contents.

Figure 6. A direct inguinal hernia passes lateral to the inferior epigastric vessels, while a direct inguinal hernia courses medial to them.

Figure 7. Ultrasound scan of an indirect inguinal hernia showing the inguinal canal at rest (a) and during Valsalva maneouvre (b): note the expansion of the inguinal canal that occurs with increased intraabdominal pressure (arrows).

Figure 8. Ultrasound scan showing a thickened loop of small bowel (arrowheads) in the inguinal canal that did not alter with Valsalva manoeuvre and did not reduce on compression. Also note the thickened mucosal folds (arrows); the thickened bowel wall and bowel loops are indicative of hernia strangulation.  

Figure 9. Ultrasound scan showing a fluid collection (calipers) at the site of a hernia repair in the early post-operative period.

Additional Info

  • TheSynapse Magazines: 2016
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Dr Pierre Vassallo MD PhD FACA Artz fur Radiologie specialised in radiology at the Institute of Clinical Radiology at the University of Muenster, Germany and the Memorial Sloan-Kettering Cancer Center, New York, US. He is currently Consultant Radiologist and Managing Director at DaVinci Health, Malta.

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  • Postgrad course on exercise as medicine is being proposed

    Dear prospective applicant,

    A proposal for a postgrad course on physical activity (PA) as a therapy for non-communicable diseases is currently being evaluated. Hereunder, a two-question survey is being forwarded for your attention in order to assess whether the idea sounds appealable or not.

    Proposed award

    M.Sc in Therapeutic Physical Activity (TPA), with postgrad certificate (PgC) and postgrad diploma (PgD) exit routes

    Proposed specialisation titles[1]

    Holders of PgC, TPA can claim the title of: ‘Clinical exercise prescriber’.

    Holders of PgD, TPA can claim the titles of: ‘Advanced exercise prescriber’ or ‘Clinical and public health exercise prescriber’.

    Holders of M.Sc, TPA can claim the title of: ‘Physical activity - health specialist’.

    Are you sure you know why physical activity is so important?

    Everyone is aware that physical inactivity is a major health concern but, do you know that through the right type of exercise you can prevent or treat at least 35 chronic conditions? In 2007 the American College of Sports Medicine officially declared an important statement: ‘Exercise is medicine’. Moreover, health-enhancing physical activity (HEPA) is important in today’s world not only in view of improving health and wellbeing but also for its economic values. For example, a lifestyle intervention involving 150 minutes of weekly PA was scientifically shown to be significantly more effective than the administration of metformin.

    Possibilities of further career development in exercise prescription

    Exercise prescription, that is, being qualified to professionally recommend the right type of exercise for health does not stop on a one-to-one basis. Do you think you are qualified to: (a) conduct research on PA interventions, and (b) develop, implement and evaluate community or population programmes involving PA strategies? Unfortunately, many wide-scale programmes that are implemented undergo no evaluation to determine how they have worked or what their effects may be. Have you ever imagined the possibility of attending a tertiary course which would be designed to: (a) give you the ability to design a project for the generation of new knowledge and be able to publish it internationally, or (b) train you on how to evaluate wide-scale interventions and how to apply strategies to sustain their continuities?


    A glimpse of the proposed programme of studies

    Intended for:

    The programme of studies is aimed at a wide and diverse cohort of students wishing to pursue any careers in HEPA sectors mainly: exercise prescription; health promotion (policies and practice); general health and fitness industry; and to further their studies (e.g. PhD). It can also serve as an adjunct to enrich one’s knowledge of his / her established profession or career. Examples include: medical practitioners; pharmacists; nurses; physiotherapists; nutritionists; public health specialists; sport medicine specialists; sport psychologists; teachers of physical education (PE); coaches; gym instructors; and personal trainers. Fitness and sport enthusiasts are also encouraged to apply.

    Duration:

    Three years part-time leading to an M.Sc in PA as an effective therapy, with postgrad certificate and postgrad diploma exit routes after the first and second years respectively.

    Mode of delivery:

    Seventy per cent will be delivered online and the rest of the thought units will be offered on a once weekly two-hour evening basis starting at 18.00hrs.

    Admission criteria:

    You should provide evidence of higher educational qualification(s) - normally, a diploma or a degree related to health and / or PA / sport. An award in PE is also ideal. Mature students without these basic qualifications would be required to present evidence of experience related to PA and health.

    Mode of assessment:

    Units will be assessed through the submission of coursework. These will vary from short assessments to long essays. If you would like to progress at Masters’ level, a traditional dissertation or paper in the format for journal publication and a final presentation (in the form of slides or poster) of your research findings will have to be undertaken.

    Round-up

    Unlike other under- and postgrad courses which only cover a fraction from the whole science of HEPA, this comprehensive programme of studies would lead to a specialization specifically on TPA. For careers in promotion, prescription and research of PA, the proposed programme of studies is a must.

    Important notice

    All the above information is subject to change and would eventually have to be approved by the Programme Validation Committee of the University of Malta. Needless to say, your feedback in the next two questions is extremely important.

    Yours in health & exercise,

    Charles Micallef B.Pharm (Hons), M.Sc PAPH (Staff)                                                8th August 2017

    The two questions hereunder.

    1. In view of the above information, would you be interested in applying for this particular postgrad course leading to a specialisation in physical activity with respect to health, that is, a qualification that gives you the right to prescribe exercise for health, even at population levels?

    Yes or No: 

    1. What would you change from or suggest to what is being proposed?

    Please state your name & surname:

    Your current job / profession:

    Please save your changes and forward your reply to Charles Micallef on: This email address is being protected from spambots. You need JavaScript enabled to view it.

    Your cooperation is greatly appreciated.


    [1] In order to professionally recommend exercise for health, you may need to be registered in the appropriate regulatory board and be in possession of a warrant to operate with the respective titles.

    University of Malta

    Written on August 19, 2017
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