Case 12- Imaging and anatomy

Question 1

The inguinal region

Answer 1

The inguinal region is also known as the groin and in located on the lower portion of the anterior abdominal wall. There are two inguinal regions on each side with a gap in the middle, the area covered by the pelvis.

Question 2

The inguinal ligament

Answer 2

From the ASIS to pubic tubercle, have one on each side. Formed from the sternal oblique muscle.

Question 3

The midpoint of the inguinal ligament

Answer 3

Halfway across the ligament, the landmark to find the femoral nerve. The opening of the inguinal canal (the deep inguinal ring) is superior to this joint

Question 4

The mid inguinal point

Answer 4

Halfway between the pubic symphysis and the anterior superior iliac spine. The femoral pulse can be palpated here

Question 5

The inguinal canal

Answer 5

A 4cm tunnel in the lower anterior abdominal wall muscles. It runs between the deep and superficial rings, in a downwards and medial direction.

Question 6

Role of the inguinal canal

Answer 6

• It allows contents of the scrotum to communicate with intra-abdominal contents
• It prevents mobile intra-abdominal contents (e.g. intestine) from entering the scrotum and possibly becoming damaged
• While, at the same time, permitting blood vessels, nerves, lymphatics, vas deferens etc. to supply the scrotal contents/genitalia region

Question 7

Contents of the inguinal canal

Answer 7

• Spermatic cord (male) or round ligament (female)
• Genital branch of genitofemoral nerve
• Ilio-inguinal nerve (doesn’t travel through the deep ring, it pierces the wall of the inguinal canal to travel through the superficial inguinal ring)
The genitofemoral and ilio-inguinal nerve are part of the lumbar plexus

Question 8

Ductus deference

Answer 8

Within the inguinal canal, transports sperm from the testes to the abdominal cavity

Question 9

Blood supply to the inguinal canal

Answer 9

The spermatic cord

Question 10

Anterior boundaries of the inguinal canal

Answer 10

The Aponeurosis of the external oblique, the internal oblique muscle (laterally) and the lateral crus of the external oblique.

Question 11

Posterior boundaries of the inguinal canal

Answer 11

Transversalis fascia, the conjoint tendon (medially). The conjoint tendon is formed from the internal oblique anastomoses and the fibres of the transversus abdominus anastomoses.

Question 12

Roof of the inguinal canal

Answer 12

Transversalis fascia. The Aponeurotic arching of the transversus abdominus and the internal oblique muscles. The medial crus of the external oblique.

Question 13

Floor of the inguinal canal

Answer 13

Iiopubic track (thickening of transversal’s fascia), the Inguinal ligament and the Lacunar ligament (external oblique muscle anastomose)

Question 14

LI- erect chest x-ray

Answer 14

Shows if there is any free gas in the intraperitoneal cavities, which may occur if there is a bowel perfusion

Question 15

LI- plain abdominal x-ray (AXR)

Answer 15

35 times the radiation of a CXR so order less. Used if there are clinical suspicions of bowel obstruction, such as absolute constipation, vomiting, abdominal pain and bloating. You also use if there is ingestion of a sharp or potentially poisonous foreign body (usually CXR first). You can also order a AXR with complications of IBD such as toxic megacolon.

Question 16

Pro’s and cons of AXR

Answer 16

• Pro’s- cheap, readily available

* Cons- uses ionising radiation, limited information (may need a CT scan for cause and site of obstruction)

Question 17

Which structures are seen in an AXR

Answer 17

BBC
• Bowel and other organs- dilation and position of bowel, gas (obstruction), masses
• Bones and joints- fractures, tumours, degeneration
• Calcification and artefacts- stones, lines, tubes, clips and jewellery

Question 18

X-ray contrast studies, type of contrast

Answer 18

• Positive contrast agents are dense so show up as bright i.e. barium
• Negative contrast agents are less dense so appear dark i.e. gas
• Double contrast is when you use a combination of agents

Question 19

What is X-ray contrast studies used to assess

Answer 19

Viewing the bowel lumen and mucosa in order to assess pathology i.e. strictures and ulcers. Cant see bowel loops unless gas filled. In the bowel you will see thickening and odema, strictures and fistulae, perforation and Abscess formation. You can also see organs, bones and vessels.

Question 20

Barium follow through contrast study

Answer 20

Contrast is swallowed you then take pictures. Used to look at the small bowel. Used to assess small intestinal ulcers, strictures, obstructions, masses and diverticula. It is contraindicated with aspiration risk, dysphagia and suspected bowel perforation

Question 21

Barium enema

Answer 21

Contrast is given rectally. It is used to assess colorectal cancer (secondary to colonoscopy) and to follow up IBD. It is contraindicated in acute inflammation due to the perforation risk.

Question 22

What can ultrasound assess in the abdomen

Answer 22

Appendicitis, Intussusception, Pyloric stenosis and IBD

Question 23

Pro’s and con’s of ultrasound

Answer 23

• Pro’s- cheap/accessible, no ionising radiation, live examination.
• Cons- operator and patient dependent, cannot see through bowel gas.

Question 24

Assessing the abdomen CT scan

Answer 24

Uses x-ray to build up 2D slices of the abdomen at different levels. It is used to assess bowel obstruction, Trauma, Perforation, Malignancy and Post-operative investigation

Question 25

Pro’s and cons of CT

Answer 25

• Pros- fast and readily available, active disease, chronic inflammation.
• Cons- requires contrast, ionising radiation.

Question 26

When might contrast not be tolerated

Answer 26

People with renal impairment

Question 27

Magnetic Resonance Imaging (MRI)

Answer 27

MR enterography is used to evaluate the small bowel (Crohn’s disease). MRI pelvis is used to assess for anal or rectal cancer and perianal fistulas

Question 28

Pro’s and cons of MRI

Answer 28

• Pro’s- no radiation, excellent soft tissue images
• Cons- requires contrast, contraindications (metal implants), larger patient may not fit into the scanner. Long scan time/patient discomfort, poorer availability.

Question 29

What is colonoscopy used for

Answer 29

Used to assess bowel cancer, poylps, diverticular disease, ulcerative colitis, crohn’s disease.

Question 30

Pro’s and cons of a colonoscopy

Answer 30

• Pro’s- direct imaging, ability to take biopsies
• Cons- sedation, patient tolerance (invasive), risks (perforation/bleeding), requires bowel preparation (taking laxatives)

Question 31

Summary of imaging techniques

Answer 31

• Plain film- bowel obstruction
• Contrast studies- mucosal detail
• Ultrasound- limited role
• CT good for assessing bowel and acute complications (obstruction, abscesses, intra-abdominal fistulae
• MRI also useful for assessing bowel and may be preferred in younger patients