Case 12- Imaging and anatomy Flashcards
The inguinal region
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.
The inguinal ligament
From the ASIS to pubic tubercle, have one on each side. Formed from the sternal oblique muscle.
The midpoint of the inguinal ligament
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
The mid inguinal point
Halfway between the pubic symphysis and the anterior superior iliac spine. The femoral pulse can be palpated here
The inguinal canal
A 4cm tunnel in the lower anterior abdominal wall muscles. It runs between the deep and superficial rings, in a downwards and medial direction.
Role of the inguinal canal
- 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
Contents of the inguinal canal
• 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
Ductus deference
Within the inguinal canal, transports sperm from the testes to the abdominal cavity
Blood supply to the inguinal canal
The spermatic cord
Anterior boundaries of the inguinal canal
The Aponeurosis of the external oblique, the internal oblique muscle (laterally) and the lateral crus of the external oblique.
Posterior boundaries of the inguinal canal
Transversalis fascia, the conjoint tendon (medially). The conjoint tendon is formed from the internal oblique anastomoses and the fibres of the transversus abdominus anastomoses.
Roof of the inguinal canal
Transversalis fascia. The Aponeurotic arching of the transversus abdominus and the internal oblique muscles. The medial crus of the external oblique.
Floor of the inguinal canal
Iiopubic track (thickening of transversal’s fascia), the Inguinal ligament and the Lacunar ligament (external oblique muscle anastomose)
LI- erect chest x-ray
Shows if there is any free gas in the intraperitoneal cavities, which may occur if there is a bowel perfusion
LI- plain abdominal x-ray (AXR)
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.
Pro’s and cons of AXR
- Pro’s- cheap, readily available
* Cons- uses ionising radiation, limited information (may need a CT scan for cause and site of obstruction)
Which structures are seen in an AXR
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
X-ray contrast studies, type of contrast
- 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
What is X-ray contrast studies used to assess
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.
Barium follow through contrast study
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
Barium enema
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.
What can ultrasound assess in the abdomen
Appendicitis, Intussusception, Pyloric stenosis and IBD
Pro’s and con’s of ultrasound
- Pro’s- cheap/accessible, no ionising radiation, live examination.
- Cons- operator and patient dependent, cannot see through bowel gas.
Assessing the abdomen CT scan
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
Pro’s and cons of CT
- Pros- fast and readily available, active disease, chronic inflammation.
- Cons- requires contrast, ionising radiation.
When might contrast not be tolerated
People with renal impairment
Magnetic Resonance Imaging (MRI)
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
Pro’s and cons of MRI
- 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.
What is colonoscopy used for
Used to assess bowel cancer, poylps, diverticular disease, ulcerative colitis, crohn’s disease.
Pro’s and cons of a colonoscopy
- Pro’s- direct imaging, ability to take biopsies
- Cons- sedation, patient tolerance (invasive), risks (perforation/bleeding), requires bowel preparation (taking laxatives)
Summary of imaging techniques
- 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
