Radiographic Anatomy of the Abdomen

Radiographic Techniques

• Abdomen regions and image parameters include AP supine, PA erect, and lateral views.
• Techniques were presented by Ahmed Jasem Abass, MSC of Medical Imaging.

Abdominal Cavity

• The abdominal cavity extends from the diaphragm to the pelvic inlet, and is surrounded by abdominal walls.
• The abdomen is divided into nine regions using two transverse and two parasagittal planes.

Planes of the Abdomen (Fig 10-1a)

• The transpyloric plane is approximately midway between the xiphisternum and the umbilicus, passing through the tips of the 9th costal cartilages and the pylorus of the stomach.
• The transtubercular plane is positioned at the level of the tubercles of the iliac crest anteriorly and near the 5th lumbar vertebrae posteriorly.
• Two parasagittal planes run vertically, passing midway between the anterior superior iliac spine and the symphysis pubis.

Body Build Types

• Individuals are categorized into hypersthenic, sthenic, hyposthenic, and asthenic body builds based on their proportions.
• Hypersthenic individuals have a massively built body, with a high diaphragm and wide costal angle, resulting in a wider upper abdomen.
• Asthenic individuals are thin and slender, with a narrow thorax and low diaphragm position.

Most Common Referral Criteria

• Radiographic examinations of the abdomen and pelvis are performed for various reasons, including bowel obstruction, perforation, renal pathology, acute abdominal pain, foreign body localization, toxic megacolon, and aortic aneurysm.
• Prior to contrast medium procedures, imaging may be performed to identify the presence of radio-opaque renal or gall stones, or calcification, or abnormal gas collections.

Typical Imaging Protocols

• Recommended projections include basic antero-posterior (AP) supine and supplementary AP erect, AP or PA lateral decubitus, and lateral dorsal decubitus.

Image Parameters

• Ensuring adequate coverage, including the diaphragm and the inferior symphysis pubis and lateral fat stripe;
• High resolution and sufficient contrast to delineate the interface between air-filled bowels and surrounding soft tissues; complete visualization of the urinary tract (from kidneys to bladder).

Radiation Protection

• Pregnancy exclusion is crucial unless in emergencies.
• Gonad shielding is recommended for males.
• A 35 x 43 cm CR cassette is typically used.
• The patient must lie supine with the median sagittal plane aligned with the table's mid-line.
• The pelvis is adjusted to align the anterior superior iliac spines equidistant from the tabletop.
• Image receptor placement ensures the region below the symphysis pubis is visible..

Patient Positioning (Fig 10.6a,b)

• The X-ray beam is positioned horizontally and centrally collimated to the image receptor.
• Ideal exposure is made on arrested respiration during full expiration, allowing abdominal contents to settle naturally.

Normal Abdominal Radiograph Faults (Fig 10.7a,b)

• Imaging may fail to include the inferior regions of the diaphragm or symphysis pubis due to patient size.
• Respiratory movement during imaging may cause unsharpness, requiring arrested breathing practice. Rotation may be caused by patient discomfort.
• The presence of artifacts like buttons or pockets in clothed patients should be noted.

Antero-posterior (AP) Erect Projection

• If possible, patients are examined standing or seated against a Bucky, using a 35 x 43 cm CR cassette to include the diaphragms.
• Legs should be positioned apart for stable standing position; care with seated patients to avoid knee obstruction.
• The mediansagittal plane is adjusted to be perpendicular to the Bucky.

Antero-posterior—Left Lateral Decubitus

• This projection is suitable for visualizing sub-diaphragmatic gas, and suspected bowel issues, when ultrasound or CT are not available or inappropriate.
• The patient lies on their left side, with their elbows flexed and hands near their head, and remain in this position for 10 minutes before the exposure. The x ray beam is positioned centred to the anterior aspect of the patient's body.

Lateral–Dorsal Decubitus (Supine)

• When a patient cannot sit or be turned to one side, the lateral projection is undertaken with the patient remaining supine.
• A 35 x 43 cm CR cassette is supported vertically against the patient's side to include the thorax to the mid-sternum, and as much of the abdomen as possible.

Urinary Tract (Kidneys, Ureters, Bladder)

• Plain radiography of the abdominal and pelvic cavity is often performed to examine the kidneys, surrounded by perirenal fat, the psoas muscles, opaque kidney stones, calcifications within the kidneys or bladder, gas presence, and acute abdominal pathology.

Antero-posterior Projection (Figs 10.10a,b)

• The patient lies in a supine position on the X-ray table.
• Hands can be placed on the chest or at the patient's sides (away from the trunk).
• The Bucky or 35 x 43 cm CR cassette includes the region from the upper kidney poles to the symphysis pubis.
• The center of the receptor should be approximately 1 cm below the line connecting the iliac crests to include the symphysis pubis.