Anatomy of the Abdomen by Sudil Paudyal

By:
Sudil Paudyal
B.Sc. MIT(51)
IOM,MMC

11/01/12 ABDOMEN PRESENTATION BY SUDIL 1

General Anatomy:
 The largest cavity of the body,
 Bounded
Anteriorly - by abdominal wall muscles
Posteriorly - by the vertebral column and posterior wall
muscles
Laterally - by lower ribs and parts of muscles of abdominal
wall
Superiorly - by the diaphragm
Inferiorly - by pelvic cavity


Abdominal walls:
 Bony support of the abdomen is minimal, consisting only of lumbar
vertebrae and portions of the pelvis (the ilium and the pubis).
 Muscles: Five pairs of muscles form anterior wall:
 Rectus abdominis
 External oblique
 Internal oblique
 Transversus abdominis
Three pairs form the posterior wall:
 Quadratus lumborum
 Psoas major
 Iliacus
Linea alba: A very strong midline tendinous cord, extends from xiphoid
process to symphysis pubis. Divides the anterior abdominal wall
longitudinally into two identical halves.

Fig: Anterior abdominal wall muscles Fig: Posterior abdominal wall muscles


Planes and regions:
Divided either into four quadrants or nine regions
Divided into four quadrants by a transverse and a mid sagittal
plane that intersect at the umbilicus.
Right Upper Quadrant (RUQ),
Right Lower Quadrant (RLQ),
Left Upper Quadrant (LUQ), and
Left Lower Quadrant (LLQ).


Divided into nine regions by two transverse and two vertical
planes
The upper transverse plane - The Transpyloric Plane,
 Lies midway between suprasternal notch and symphysis pubis,
approximately midway between the upper border of
xiphisternum and umbilicus.
 Posteriorly, passes through the body of the first lumbar
vertebra;
 Anteriorly, passes through the tips of the right and left ninth
costal cartilages.
The lower transverse plane - The Transtubercular Plane,
 Lies at the level of tubercles of iliac crest anteriorly, and near
the upper border of fifth lumbar vertebra posteriorly.

The two parasagittal (vertical) planes –
 Lie at right-angles to the two transverse planes.
 They run vertically, passing through a point midway between
the anterior superior iliac spine and the symphysis pubis on
each side.
These planes divide the abdomen into nine regions:
 centrally from above to below epigastric, umbilical and
hypogastric regions and
 laterally from above to below right and left hypochondriac,
lumbar and iliac regions.


Contents:
 contains the greater part of the alimentary tract,
 some of the accessory organs to digestion, viz. the liver,
pancreas and spleen,
 some of the urinary organs i.e. the kidneys,upper part of the
ureters and the suprarenal glands.
 Most of these structures, as well as the wall of the cavity are
more or less covered by an extensive and complicated serous
membrane, the peritoneum.


Fig: organs of anterior part of abdominal cavity


Fig: organs of posterior part of abdominal cavity


Peritoneum:
The serous membrane related to the viscera of the abdominal
cavity.
 Divided into two layers:
 Parietal Layer : Lines the body wall and covers the
retroperitoneal organs.
 Visceral Layer : Composed of two parts :
Covering of the surface of the peritoneal organs.
Mesentery-a double layer of peritoneum that suspends
part of the GI tract from the body wall.

 Peritoneal cavity : The potential space located between the
parietal and visceral layers.

Abdominal Viscera

Viscera are classified as:

Peritoneal organs - have a mesentery and are almost
completely
enclosed in peritoneum. These organs are mobile.

Retroperitoneal organs - are partially covered with peritoneum
and are immobile or fixed organs.


In a nutshell
Major Peritoneal organs: Stomach, Liver and gallbladder,
Spleen, Beginning of duodenum, Tail of pancreas, Jejunum,
Ileum, Appendix , Transverse colon, Sigmoid colon
Major Secondary Retroperitoneal organs: Most of duodenum,
Most of pancreas, Ascending colon ,Descending colon , Upper
rectum
Major Primary Retroperitoneal Organs: Kidney , Adrenal
gland, Ureter, Aorta, Inferior venacava, Lower rectum, Anal
canal


Liver:
Lies mostly in the right hypochondrium, and protected by rib
cage.
Divided into two lobes of unequal size by the falciform
ligament.
Fissures for the ligamentum teres and the ligamentum
venosum, the porta hepatis, and the fossa for the gallbladder
further subdivide the right lobe into the right lobe proper, the
quadrate lobe, and the caudate lobe.
Has a central hilus, or porta hepatis, which receives venous
blood from the portal vein and arterial blood from the hepatic
artery.


The central hilus also transmits the common bile duct, which
collects bile produced by the liver.
These structures, known collectively as the portal triad
The hepatic veins drain the liver by collecting blood from the
liver sinusoids and returning it to the inferior vena cava.

Gallbladder :
 lies in a fossa on the visceral surface of the liver to the right of
the quadrate lobe.
It stores and concentrates bile, which enters and leaves through
the cystic duct. The cystic duct joins the common hepatic duct
to form the common bile duct.


Fig: Liver, turned up to show posterior surface


Pancreas
Most of the pancreas is secondarily retroperitoneal, but the
distal part of the tail of the pancreas remains peritoneal . The
tip of the tail of the pancreas reaches the hilus of the spleen.
Both pancreatic ducts open into the second portion of the
duodenum.
Spleen
a peritoneal organ in the upper left quadrant that is related to
the left 9th, 10th, and 11th ribs. Fracture of these ribs may
lacerate the spleen.


Stomach:
has a lesser curvature, which is connected to the porta hepatis
of the liver by the lesser omentum, and a greater curvature
from which the greater omentum is suspended.

The cardiac region receives the esophagus.

The dome-shaped upper portion of the stomach, which is
normally filled with air, is the fundus.

The main center portion of the stomach is the body.

The pyloric portion of the stomach has a thick muscular wall
and narrow lumen that leads to the duodenum.

Fig: Abd. cavity showing greater and lesser Fig:Longitudinal section of stomach
omentum

Kidneys and ureters:

Kidney's Relation to the Posterior Abdominal Wall
Both kidneys are in contact with the diaphragm, psoas major,
and quadratus lumborum .
Right kidney-contacts the above structures and the 12th rib.
Left kidney-contacts the above structures and the 11th and
12th ribs
Ureter's Relation to the Posterior Abdominal Wall
The ureter lies on the anterior surface of the psoas major.


Fig: Relation of kidneys and ureters to posterior abdominal wall


Kidneys:
A pair of bean-shaped organs approximately 12 cm long. They
extend from vertebral level T12 to L3 when the body is in the
erect position. The right kidney is positioned slightly lower
than the left because of the mass of the liver.

Internal structure
Within the dense, connective tissue of the renal capsule, the
kidney substance is divided into an outer cortex and an inner
medulla


Cortex-contains glomeruli, Bowman's capsules, and proximal
and distal convoluted tubules. It forms renal columns, which
extend between medullary pyramids.

Medulla--consists of 10 to 18 striated pyramids and contains
collecting ducts and loops of Henle. The apex of each pyramid
ends as a papilla where collecting ducts open.

Calyces-the minor calyces receive one or more papillae and
unite to form major calyces,of which there are two to three per
kidney.

Renal pelvis--the dilated upper portion of the ureter that
receives the major calyces.


Fig: cross section of a kidney


Ureters : are fibro-muscular tubes that connect the kidneys to
the urinary bladder in the pelvis.

Urinary Bladder:
The urinary bladder is covered superiorly by peritoneum.
The body is a hollow muscular cavity.
The neck is continuous with the urethra.
The trigone is a smooth triangular area of mucosa located
internally at the base of the bladder.
The base of the triangle is superior and bounded by the two
openings of the ureters.
 The apex of the trigone points inferiorly and is the opening
for the urethra.

Fig: Kidneys, Ureters and
Bladder

For any body habitus whether hypersthenic or asthenic,
abdominal viscera occupy a lower position:
 in inspiration compared with expiration;
 in the erect position compared with the recumbent position;
 with age and the associated loss of muscle tone.


Radiography:
Preparation:
 Careful preliminary patient preparation of the intestinal and
gastric contents is important for a clear view of all the
abdominal structures.
 For non-acute conditions, patient preparation is as follows:
(1) Patient placed on a low-residue diet for (2 days) prior to x-
ray examination to prevent formation of gas due to excessive
fermentation of the intestinal contents
(2) Patient should be instructed to take some laxative the night
before the examination.


Exposure technique:
 In examinations of the abdomen without a contrast medium, it
is necessary to obtain maximum soft tissue differentiation
throughout its different regions.
 Because of the wide range in thickness of the abdomen and the
delicate differences in physical density between the contained
viscera, it is necessary to use a more critical exposure
technique than is required to demonstrate the difference in
density between an opacified organ and the structures adjacent
to it.
 The exposure factors should thus be adjusted to produce a
radiograph with moderate gray tones and less black and white
contrast.


 A sharply demonstrated outline of the psoas muscles, lower
border of liver, kidneys ribs and spinous processes of the
lumbar vertebra are the best criteria for judging the quality of
an abdominal radiograph.

High mA and shorter exposure times must be used to freeze
voluntary and involuntary organ movements (breathing and
bowel peristalsis).
Exposure is taken on second full arrested expiration (to
displace diaphragm upward ) to give a better view of the
abdominal structures.

Immobilization:
One of the prime requisite in abdominal examinations is the
prevention of movement, both voluntary and involuntary.
 To prevent muscle contraction, the patient must be adjusted
in a comfortable position so that he can relax.
 A compression band may be applied across the abdomen for
immobilization but not compression.
 The exposure should be made 1-2 sec after suspension of
respiration to allow involuntary movement of viscera to
subside.


Radiation protection:
 Gonadal shields should often be used on males (upper edge of
the shield at the symphysis pubis). For females, shields are
used only where they could not obscure essential anatomical
structures (the lower border of the shield should be at the
symphysis pubis).
 For potential early pregnancy, the ‘10-day Rule’ (the LMP)
must always be observed, unless permission has been given by
the medical specialist as to ‘ignore’ it, e.g., in the case of an
emergency (e.g., trauma), or in case of a female with a
removed uterus.


Radiographic projections:
Basic : Antero-posterior – supine (KUB) (so named because it
includes the kidneys, ureters and bladder).
Alternative: Postero-anterior – prone
Supplementary: Antero-posterior –erect
Anteroposterior – left lateral decubitus
Lateral
Lateral- dorsal decubitus
Anterior and posterior obliques ( for
contrast studies)


Indications:
 Bowel obstruction
 Perforation
 Renal pathology
 Acute abdomen
 Foreign body localization
 Toxic megacolon
 Aortic aneurysm
 Control or preliminary films for contrast studies
 Detection of calcification or abnormal gas collection


AP-supine (KUB)
Patient position:
 Patient supine, with the median sagittal plane at right angles
 Pelvis adjusted so that the ASIS are equidistant from the table
 Cassette placed longitudinally and positioned so that the symphysis pubis is
included
 Arms placed alongside the trunk or above the head.


Centering of beam:
 Vertical central ray directed approx. at the level of a point 1 cm below the
line joining the iliac crests.
Equipment setting: ( for screen film combination)

Kv mA S mAs FFD Film Grid focus
size
65 300 0.12 36 100 cm 35 X 43 Yes large
cm


Picture criteria:
 Whole of abdomen from upper abdomen to symphysis pubis.
 Lateral abdominal wall and the properitoneal fat layer.
 Psoas muscle, lower border of liver and the kidneys.
 Ribs and spinous processes of the lumbar vertebra.
 Whole of the urinary tract should be visualized.
 Bowel gas pattern with minimal unsharpness.


PA- prone
 When kidneys are not of primary interest, PA projection should be used.
 It reduces patient gonad dose compared to the AP projection
Patient position:
 Patient prone, with median sagittal plane at right angles to the table
 Arms up beside the head and both legs extended


 CR, equipment setting, picture criteria same as supine projection.


Lateral:
Position of patient:
 Patient turned onto the side of examination, with hands resting near the
head. The hips and knees are flexed for stability.
 With the MSP parallel to the table, the vertebral column( abt 8 cm anterior
to the posterior skin surface) positioned over the midline of the table
 Immobilization band applied across the pelvis.
 Cassette centered at the level of iliac crests.


Centring of the beam:
 Vertical central ray directed to the centre of the cassette

Equipment setting:
size
75 300 0.12 64 100 cm 35 X 43 Yes large
cm


Picture criteria:
 The prevertebral space along with abdominal aorta
 Any other intra abdominal calcifications or tumour masses should be
clearly visible.


AP -erect
Patient position:
 Patient stands with the back against the
vertical bucky.
 Patient’s legs separated well apart to
maintain a comfortable position.
 The median sagittal plane is adjusted at
right angles and coincident with the midline
of the table.
 The pelvis is adjusted so that the anterior
superior iliac spines are equidistant.


Centring of beam:
 The horizontal central ray is directed perpendicular to midpoint at the level
of iliac crests.
Equipment setting:
size
65 300 0.12 36 100 cm 35 X 43 Yes large
cm


Picture criteria:
 Both domes of diaphragm to ensure that any free air in the peritoneal cavity
is demonstrated.
 Lateral abdominal wall and properitoneal fat
 Psoas muscle, lower border of liver and kidney shadows
 Vertebra in center of film.
 Side identification marker placed properly.


Lateral Decubitus -AP
Lateral decubitus is done instead of abdomen erect if
patient is unable to stand or sit.
Patient position:
 Patient in lateral recumbent position
 Elbows and arms flexed and hand resting near head
 Cassette positioned in vertical bucky against the posterior aspect of the
trunk


Centring of beam:
 The central ray is directed perpendicular to midpoint at the level of iliac
crest with x-ray tube horizontally.
Equipment setting:
size
65 300 0.12 36 100 cm 35 X 43 Yes large
cm

 Note: Patient should be placed in lateral decubitus position for 5-10 mins to
allow the free air to rise


Picture criteria:
 Air fluid levels when an erect abdomen cannot be obtained.
 Lung area above dome of diaphragm
 Lateral abdominal wall and properitoneal fat
 Psoas muscle, lower border of liver and kidney shadows
 No rotation


Lateral dorsal decubitus (supine):
Occasionally, the patient cannot sit or even be rolled on to the
side, in which case the patient remains supine and a lateral
projection is taken using a horizontal central ray.
Patient position:
 Patient supine
 Arms raised away from the abdomen and thorax.
 Cassette positioned vertically against patient’s side


Centring of the beam:
 The horizontal central ray is directed to the lateral aspect of the trunk so
that it is at right-angles to the cassette and centred to it.
Equipment setting:
size
75 300 0.12 36 100 cm 35 X 43 Yes large
cm


Picture criteria:
 Thorax to the level of mid-sternum and as much of the abdomen as
possible.
 Pre-vertebral space for determining the air fluid levels in abdomen.
 Lung area above dome of diaphragm, without motion.
 Patient elevated to demonstrate entire abdomen


References:
Clark’s positioning in radiography, 12th edition
Merrill’s atlas of radiographic positions and radiologic
procedures, 12th edition
Different other books and websites


THANK YOU

Anatomy of the Abdomen by Sudil Paudyal

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