This document provides a detailed overview of normal abdominal anatomy and findings on abdominal x-rays. It describes the planes used to divide the abdomen into regions and lists the typical appearance and locations of abdominal organs. Key points about small bowel, large bowel, bones, vessels and variations are summarized. Imaging techniques for abdominal x-rays including patient positioning and normal findings are outlined.

1. NORMAL
ABDOMEN
X-RAY
NASIN USMAN

2. PLANES AND REGIONS
 EXTEND: Inferior surface of diaphragm (superior) to the pelvic inlet
(inferior) and contained by muscles of abdominal walls.
 PLANES: Divided into nine regions by two transverse and two
parasagittal planes
I. Transpyloric plane: midway between the suprasternal notch
and the symphysis pubis (level of L1 vertebra and tips of Rt and
Lt 9th CC)
II. Transtubercular plane: level of tubercles of iliac crest and
upper border of L5
III. 2 X Parasagittal planes: run at Right angles to the transverse
planes vertically passing through a point midway between ASIS
and symphysis pubis on each side in the mid clavicular line.

3.  REGIONS:

4. Five basic densities on x-
rays
 Gas: Black
 Fat: Dark grey
 Soft tissue: Light grey
 Bone / calcification: White
 Metal: Intense white

5. Abdominal Organs
 Liver
 right upper quadrant
 extends to the hemidiaphragm and past the midline
 Chilaiditi’s syndrome
 Spleen
 left upper quadrant
 extends to the hemidiaphragm
 Its lower pole may be outlined by fat
 Measurement of its length from the dome of the diaphragm
to the tip. This is usually less than 14 cm
 Relationship of the spleen to the ninth, tenth and eleventh
ribs

6.  Normal gallbladder or biliary system are not visible. Gas
may be seen in the extrahepatic ducts in the elderly where
the ampullary tone is low, after sphincterotomy, or after
surgical anastomosis of bile ducts to small bowel
 Pancreas is not visible unless calcified. If calcification is
distributed throughout the gland it is seen as a transverse
structure at L 1 level, with a larger head on the right side and
a body and tail extending to the left and upwards.
 Psoas muscle
 symmetrical triangles either side of the lumbar spine
 Arise from the transverse processes of lumbar vertebrae
and combine with iliacus muscles to insert to lesser
trochanter of femur
 narrowest near the diaphragm, widest at the pelvis

7.  Stomach
 left of midline, beneath hemidiaphragm
 Gastric fundus fixed in location: within 2.5cm of left
hemidiaphragm.
 sometimes just a small volume of gas in the fundus
 do not mistake a rim of gas for pneumoperitoneum
 Kidneys
 sit on the psoas muscles at level of T12 to L3
 often just see the rounded lower pole
 Perirenal fat often makes part or all of the renal outlines
visible
 Renal size is variable, with a normal range of 10 – 15 cm on
a radiograph or approximately three-and-a-half vertebral
bodies in height
 The left kidney is usually larger, but a difference in size of
more than 2 cm is abnormal
 The kidneys are relatively larger in the child (approximately
four vertebral bodies in height)
 Adrenal glands visible only if calcified.

8.  Small bowel
 less than 3 cm wide
 tends to be central
 only seen if it contains gas
 3 or more air fluid levels - abnormal
 mucosal folds (valvulae conniventes) traverse the
bowel lumen
 Large bowel
 less than 6 cm wide, caecum and sigmoid up to 9
cm
 peripheral
 ascending and descending colon in fixed positions
laterally
 transverse colon and sigmoid variable position on a
mesentery
 Haustral folds do not go all the way across the
lumen
 Any air fluid levels – abnormal (?)
 Numerous gas – fluid levels may be normal and
18% of normal films have fluid levels in the
caecum
 contains faeces - mottled appearance
THE 3/6/9
RULE

9. VALVULAE CONNIVENTES HAUSTRAL FOLDS
 Faecoliths or fluid levels of the appendix may be visible on plain films of
the abdomen in the right iliac fossa in approximately 10% of individuals.

10.  Haustra:
I. The sacculation of the colon by the taeniae coli gives rise
to septa called haustra
II. The haustra are fixed anatomical structures in the
proximal colon, but in the distal colon require active con-
traction for their formation
III. Haustra may be absent distal to the midtransverse colon.

11.  Normal portal veins are not visible
• Gas in the portal vein and its radicles may occur in cases of
ischaemic bowel
• Portal vein gas may also be seen in well patients after
insertion of feeding tubes into the jejunum because of
physical mucosal damage caused by tunnelling of the tube.
 Lung bases
 pulmonary vessels in the bases projected over
upper abdomen
 Also look for free intra abdominal air below
the diaphragm, costophrenic angles, or for a
raised or flattened diaphragm.

12. Bladder: has variable appearance depending on how full it is. It has
the same density as other soft tissue structures, due to its water content.

14. Bones and Joints
 Spine
 lower thoracic and lumbar spine should be of similar height
 intervertebral disc spaces should be similar
 spinous processes should be visible
 Lower ribs
 Sacrum and pelvis
 Sacroiliac Joints And Hip Joints are often visualised on
abdominal radiographs. Make sure that you look at the bones
to check for other causes of abdominal pain. Evidence of
discitis, bony metastases etc.
 Bones can be used as landmarks for invisible soft tissue
structures. E.g. the transverse processes of the lumbar
vertebrae(L2 to L5) act as landmarks for the course of the
ureters. The vesico-ureteric junctions are located at the level
of the ischial spines.

15. Vessels
 Aorta is visible only if calcified It is then seen as linear
calcification vertically in the midline and to the left
 The shadow of the inferior vena cava can be identified as it
pierces the right hemidiaphragm and enters the heart. On a
lateral chest radiograph it identifies a hemidiaphragm as
being the right-sided one

16.  Factors affecting position and surface marking of organs:
a) Body build
b) Phase of respiration
c) Posture
d) Age: loss of tone of abdominal musculature
e) Pathology of organs
f) Contents of hollow viscera
g) Presence of abnormal mass
h) Normal variants within the population

17. Normal Variant
 Riedel’s Lobe
I. is a tongue-like, inferior
projection of the right lobe of
the liver beyond the level of
the most inferior costal
cartilage on cross-sectional
images.
II. It is not considered a true
accessory lobe of the liver
but an anatomical variant of
the right lobe of the liver.

18. Referral criteria
 A preliminary evaluation of bowel gas in an emergent setting: 50%
sensitivity for acute bowel obstruction
 Evaluation of radiopaque tubes and lines
 Evaluation for radiopaque foreign bodies
 Evaluation for post procedural intraperitoneal/retroperitoneal free
gas
 Monitoring the amount of bowel gas in postoperative ileus
 Monitoring the passage of contrast through the bowel
 Monitoring renal calculi: 80 – 90% sens if radiolucent stone

19. Procedure
 The patient should be gowned with minimum clothing.
 Radiopaque materials (zippers, belts, etc.) should be removed.
 If relevant, enteric tube suction should be avoided before the
study. Ideally, the patient's bladder should be emptied as well.
 Abdominal radiographs may be obtained in the radiology
department or may be performed portably. Portable abdominal
radiographs may be necessary due to patient immobility but are
of much poorer quality.
 Gonadal shielding may be provided for men
 Views should generally include either the diaphragm or inferior
pubic ramus

20. projections
 Basic: Antero-posterior - supine
 Alternative: Postero-anterior - prone
 Supplementary: * Antero-posterior – erect
* Antero-posterior or Postero-anterior
- left lateral decubitus
* Lateral – dorsal decubitus
* Anterior/Posterior obliques

21. AP Supine
 POSITION of patient:
I. Supine with pelvis adjusted so that ASIS are equidistant from
the tabletop. Arms placed alongside the trunk or above the
head. Median sagittal plane right angle to table.
II. CR casette positioned so that region below symphysis pubis
included.
III. Centre of image receptor located 1 cm below line joining iliac
crests.
IV. Ideally respiration arrested on full expiration.

22.  Picture Criteria:
I. Bowel pattern should be demonstrable with minimal
unsharpness
II. Diaphragm to symphysis pubis
III. Lateral abdominal wall and peritoneal fat layer
IV. Sharply demonstrated outline of psoas muscles, lower
border of liver, kidney.
V. Ribs and spinous processes of lumbar vertebrae
VI. Whole of urinary tract
VII. The abdomen should be free from rotation with symmetry
of the: ribs (superior), iliac crests (middle), obturator
foramen (inferior)

24. Free intraperitoneal gas may outline the
umbilical ligaments and falciform ligament
making them visible, thus making a
diagnosis of pneumoperitoneum possible
on a supine radiograph.

25. PA PRONE
 When kidneys are not of primary interest
 Reduces gonad dose
 POSITION of the patient:
I. Prone with median sagittal plane at right angles to table
II. Arms up beside head and both legs extended.
III. CR, equipment setting and picture criteria same as supine
projection.

26. PA ERECT
 Valuable projection in assessing air fluid levels,
and free air in the abdominal cavity.
 Perforation of a hollow abdominal viscus:
most sensitive to detect the presence of free
gas in the abdomen IS ERECT CHEST X-RAY
AND NOT ABDOMEN ERECT.

27.  POSITION of the patient:
I. Patient stands with back against the receptor or vertical
Bucky
II. Legs separated well apart to maintain comfortable position
III. Pelvis is adjusted so that the ASIS are equidistant
IV. Horizontal central ray directed perpendicular to midpoint
at the level of iliac crests.

28.  Picture criteria same as that of supine with both domes of
diaphragm visible to ensure any free air in the peritoneal
cavity.
Air fluid
levels

29. Lateral
 For identification and localization of foreign bodies.
 POSITION of the patient:
I. Patient turned onto the side of examination with hands
resting near the head
II. Hips and knees flexed for stability
III. Median sagittal plane parallel to table
IV. Vertebral column positioned over midline of the table
V. Immobilization band applied across pelvis
VI. Cassette centered at the level of iliac crest
VII. Vertical central ray directed to the center of
the cassette.
 Picture criteria: The prevertebral space along
with the abdominal aorta.

31. Lateral Decubitus
 Performed as an alternative to the PA erect view to assess
for free gas in the abdominal cavity if the patient is unable to
sit or stand.
 POSITION of the patient:
I. Patient in lateral recumbent position
II. Elbows and arms flexed and hands resting near head
III. Cassette positioned in vertical bucky against the posterior
aspect of the trunk.
IV. Central ray is directed perpendicular to the midpoint at the
level of iliac crest with x-ray tube horizontally

32.  Picture Criteria: elevated lateral abdominal wall included
on the image to detect any free intraperitoneal gas.

33. Dorsal Decubitus
 Used when it is unsafe to perform both a PA erect or a lateral
decubitus view
 This projection requires no patient movement.
 Xray beam: 5 cm above the iliac crests at the midcoronal plane
of the patient
 Picture Criteria:
I. The anterior abdominal wall and the diaphragms are
included on the image to detect any free intraperitoneal gas.
II. There should be no blurring of the bowel gas due to
respiratory motion.
III. Due to the high exposure of this examination and the need to
demonstrate soft tissue, the use of an aluminium filter over
the anterior portion of the patient is advantageous to even
out density and filter out higher energy x-rays

35. Pediatric Abdominal X-ray
Pockets of gas scattered
in several areas such as
Small bowel
Colon
Rectum
No excessive dilated
bowel
No air fluid levels

36. Imaging
 Film or IR size: 14 x 17 inches
 Moving or stationary grid
 65 – 80 kVr range
 mAs 30

37. Contraindications
 Pregnancy is a relative contraindication
I. Ten day rule : Whenever possible, one should confine the
radiological examination of the lower abdomen and pelvis
to the 10-day interval following the onset of menstruation.
Now this is applied only to examinations falling under high
dose.
II. 28 day rule: In case if the women
confirms she is certain she is not
pregnant and the LMP is within
28 days, it is regarded as safe.

38. Things to look for
 Name, Date
 Position of film and view
 Adequate area covered or not
 Bowel preparation
 Pre- Peritoneal fat lines
 Visualized organs are normal in size
 Visualized bones and joints are normal
 Visualized shadows
 Any Radio opacity
 Any artifacts
 Any calcification