Abdomen

X-Ray

< 3 cm

Normal Value

Small bowel loops usually central, with valvulae conniventes (folds crossing entire lumen). Dilatation >3 cm suggests obstruction.

< 6 cm

Normal Value

Haustral folds do not cross entire lumen. Peripheral distribution. >6 cm = obstruction / colonic ileus.

< 9 cm

Normal Value

The cecum is most prone to perforation. >9 cm indicates risk of toxic megacolon or impending perforation.

Present in LUQ, variable size

Normal Value

Seen under left hemidiaphragm. Grossly distended stomach with air-fluid levels may indicate gastric outlet obstruction.

Few, short (<2 cm), scattered

Normal Value

Multiple long levels (>2 cm), step-ladder appearance, or unequal heights suggest obstruction.

Symmetric, well-defined bilaterally

Normal Value

Obscuration suggests retroperitoneal disease (hemorrhage, abscess, neoplasm).

Height < 15–16 cm (approximate on upright film)

Normal Value

Inferior displacement of bowel loops indicates hepatomegaly.

Width < 12 cm

Normal Value

Visible below left costal margin may indicate splenomegaly.

Absent physiologically (phleboliths may be seen)

Normal Value

Pathological: renal, biliary, pancreatic, vascular, lymph node calcifications.

None

Normal Value

Seen under diaphragm (upright) → perforation. Left side easier to detect (contrast with stomach bubble).

Measurement	Normal Value	Comments
Small Bowel Diameter	< 3 cm	Small bowel loops usually central, with valvulae conniventes (folds crossing entire lumen). Dilatation >3 cm suggests obstruction.
Large Bowel Diameter	< 6 cm	Haustral folds do not cross entire lumen. Peripheral distribution. >6 cm = obstruction / colonic ileus.
Cecal Diameter	< 9 cm	The cecum is most prone to perforation. >9 cm indicates risk of toxic megacolon or impending perforation.
Stomach Gas Bubble	Present in LUQ, variable size	Seen under left hemidiaphragm. Grossly distended stomach with air-fluid levels may indicate gastric outlet obstruction.
Air–Fluid Levels	Few, short (<2 cm), scattered	Multiple long levels (>2 cm), step-ladder appearance, or unequal heights suggest obstruction.
Psoas Shadows	Symmetric, well-defined bilaterally	Obscuration suggests retroperitoneal disease (hemorrhage, abscess, neoplasm).
Liver Shadow / Size	Height < 15–16 cm (approximate on upright film)	Inferior displacement of bowel loops indicates hepatomegaly.
Splenic Shadow	Width < 12 cm	Visible below left costal margin may indicate splenomegaly.
Calcifications	Absent physiologically (phleboliths may be seen)	Pathological: renal, biliary, pancreatic, vascular, lymph node calcifications.
Free Intraperitoneal Air	None	Seen under diaphragm (upright) → perforation. Left side easier to detect (contrast with stomach bubble).