CBC
WBC >20K suggests bowel gangrene, abscess, or peritonitis
WBC >40K suggests mesenteric vascular occlusion
Chemistry - degree of dehydration, evidence of ischemia (acidosis)
Lactate - sensitive (90-100%), though not specific marker of strangulation
WBC >20K suggests bowel gangrene, abscess, or peritonitis
WBC >40K suggests mesenteric vascular occlusion
Use the 3/6/9 rule for bowel imaging
Upper limit of 3cm for<unk>  bowel, 6cm for colon, and 9cm for cecum
Xray
Acute Abdominal Series
Upright chest film: rule out free air
Upright abdominal film: air-fluid levels:
Supine abdominal film: width of bowel loops most visible (estimate of amount of distention)
String of pearls sign<unk>  pockets of gas along the<unk>  bowel that are trapped between the valvulae conniventes) is virtually diagnostic<unk>  bowel diameter ≥3cm is associated with<unk> 
Sen 75% Spec 66% +LR 1.6 -LR 0.43
Air in colon or rectum makes complete<unk>  less likely (esp if symptoms >24hr)
If patient does not tolerate upright position left lateral decub abdominal film can substitute
CT A/P with IV contrast
Consider if plain films are non-diagnostic
Can show closed-loop<unk> , evidence of ischemia
Per American College of Radiology PO contrast is no longer indicated
Modern CT Scanner (0.75mm slices): Sen 96%, Spec 100%, +LR infinity -LR 0.04
Historical CT scanner meta-analysis: Sen 87%  Spec 81%,  +LR 3.6  -LR 0.18
Ultrasound for<unk> 
Sen 97%, Spec 90%, +LR 9.5, -LR 0.04 (four studies, 2 done by EM residents and 2 by radiology residents)
MRI for<unk>  - Sen 92%, Spec 89% +LR 6.7 -LR 0.11
Upper limit of 3cm for<unk>  bowel, 6cm for colon, and 9cm for cecum
Acute Abdominal Series
Upright chest film: rule out free air
Upright abdominal film: air-fluid levels:
Supine abdominal film: width of bowel loops most visible (estimate of amount of distention)
String of pearls sign<unk>  pockets of gas along the<unk>  bowel that are trapped between the valvulae conniventes) is virtually diagnostic<unk>  bowel diameter ≥3cm is associated with<unk> 
Sen 75% Spec 66% +LR 1.6 -LR 0.43
Air in colon or rectum makes complete<unk>  less likely (esp if symptoms >24hr)
If patient does not tolerate upright position left lateral decub abdominal film can substitute
Sen 75% Spec 66% +LR 1.6 -LR 0.43
Air in colon or rectum makes complete<unk>  less likely (esp if symptoms >24hr)
If patient does not tolerate upright position left lateral decub abdominal film can substitute
Consider if plain films are non-diagnostic
Can show closed-loop<unk> , evidence of ischemia
Per American College of Radiology PO contrast is no longer indicated
Modern CT Scanner (0.75mm slices): Sen 96%, Spec 100%, +LR infinity -LR 0.04
Historical CT scanner meta-analysis: Sen 87%  Spec 81%,  +LR 3.6  -LR 0.18
Modern CT Scanner (0.75mm slices): Sen 96%, Spec 100%, +LR infinity -LR 0.04
Historical CT scanner meta-analysis: Sen 87%  Spec 81%,  +LR 3.6  -LR 0.18
Sen 97%, Spec 90%, +LR 9.5, -LR 0.04 (four studies, 2 done by EM residents and 2 by radiology residents)
Small bowel obstruction
Abdominal aortic aneurysm
Large bowel obstruction
Aortocaval fistula
Malignant bowel obstruction
Acute gastroenteritis
Epiploic appendagitis
Aortoenteric fisulta