1. Evaluation of the Acute Abdomen Evidenced-based Testing Strategies
Thomas W. Lukens MD PhD FACEP
MetroHealth Medical Center
Cleveland, OH
Associate Professor of Emergency Medicine
Case Western Reserve University School of Medicine

2. Greetings from Cleveland, OH

3. The Acute Abdomen Pain less than one week Sudden onset Surgery needed
Peritonitis
Severe pain
Any condition that needs rapid
decision making and/or operative intervention

4. Emergency Department:
ABDOMINAL PAIN
Emergency Department:
Undifferentiated patients
A collection of symptoms and signs are gathered to predict the conditional probability of a diagnosis
Traditional teaching is the reverse
Few evidenced based studies in undifferentiated conditions

5. ABDOMINAL PAIN Emergency Department Series
Discharge Diagnosis Undifferentiated (UDAP) 41% 39% % GI causes % 19% % Gastroenteritis % 12% % Surgical GI % 18% % UTI % % Pelvic Disorder % % Admission rate % 42% %
Ref: Brewer, Am J Surg, 1976; Jazon, AC Scand, 1982; Powers, AJEM, 1995

6. Acute Abdomen Testing History and Physical Examination Laboratory
Serial examinations
Laboratory
WBC
Urinalysis/pregnancy test
Plain Radiography CT
Ultrasound
Color flow Doppler
Nuclear Medicine
MRI

7. Acute Abdomen History & Physical Examination
Intraabdominal
3 G’s-- GI, GU, GYN
Vascular
Extraabdominal
Cardiovascular
Metabolic
Abdominal wall
Neurogenic

8. Acute Abdomen History & Physical Examination
Accuracy is lacking at times
Atypical presentations
Missed findings
Appendicitis
50-87% sensitive
false positive = negative laporatomy
false negative = perforation
Acute Abdominal Aneurysm (AAA)
< 50% sensitive
Diverticulitis - 34% sensitivity
LR+ = 2-3, LR- = 0.4
Bergeron, Am J Surg, 1999;177:460, Chervu Surg 1995;117:454,
Korner, World J Surg 1997;21:313

9. A way to measure performance
Likelihood ratios
A way to measure performance
LR of positive test: sensitivity of test/1-specificity
LR of negative test: 1-sensitivity/specificity
LR+ - the likelihood of the test being positive in a patient with the disorder, compared to the likelihood of a positive test in someone without the disorder
LR- the likelihood of a negative test in someone with the disorder compared to a negative test in one without the disorder

10. Likelihood ratios Calculating probabilities
LR times the (estimated) pretest probability = post test odds of the disease
Appendicitis- all ED abdominal pain patients
Estimated pretest probability ~ 4%
LR+ of the “test” ~4, LR- is 0.3
If all received the test for appendicitis (4 X 1:25) = ~16%
chance that a positive test is actually detecting appendicitis in
the patient. If negative test (0.3 x 1:25), there is still a 1.2%
probability of patient having appendicitis (lowered pre-test
probability by about a third)
Not a particularly accurate test in undifferentiated
patients

11. Acute Abdomen Laboratory testing
WBC - limited utility
WBC > 11,000 LR+ = ~ 2
< 11,000 LR- = ~ 0.5
WBC alone doesn’t distinguish patients with surgical disease from non-specific abdominal pain
Urinalysis
AAA - misleading
Hematuria in up to 30% with AAA
Most common misdiagnosis in AAA- kidney stone
Renal colic - hematuria
LR+ ~ 2 , LR- = 0.3

12. Acute Abdomen Laboratory testing
Liver function tests
Normal in up to 40% with acute cholecystitis
Not specific for any disease entity
Amylase/Lipase
Often normal in active pancreatitis
Sensitivity ~60%

13. Acute Abdomen Imaging Plain films- provide little in addition to H & P
Few specific findings
Sensitive for free air %
Bowel obstruction- 70% sensitive (LR+ ~3, LR- 0.6)
Appendicitis
LR+ = 1
LR- = 0.4
Cholecystitis
LR+ = 2
LR- = 0.5
Frager, AJR, 1994,162:37, Gruber, Ann Emerg Med, 1996,28:273,
Izbicki, Eur J Surg,1992,158:227,

14. Acute Abdomen Imaging-CT
CT- test of choice in most abdominal conditions
LR LR-
Appendicitis
Unenhanced focused
Contrast focused
Abdomen/pelvis (contrast)
Small bowel obstruction
low grade
Diverticulitis

15. Acute Abdomen Imaging-CT
LR LR-
AAA
Renal colic (Unenhanced)
Mesenteric ischemia
CT angiography
MRA enhanced gadolinium
Biliary tract (stones)
Common duct
MR cholangiography

16. Acute Abdomen Imaging-Ultrasound
LR LR-
Biliary tract (stones)
Cholecystitis
Common duct obst
Common duct stone
HIDA scan
AAA (nonleaking)
Diverticulitis
Appendicitis
Ectopic TVS (BHGC>1500)

17. Appendicitis - CT Liberal use of CT has lowered negative
appendectomy rate to 5.4%
Peck, Am J Surg 2000;180:133
CT for appendicitis has lowered hospital stay
by 1/ Raptopoulos, Radiology 2003;226:521
Appendicitis - most common operation but
accuracy hasn’t changed significantly in
past decade (data through 1999) Flum, JAMA 2001;286:1748

18. Appendicitis - CT Use in equivocal cases- not high or low
probability patients- not routinely
Ujiki, J Surg Research 2002;105:119
Call for a surgeon not a CT- more cost
effective and accurate to have the surgeon
see the patient first Morris. Am J Surg, 2002;183:547

19. Acute Abdominal Pain -Imaging
History & examination and simple lab tests have about a % accuracy (initial to final diagnosis)
Technological advances in imaging are responsible for our increased accuracy in diagnosing patients with acute abdominal pain
Helical CT
Ultrasound by EM physicians 24/7
MRI

20. Good judgment comes from experience, and a lot of that comes from bad judgment. Will Rodgers