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Evaluation of the Acute Abdomen Evidenced-based Testing Strategies Thomas W. Lukens MD PhD FACEP MetroHealth Medical Center Cleveland, OH Associate Professor.

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Presentation on theme: "Evaluation of the Acute Abdomen Evidenced-based Testing Strategies Thomas W. Lukens MD PhD FACEP MetroHealth Medical Center Cleveland, OH Associate Professor."— Presentation transcript:

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 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% 25% GI causes 13% 19% 18% Gastroenteritis 7% 12% 5% Surgical GI 10% 18% 8% UTI 11% -- 11% Pelvic Disorder 12% -- 12% Admission rate 27% 42% 18% Ref: Brewer, Am J Surg, 1976; Jazon, AC Scand, 1982; Powers, AJEM, 1995

6 Acute Abdomen Testing History and Physical Examination 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 Gs-- 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 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 doesnt 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 90-95% 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 1/2 Raptopoulos, Radiology 2003;226:521 Appendicitis - most common operation but accuracy hasnt 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


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