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

Greetings from Cleveland, OH

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

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

ABDOMINAL PAIN Emergency Department Series Discharge Diagnosis 1972 1977 1993 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

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

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

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

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

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

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

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%

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,

Acute Abdomen Imaging-CT CT- test of choice in most abdominal conditions LR+ LR- Appendicitis Unenhanced focused 29 0.1 Contrast focused 49 0.02 Abdomen/pelvis (contrast) 18 0.1 Small bowel obstruction 22 0.1 low grade 3 0.5 Diverticulitis 98 0.02

Acute Abdomen Imaging-CT LR+ LR- AAA 19 0.03 Renal colic (Unenhanced) 32 0.02 Mesenteric ischemia CT angiography 5 0.3 MRA enhanced gadolinium 8 0.2 Biliary tract (stones) 28 0.2 Common duct 8 0.3 MR cholangiography 32 0.05

Acute Abdomen Imaging-Ultrasound LR+ LR- Biliary tract (stones) 30 0.1 Cholecystitis 29 0.1 Common duct obst 11 0.1 Common duct stone 8 0.2 HIDA scan 10-20 0.05 AAA (nonleaking) 9 0.1 Diverticulitis 18 0.2 Appendicitis 11 0.5 Ectopic TVS (BHGC>1500) 80 0.2

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 hasn’t changed significantly in past decade (data through 1999) Flum, JAMA 2001;286:1748

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

Acute Abdominal Pain -Imaging History & examination and simple lab tests have about a 50-60 % 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

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