Chin Med J (Taipei) 1998;61:S183.

CT of the Acute Abdomen

Jen-Dar Chen, M.D.

Department of Radiology, Veterans General Hospital-Taipei, R.O.C.

Abstract

Introduction

The accurate diagnosis of acute abdominal disorders is one of the most challenging field in emergency medicine. This is due to their overlapping clinical presentations and non-specific findings of physical examination, laboratory data and plain radiographs. The application of high resolution cross-sectional imaging with computed tomography (CT) to the emergency department has had a revolutionary impact on the clinical diagnosis and management of acute abdomen. CT can correctly diagnose the cause of acute abdomens in 95% of patients, and therefore reduce the incidence of negative exploratory laparotomies. Although the patients must be hemodynamically stable enough to undergo a 30- to 45-minute CT study, unlike sonography, CT is not limited in evaluating acutely ill patients with marked obesity, open wounds or severe gastrointestinal ileus. Furthermore, contrast-enhanced CT provides important information of organ perfusion and renal function. The development of spiral CT has even greatly reduced acquisition time, increased scan speed and provided multiplanar reformation for complex anatomic pathology.

CT Application in Acute Abdominal Disorders

A. Blunt and penetrating abdominal trauma
Contrast CT is the imaging modality of choice for abdominal trauma in hemodynamically stable patients. CT can define abdominal solid and hollow organ injuries, either intra- or extraperitoneally, and stage the anatomic extent of organ injuries for guiding initial management.

B. Hepatobiliary diseases
The number and extent of liver abscesses can be sensitively defined by CT scan, although the image features may be variable and often non-specific. Spontaneous rupture of hepatocellular carcinoma with hemoperitoneum can be readily suggested by CT scan. CT is a useful adjunct to sonography in evaluating acute cholecystitis and choledocholithiasis. Furthermore, contrast CT is the best screening examination for infectious cholangitis.

C. Spleen diseases
Splenic abscess and infarction can be defined by contrast CT, but often nonspecific. Clinical correlation and guided needle aspiration is essential for accurate diagnosis.

D. Pancreatic diseases
CT is used to confirm the diagnosis of acute pancreatitis and assess its extent and potential complications, as a guide to management.

E. Urinary system
CT is very valuable in patients with urosepsis who fail to respond to appropriate antibiotic therapy. CT superiorly diagnoses inflammatory diseases of kidneys such as acute pyelonephritis, emphysematous pyelonephritis, renal and perirenal abscesses, pyonephrosis and xanthogranulornatous pyelonephritis. CT can often define the cause of obstructive uropathy and evaluate the renal excretory function. Contrast CT is the preferred non-invasive imaging modality for acute renal infarcts and renal vein thrombosis. Other retroperitoneal and psoas abnormalities are also best evaluated by CT scan.

F. Pelvic disorders
Some pelvic inflammatory diseases (PID) can be occasionally defined by CT.

G. Gastrointestinal (GI) tract disorders
Although plain abdominal radiographs and water-soluble contrast study are the initial diagnostic method of choice in patients with clinically suspected hollow organ perforation, CT is most valuable in diagnosing clinically unsuspected perforations. In cases of GI obstructions, CT can clarify the obstruction sites and causes (GI tumor, peritoneal carcinomatosis, inflammation and adhesions). Closedloop obstruction, intussusception, internal and external hernias, volvulus, gallstone ileus and afferent loop obstruction are readily diagnosed by CT. Contrast CT is the screening imaging examination of choice for ischernic bowel diseases (IBD). CT findings indicating a high probability of IBD include SMA or SMV thrombus, portal or mesenteric venous gas, intramural gas and lack of bowel wall enhancement. Like graded-compression sonography, CT is a useful adjunct to clinical assessment of acute appendicitis. CT is the imaing method of choice in evaluating suspected appendiceal perforation, complicated periappendiceal inflammation, complicated diverticulitis and severe colitis. Spontaneous intramural hemorrhage of the bowel can be well diagnosed by CT in proper clinical settings.

H. Vascular disorders
CT is quite accurate in demonstrating dissection and aneurysm of abdominal aorta and para-aortic hemorrhage, and may be performed in hemodynamically stable patients with questionable aneurysm rupture. Contrast spiral CT angiography (CTA) can provide multiplanar reformated images and 3D display of aortic aneurysm non-invasively.

Conclusion
CT has become the preferred and invaluable imaging modality of choice in evaluating patients with acute abdomens in emergency department, because it is a convenient non-operator-dependent exam that can scan whole abdomen with superb anatomic delineation and reliable organ perfusion evaluation.

[Chin Med J (Taipei) 1998;61:S183.]