Evidence‑Based Assessment of the Acute Abdomen

Clinical Examination Findings

• Large‑bowel obstruction is strongly suggested by abdominal distension together with absence of flatus (≈ 90 %) and absence of feces (≈ 80 %). – World Journal of Emergency Surgery 2018. 1
• Absent bowel sounds are a typical sign of peritonitis or ileus. – World Journal of Emergency Surgery 2018. 2
• Diffuse or localized tenderness with guarding and rebound tenderness indicates peritonitis. – World Journal of Emergency Surgery 2018. 2
• Fever, tachypnea, tachycardia and confusion characterize an acutely ill patient with perforation. – World Journal of Emergency Surgery 2018. 2
• Toxic systemic signs of peritonitis are usually delayed but represent an ominous prognostic indicator. – World Journal of Emergency Surgery 2018. 1
• Positive psoas sign, fever, or migratory pain to the right lower quadrant increases the likelihood of appendicitis. – World Journal of Emergency Surgery 2017. 3
• Vomiting that precedes abdominal pain makes appendicitis unlikely. – World Journal of Emergency Surgery 2017. 3
• Digital rectal examination is indicated when lower‑gastrointestinal pathology is suspected, including palpable rectal cancer. – World Journal of Emergency Surgery 2018. 1

Laboratory Indicators

• Leukocytosis with neutrophilia, elevated serum amylase and lactic acidosis are laboratory patterns that suggest perforation or necrotic abdominal disease. – World Journal of Emergency Surgery 2018 (both studies). [1][2]
• C‑reactive protein > 75 mg/L together with a white‑blood‑cell count > 10 000 mm³ supports a diagnosis of peritonitis, although sensitivity and specificity are modest. – World Journal of Emergency Surgery 2018. 4
• Elevated blood urea nitrogen and metabolic alkalosis are commonly observed in patients with vomiting and dehydration secondary to bowel obstruction. – World Journal of Emergency Surgery 2018. 1
• Stool testing for Clostridioides difficile toxin is recommended when an infectious cause of acute abdomen is suspected. – Journal of Crohn’s and Colitis 2013. 5

Imaging Strategies

• Contrast‑enhanced CT of the abdomen is the primary imaging modality for suspected intra‑abdominal pathology, providing 93–96 % sensitivity and 93–100 % specificity. – World Journal of Emergency Surgery 2018. 2
• For suspected bowel obstruction, bedside abdominal ultrasound (≈ 88 % sensitivity) or plain abdominal radiography (74–84 % sensitivity) serve as first‑line screening tools. – World Journal of Emergency Surgery 2018. 2
• Definitive evaluation of obstruction with CT yields 93–96 % sensitivity and 93–100 % specificity, and also delineates complications such as strangulation. – World Journal of Emergency Surgery 2018. 2
• When CT is unavailable, a water‑soluble contrast enema provides 96 % sensitivity and 98 % specificity for diagnosing obstruction. – World Journal of Emergency Surgery 2018. 2
• In stable patients with suspected perforation, CT is recommended to identify the site and cause of perforation. – World Journal of Emergency Surgery 2018. 2
• If clinical signs of diffuse peritonitis are evident, imaging should not delay urgent surgical intervention. – World Journal of Emergency Surgery 2018. 2
• Ultrasound for perforation demonstrates 76 % specificity, outperforming plain radiography but remaining inferior to CT. – World Journal of Emergency Surgery 2018. 2
• In pregnant patients, ultrasound and magnetic resonance imaging are preferred to limit radiation exposure; low‑dose CT may be employed selectively when diagnosis remains uncertain. – Journal of the American College of Radiology 2020. 6

Diagnostic Accuracy and Pitfalls

• Physical examination detects bowel strangulation with only 48 % sensitivity, even among experienced clinicians. – World Journal of Emergency Surgery 2018. 4
• Plain abdominal radiographs have limited diagnostic value (sensitivity 74–84 %, specificity 50–72 %) and should be reserved for settings where advanced imaging is unavailable. – World Journal of Emergency Surgery 2018. 2
• Incomplete bowel obstruction may present with watery diarrhea, which can be mistaken for gastroenteritis. – World Journal of Emergency Surgery 2018. 4
• Stool passage may still occur in patients with relatively high‑grade obstruction who present early in the disease course. – World Journal of Emergency Surgery 2018. 4
• Elderly patients with bowel obstruction often exhibit less pronounced abdominal pain. – World Journal of Emergency Surgery 2018. 4

Management Recommendations

• Early involvement of a surgical team is essential when perforation is suspected. – World Journal of Emergency Surgery 2018. 2

Abdominal Examination Guidelines

Systematic Approach to Abdominal Examination

• The World Journal of Emergency Surgery recommends observing for abdominal distension, visible peristalsis, pulsations, skin changes, surgical scars, and asymmetry during inspection 7
• Note any signs of peritonitis including guarding, rebound tenderness, or rigidity which may indicate perforation 7
• Be aware that clinical examination may be unreliable in patients with excess skin or flaccid abdomen (such as post-bariatric surgery patients) 8
• Listen for bowel sounds in all four quadrants, noting character, frequency, and pitch during auscultation 7
• Absent bowel sounds may suggest peritonitis or ileus 7
• Hyperactive, high-pitched bowel sounds may indicate early bowel obstruction 7
• Percuss all four quadrants to detect abnormal fluid, masses, or organomegaly 7
• Shifting dullness and fluid thrill should be assessed when ascites is suspected 7
• Percussion can help identify tympany associated with bowel distension or pneumoperitoneum 7
• Begin with light palpation away from areas of reported pain, progressing to deeper palpation 7
• Assess for masses, organomegaly, tenderness, guarding, and rebound tenderness 7
• Perform special maneuvers as indicated (Murphy's sign, psoas sign, obturator sign) 7
• Digital rectal examination should be performed when indicated, especially for suspected lower GI pathology 7

Laboratory Assessment

• Complete blood count, electrolytes, liver enzymes, and inflammatory markers (ESR, CRP) are mandatory in assessing acute abdomen 9
• Serum albumin and pre-albumin help assess nutritional status and degree of inflammation 9
• In suspected infectious causes, rule out Clostridium difficile and Cytomegalovirus 9
• Leukocytosis, neutrophilia, elevated amylase levels, and lactic acidosis may suggest perforation or necrosis 7

Imaging Studies

• CT scan with IV contrast is the recommended primary imaging study for suspected abdominal pathology, with superior sensitivity (93-96%) and specificity (93-100%) 10, 11
• Abdominal ultrasound can be used as a screening test with moderate sensitivity (88%) when CT is unavailable 10
• Plain abdominal X-rays have limited sensitivity (74-84%) and specificity (50-72%) and should only be used when other modalities are unavailable 10
• For suspected bowel obstruction: CT scan is preferred; if unavailable, water-soluble contrast enema is a valid alternative 10
• For suspected perforation: CT scan is recommended for stable patients; however, if there are clear signs of diffuse peritonitis, CT should not delay appropriate treatment 10, 11
• For pregnant patients: Ultrasound and MRI are recommended to limit radiation exposure 8
• For suspected appendicitis: Helical CT of abdomen and pelvis with intravenous contrast is recommended 12
• For female patients of childbearing potential, pregnancy testing should be performed prior to imaging with ionizing radiation 12
• In pregnant women, ultrasound and MRI are preferred; low-dose CT can be used in selected cases 8

Common Pitfalls and Caveats

• Do not delay surgical exploration if there is a high index of clinical suspicion and alarming clinical signs/symptoms, even with negative radiological assessment 8
• Clinical examination may be unreliable in post-bariatric surgery patients due to excess skin and flaccid abdomen 8
• CT scan, even when readily available, should never expose the patient to unsafe delays in appropriate treatment for conditions requiring immediate intervention 10, 11
• Early involvement of a surgeon is required in cases of suspected perforation 11

Abdominal Examination Guidelines

Preparation and Examination Techniques

• The American College of Emergency Physicians recommends having the patient empty their bladder before examination if possible, and documenting all findings systematically, including location and characteristics of any abnormalities, to guide clinical decision-making 13
• For pelvic assessment, consider transvaginal ultrasound with empty bladder or transabdominal ultrasound with full bladder if indicated, as recommended by the American College of Emergency Physicians 13
• Documenting all findings systematically, including location and characteristics of any abnormalities, is crucial for accurate assessment and diagnosis, as emphasized by the American College of Emergency Physicians 13