- Sudden onset of severe abdominal pain caused by acute disease of, or injury to, the internal organs
- Abdominal pain is usually accompanied by signs of peritonitis
- In extreme cases gangrene and perforation can occur in under 6 hours
Etiology
Intra-abdominal
- Ruptured abdominal aortic aneurysm (AAA)
- Perforated viscus
- Mesenteric ischemia – suspected in patients with cardiac or atherosclerotic disease
- Ruptured ectopic pregnancy
- Intestinal obstruction
- Appendicitis
- Severe acute pancreatitis
Extra-abdominal
- Testicular torsion or rectus muscle hematoma
- Metabolic – diabetic/alcoholic ketoacidosis, sickle cell disease
- Toxic – spider bite, opioid withdrawal
- Thoracic – myocardial infarction, pneumonia, pulmonary embolism
Pathophysiology
Visceral pain
- Pain from internal organs innervated by autonomic nerve fibres
- Respond mainly to sensations of distension and muscular contraction (not cutting, tearing, irritation)
- Vague, dull, nauseating pain – poorly localised
- Upper abdominal pain from foregut structures – stomach, duodenum, pancreas, liver
- Periumbilical pain from midgut structures – small intestine, proximal colon, appendix
- Lower abdominal pain from hindgut – distal colon, genitourinary tract
Somatic pain
- Pain from parietal peritoneum, which is innervated by somatic nerves
- Respond to irritation from infectious, chemical, inflammatory processes
- Somatic pain – sharp and well localised
Referred pain
- Pain is felt distant from source
- Scapular pain from biliary colic
- Groin pain from renal colic
- Kehr’s sign – pain in the left shoulder due to ruptured spleen
History of present illness
- Age
- Over 50 years old -cholecystitis is more likely than appendicitis
- Under 50 years old – appendicitis, pancreatitis, diverticular disease
- Timing – onset, duration
- Location and character
- Abrupt excruciating pain – ruptured AAA, perforated ulcer, myocardial infarction, biliary/renal colic
- Rapid onset severe pain – acute pancreatitis, ectopic pregnancy, ischemic bowel
- Gradual steady pain – acute cholecystitis, hepatitis, acute app, acute salphingitis
- Relieving/exacerbating factors – position, food
- Associated symptoms
- Gastroenteritis sequence of features – pain → vomiting → diarrhoea
- Acute intestinal obstruction – no peristalsis
- Oesophageal perforation – severe vomiting → intense chest and upper abdominal pain
Physical exam
- Inspection for old surgical scars and distension
- Check for shock signs – diaphoresis, hypotension, pallor, tachycardia, tachypnea
- Percussion for shifting dullness
- Auscultate for bowel sounds
- Palpate and watch for guarding – voluntary or involuntary guarding
- Blumberg sign – rebound tenderness
- Rovsing’s sign – pain in right lower quadrant when left lower quadrant is palpated (appendicitis)
- Murphy’s sign – right upper quadrant pain upon inspiration (cholecystitis)
- Kehr’s sign – splenic rupture and left shoulder pain
- Rectal exam – check tone, prostate, blood, masses, haemorrhoids
Investigations
- Labs
- CBC with differential – Hct (volume status); WBC (infection)
- Urea and electrolytes
- Urine analysis – presence of RBC, WBC, ketones, glucose, bilirubin, specific gravity
- BhCG – pregnancy
- Serum amylase – acute pancreatitis
- Serum aspartate aminotransferase (AAT) – acute hepatitis
- Diagnostic peritoneal lavage – presence of intraperitoneal blood, fluid, pus
- Studies
- XR, US
- Angiogram
- Abdominal CT – AAA, abscess, diverticulitis
Management
- Indications for immediate laparotomy
- Hemodynamically unstable, ruptured AAA, ruptured ectopic pregnancy, hepatic/splenic ruptures
- Indications for urgent laparotomy
- Involuntary guarding; increasing tenderness; sepsis/ischemia
- Abdominal XR shows pneumoperitoneum or intestinal distension
- Angiogram shows mesenteric occlusion
- Complications of acute abdomen
- Obstruction and infarction of tissue
- Perforation
- Abscess formation
- Bacteraemia and septicaemia