The acute abdomen

• The acute abdomen refers to the rapid onset of severe symptoms of abdominal pathology, which may require surgical intervention.
• Surgical GI causes:

  • Appendicitis
  • Mechanical bowel obstruction
  • Perforated viscus
  • Bowel ischaemia
  • Diverticulitis
  • Strangulated hernia
  • Sigmoid volvulus
• Surgical hepatopancreaticobiliary causes:

  • Acute pancreatitis
  • Acute cholecystitis
  • Biliary colic
  • Obstructive +/- cholangitis
• Surgical urological causes:

  • Ureteric colic
  • Testicular torsion
• Surgical gynaecological causes:

  • Ruptured ectopic pregnancy
  • Ovarian torsion
  • Ovarian cyst rupture
  • Salpingitis
• Surgical vascular causes:

  • Ruptured AAA
  • Aortic dissection
• Medical differentials of an acute abdomen:

  • Myocardial infarction
  • Spontaneous bacterial peritonitis
  • Colitis (inflammatory or infective)
  • DKA
  • Pyelonephritis
  • Acute urinary retention
  • Constipation
  • Gastroenteritis
• Typical symptoms:

  • Severe abdominal pain - often sudden onset, may be localised or diffuse
  • Nausea and vomiting
  • Change to bowel habit
• Patterns of pain:

  • Appendicitis - migratory
  • Mechanical BO - colicky, often intermittent
  • Diverticulitis - LLQ pain (can be RLQ, especially in Asians)
  • Pancreatitis - epigastric pain radiating to the back
  • Cholecystitis - RUQ pain radiating to right shoulder or back, triggered by fatty foods
  • Ureteric/renal colic - colicky, loin to groin pain
  • Ovarian torsion - sharp lower quadrant pain radiating to the leg or back
  • Aortic dissection - sudden tearing pain radiating to the back
• Other important areas to cover in the history include:

  • Urinary and gynaecological symptoms: dysuria, haematuria, vaginal bleeding or discharge
  • Type and time of last meal
  • Past medical and surgical history
  • Last menstrual period: in women of reproductive age
  • Medication use: anticoagulants, corticosteroids, regular non-steroidal anti-inflammatory drugs, immunosuppressants
  • Social history: alcohol, smoking
  • Family history
• AMPLE is a useful acronym for remembering key features of a surgical history, especially in an acute situation: 

  • Allergies
  • Medications
  • Past medical history
  • Last eaten/drunk
  • Events leading to admission
• Clinical findings on exam:

  • Abdominal tenderness: localised or diffuse
  • Peritoneal signs: guarding or rigidity, percussion tenderness, pain on coughing, patient lying very still
  • Abdominal distension
  • Altered bowel sounds: tinkling (early bowel obstruction), reduced or absent (late bowel obstruction, bowel perforation)
  • Irreducible hernia
  • Surgical scars: possible adhesions
• Other relevant clinical examinations may include:

  • PR examination: blood (fresh or black tar-like (melaena)), faecal impaction, tumour
  • Testicular examination: swollen, tender, high-riding testicle in testicular torsion, which may present as lower abdominal pain
  • Pelvic examination: performed if gynaecological pathology is suspected
• Red flags:

  • Signs of shock
  • Pain characteristics - sudden onset severe pain, interrupting sleep, worst ever or tearing, pain out of proportion to findings
  • Signs of peritonitis - guarding or rigidity, percussion tenderness
  • Associated symptoms - faeculent or bilious vomiting, haematemesis, haematochezia or melaena
  • Exam findings - gross distension, absent or altered bowel sounds
• Bedside investigations:

  • Vital signs
  • Urinalysis - identify infection or isolated haematuria suggestive of renal stone
  • Pregnancy test - ectopic pregnancy
  • ECG - MI in patients with epigastric pain or AF as a risk factor for mesenteric ischaemia
• Lab investigations:

  • FBC
  • U&Es - AKI with vomiting and dehydration or obstructive urinary pathology, deranged electrolytes with vomiting
  • CRP
  • LFTs - gall stone pathology
  • Amylase - significantly raised in pancreatitis, moderately raised in other acute pathology
  • Coagulation
  • Group and save
• Imaging:

  • Guided by clinical status and working diagnosis
  • Rarely, patients may be taken to surgery without definitive imaging
  • CT abdomen and pelvic with IV contrast is the imaging of choice in patients who are critically unwell and can diagnose most causes of acute abdomen
  • In stable patients, certain diagnoses are best investigated with alternative imaging modalities
• Ultrasound abdomen:

  • Gallstones
  • Acute cholecystitis
  • Acute pancreatitis
• non contrast CT KUB:

  • Renal colic
• CT angiogram:

  • Mesenteric ischaemia
• Transverse ultrasound:

  • Gynaecological
• In pregnant women with acute abdominal pain, ultrasound and/or MRI abdomen & pelvis are the preferred first-line imaging modalities to avoid foetal radiation exposure. 
• Plain X-rays are less useful in diagnosing acute surgical pathology but may be performed as screening tools:

  • Erect chest X-ray: free air under diaphragm suggestive of bowel perforation
  • Abdominal X-ray: dilated bowel loops suggestive of obstruction
• Initial management consists of:

  • ABCDE approach
  • Nil-by-mouth (NBM): pre-operative or bowel rest in obstruction
  • Intravenous fluids: replace losses associated with vomiting and sepsis
  • Broad-spectrum antibiotics: according to local guidelines
  • Analgesia
  • Anti-emetics
  • Nasogastric tube (NGT): if significant vomiting
  • Urinary catheter: in acute urinary retention and/or to monitor fluid balance