Acute abdomen
DEFINITION AND SURGICAL IMPORTANCE
Acute abdomen is sudden or rapidly progressive abdominal pain requiring urgent assessment because a time-critical intra-abdominal or extra-abdominal disorder may need emergency treatment. It is a clinical syndrome, not a final diagnosis. The immediate priorities are to identify shock, peritonitis, haemorrhage, obstruction, ischaemia and pregnancy-related emergencies.
CLASSIFICATION AND CAUSES
Major mechanisms include inflammatory (appendicitis, cholecystitis, pancreatitis, diverticulitis), perforation (peptic ulcer or bowel), obstruction (adhesions, hernia, tumour, volvulus), vascular (mesenteric ischaemia, ruptured aneurysm), haemorrhagic (ectopic pregnancy, splenic rupture), traumatic and gynaecological/urological causes. Extra-abdominal mimics include myocardial infarction, pneumonia, pulmonary embolism, diabetic ketoacidosis and herpes zoster.
PATHOPHYSIOLOGY AND PAIN PATTERNS
Visceral pain arises from distension, stretch or ischaemia of hollow organs and is often poorly localised. Parietal pain results from peritoneal irritation and is sharp and localised, worsened by movement or coughing. Referred pain is perceived at a distant site sharing spinal segments. Peritonitis produces guarding and rigidity; vascular compromise may cause severe pain out of proportion to early examination findings.
HISTORY AND EXAMINATION
Establish onset, site, character, radiation, severity, progression, migration, aggravating/relieving factors and associated vomiting, bowel changes, urinary symptoms, fever, bleeding or syncope. Ask about previous operations, hernias, gallstones, ulcers, vascular disease, medications, anticoagulants, alcohol and pregnancy possibility. Examine vital signs and general appearance first, then inspect, auscultate, percuss and palpate gently. Look for distension, scars, hernias, masses, organomegaly, peritonism and pulsatile aneurysm. Examine groins, external genitalia and perform pelvic/rectal examination when clinically indicated.
INVESTIGATIONS
Immediate tests commonly include FBC, electrolytes, renal function, liver tests, lipase, CRP, glucose, venous blood gas/lactate, coagulation, urinalysis, pregnancy test and group/crossmatch. ECG and troponin are appropriate when cardiac disease is possible. Ultrasound is useful for biliary, pelvic, pregnancy and aortic pathology. Contrast CT abdomen/pelvis is central in stable adults when diagnosis is uncertain or serious pathology is suspected. Imaging must not delay surgery in an unstable patient with clear peritonitis or haemorrhage.
MANAGEMENT AND RED FLAGS
Resuscitate using ABCDE, IV access, fluids/blood as indicated, analgesia, antiemetics, nil by mouth and urine-output monitoring. Give early antibiotics for suspected intra-abdominal sepsis/perforation. Obtain urgent surgical review for haemodynamic instability, peritonitis, persistent severe pain, gastrointestinal bleeding, suspected ischaemia, incarcerated hernia, obstruction or pregnancy-related emergency. Definitive treatment is cause-specific and may be operative, endoscopic, radiological or medical. Reassess repeatedly: evolving signs are often more informative than a single examination.