--- module: 049-02 language: en chapter: 49 title: "Gastrointestinal History, Examination, Investigations, and Acute Presentations" module_title: "Bedside abdominal reasoning, physiological consequences, and time-critical investigation" source_sha256: 0da3ce892f5b437308d7938c46ef728a9c813b01997630a0018d54ca5cacd3c2 --- # Bedside abdominal reasoning and time-critical tests ## History as a physiological map ### Pain onset and movement trace inflammation spread ### Vomit content estimates level and duration ### Stool features separate bleeding, inflammation, malabsorption ### Urgency: perfusion, sepsis, peritonism, organ failure ## Pain mechanisms and history ### Visceral pain poorly localised #### Afferents converge across spinal segments #### Foregut epigastric, midgut periumbilical, hindgut lower ### Parietal peritoneum: sharp, local, worse on cough #### Central to focal migration reflects this shift #### Muted in older, immunosuppressed, pregnant patients ### Sudden maximal pain: perforation, occlusion, rupture ### Colic: contraction against resistance #### Biliary pain often steady after onset ### Pain out of proportion suggests mesenteric ischaemia #### Mucosa hypoxic before peritoneum inflamed ### Give analgesia promptly, examine repeatedly ### Record timing, radiation, pretest modifiers #### Improvement alone does not exclude danger ## Consequences of vomiting ### Gastric acid loss gives metabolic alkalosis #### Volume contraction drives sodium retention #### Distal potassium and hydrogen loss follows ### Low potassium impairs motility and conduction #### Worsens obstruction and vomiting ### Distal bowel loss of bicarbonate gives acidosis ### Replace chloride and potassium, not only water ### Stopped vomiting is not resolved obstruction ## Bleeding severity and resuscitation ### Colour does not indicate severity #### Coffee grounds can coexist with active bleeding #### Melaena may come from small bowel or right colon #### Brisk upper bleeding can give bright rectal blood ### First haemoglobin may be normal ### Perfusion signs and ongoing loss guide resuscitation ### Haemoglobin fall also reflects dilution ### Source, haemostasis, restarting antithrombotics separate ## Examination ### Starts before touch #### Motionless patient suggests peritoneal irritation #### Restlessness more typical of colic ### Resuscitate first if shock or altered consciousness ### Voluntary guarding eases, rigidity persists ### Rebound testing unnecessary and painful ### Pulsatile mass with shock: do not press ### Bowel sounds have low discriminatory accuracy #### Distension, obstipation, imaging more useful ## Laboratory tests and pregnancy ### Tests measure consequences and competing mechanisms ### Lipase supports pancreatitis only in a compatible syndrome ### Normal lactate possible in early ischaemia #### Biomarker never overrides high-risk anatomy ### Pregnancy testing whenever biologically possible #### Do not rely on relationship status alone #### Uterus displaces organs, signs differ #### Needed imaging not delayed by fear ## Imaging and endoscopy ### Imaging follows the question and stability ### Ultrasound fast but operator and gas dependent ### Computed tomography finds transition points ### Angiography urgent: portal phase misses vessels ### Uncontrolled bleeding may need theatre instead ### Endoscopy needs physiological preparation #### Bowel preparation worsens dehydration, electrolytes #### Full colonoscopy in severe colitis risks perforation #### Capsule may lodge, patency assessment reduces risk ## Obstruction and perforation ### Mechanical or functional, simple or strangulated ### Closed loop obstructed at two points #### Distension compromises venous then arterial flow ### Distension creates a self-worsening cycle #### Barrier fails, translocation, necrosis, perforation ### Colicky to constant pain demands reassessment ### Perforation releases gas and contents #### Free gas absent in contained or small leaks #### Question is controllable contamination and viability ## Mimics and serial reassessment ### Extra-abdominal causes: myocardial, pneumonia, ketoacidosis ### Fluid response does not prove the problem solved ### Compare the same sites with time and examiner ### A soft abdomen does not exclude ischaemia ## Safe discharge ### Needs more than pain improvement ### Explicit return triggers explained ### Owners assigned for pending results ### Teach-back of warning signs and plan ### Discharge transfers surveillance to the community