Overview: Gastrointestinal Dysfunction 

GI dysfunction occurs when normal processes of motility, secretion, digestion, absorption, or elimination are impaired. Causes can be mechanical, inflammatory, infectious, ischemic, or neurogenic, and are often multifactorial. 

1. Obstruction 

Definition: A mechanical or functional blockage preventing passage of intestinal contents. 

Causes 

Mechanical 

Adhesions (most common cause of small bowel obstruction) 
Hernias 
Tumours (colon cancer) 
Volvulus (twisting of bowel) 
Intussusception 
Faecal impaction 

Functional (Ileus) 

Postoperative ileus 
Electrolyte disturbances (↓ K⁺) 
Medications (opioids) 

Effects 

Distension 
Pain (colicky in mechanical obstruction) 
Vomiting 
Constipation or obstipation 
Risk of ischaemia and perforation 

2. Inflammation 

Definition: Tissue injury due to immune or chemical processes. 

Causes 

Inflammatory bowel disease (IBD) 
Crohn’s disease 
Ulcerative colitis (UC) 
Appendicitis 
Pancreatitis 
Cholecystitis 
Diverticulitis 
Gastritis 

Effects 

Oedema → impaired absorption 
Pain 
Altered motility (diarrhoea or ileus) 
Bleeding (especially in UC) 

3. Perforation 

Definition: Full-thickness rupture of the GI wall. 

Causes 
Peptic ulcer disease 
Trauma 
Ischaemia 
Obstruction with pressure necrosis 
Iatrogenic (endoscopy, surgery) 
Severe inflammation (toxic megacolon) 

Effects 

Leakage of bowel contents into peritoneal cavity 
Peritonitis 
Sepsis 
Acute abdomen (surgical emergency) 

4. Infection 

Definition: Invasion of GI tract by pathogenic organisms. 

Types 

Bacterial 
Salmonella 
Shigella 
Campylobacter 
Clostridioides difficile 

Viral 
Norovirus 
Rotavirus 

Parasitic 
Giardia 
Entamoeba histolytica 

Effects 
Diarrhoea 
Vomiting 
Fever 
Dehydration 
Malabsorption (chronic infections) 

5. Ulceration 

Definition: Breakdown of mucosal integrity leading to open lesions. 

Causes 
Helicobacter pylori infection 
NSAIDs 
Stress-related mucosal disease (ICU patients) 
Smoking 
Excess gastric acid (Zollinger–Ellison syndrome) 

Effects 
Epigastric pain 
GI bleeding 
Perforation 
Gastric outlet obstruction (chronic ulcers) 

6. Factors Affecting Gastrointestinal Motility 

A. Autonomic Nervous System 

Parasympathetic (vagus nerve) 
↑ Motility and secretion 

Sympathetic 
↓ Motility and blood flow 
Stress → ileus or constipation 

B. Drugs 

Decrease Motility 
Opioids 
Anticholinergics 
Tricyclic antidepressants 
Antipsychotics 

Increase Motility 
Prokinetics (metoclopramide, erythromycin) 
Laxatives 
Cholinergic agents 

C. Surgery 

Postoperative ileus (especially abdominal surgery) 
Handling of bowel → inflammatory response 
Anaesthesia effects 
Pain and opioid use 

D. Metabolic & Systemic Factors 

Electrolyte imbalances (↓ K⁺, ↓ Mg²⁺) 
Diabetes mellitus (autonomic neuropathy → gastroparesis) 
Hypothyroidism (↓ motility) 
Sepsis and shock (↓ perfusion) 

Key Points

GI dysfunction often involves multiple overlapping mechanisms 
Obstruction + inflammation increases risk of perforation 
Motility disorders may be functional rather than structural 
Always consider medications and recent surgery in assessment