Gastrointestinal Disorders: Anatomy, Physiology, and Clinical Considerations

Overview of Abdominal Cavity

Anatomical Locations

The abdominal cavity contains several vital organs, which are grouped into four quadrants for clinical assessment. Understanding these locations is essential for identifying sources of gastrointestinal symptoms.

Right Upper Quadrant	Left Upper Quadrant
Liver Gallbladder Duodenum Head of pancreas Right kidney & adrenal gland Part of ascending & transverse colon	Stomach Spleen Left lobe of liver Body of pancreas Left kidney & adrenal gland Part of transverse and descending colon
Right Lower Quadrant	Left Lower Quadrant
Cecum Appendix Right ovary and tube Right ureter Right spermatic cord	Part of descending colon Sigmoid colon Left ovary and tube Left ureter Left spermatic cord

Anatomical Considerations: Infants, Children & Older Adults

Infants & Children

Developmental anatomy affects the presentation and assessment of gastrointestinal disorders in pediatric populations.

• Newborns: The umbilical cord is prominent, containing two arteries and one vein.

• Liver: Occupies more space in the abdomen at birth than later in life.

• Term neonates: The lower edge of the liver may be palpated 0.5 to 2.5 cm below the right costal margin.

• Urinary bladder: Located higher in the abdomen than in adults.

• Early childhood: The abdominal wall is less muscular, making organs easier to palpate.

Older Adults

Aging leads to anatomical and physiological changes that impact gastrointestinal function.

• Musculature: Abdominal wall relaxes.

• Salivation: Decreases, causing dry mouth and reduced taste.

• Gastric function: Esophageal emptying and gastric acid secretion are delayed.

• Gallstones: Incidence increases with age.

• Liver: Size decreases, but most functions remain normal; drug metabolism is impaired.

• Constipation: More common due to slower colon motility, medications, and reduced mobility.

• Bowel sensation: Reduced urge to empty bowel; diminished ability to discriminate between passing solids, liquids, or gas.

Normal Bowel Function, Constipation & Bowel Obstruction

Normal Bowel Function

Normal bowel function varies among individuals but is generally defined by regular, strain-free bowel movements and a sense of complete evacuation.

• Frequency: 3 times per day to once every 3 days.

• Quality: Should pass without straining and result in a feeling of complete emptiness.

Constipation

Constipation is characterized by difficulty passing stools or infrequent bowel movements (less than two stools per week).

• Functional constipation: Normal transit but infrequent or difficult passage.

• Mechanical constipation: Obstructive emptying, such as from inflammatory bowel disease.

Bowel Obstruction

Bowel obstruction occurs when the lumen of the bowel is partially or completely blocked, affecting the small or large intestine. It can be functional or mechanical.

• Functional obstruction: Due to impaired motility (e.g., paralytic ileus).

• Mechanical obstruction: Due to physical blockage (e.g., tumor, adhesions).

Common Causes of Constipation in Older Adults

Constipation in older adults is multifactorial, often related to lifestyle, medical conditions, and medications.

• Decreased physical activity

• Inadequate intake of water

• Low-fibre diet

• Side effects of medications (e.g., opioids)

• Irritable bowel syndrome

• Bowel obstruction

• Hypothyroidism

• Inadequate toilet facilities or difficulty ambulating to toilet, leading to stool retention

Constipation: Signs & Symptoms

Recognizing the signs and symptoms of constipation is essential for diagnosis and management.

• Abdominal distension

• Abdominal discomfort

• Reduced appetite

• Headache

• Indigestion

• Trouble passing stool

• Change to usual bowel routine (more infrequent)

• Passing hard stools

• Straining when trying to pass stool

• Passing only small amounts of faeces

• Feeling as though bowels are not completely emptied following bowel motion

Constipation Management

Management of constipation involves lifestyle modifications, dietary changes, and documentation for monitoring.

• Fibre intake:

  • Men: 30 mg/day

  • Women: 25 mg/day

  • Documentation: Food intake chart

• Fluid intake:

  • Women: 2 Litres/day

  • Men: 2.6 Litres/day

  • Documentation: Fluid balance chart

• Physical activity: Increase activity such as walking or swimming

• Documentation of bowel motions:

  • Bowel chart/Bristol stool chart

  • Integrated progress notes

Additional info:

• Pharmacological management of constipation may include bulk-forming agents, osmotic laxatives, and stimulant laxatives, each with specific modes of action and potential adverse effects (e.g., nausea, diarrhoea).

• Assessment of gastrointestinal disorders involves both subjective (patient-reported) and objective (clinically observed) data collection.

• Common causes of gastrointestinal upset include cultural and genetic factors, medications, infections, and metabolic disturbances.