The small and large intestines are susceptible to numerous conditions ranging from inflammatory diseases to functional disorders, each requiring specific diagnostic and treatment approaches.

• Coeliac Disease

Disease Overview

Coeliac disease is an autoimmune condition triggered by gluten consumption in genetically susceptible individuals. The immune response damages the small intestinal villi, leading to malabsorption and various systemic symptoms.

Symptoms

Classical symptoms include diarrhoea, weight loss, abdominal distension, and failure to thrive in children. Non-classical presentations may involve fatigue, anaemia, osteoporosis, dermatitis herpetiformis, or neurological symptoms. Some patients remain asymptomatic despite intestinal damage.

Diagnosis

Diagnosis combines serological testing for specific antibodies (anti-tissue transglutaminase, anti-endomysial) with duodenal biopsy showing characteristic villous atrophy. Genetic testing for HLA-DQ2/DQ8 may support diagnosis in uncertain cases.

Treatment

The only effective treatment is lifelong adherence to a strict gluten-free diet, which allows intestinal healing and symptom resolution. Nutritional deficiencies require specific supplementation, and regular monitoring assesses dietary compliance and intestinal recovery.

• Inflammatory Bowel Disease

Crohn’s Disease

Crohn’s disease can affect any part of the gastrointestinal tract, characteristically causing transmural inflammation with skip lesions. The disease often involves the terminal ileum and colon but may affect the mouth, oesophagus, stomach, or perianal area.

Symptoms

Common presentations include abdominal pain, diarrhoea (which may be bloody), weight loss, and fatigue. Extraintestinal manifestations may affect joints, skin, eyes, and liver. Complications include strictures, abscesses, and fistula formation.

Diagnosis

Diagnosis combines clinical presentation with endoscopic findings, histological changes, and imaging studies. Colonoscopy with ileoscopy reveals characteristic features including deep ulcerations, cobblestone appearance, and skip lesions.

Treatment

Treatment aims to induce and maintain remission whilst preventing complications. Options include aminosalicylates for mild disease, corticosteroids for acute flares, immunomodulators for maintenance therapy, and biologic agents for moderate to severe disease.

 • Ulcerative Colitis

Disease Characteristics

Ulcerative colitis causes continuous inflammation limited to the colonic mucosa, typically beginning in the rectum and extending proximally. The extent of disease influences symptoms and treatment approaches.

Symptoms

Characteristic symptoms include bloody diarrhoea, urgency, tenesmus, and lower abdominal cramping. Systemic symptoms such as fatigue, weight loss, and fever may accompany moderate to severe disease.

Diagnosis

Colonoscopy reveals continuous mucosal inflammation with loss of vascular pattern, friability, and ulceration. Histological examination confirms inflammatory changes limited to the mucosa and submucosa.

Treatment

Treatment is tailored to disease extent and severity. Topical aminosalicylates are effective for distal disease, while oral preparations treat more extensive colitis. Severe disease may require hospitalisation and intravenous corticosteroids or rescue therapy with ciclosporin or infliximab.

• Irritable Bowel Syndrome

Understanding IBS

IBS is a functional gastrointestinal disorder characterised by recurrent abdominal pain associated with altered bowel habits. The condition affects gut-brain interactions and intestinal motility without structural abnormalities.

Symptoms

Symptoms include abdominal pain relieved by defecation, altered stool consistency, and changes in bowel frequency. Patients may experience predominantly diarrhoea, constipation, or mixed patterns. Associated symptoms include bloating, mucus in stools, and incomplete evacuation.

Diagnosis

Diagnosis relies on Rome IV criteria requiring recurrent abdominal pain associated with altered bowel habits for at least three months. Investigation focuses on excluding organic disease rather than confirming IBS.

Treatment

Treatment is individualised based on predominant symptoms. Dietary approaches include fibre modification and low FODMAP diets. Pharmacological options target specific symptoms with antispasmodics, laxatives, antidiarrhoeals, or newer agents like eluxadoline.

• Chronic Constipation

Clinical Presentation

Chronic constipation involves infrequent bowel movements, hard stools, straining, or sensation of incomplete evacuation persisting for several months. The condition significantly impacts quality of life and may indicate underlying disorders.

Causes

Primary causes include slow transit constipation and pelvic floor dysfunction. Secondary causes encompass medications, endocrine disorders, neurological conditions, and structural abnormalities.

Treatment

Treatment begins with lifestyle modifications including increased fibre intake, adequate hydration, and regular exercise. Laxatives progress from bulk-forming agents to osmotic and stimulant types. Newer agents like linaclotide and prucalopride offer additional options for refractory cases.

• Obstructive Defecation Syndrome

Pathophysiology

Obstructive defecation syndrome involves functional or structural abnormalities preventing effective rectal evacuation despite adequate propulsive forces. Conditions include pelvic floor dyssynergia, rectocele, and rectal prolapse.

Symptoms

Patients experience prolonged straining, sensation of incomplete evacuation, need for manual assistance, and reduced stool frequency. Associated symptoms may include pelvic pressure or pain.

Treatment

Treatment focuses on the underlying cause and may include pelvic floor physiotherapy, biofeedback training, dietary modifications, and laxative therapy. Severe structural abnormalities may require surgical intervention.

• Colonic Polyps and Colorectal Cancer

Polyp Types and Significance

Colonic polyps represent various growths protruding from the colonic mucosa. Adenomatous polyps carry malignant potential and require removal, while hyperplastic polyps are generally benign.

Screening and Detection

Colorectal cancer screening programmes utilise various methods including faecal immunochemical testing, flexible sigmoidoscopy, and colonoscopy. Colonoscopy remains the gold standard for detection and treatment of polyps.

Treatment

Polypectomy during colonoscopy removes most polyps safely and effectively. Large or complex lesions may require advanced endoscopic techniques or surgical resection. Follow-up surveillance is tailored to polyp characteristics and family history.