Las enfermedades gastrointestinales inferiores afectan el colon, recto y ano — un espectro que va desde trastornos funcionales (el SII afecta al ~10–15 % de la población mundial) hasta malignidades potencialmente mortales (el cáncer colorrectal es el 3er cáncer más común en el mundo, con 1,9 millones de nuevos casos al año). La colonoscopia es la piedra angular del diagnóstico y tratamiento del GI inferior — permitiendo visualización directa, biopsia, extirpación de pólipos (polipectomía, EMR, ESD) e intervenciones terapéuticas incluyendo dilatación con balón para las estenosis de la enfermedad de Crohn. Esta guía cubre las principales enfermedades del GI inferior, los procedimientos colonoscópicos y las estrategias de manejo alineadas con las guías BSG, ESGE y ECCO.
Overview of Lower GI Diseases
The lower gastrointestinal tract comprises the small intestine (jejunum and ileum), the large intestine (colon), the rectum, and the anus. Diseases affecting this region range from common functional disorders like irritable bowel syndrome (IBS) to serious conditions including colorectal cancer, inflammatory bowel disease (IBD), and diverticular disease.
Colonoscopy — a flexible camera examination of the entire colon — is the gold-standard diagnostic and therapeutic tool for lower GI disease. It allows direct visualisation of the colonic mucosa, biopsy of suspicious lesions, and removal of polyps before they become cancerous.
When to see a doctor
Rectal bleeding, persistent change in bowel habits, unexplained weight loss, abdominal pain lasting more than a few weeks, or anaemia without obvious cause should all prompt prompt medical evaluation.
Lower GI pathology encompasses neoplastic, inflammatory, functional, vascular, and structural disease. Risk stratification tools — including the FIT (faecal immunochemical test), NICE DG30 guidelines, and Manchester scoring — guide appropriate investigation pathways. Colonoscopy remains the definitive tool; however, CT colonography (virtual colonoscopy) is an accepted alternative in patients unfit for or declining optical colonoscopy. Capsule colonoscopy and AI-assisted adenoma detection are emerging adjuncts.
| Condition | Category | Key Investigation | Colonoscopy Role |
|---|---|---|---|
| Colorectal Cancer | Neoplastic | Colonoscopy + biopsy, CT staging, CEA | Diagnosis, tattooing, palliative stenting |
| Colorectal Polyps | Pre-neoplastic | Colonoscopy | Polypectomy (snare, EMR, ESD) |
| Crohn's Disease | Inflammatory (IBD) | Colonoscopy + ileoscopy, MRE, CRP, calprotectin | Diagnosis, surveillance, stricture dilation |
| Ulcerative Colitis | Inflammatory (IBD) | Colonoscopy + biopsy, calprotectin, CRP | Diagnosis, dysplasia surveillance |
| Diverticular Disease | Structural | CT abdomen, colonoscopy (elective) | Diagnosis, haemostasis for bleeding |
| IBS | Functional | Clinical (Rome IV criteria); exclusion of organic disease | Exclusion of IBD / malignancy |
Anatomy of the Lower GI Tract
Small Intestine
6–7 metres long; divided into duodenum, jejunum, and ileum. Primary site of nutrient absorption. Crohn's disease frequently affects the terminal ileum.
Colon (Large Intestine)
~1.5 metres long; divided into ascending, transverse, descending, and sigmoid segments. Absorbs water and electrolytes; forms and stores faeces. Most colorectal cancers arise here.
Rectum
The final 15 cm of the large bowel before the anus. Stores faeces before defecation. Rectal cancer has distinct treatment pathways from colon cancer, including neoadjuvant chemoradiotherapy.
Caecum & Appendix
The caecum is the junction between small and large intestine. The appendix is a small pouch arising from the caecum; appendicitis is one of the most common surgical emergencies.
Clinical Note — Colonoscopic Landmarks
Complete colonoscopy is defined by caecal intubation, confirmed by visualisation of the appendiceal orifice and ileocaecal valve, ideally supplemented by photodocumentation. The hepatic and splenic flexures are technically demanding; right-sided colon (ascending + caecum) harbours a disproportionate share of interval cancers — often flat or sessile serrated lesions missed on inadequate withdrawal. Withdrawal time ≥6 minutes is strongly correlated with adenoma detection rate (ADR). The ADR benchmark is ≥25% (≥20% in women, ≥30% in men) per BSG / ESGE quality standards.
Colorectal Cancer (CRC)
Colorectal cancer (CRC) is cancer of the colon or rectum. It is the third most common cancer worldwide and the second leading cause of cancer-related death. The good news is that it is one of the most preventable and treatable cancers when caught early — which is why screening programmes are so important.
Most colorectal cancers develop slowly over many years from benign growths called polyps. Regular colonoscopy screening allows these polyps to be detected and removed before they become cancerous — effectively preventing the disease from developing.
CRC staging follows the TNM system (UICC/AJCC 8th edition) and is complemented by the Dukes classification. MSI (microsatellite instability) and KRAS/NRAS/BRAF mutational status are mandatory for metastatic CRC to guide immunotherapy and anti-EGFR therapy eligibility. Lynch syndrome (hereditary non-polyposis colorectal cancer) accounts for 3–5% of all CRC; universal MMR/MSI testing of all CRC specimens is recommended by ESGE and BSG.
Warning Signs
Symptoms to Watch For
- Rectal bleeding or blood in stool
- Persistent change in bowel habits (>3 weeks)
- Unexplained weight loss
- Abdominal pain or bloating
- Feeling of incomplete bowel emptying
- Iron-deficiency anaemia (fatigue, pallor)
Key Risk Factors
- Age over 50
- Family history of CRC or polyps
- Personal history of polyps or IBD
- Hereditary syndromes (Lynch, FAP)
- High-red-meat / processed-meat diet
- Obesity, physical inactivity, smoking, alcohol
| TNM Stage | Dukes | Description | 5-yr Survival |
|---|---|---|---|
| I | A | Confined to bowel wall (submucosa or muscularis propria) | ~90% |
| II | B | Through bowel wall, no node involvement | ~75% |
| III | C | Regional lymph node involvement | ~50% |
| IV | D | Distant metastases (liver, lung, peritoneum) | ~14% |
Colorectal Polyps
Colorectal polyps are small growths on the inner lining of the colon or rectum. Most are harmless, but certain types — particularly adenomatous polyps — can slowly become cancerous over 10–15 years if left untreated. Removing them during colonoscopy (polypectomy) is one of the most effective cancer-prevention strategies available.
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Tubular Adenoma
Most common; low-grade dysplasia; low cancer risk if small
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Villous Adenoma
Higher malignant potential; often sessile and larger
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Sessile Serrated Lesion
Flat, right-sided; responsible for many interval cancers; easily missed
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Hyperplastic Polyp
Generally benign; no surveillance required if small and distal
Post-Polypectomy Surveillance — BSG 2020 Guidelines
| Risk Category | Finding | Surveillance Interval |
|---|---|---|
| Low | 1–2 adenomas <10 mm, low-grade dysplasia | No surveillance; return to population screening |
| Intermediate | 3–4 small adenomas, or 1–2 adenomas ≥10 mm | 3 years |
| High | ≥5 adenomas, or ≥1 adenoma ≥20 mm, or any HGD | 1 year |
| Serrated | SSL ≥10 mm or with dysplasia; ≥3 SSLs | 3 years |
Inflammatory Bowel Disease (IBD)
Inflammatory bowel disease (IBD) is a term for two chronic conditions that cause inflammation of the digestive tract: Crohn's disease and ulcerative colitis (UC). IBD is a lifelong condition that follows a relapsing-remitting course. While there is currently no cure, effective treatments can control symptoms and achieve long-term remission.
Crohn's Disease
- Can affect any part of the GI tract (mouth to anus)
- Transmural inflammation; skip lesions; cobblestone appearance
- Symptoms: diarrhoea, abdominal cramps, weight loss, fatigue
- Complications: strictures, fistulae, abscesses, perianal disease
- Endoscopic balloon dilation used for short fibrostenotic strictures
Ulcerative Colitis
- Confined to the colon and rectum; always involves the rectum
- Mucosal inflammation only; continuous involvement
- Symptoms: bloody diarrhoea, urgency, tenesmus, cramping
- Complications: toxic megacolon, fulminant colitis, dysplasia / CRC
- CRC surveillance colonoscopy from 8–10 years after diagnosis
IBD Therapy Ladder & Biologics
| Step | Drugs | Indication |
|---|---|---|
| 1st line | 5-ASA (mesalazine) — UC; corticosteroids (induction) | Mild-moderate UC; induction of remission |
| 2nd line | Azathioprine, 6-MP, methotrexate | Steroid-dependent / chronic active disease |
| 3rd line | Anti-TNF (infliximab, adalimumab), vedolizumab, ustekinumab, JAK inhibitors | Moderate-severe IBD refractory to immunomodulators |
| Surgery | Colectomy (UC), resection / strictureplasty (Crohn's) | Medically refractory disease, complications, dysplasia, CRC |
Diverticular Disease
Diverticula are small pouches that bulge outward through weak spots in the colon wall. Having these pouches — diverticulosis — is very common and usually causes no problems. Diverticulitis occurs when one or more of the pouches becomes inflamed or infected, causing pain and other symptoms.
Diverticulosis
Presence of diverticula without inflammation. Affects >50% of people over 70. Often asymptomatic — discovered incidentally during colonoscopy.
Acute Diverticulitis
Inflammation / infection of diverticula. Left iliac fossa pain, fever, altered bowel habit. CT abdomen is the diagnostic standard. Treated with antibiotics ± surgery for complications.
Diverticular Bleeding
Most common cause of significant lower GI bleeding in the elderly. Usually painless, right-sided, and self-limiting. Colonoscopy + haemostasis (clip, thermal) for persistent bleeding.
Prevention & Management
Irritable Bowel Syndrome (IBS)
IBS is a common functional bowel disorder characterised by abdominal pain associated with altered bowel habits (diarrhoea, constipation, or both) in the absence of structural or biochemical abnormalities. It affects up to 10–15% of the global population and significantly impairs quality of life.
IBS is a diagnosis of exclusion — meaning other serious conditions must be ruled out first. Colonoscopy may be recommended to exclude IBD, microscopic colitis, or colorectal cancer, particularly in patients with alarm features (rectal bleeding, weight loss, age >45 at onset, family history of CRC).
IBS is diagnosed using Rome IV criteria: recurrent abdominal pain ≥1 day/week for the last 3 months, associated with ≥2 of: related to defecation; associated with change in stool frequency; associated with change in stool form. Subtypes: IBS-D (diarrhoea-predominant), IBS-C (constipation-predominant), IBS-M (mixed), IBS-U (unsubtyped). Investigation: FBC, CRP, tTG-IgA (coeliac serology), faecal calprotectin (<50 µg/g has high NPV for IBD). Colonoscopy indicated if FCP elevated or alarm features present.
Dietary Management
- • Low-FODMAP diet (first-line dietary intervention)
- • Regular meal timing; avoid large meals
- • Reduce caffeine, alcohol, and carbonated drinks
- • Soluble fibre for IBS-C; avoid insoluble fibre in IBS-D
- • Probiotics: limited but emerging evidence
Pharmacological Options
- • Antispasmodics (mebeverine, hyoscine) — abdominal cramps
- • Loperamide — IBS-D symptom control
- • Laxatives (macrogol) — IBS-C
- • Low-dose tricyclic antidepressants — pain modulation
- • Linaclotide / plecanatide — IBS-C (NICE-approved)
Colonoscopia y diagnóstico: polipectomía, EMR, ESD y dilatación con balón
Colonoscopy is the most thorough way to examine the entire colon. A thin flexible tube with a camera and light is guided through the rectum and colon while the patient is under mild sedation. Polyps found during the procedure can often be removed immediately. The preparation involves bowel cleansing the day before with a laxative solution.
Optical Colonoscopy
Gold standard; diagnostic and therapeutic in the same session
CT Colonography
Non-invasive alternative; no biopsy capability; detects polyps ≥6 mm
FIT / Stool Testing
Non-invasive screening; positive result triggers colonoscopy referral
Endoscopic Resection Techniques
| Technique | Indication | Key Points |
|---|---|---|
| Cold snare polypectomy | Polyps <10 mm (especially <5 mm) | No electrocautery; lower bleeding risk; preferred for SSLs |
| Hot snare polypectomy | Pedunculated polyps 10–20 mm | Electrocautery; risk of delayed bleeding; clip prophylaxis for large stalks |
| EMR (Endoscopic Mucosal Resection) | Sessile lesions 10–20 mm | Submucosal injection lifts lesion; piecemeal if large; surveillance at 3–6 months |
| ESD (Endoscopic Submucosal Dissection) | >20 mm lesions requiring en-bloc resection | Technically demanding; longer procedure; lower recurrence vs piecemeal EMR |
| Balloon Dilation | Crohn's strictures of the colon / ileocolonic anastomosis | Short (<5 cm), fibrostenotic strictures; through-the-scope balloon; fluoroscopy optional |
Clinical Insights & Current Guidelines
BSG / ESGE 2023–2024 Key Updates
- • ESGE 2022 Quality Colonoscopy guideline: ADR ≥25% is a mandatory performance indicator; ADR <15% is a patient safety concern requiring retraining.
- • Bowel preparation: split-dose or day-of preparation is superior to previous day-only; BSG 2022 endorses low-volume preparations (1L + ascorbic acid) as equivalent to 2L or 4L high-volume preparations.
- • AI-assisted colonoscopy (CADe systems): ESGE recommends CADe systems as adjuncts to improve ADR, particularly for right-sided flat lesions. Not yet a substitute for technique.
- • Lynch syndrome: universal MMR testing of all new CRC diagnoses now recommended (BSG/ACPGBI 2020); colonoscopic surveillance every 1–2 years from age 25.
- • Crohn's stricture dilation: short (<5 cm), non-prestenotic, fibrostenotic ileocolonic strictures are suitable for through-the-scope balloon dilation; success rate ~85% at 12 months.
Balloon Dilation in Lower GI Disease
Endoscopic balloon dilation of colonic and ileocolonic strictures in Crohn's disease is a well-established technique that delays or avoids surgery in selected patients. The Amara 3-Stage Balloon Dilator provides progressive, controlled radial force across three sequential stages within a single catheter, reducing the need for multiple device exchanges and allowing the endoscopist to titrate dilation precisely. For anastomotic strictures post-colonic resection, stepwise dilation (typically 15→18→20 mm) minimises perforation risk. High-pressure balloons are required for fibrotic post-inflammatory strictures. Injection of long-acting corticosteroid (triamcinolone) at the stricture margin at time of dilation reduces recurrence in refractory cases.
Single-Use Endoscopes in Lower GI Endoscopy
The lower GI endoscopy landscape is seeing increasing adoption of single-use flexible sigmoidoscopes and colonoscopes, driven by infection control requirements (particularly post-COVID-19), reducing reprocessing burden, and improving access in outpatient and remote settings. Single-use devices eliminate the risk of transmission of prions, biofilm-forming organisms, and emerging pathogens (e.g. CRE) that have been linked to reusable endoscope channels despite high-level disinfection. Envaste's single-use scope portfolio supports this transition.
Preguntas frecuentes: Enfermedades del GI inferior
¿Cuáles son las señales de alarma del cáncer colorrectal?
Las señales de alarma del cáncer colorrectal incluyen sangrado rectal o sangre en las heces, un cambio persistente en los hábitos intestinales de más de 3 semanas, pérdida de peso inexplicada, dolor o distensión abdominal, sensación de evacuación incompleta y anemia ferropénica. Estos síntomas requieren evaluación médica urgente. El cáncer colorrectal es muy tratable cuando se detecta precozmente — con tasas de supervivencia a 5 años superiores al 90 % en estadio I.
¿Cuál es la diferencia entre la enfermedad de Crohn y la colitis ulcerosa?
Ambas son formas de enfermedad inflamatoria intestinal (EII). La enfermedad de Crohn puede afectar cualquier parte del tracto GI de la boca al ano, causa inflamación transmural (de espesor completo) y puede implicar lesiones en salto, estenosis y fístulas. La colitis ulcerosa se limita al colon y recto, causa inflamación mucosa continua comenzando siempre en el recto, y se presenta con diarrea sanguinolenta, urgencia y tenesmo. La colonoscopia con biopsia es esencial para el diagnóstico y la diferenciación.
¿Con qué frecuencia debo hacerme una colonoscopia de cribado del cáncer?
Para personas de riesgo promedio, el cribado por colonoscopia se recomienda generalmente a partir de los 45–50 años (según las guías nacionales). Si no se encuentran pólipos, la siguiente colonoscopia se recomienda en 10 años. Las personas con pólipos adenomatosos requieren vigilancia más temprana (1–3 años según tamaño y número). Quienes tengan antecedentes familiares de cáncer colorrectal, síndrome de Lynch, PAF o EII de larga evolución pueden necesitar cribado a una edad más joven y con mayor frecuencia.
¿Qué es una colonoscopia y qué ocurre durante el procedimiento?
Una colonoscopia utiliza una cámara fina y flexible (colonoscopio) introducida por el recto para examinar todo el colon. Se realiza con sedación suave. El día anterior, se toma una preparación intestinal (solución laxante) para vaciar el colon. Durante el procedimiento, el endoscopista visualiza la mucosa colónica, toma biopsias y extirpa pólipos inmediatamente mediante polipectomía. El procedimiento dura 20–45 minutos. La colonografía CT (colonoscopia virtual) es una alternativa no invasiva para pacientes que no pueden someterse a una colonoscopia óptica.
¿Puede la dilatación con balón tratar las estenosis de la EII sin cirugía?
Sí — la dilatación endoscópica con balón es un tratamiento bien establecido para estenosis ileocolónicas y anastomóticas cortas (<5 cm) y fibrostenóticas en la enfermedad de Crohn. Se introduce un catéter con balón a través del colonoscopio y se infla para dilatar gradualmente el segmento estenótico. Las tasas de éxito alcanzan aproximadamente el 85 % a los 12 meses. Evita o retrasa la cirugía en pacientes seleccionados. Se utilizan balones de alta presión para estenosis fibróticas, y la inyección de corticoides en el momento de la dilatación puede reducir la recurrencia en casos refractarios.