Diverticulosis and symptomatic uncomplicated disease

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Most acquired colonic diverticula are asymptomatic anatomical findings. Symptomatic uncomplicated diverticular disease is a clinical attribution made when recurrent symptoms plausibly arise from diverticula but there is no acute diverticular inflammation, abscess, perforation, fistula, stricture or active haemorrhage. Because diverticulosis is common with age, its presence does not close the differential diagnosis.

Assessment therefore has two jobs: characterise the chronic symptom pattern and decide whether present-day evidence requires another route. Conservative care focuses on a balanced fibre-containing diet, adequate fluid, activity and treatment of constipation when needed. Antibiotics do not treat non-inflammatory diverticular symptoms. NICE advises simple analgesia such as paracetamol and avoiding NSAIDs and opioids where possible because of perforation risk; a changed presentation must be re-investigated rather than explained by an old colonoscopy report.

Key points

Diverticulosis means diverticula are present; symptomatic uncomplicated diverticular disease attributes chronic symptoms only after acute inflammation and important alternatives are excluded.
Intermittent left iliac fossa pain with constipation, diarrhoea or mucus may fit, but no symptom pattern proves that incidental diverticula are the cause.
Check prior colonic imaging for quality and date; new anaemia, weight loss, bleeding or persistent bowel-habit change requires a current cancer assessment.
NICE recommends a healthy balanced diet, enough fluid and gradual fibre increase; wholegrain foods, fruit and vegetables are suitable sources.
Do not offer antibiotics without acute diverticulitis. For pain, a suitable adult over 50 kg may use paracetamol 500–1000 mg orally every 6 hours when needed, maximum 4 g in 24 hours; avoid NSAIDs and opioids where possible because NICE links them to perforation risk.
Escalate fever, guarding, vomiting, distension, systemic deterioration or major bleeding instead of continuing chronic symptom treatment.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Age and connective tissue

Diverticula become more common with age as colonic wall structure and neuromuscular function change at vascular penetration points.

Pressure and motility

Segmental pressure, stool consistency, diet, activity and genetic susceptibility interact rather than one factor explaining every diverticulum.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Mucosal herniation
Mucosa and submucosa protrude through weak points where vasa recta cross the circular muscle, creating acquired pseudodiverticula.
2
Altered segmental motility
High-amplitude contractions and disordered neuromuscular signalling can contribute to pain and bowel-habit symptoms without acute inflammation.
3
Visceral sensitivity
Persistent symptoms may reflect sensitisation after inflammation or overlap with functional bowel mechanisms rather than ongoing infection.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Terminology

Diverticulosis is an anatomical finding, whereas symptomatic diverticular disease attributes chronic symptoms to diverticula without acute inflammatory complications.

Symptom pattern

Pain is often intermittent in the left lower abdomen with constipation, diarrhoea or passage of mucus, but no pattern is specific enough to exclude cancer.

Diet and behaviour

A varied fibre-containing diet, adequate fluid and physical activity support bowel function; gradual change reduces bloating and tolerance problems.

Diagnostic uncertainty

Diverticula are common and may be incidental, so persistent symptoms require consideration of irritable bowel syndrome, malignancy, colitis and gynaecological or urinary disease.

Red flags requiring action

Unintentional weight loss, iron-deficiency anaemia, an abdominal or rectal mass, or a persistent new bowel-habit change requires colorectal cancer assessment even when diverticula are already documented.
Fever with constant focal pain or guarding suggests acute diverticulitis, while vomiting and distension raise concern for obstruction.
Large-volume painless haematochezia, syncope or haemodynamic change should be treated as acute lower gastrointestinal bleeding.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Previous colon imagingFirst step
Why
confirm the presence and distribution of diverticula.
Interpretation and limitations
A past finding supports anatomy but does not prove that current symptoms arise from diverticula.
02
Full blood count and CRP
Why
look for anaemia or unexpected inflammation.
Interpretation and limitations
Raised markers or iron deficiency should prompt reconsideration of uncomplicated disease.
03
Colonoscopy or CT colonography
Why
exclude alternative structural disease when indicated.
Interpretation and limitations
Choose the test by cancer risk, symptom pattern, fitness and need for biopsy.
04
Focused abdominal examination
Why
identify focal tenderness, mass or obstruction features.
Interpretation and limitations
Guarding, distension or physiological abnormality changes the route to acute assessment.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Colorectal cancer

Weight loss, anaemia, bleeding or persistent change requires structural assessment because diverticula can coexist with malignancy.

Irritable bowel syndrome

Chronic pain related to defaecation and altered stool may overlap, especially when inflammatory and structural investigations are reassuring.

Inflammatory bowel disease

Bleeding, urgency, nocturnal diarrhoea and raised inflammatory markers suggest colitis; ileocolonoscopy with biopsies defines the distribution and histological pattern.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01Worked case: chronic symptoms with reassuring reassessmentConfirm an uncomplicated pattern and measure responseFirst stepA 64-year-old with sigmoid diverticula documented on a complete, well-prepared colonoscopy 18 months ago has intermittent left-sided discomfort relieved by stool and constipation. Temperature is 36.7°C, abdomen is soft, haemoglobin is 142 g/L and CRP is 2 mg/L; there is no bleeding or weight loss.

1Verify that pain remains intermittent and linked to bowel function, and ask specifically about nocturnal symptoms, bleeding, fever, vomiting, weight change and family history.
2Review the original colonoscopy for caecal intubation, bowel preparation and the absence of a lesion rather than accepting a problem-list label of diverticulosis.
3Explain that diverticula may contribute but are not infected; agree a gradual increase in dietary fibre and fluid and, for painful episodes, paracetamol 1 g orally up to every 6 hours when needed for this adult over 50 kg, without exceeding 4 g in 24 hours or taking another paracetamol-containing product.
4Avoid antibiotics, NSAIDs and opioids, assess liver disease and alcohol intake before the paracetamol plan, and record a baseline of four painful days weekly and bowel movements every three days so benefit can be judged.
5At six-week review the patient reports daily soft stool and one mild painful day weekly, with no alarm feature; continue the tolerated plan and retain explicit acute and cancer safety-netting.

02Changed chronic symptomsDo not let known diverticula mask colorectal cancerA 72-year-old previously labelled with diverticular disease now reports six kilograms of weight loss, daily altered bowel habit and fatigue; haemoglobin is 96 g/L with ferritin 7 micrograms/L.

1Recognise iron-deficiency anaemia and weight loss as discordant with a benign symptom-only label and examine the abdomen and rectum for a mass.
2Use the current symptomatic colorectal pathway, including FIT when appropriate, without allowing a low result to delay referral if a mass or other strong clinical concern is present.
3Arrange urgent complete colonic investigation rather than restarting fibre alone or prescribing empirical antibiotics.
4When colonoscopy shows a stenosing sigmoid adenocarcinoma beside diverticula, take biopsies and enter the staging and colorectal multidisciplinary pathway.
5Document histological confirmation and staging completion, correcting the record so future clinicians do not attribute tumour symptoms to diverticular disease.

03Acute change in painReclassify fever and guarding as possible diverticulitisA patient managed for intermittent symptoms develops constant left iliac fossa pain, temperature 38.4°C, pulse 106/min, focal guarding and CRP 158 mg/L.

1Stop the chronic-care route and arrange same-day surgical assessment because fever, tachycardia and guarding suggest an acute inflammatory complication.
2Assess sepsis and hydration, provide analgesia and obtain blood tests while senior review determines whether immediate treatment is required.
3Obtain contrast CT in secondary care to distinguish uncomplicated diverticulitis from abscess, obstruction or perforation.
4Act on the demonstrated anatomy: a 3.8 cm pericolic abscess requires intravenous antibiotics and discussion of drainage feasibility or surgery.
5Verify source control through serial observations, examination and inflammatory markers rather than returning automatically to the previous dietary plan.

Key medicines and prescribing safety1 treatment · regimens, roles and cautions

Provides a practical non-opioid analgesic option for intermittent symptomatic diverticular disease after an acute complication and important alternative diagnoses have been excluded.

Paracetamol for uncomplicated diverticular pain

For the cited 500 mg effervescent product in an adult aged at least 16 years, weighing more than 50 kg and with normal renal function, dissolve the tablet completely in a full tumbler of water and give 500–1000 mg orally every 6 hours when necessary, maximum 4 g in 24 hours. If GFR is 10–50 mL/min use 500 mg every 6 hours; if GFR is below 10 mL/min use 500 mg every 8 hours.

Check all combination products to prevent duplicate paracetamol, and reduce or avoid dosing in low body weight, liver disease, malnutrition, dehydration or chronic excess alcohol use; overdose can cause fatal hepatic injury. This effervescent product contains 463.01 mg sodium per tablet, so include that load when sodium restriction matters. Repeated or escalating analgesic use requires clinical review of the diagnosis rather than unsupervised continuation.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Acute diverticulitis

Obstruction and inflammation at a diverticular neck can progress from local microperforation to abscess or free contamination.

Diverticular bleeding

A vasa recta stretched over a diverticulum can rupture and produce sudden painless lower gastrointestinal haemorrhage.

Fibrosis or fistula

Repeated complicated inflammation may heal with narrowing or erode into bladder, vagina, skin or adjacent bowel.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Record the frequency, duration and relation of pain to stool so dietary or bowel-regimen benefit is judged against a defined baseline.
Increase fibre gradually and review bloating, stool consistency and hydration; reduce or change the source if symptoms worsen with rapid escalation.
Repeat blood count and activate appropriate colonic investigation when bleeding, anaemia, weight loss or a sustained change in bowel habit appears.
Reclassify constant pain with fever, guarding, vomiting or systemic change as possible acute diverticulitis or obstruction and assess the same day.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Diverticula can be incidental

Common anatomical pouches do not automatically explain every episode of abdominal pain or altered stool.

Inflammation changes the diagnosis

Acute constant pain, fever and raised inflammatory markers move assessment from chronic diverticular disease toward diverticulitis.

Antibiotics have no chronic role

NICE advises against antibacterial treatment for diverticular disease in the absence of acute diverticulitis.

Cancer safety-net remains

New rectal bleeding, iron deficiency, weight loss or sustained bowel-habit change requires a colorectal diagnostic pathway.

11Common pitfallsFrequent interpretation and management errors.

01
Labelling any left-sided abdominal pain diverticular disease without checking alarm features can delay another diagnosis.
02
Prescribing antibiotics for chronic uncomplicated symptoms adds adverse effects and resistance without treating the mechanism.
03
Increasing fibre abruptly despite poor fluid intake may worsen bloating or constipation.
04
Assuming an old complete colonoscopy explains a materially changed presentation can create false reassurance.
05
Using regular NSAIDs or opioids for chronic diverticular discomfort disregards NICE advice to avoid them where possible because they may increase perforation risk.

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