Diverticulitis — Assessment & Management

Safety

Red Flags — Perforation, Abscess, Fistula & Malignancy

Done

Left iliac fossa pain + generalised peritonism + rigidity + absent bowel sounds + haemodynamic instability Perforated diverticulitis (Hinchey III-IV — purulent or faecal peritonitis). → 999. Emergency Hartmann's procedure (colectomy + end colostomy) or peritoneal lavage. Mortality 25-40%.

Persistent severe LIF pain + fever + failure to resolve after 72h antibiotics + palpable tender LIF mass Diverticular abscess (Hinchey II — pericolic abscess ≥3 cm). → Same-day hospital. CT abdomen/pelvis with contrast. IR-guided percutaneous drainage (abscesses >3 cm). IV antibiotics.

LIF pain + pneumaturia (gas passed per urethra) + faecaluria + recurrent UTIs with mixed organisms Colovesical fistula from diverticular disease (most common cause of colovesical fistula). → Urgent colorectal surgery. CT cystogram or cystoscopy. Elective surgical resection (laparoscopic sigmoidectomy).

Diverticulitis episode in patient age <40 + family history of CRC + iron deficiency anaemia + rectal bleeding Colorectal cancer (CRC) may mimic or complicate diverticular disease — particularly in younger patients. → 2WW colorectal cancer. Colonoscopy 6-8 weeks after acute episode resolves.

Massive painless lower GI haemorrhage (filling toilet bowl with blood) in a patient with known diverticular disease Diverticular haemorrhage — most common cause of major lower GI bleed in the UK. → 999. IV access. Cross-match 4 units. CT angiography. Colonoscopic haemostasis or interventional radiology embolisation.

Recurrent diverticulitis (≥2 episodes) + ongoing LIF pain between episodes + worsening + young patient (<50) Complicated diverticular disease — high recurrence risk. Consider elective laparoscopic sigmoid colectomy. → Colorectal surgery referral. CRC exclusion colonoscopy first.

The Hinchey classification of perforated diverticulitis determines surgical management and prognosis — Stage I: pericolic abscess (confined to mesentery adjacent to perforated segment) — IV antibiotics, likely conservative; Stage II: pelvic/distant abscess — IR drainage + IV antibiotics; Stage III: generalised purulent peritonitis (ruptured pericolic or pelvic abscess — not bowel contents) — emergency laparotomy + Hartmann's procedure; Stage IV: generalised faecal peritonitis (free perforation with bowel contents in peritoneal cavity) — emergency Hartmann's, mortality 40-50%. The key practical point for GPs: any patient with diverticulitis who develops signs of generalised peritonism (not just localised LIF tenderness) has progressed to Hinchey III or IV and requires 999 immediately. A normal-appearing patient with localised LIF pain and tenderness without peritonism is likely Hinchey I and may be suitable for outpatient oral antibiotic treatment.

Diagnose

Diverticulitis Severity — Outpatient vs Hospital Classification

Done

Uncomplicated diverticulitis (suitable for community management)

Left iliac fossa (LIF) pain + fever <38.5°C + localised tenderness (not generalised peritonism) + WBC <15 × 10⁹/L + CRP <150 mg/L + no abscess or perforation on imaging. Suitable for oral antibiotic management at home — provided: able to tolerate oral medications, not immunocompromised, not pregnant, adequate social support, reliable to return if deteriorating. Hinchey Ia (modified classification — mild pericolic inflammation without abscess).

Complicated diverticulitis — hospital required

Any of the following: generalised peritonism · abscess ≥3 cm on CT (Hinchey Ib-II) · suspected perforation (pneumoperitoneum on AXR/CT — Hinchey III-IV) · failure of outpatient treatment at 72h · unable to tolerate oral medications · fever >38.5°C + WBC >15 or CRP >150 · immunocompromised patient · not socially supported. Admit for IV antibiotics + CT + surgical assessment.

Diverticular haemorrhage (separate presentation)

Painless massive rectal haemorrhage — typically fresh blood. Right-sided diverticula bleed more than left (right-sided have thinner walls, more arterial pressure). 80% self-limiting. CXR/AXR + CT angiography (active bleeding if ≥0.5 mL/min detectable). Colonoscopy haemostasis (clips, adrenaline injection). IR: superselective mesenteric arterial embolisation. Surgery: if bleeding fails to stop or recurs.

The evidence-based shift away from routine antibiotics for uncomplicated diverticulitis is one of the most significant paradigm changes in diverticular disease management over the past decade — multiple randomised controlled trials and systematic reviews (including the AVOD trial, Sweden 2012; the DIABOLO trial, Netherlands 2017; and Chabok et al., BMJ 2012) have demonstrated that in uncomplicated acute diverticulitis (CT-confirmed, no abscess, no peritonism, WBC/CRP not markedly elevated), antibiotics do not reduce complications, hospital admission rates, elective surgery rates, or recurrence compared to symptom management alone with analgesia and dietary modification. NICE NG147 (2019) reflects this evidence: 'Consider no antibiotic treatment for people with uncomplicated acute diverticulitis.' However, antibiotics are still indicated for: immunocompromised patients, patients with significant systemic features (fever >38.5°C, WBC >15), and as part of hospital management. This represents a clinically important practice change — many GPs continue to reflexively prescribe antibiotics for all diverticulitis presentations.

Diagnose

Assessment — History, Examination & Investigations

Done

History

Location and character of pain: left iliac fossa (sigmoid — most common, 95%), right iliac fossa (right-sided diverticulosis or ascending colon — less common, may mimic appendicitis). Onset (acute — hours vs insidious — days). Fever. Change in bowel habit (constipation + pain before = typical; diarrhoea = colitis or complicated). Rectal bleeding (purulent or bloody discharge per rectum = complicated; massive painless = diverticular haemorrhage). Urinary symptoms: dysuria, pneumaturia, faecaluria (colovesical fistula). Vaginal discharge (colovaginal fistula). Previous episodes (recurrence risk, cumulative complications). Diet: low-fibre diet (diverticular disease risk factor). NSAID use (increases risk of diverticular complications). Immunosuppression status.

Examination

Temperature. Abdominal: LIF tenderness — localised (uncomplicated) vs generalised peritonism (complication/perforation). Guarding + rigidity (surgical emergency). Bowel sounds: normal vs hyperactive (obstruction) vs absent (perforation/peritonitis). Palpable LIF mass (pericolic abscess or phlegmon). Rectal examination: blood on glove (lower GI bleed), pelvic collection (anterior rectal tenderness).

Investigations

CT abdomen + pelvis with IV contrast (gold standard for confirming diverticulitis and excluding complications — recommended for all suspected diverticulitis, NICE NG147) · FBC + CRP + U&Es (infection severity markers) · AXR + CXR (if perforation suspected — free gas under diaphragm) · Urine dipstick + MSU (exclude UTI; pyuria common in diverticulitis from adjacent inflammation without true UTI) · Urine culture (mixed organisms in UTI = colovesical fistula indicator) · Colonoscopy 6-8 weeks post-episode (exclude CRC — NOT during acute episode, risk of perforation)

The CT scan recommendation for all suspected acute diverticulitis is a NICE NG147 (2019) quality standard that has not been fully implemented in UK primary care — CT with IV contrast has a sensitivity of approximately 97-98% and specificity of approximately 97-99% for acute diverticulitis, compared to clinical diagnosis alone which misclassifies approximately 35-40% of cases (a proportion have alternative diagnoses including CRC, appendicitis, ovarian pathology, and ischaemic colitis). NICE explicitly recommends that CT abdomen/pelvis with IV contrast should be offered to all adults in whom acute diverticulitis is suspected. In practice, many GPs make a clinical diagnosis without CT and treat empirically — this approach risks: missing complications (abscess, perforation), missing alternative diagnoses (particularly CRC in the same age group), and overprescribing antibiotics. GPs with access to community CT (direct-access) should use it for suspected diverticulitis. If CT is not available in the community and the diagnosis is certain clinically: consider same-day hospital assessment for imaging.

Diagnose

Diverticular Disease vs CRC Distinction & Recurrence Risk

Done

Post-diverticulitis CRC exclusion colonoscopy

After every episode of acute diverticulitis (CT-confirmed): colonoscopy should be performed 6-8 weeks after full clinical recovery to exclude colorectal cancer. Rationale: CRC can mimic diverticulitis clinically and on CT; CRC can complicate existing diverticular disease; a diverticulitis episode may be the first presentation of a pericolonic CRC. Colonoscopy cannot be done during the acute episode (risk of perforation of inflamed bowel). If colonoscopy declined or not available: CT colonography (virtual colonoscopy) as alternative. Urgent colonoscopy (not 6-8 weeks) if: change in bowel habits persisting after recovery, rectal bleeding, unexplained anaemia, age <40.

Recurrence risk after acute diverticulitis

After first episode: approximately 20-25% recur within 5 years. After second episode: approximately 50-60% recur within 5 years. Risk factors for recurrence: immunosuppression, obesity, physical inactivity, high-fat low-fibre diet, NSAIDs, younger age. Indications for elective sigmoid colectomy: ≥2 documented episodes of acute diverticulitis in a fit patient, young patient (<50) with first severe episode, complicated diverticulitis (abscess, fistula), immunocompromised patients (lower threshold). NICE NG147 recommends offering elective colectomy to patients after a second episode — discuss risks and benefits.

Chronic diverticular pain

Chronic low-grade LIF pain without acute inflammation: painful diverticular disease / post-diverticulitis IBS-like syndrome. Features: diarrhoea, bloating, persistent LIF pain without fever or elevated CRP. Management: high-fibre diet, adequate hydration, avoid constipation, mebeverine or antispasmodics. Not an acute diverticulitis episode — no antibiotics needed.

The post-diverticulitis colonoscopy (at 6-8 weeks) is a critical safety standard that every GP managing diverticulitis should ensure is arranged — the reason: a National Health Service audit in England found that approximately 5-10% of patients managed as uncomplicated diverticulitis (confirmed on CT) are subsequently found to have colorectal cancer on follow-up colonoscopy. The CT appearance of perforated CRC can be identical to perforated diverticulitis. A colonoscopy at 6-8 weeks is the minimum standard for any patient who has had a documented episode of acute diverticulitis. GPs should: (1) code the acute diverticulitis episode in the clinical record with a specific SNOMED code; (2) arrange follow-up colonoscopy referral at the time of the acute presentation (so the referral is not forgotten); and (3) have a recall system to confirm colonoscopy was completed.

Refer

Referral Pathways

Done

999

Generalised peritonism (perforation) · Haemodynamic instability · Massive rectal haemorrhage · Complete bowel obstruction

Same-day surgical assessment

Suspected abscess (CT pericolic mass >3 cm) · Failed outpatient treatment at 72h · Fever >38.5°C + WBC >15 + not tolerating oral medications · Any immunocompromised patient · Pregnancy

GP management + 6-8 week colonoscopy referral

Confirmed uncomplicated diverticulitis (CT-confirmed, no complications, able to tolerate oral, not immunocompromised): NICE NG147 — offer analgesia and observe (no antibiotics unless systemic features). If antibiotics indicated: co-amoxiclav 625 mg TDS x 5-7 days. Arrange colonoscopy referral at 6-8 weeks. Review within 48-72h.

Colorectal surgery (elective)

≥2 episodes of acute diverticulitis · Colovesical / colovaginal fistula · Refractory recurrent diverticular haemorrhage · Young patient (<50) post-first severe episode

The co-amoxiclav choice for acute diverticulitis antibiotic therapy covers the polymicrobial enteric flora implicated in diverticular inflammation — acute diverticulitis is caused by micro-perforation of a diverticulum, leading to pericolic infection with enteric gram-negative bacteria (E. coli, Klebsiella pneumoniae) and anaerobes (Bacteroides fragilis). Co-amoxiclav 625 mg TDS provides effective coverage for both aerobic gram-negatives and anaerobes as a single agent. Alternatives: metronidazole 400 mg TDS + ciprofloxacin 500 mg BD (combination for penicillin allergy — ciprofloxacin resistance rates are rising in E. coli). IV regimens in hospital: piperacillin-tazobactam (Tazocin) 4.5g TDS or meropenem for severe/complicated diverticulitis. Duration: 5-7 days for uncomplicated; 10-14 days for complicated.

Treat

Acute Diverticulitis Management — Outpatient Protocol

Done

Uncomplicated diverticulitis — NICE NG147 outpatient pathway

Analgesia: paracetamol 1g QDS (first-line — avoid NSAIDs, which increase diverticular complications; avoid opioids as they may worsen constipation). Clear fluids for 24-48h (then light diet as tolerated). Rest. No antibiotics unless systemic features (NICE NG147). If antibiotic treatment clinically indicated (fever + systemic illness): co-amoxiclav 625 mg TDS x 5-7 days. Review at 48-72h. If no improvement or worsening: CT abdomen (if not already performed) + hospital assessment.

Inpatient management (hospital)

IV co-amoxiclav 1.2g TDS (or piperacillin-tazobactam 4.5g TDS if severe). IV fluids + NBM initially then clear fluids as tolerated. CT-guided percutaneous drainage for abscesses ≥3 cm. NG drainage if obstructive. Surgical review daily. Sigmoid colectomy threshold: failure to improve at 48-72h + worsening peritonism + Hinchey III/IV.

Hartmann's procedure

Emergency sigmoid resection + end colostomy + rectal stump closure (Hartmann's). Gold standard for Hinchey III/IV perforated diverticulitis. Stoma reversal: possible in 50-70% at 3-6 months after recovery. Primary anastomosis (laparoscopic peritoneal lavage ± resection + anastomosis): evidence emerging for selected patients with Hinchey III — avoids permanent stoma but higher anastomotic leak risk. Multidisciplinary surgical decision.

The NICE NG147 no-antibiotic recommendation for uncomplicated diverticulitis represents a practice-changing departure from historical standard care and is supported by level 1 evidence — the AVOD trial (Randomized Clinical Trial of Antibiotics in Uncomplicated Acute Diverticulitis, Chabok et al., BJS 2012) randomised 623 patients with CT-confirmed uncomplicated acute diverticulitis to antibiotics or observation: no difference in complication rates (1.9% vs 2.0%), time to recovery, or recurrence at 1 year. A subsequent Cochrane review (2018) concluded: 'There is no evidence of benefit from antibiotics for uncomplicated acute diverticulitis in terms of symptom relief, complications, or length of hospital stay.' Despite this evidence, surveys show that approximately 80-90% of GPs and hospital doctors continue to prescribe antibiotics for all cases of diverticulitis. The NICE recommendation therefore represents the current evidence-based best practice, with antibiotics reserved for cases with systemic features (fever >38.5°C, WBC >15, immunosuppression).

Treat

Elective Management & Prevention

Done

Elective laparoscopic sigmoid colectomy

Indication: ≥2 episodes of complicated diverticulitis, young patient with complicated first episode, fistula, persistent symptoms affecting QoL. Laparoscopic approach: preferred — shorter hospital stay, faster recovery, lower morbidity vs open. Anastomosis: primary anastomosis in elective setting is safe (vs emergency Hartmann's). Stoma rate in elective surgery: approximately 5-10% (vs approximately 95% in emergency Hartmann's). Outcomes: recurrence rate after sigmoid resection approximately 2-5% (vs 25% without surgery). Patient counselling: risks include anastomotic leak (approximately 2-5%), wound infection, bladder/sexual dysfunction (from pelvic dissection near autonomic nerves), stoma risk.

Preventing diverticulitis recurrence

High-fibre diet: 30 g fibre per day reduces new diverticular disease by approximately 40% and may reduce recurrence frequency. Water intake: 1.5-2 L/day (fibre absorbs water — inadequate fluid with high fibre causes constipation). Physical activity: 30 min moderate aerobic exercise 5x/week — reduces diverticulitis incidence by approximately 20-25%. Avoid NSAIDs (increases acute diverticulitis risk by approximately 2-3x — prostaglandin inhibition reduces mucosal integrity). Avoid opioids (constipation — increases diverticular pressure). Rifaximin 400 mg BD x 7 days per month (non-absorbable antibiotic — limited evidence for recurrence prevention; not routinely recommended NICE).

Mesalazine for diverticular disease

Mesalazine 1.6-3 g/day: used in some centres for painful diverticular disease and recurrence prevention — based on hypothesis of mucosal inflammation. Cochrane review: insufficient evidence to recommend routine use. Not NICE-recommended. Reserved for: patients with proven chronic diverticular inflammation on biopsy or colonoscopy who are not surgical candidates.

The high-fibre diet recommendation for diverticular disease prevention is one of the most strongly evidence-based dietary interventions in gastroenterology — the Painter and Burkitt hypothesis (1971) proposed that the low-fibre Western diet increases colonic intraluminal pressure (by producing small, hard, high-pressure stools) and causes diverticular formation at weak points where arteries penetrate the colonic wall. The UKBBSS (UK Women's Cohort Study) and multiple prospective cohorts confirm that dietary fibre intake above 25-30 g/day is associated with approximately 40% lower incidence of diverticular disease and approximately 30% lower risk of diverticular complications. The practical dietary advice: aim for 30 g fibre daily — from: wholegrains (wholemeal bread, porridge oats, brown rice), vegetables (broccoli, carrots, sweet potato — skins), pulses (lentils, chickpeas, beans — 8 g fibre per 80g serving), fruit (with skin, dried fruit). Psyllium husk supplements (Fybogel — 3.5 g ispaghula per sachet): excellent soluble fibre supplement if dietary fibre inadequate. Ensure adequate fluid intake (1.5-2 L/day) when increasing fibre.

Lifestyle

Diet, Hydration & Long-Term Prevention

Done

High-fibre diet for prevention Target 30 g fibre per day. Sources: wholegrain bread and pasta (3-4g per slice/serving), porridge and bran cereals (4-8g per serving), lentils and legumes (8g per 80g cooked serving), broccoli and Brussels sprouts (3-4g per portion), apples with skin (3g), pears (5g). Increase gradually over 2-4 weeks to avoid bloating and gas. With increased fibre: increase water intake proportionally. Low-fibre diet (white bread, processed food, low fruit/vegetable intake): increases colonic transit time, increases intraluminal pressure, increases diverticular formation.

Nut, seed, and popcorn safety Historical advice to avoid nuts, seeds, and popcorn in diverticular disease (concern about impacting in diverticula) was based on theoretical concern without evidence — a large prospective cohort study (HPFS — Health Professionals Follow-Up Study, Strate et al., JAMA 2008) showed that nut and seed consumption was NOT associated with increased diverticulitis risk and was actually inversely associated with acute diverticulitis. Current NICE NG147 advice: no dietary restrictions in diverticular disease. Patients may safely eat nuts, seeds, and high-fibre foods. Advise against: restrictive low-residue diet in diverticular disease (it worsens constipation and diverticular disease).

NSAID avoidance NSAIDs (ibuprofen, naproxen, diclofenac, aspirin — except low-dose cardioprotective) increase the risk of acute diverticulitis by approximately 2-3-fold and increase the risk of haemorrhage from diverticular disease. Mechanism: NSAIDs impair prostaglandin-mediated mucosal defence, reduce colonic blood flow, and impair platelet function (haemorrhage risk). For analgesia in diverticular disease: use paracetamol as first-line. If NSAID is required (arthritis, cardiovascular): use minimum effective dose + PPI + advise patient of risk. Low-dose aspirin (75-100 mg daily) for cardioprotection: the risk-benefit decision is complex — generally continue cardioprotective aspirin but advise on diverticular risk.

Constipation prevention Constipation increases intraluminal pressure and precipitates diverticular disease progression. Management: adequate dietary fibre + 1.5-2 L water/day + regular exercise. Laxatives if required: bulk-forming (Fybogel — ispaghula husk — first-line), osmotic (macrogol), or stool softeners (docusate). Avoid stimulant laxatives long-term (bisacodyl, senna) — do not address the underlying constipation mechanism. Toilet posture: squatting position (raised footstool) reduces straining.

Physical activity for diverticular disease prevention Prospective cohort studies show that physically active individuals have approximately 20-25% lower incidence of symptomatic diverticular disease. The mechanism: physical activity promotes colonic motility, reduces constipation, and reduces intra-abdominal fat (which is associated with diverticular inflammation). Target: 150 min moderate aerobic activity per week (brisk walking, cycling, swimming). Sedentary lifestyle is an independent risk factor for diverticulosis and diverticulitis.

Weight management Obesity (BMI >30) is associated with increased diverticular disease incidence and increased severity of diverticulitis (higher complication rate, higher recurrence rate). Visceral adiposity specifically increases pericolic inflammation risk. Weight management programme (NICE NG189 pathway for BMI ≥30) reduces diverticulitis risk and improves outcomes after surgical resection.

Patient education and warning signs Every patient diagnosed with acute diverticulitis should receive written information about: warning signs requiring emergency assessment (generalised abdominal pain + rigidity = 999, fever not responding to antibiotics = same-day assessment, massive rectal bleeding = 999), dietary modifications, the need for colonoscopy at 6-8 weeks, and what diverticulitis means for long-term bowel care. Guts UK (gutscharity.org.uk): comprehensive patient information on diverticular disease.

Bowel cancer awareness in diverticular disease Diverticular disease and CRC occur in the same age group (peak age 65-80), in the same anatomical location (sigmoid colon), and produce overlapping symptoms (change in bowel habits, rectal bleeding, LIF pain). The key patient message: diverticular disease does NOT protect against CRC — these two conditions can coexist and CRC can arise within a diverticular segment. Any change in symptom pattern, unexplained weight loss, new rectal bleeding, or anaemia in a patient with diverticular disease must trigger prompt GP review and colonoscopy consideration.

The stool frequency and quality monitoring after acute diverticulitis is important for identifying when to re-refer patients who continue to have symptoms — the typical recovery trajectory from uncomplicated acute diverticulitis is: pain and tenderness improve within 48-72h of antibiotic treatment, fever resolves within 48h, normal diet is resumed within 5-7 days, and the patient is well within 10-14 days. Patients who have not improved significantly by 72h on oral antibiotics should be reassessed (re-examine, check CRP trend, consider CT if not previously done). Patients who recover from the acute episode but have ongoing low-grade LIF discomfort for weeks afterwards may have: persistent pericolic inflammation, chronic diverticular disease, IBS-like post-diverticulitis syndrome, or — importantly — an underlying CRC. Any symptom persistence beyond 4-6 weeks after acute diverticulitis requires colonoscopy referral to exclude CRC, even if the 6-8 week post-episode colonoscopy was already planned.

Safety

Follow-Up & Colonoscopy Surveillance

Done

Outpatient review timeline

48-72h telephone or face-to-face: temperature normalised? LIF tenderness improving? Tolerating diet? If not improving: CT abdomen (if not done) + hospital assessment. At 2 weeks: full clinical recovery confirmed. At 6-8 weeks: arrange colonoscopy referral.

Post-colonoscopy actions

Normal colonoscopy (diverticular disease + no polyps): reassure + fibre advice + 5-yearly routine surveillance if no other risk factors. Adenomatous polyps: polypectomy + surveillance schedule per adenoma grade. CRC found: urgent MDT + staging.

Recurrence monitoring

Any second episode of diverticulitis: colorectal surgery referral for elective sigmoid colectomy discussion. CRP monitoring during recovery (normalisation by 2 weeks expected). If CRP remains elevated at 2 weeks: CT repeat (persistent abscess or alternative diagnosis).

Safety netting message to patient

Return to GP same day if: pain worsens significantly or becomes generalised, fever increases or returns, new rectal bleeding, vomiting, unable to drink fluids. Call 999 if: collapse, severe generalised pain, or unable to move. Do not wait for scheduled appointment if significantly worse.

999

Generalised peritonism · Massive rectal haemorrhage · Haemodynamic collapse · Haemodynamic instability

Same-day hospital

Failure to respond to 72h oral antibiotics · Fever >38.5°C persisting · Palpable LIF mass developing · Unable to tolerate oral medications

The 48-72h review after discharging a patient home with acute uncomplicated diverticulitis is a patient safety standard recommended by NICE NG147 — it is not optional. The review can be by telephone (for low-risk presentations) or face-to-face (for patients with borderline features). The key questions: Is the pain improving (not worsening)? Is the temperature normalising? Is the patient tolerating adequate fluids and diet? Is the CRP trending down (if checked)? Any 'no' answer to these questions should lower the threshold for hospital referral. The medicolegal principle: a GP who discharges a patient home with diverticulitis without arranging 48-72h review, and who does not see the patient again until a perforation occurs, has a defensible position only if the initial clinical assessment clearly documented uncomplicated features and the patient was given unambiguous safety-netting instructions (in writing) about when to call 999 or return.