01Approach to the Critical Patient/attcp35

Red flag recognition

›Alarm features mandating immediate assessment

›Hemodynamic instability

›Tachycardia with hypotension

›SBP < 90 mmHg

›Cool or clammy extremities

›Peritonitis signs

›Diffuse abdominal guarding

›Rigid abdomen

›Rebound tenderness

›Sepsis criteria

›Suspected infection with organ dysfunction

›Lactate >= 2 mmol/l

›High fever > 38.5 C with persistent chills

›Palpable abdominal mass suggesting abscess

Escalation and branching

›Uncomplicated vs complicated differentiation

›Uncomplicated disease

›No abscess, perforation, fistula, obstruction, or bleeding

›Approximately 85% of all diverticulitis cases

›Majority managed outpatient

›Complicated disease triggers

›CT evidence of free air, abscess, or extraluminal fluid

›WBC > 15 x 10^9/L

›CRP > 140 mg/L

›Symptoms > 5 days with high pain score

›If complicated disease suspected, surgical consultation

›Hinchey grade III or IV requires emergent surgical evaluation

02History/hx59

Presentation pattern

›Classic symptom complex

›Left lower quadrant pain

›Present in approximately 70% of cases

›Gradual onset subacute course

›May be suprapubic or right-sided with right colonic diverticulitis

›Associated symptoms

›Nausea and vomiting in approximately 30%

›Low-grade fever in approximately 33%

›Change in bowel habits

›Anorexia and malaise

›Duration of symptoms

›Symptoms > 5 days before presentation predict progression to complicated disease

Key historical negatives

›Atypical features that raise alternative diagnoses

›Rectal bleeding

›Not commonly seen in acute diverticulitis

›Presence prompts alternative diagnosis consideration

›Severe haematochezia

›Diverticular bleeding is a separate entity from diverticulitis

›Painless per rectal bleeding

›Colorectal cancer concern

Fistula and complication screening

›Colovesical fistula symptoms

›Fecaluria

›Pneumaturia

›Recurrent urinary tract infections

›Colovaginal fistula symptoms

03Physical Exam/exam40

Vitals and general

›Vital sign interpretation

›Temperature

›Fever present in approximately 33%

›High fever > 38.5 C associated with complicated disease

›Heart rate

›Tachycardia in approximately 27%

›Tachycardia with hypotension indicates sepsis or haemorrhage

›Blood pressure

›Hypotension is a red flag for complicated disease

›SBP < 90 mmHg triggers urgent surgical evaluation

Abdominal exam

›Classic findings

›Left lower quadrant tenderness

›Localised guarding is the classic finding

›Severity correlates with degree of inflammation

›Peritoneal signs

›Rebound tenderness

›Guarding

›Rigidity suggests perforation

›Abdominal distension

›May indicate obstruction

›Palpable mass

›LLQ mass present in approximately 20% of complicated cases

›Suggests phlegmon or abscess formation

Rectal and pelvic exam

›Rectal examination

›Tenderness may indicate pelvic abscess

04Differential Diagnosis/ddx57

Life-threatening mimics

›Cannot-miss diagnoses

›Colorectal cancer

›ICD-10 C18.9

›Clinical diagnosis of diverticulitis accurate only 40 to 65% of the time

›Colonoscopy recommended 6 weeks after resolution of complicated diverticulitis

›CRC risk 6 to 8% in complicated diverticulitis

›Perforated viscus

›ICD-10 K63.1

›Free air on imaging

›Peritonitis physiology

›Mesenteric ischaemia

›ICD-10 K55.1

›Disproportionate pain to exam

›Vascular risk factors

›Ectopic pregnancy

›ICD-10 O00.9

›Women of reproductive age with LLQ or pelvic pain

›Pregnancy test mandatory

Common mimics

›Inflammatory and infectious mimics

›Appendicitis

›ICD-10 K37

›Right lower quadrant pain predominantly

›May overlap with right-sided diverticulitis

›Inflammatory bowel disease

›ICD-10 K50 Crohn disease

›ICD-10 K51 ulcerative colitis

05Laboratory Tests/lt37

Core inflammatory markers

›Complete blood count

›Leukocytosis present in approximately 55% of febrile patients

›WBC > 15 x 10^9/L predicts progression to complicated disease

›Leukopenia may indicate overwhelming sepsis

›C-reactive protein

›CRP > 140 mg/L predicts complicated disease and progression

›CRP > 150 mg/L discriminates uncomplicated from complicated diverticulitis

›Useful to guide antibiotic decision in uncomplicated disease

›Trend over 24 to 48 hours more informative than single value

Metabolic and renal function

›Basic metabolic panel

›Renal function for antibiotic dosing

›Creatinine and eGFR

›Electrolytes for dehydration assessment

›Liver function if cirrhosis suspected

›Bilirubin and albumin

›Coagulopathy screening

›Urinalysis

›Rule out urinary tract infection

›Sterile pyuria may suggest colovesical fistula

›Haematuria may suggest nephrolithiasis

Sepsis and perfusion assessment

›Lactate

›>= 2 mmol/l indicates organ hypoperfusion

›Repeat at 2 to 4 hours if elevated

›Clearance target > 10% over 2 hours

›Blood cultures

06Diagnostic Tests/dt76

Scoring Systems

›Hinchey classification

›Grades severity of diverticulitis on CT imaging

›Hinchey 0: uncomplicated disease, no CT complications

›Hinchey Ia: confined pericolic abscess

›Hinchey Ib: pelvic abscess adjacent to sigmoid

›Hinchey II: distant abscess in pelvis or retroperitoneum

›Hinchey III: purulent peritonitis

›Hinchey IV: fecal peritonitis

›Uncomplicated diverticulitis corresponds to Hinchey 0

›Hinchey III and IV require emergent surgical intervention

Predictor scoring

›Composite risk predictors for complicated disease

›High-risk features on presentation

›Pain score > 7

›Vomiting

›Symptoms > 5 days

›WBC > 15 x 10^9/L

›CRP > 140 mg/L

›CT risk features

›Pericolic extraluminal air

›Fluid collection

›Long inflamed segment > 86 mm

›CRP > 150 mg/L combined with free fluid on CT predicts higher mortality

MRI

›MRI abdomen and pelvis

›Indications for MRI

›Pregnancy where radiation avoidance is preferred

07Disposition/dispo58

Outpatient management criteria

›Criteria for outpatient treatment

›Immunocompetent patient

›No high-dose steroids or immunosuppressants

›No active chemotherapy or organ transplant

›Mild clinical presentation

›Able to tolerate oral fluids

›Pain manageable with oral analgesics

›No vomiting

›Inflammatory markers below high-risk thresholds

›WBC < 15 x 10^9/L

›CRP < 140 mg/L

›CT confirmed uncomplicated disease

›Hinchey 0 on imaging

›No free air, abscess, or obstruction

›Adequate home support

›Access to follow-up within 48 to 72 hours

›Reliable social circumstances

›Approximately 95% of uncomplicated diverticulitis cases can be managed outpatient

Admission indications

›Criteria for hospital admission

›Immunocompromised status

›Active malignancy or chemotherapy

›Organ transplant recipient

›High-dose corticosteroids

›HIV with low CD4

›Significant comorbidities affecting management

›Cirrhosis

08Treatment/t87

Analgesia

›Pain management strategy

›Preferred analgesic

›Acetaminophen (paracetamol) is preferred analgesic

›500 mg to 1 g PO or IV every 4 to 6 hours

›Maximum 4 g per day in healthy adults

›Maximum 2 g per day in hepatic impairment or significant alcohol use

›NSAID avoidance

›NSAIDs contraindicated during acute episodes

›Associated with increased risk of complications and perforation

›Opioid consideration

›Morphine 2 to 4 mg IV every 4 to 6 hours for severe pain

›Short-course only

›Opioid use associated with higher complication risk long-term

Antibiotics — when not indicated

›Antibiotic-sparing approach in uncomplicated disease

›Observation with pain control alone appropriate for selected patients

›Immunocompetent

›Mild uncomplicated diverticulitis

›No systemic inflammatory response syndrome

›No vomiting

›WBC < 15 x 10^9/L

›CRP < 140 mg/L

›Evidence base

›Supported by ACP, AGA, and Cochrane systematic review

›Randomized controlled trial evidence supports non-inferiority of antibiotic-sparing approach

Antibiotics — when indicated

›Indications for antibiotic therapy

›Persistent fever or chills

›Rising WBC

›Sepsis features

›Age > 80 years

›Immunocompromised state

›Cirrhosis

›Chronic kidney disease

›Heart failure

›Poorly controlled diabetes

›Persistent vomiting

›CRP > 140 mg/L

›WBC > 15 x 10^9/L

Oral antibiotic regimens

›First-line oral regimens for 4 to 7 days

›Amoxicillin-clavulanate

›875 mg / 125 mg PO twice daily

›Duration 4 to 7 days

›Preferred first-line oral agent

›Cefalexin plus metronidazole

›Cefalexin 1 g PO three times daily

›Metronidazole 500 mg PO three times daily

›Duration 4 to 7 days

›TMP-SMX plus metronidazole

›TMP-SMX DS tablet PO twice daily

›Metronidazole 500 mg PO three times daily

›Duration 4 to 7 days

›Alternative oral regimen

›Ciprofloxacin plus metronidazole

›Ciprofloxacin 500 mg PO twice daily

›Metronidazole 500 mg PO three times daily

›Duration 7 to 10 days

›Reserve for penicillin allergy or intolerance

Intravenous antibiotic regimens

›IV regimens when oral not tolerated

›Ceftriaxone plus metronidazole

›Ceftriaxone 2 g IV once daily

›Metronidazole 500 mg IV every 8 hours

›Step down to oral when tolerating

›Ampicillin-sulbactam IV

›3 g IV every 6 hours

›Renal dose adjustment when eGFR < 30

›Piperacillin-tazobactam for complicated or severe disease

›4.5 g IV every 6 hours

›Extended 4-hour infusion per local protocol for severe sepsis

Diet management

›Dietary approach during acute phase

›Clear liquid diet for 1 to 2 days initially

›Evidence for strict liquid diet is limited

›Advance as symptoms improve

›If unable to advance diet after 3 to 5 days

›Immediate clinical reassessment required

›Adequate hydration

›Oral rehydration preferred when tolerating

›IV fluids if vomiting or poor oral intake

Long-term prevention

›Lifestyle modifications for recurrence prevention

›High-quality diet

›Rich in fruits, vegetables, whole grains, and legumes

›Limit red meat and processed foods

›Limit sweets

›Outdated advice no longer recommended

›Avoidance of nuts, seeds, and popcorn not supported by evidence

›Physical activity

›Regular aerobic exercise associated with reduced risk

›Weight management

›Target BMI < 30

09Special Populations/sp57

Pregnancy

›Pregnancy-specific considerations

›Diagnostic approach

›Ultrasound preferred first-line imaging

›MRI preferred if ultrasound inconclusive

›Sensitivity 86 to 94%, specificity 88 to 92%

›CT with IV contrast if diagnostic uncertainty and clinical urgency

›Radiation risk to fetus weighed against diagnostic necessity

›Antibiotic selection

›Amoxicillin-clavulanate generally considered acceptable

›Cephalosporins preferred if beta-lactam concerns

›Metronidazole use acceptable after first trimester

›Fluoroquinolones avoided due to fetal cartilage risk

›Tetracyclines contraindicated

›Surgical risk

›Surgery in pregnancy carries increased maternal and fetal risk

›Multidisciplinary approach with obstetrics

›Fetal monitoring when viable gestation

›Pain management

›Acetaminophen preferred analgesic in pregnancy

›NSAIDs contraindicated particularly in third trimester

Geriatric

›Older adult considerations

›Atypical presentation

›Pain may be attenuated or absent despite severe disease

›Lower threshold for CT imaging

›Fever may be absent in up to 40% of elderly with infection

›Higher complication risk

10Background/b69

Epidemiology

›Prevalence and incidence

›Diverticular disease prevalence

›Present in approximately 5 to 10% of population by age 45

›Present in approximately 65% of population by age 85

›Diverticulitis incidence

›Approximately 4 to 5 per 1000 person-years in those with diverticulosis

›Approximately 200,000 hospitalisations annually in the United States

›Uncomplicated diverticulitis proportion

›Accounts for approximately 85% of all diverticulitis cases

›Approximately 95% can be managed in the outpatient setting

›Demographic distribution

›Age distribution

›Incidence increases significantly with age > 50 years

›Age > 65 years is strongest demographic risk factor

›Sex distribution

›In younger patients (< 50 years), diverticulitis more common in males

›After age 70 years, more common in females

›Geographic variation

›Higher prevalence in Western countries

›Left-sided predominantly in Western populations

›Right-sided more common in Asian populations

Pathophysiology

›Diverticulum formation

›Mucosal and submucosal herniation through colonic wall

›Occurs at points of vessel penetration into muscle layer

›Areas of relative weakness in the muscular coat

›Sigmoid colon involvement

›Most common site due to high intraluminal pressure

›Narrower lumen generates higher wall tension by Laplace's law

›Inflammation mechanism

›Microperforation or obstruction of diverticulum ostium

›Fecalith impaction initiates cascade

›Increased intraluminal pressure causes micro-perforation

›Localised inflammation

›Pericolonic fat and soft tissue involved

›Contained by pericolonic fat in uncomplicated disease

›Progression pathways

›Abscess formation if inflammation not contained

›Free perforation if macro-perforation occurs

›Fistula if adjacent organ involved

›Role of gut microbiome

›Dysbiosis may contribute to acute flares

›Reduced diversity associated with diverticular disease

›Research area with evolving evidence

Therapeutic Considerations

›Antibiotic stewardship principles

›Paradigm shift from routine antibiotics

›Multiple RCTs demonstrate non-inferiority of no-antibiotic approach in uncomplicated disease

›Supported by AGA, ACP, European guidelines

›Key benefit: reduced antibiotic resistance, C difficile risk, side effects

›Selective antibiotic use criteria

›Reserve for high-risk or complicated cases

›Reassess at 48 to 72 hours if observation strategy used

›Recurrence risk and prevention

›Recurrence after first episode

›Approximately 20 to 30% recur after first episode

›Risk of complicated disease on recurrence not significantly higher

›Elective sigmoid colectomy indications

›After two or more episodes of complicated diverticulitis

›Complicated diverticulitis in immunocompromised patients

›Persistent symptoms between episodes

›No longer recommended after arbitrary number of uncomplicated attacks

›Mesalazine and rifaximin

›Evidence does not support routine use for prevention of recurrence

›Colonoscopy after diverticulitis

›Timing

›6 weeks after resolution of complicated diverticulitis

›Patients without recent high-quality colonoscopy

›Rationale

›CRC risk 6 to 8% in complicated diverticulitis

›Exclusion of alternative diagnoses including IBD and CRC

11Patient Discharge Instructions/pdi37

copy discharge instructions

›Diverticulitis home care instructions

›Diet progression

›Clear fluids for first 1 to 2 days then advance as tolerated

›Soft, easily digestible foods when symptoms improve

›Eat small frequent meals

›Avoid nuts, seeds, and high-fibre foods until fully recovered

›Medications

›Take all antibiotics as prescribed for the full course even if feeling better

›Take acetaminophen for pain as directed

›Do not take ibuprofen, aspirin, or other NSAIDs for pain

›Avoid opioid pain medication unless specifically prescribed

›Activity

›Rest as needed

›Light activity is acceptable when pain allows

›Avoid strenuous activity during acute illness

›Hydration

›Drink at least 8 glasses of water per day

›Avoid alcohol during antibiotic course

›Return to emergency department warning signs

›Worsening or severe abdominal pain

›Fever above 38.5 C or rigors

›Vomiting preventing oral intake

›Inability to take antibiotics or analgesics orally

›Blood in stool or dark tarry stools

›Signs of urinary problems such as pneumaturia or fecaluria

›Significant weakness, dizziness, or fainting

›No improvement after 48 to 72 hours of antibiotics

12References/r22

Guidelines and key sources

›Society guidelines

›American Gastroenterological Association (AGA) guideline on diverticulitis management

›Supports observation without antibiotics in uncomplicated disease

›Selective CT use for clinically confirmed mild recurrence

›American College of Physicians (ACP) guideline

›Antibiotic-sparing approach for uncomplicated diverticulitis

›American Society of Colon and Rectal Surgeons (ASCRS) practice parameters

›Indications for elective surgery

›Colonoscopy timing after complicated diverticulitis

›European Association for Endoscopic Surgery (EAES) consensus

›Laparoscopic sigmoid colectomy approach

›Key clinical evidence

›AVOD trial

›Randomized controlled trial supporting no-antibiotic treatment in uncomplicated diverticulitis

›DIABOLO trial

›Non-inferiority of observational management without antibiotics

›2025 JAMA review of diverticulitis management algorithm

›Grounding evidence for this document

›Coding references

›ICD-10 K57.32 diverticulitis of large intestine without perforation or abscess without bleeding

›ICD-10 K57.30 diverticulitis of large intestine without perforation or abscess with bleeding

›SNOMED CT diverticulitis of colon disorder

Evidence & Review

Evidence & Review