01Approach to the Critical Patient/attcp60

Immediate priorities

›Sepsis and hemodynamic threats

›Sepsis screening

›Suspected intraabdominal infection with organ dysfunction

›Lactate >= 2 mmol/l

›Septic shock indicators

›SBP < 90 mmHg

›MAP < 65 mmHg

›Tachycardia with cold extremities

›If septic shock, broad spectrum IV antibiotics within 1 hour

›Class I recommendation

›Piperacillin-tazobactam 4.5 g IV or imipenem 500 mg IV

›Peritonitis and perforation threats

›Free perforation indicators

›Diffuse board-like rigidity

›Guarding across all quadrants

›Extraluminal free air on imaging

›Hinchey III or IV pattern

›Purulent peritonitis

›Fecal peritonitis

›If free perforation, emergent surgical consultation

›Do not delay for imaging when peritonitis is diffuse

›Resuscitate simultaneously

›Abscess identification triggers

›Palpable LLQ mass

›Large abscess or phlegmon concern

›Failure to improve with outpatient antibiotics

›Duration > 48 hours without improvement

02History/hx70

Presentation pattern

›Core syndrome

›Left lower quadrant pain

›Constant or cramping quality

›Acute onset over hours to days

›Right-sided in Asian populations or redundant sigmoid

›Fever and constitutional symptoms

›Chills and rigors

›Anorexia and nausea

›Bowel habit change

›Constipation more common than diarrhea

›Obstipation suggests obstruction

›Alarm features

›Worsening pain despite prior outpatient antibiotics

›Duration > 5 days associated with higher complication risk

›Treatment failure definition: no improvement within 48 hours of appropriate antibiotics

›Urinary symptoms

›Dysuria and frequency

›Pneumaturia or fecaluria suggests colovesical fistula

›Vaginal symptoms

›Vaginal passage of stool or gas suggests colovaginal fistula

›Rectal bleeding

›NOT typical in acute diverticulitis

›Presence warrants consideration of alternative diagnosis

Risk factors

›Patient-level risk factors

›Age > 65 years

›Diverticulosis prevalence increases with age

03Physical Exam/exam49

Vitals and general

›Hemodynamic assessment

›Blood pressure

›SBP < 90 mmHg as septic shock threshold

›Pulse pressure narrowing

›Heart rate

›Tachycardia as sepsis marker

›Rate > 120 bpm associated with higher severity

›Temperature

›Fever >= 38.5 C typical

›Hypothermia as severe sepsis marker

›Respiratory rate

›Tachypnea in sepsis

›Baseline not elevated in uncomplicated cases

Abdominal exam

›Localized findings

›LLQ tenderness

›Most common finding in left-sided diverticulitis

›Point tenderness at McBurney equivalent for sigmoid

›Palpable mass

›Large abscess or phlegmon

›May be tender or non-tender

›Abdominal distension

›Ileus from inflammation

›Obstruction pattern if colonic narrowing

›Peritoneal findings

›Voluntary guarding

›Localized inflammation

04Differential Diagnosis/ddx61

Life threats and close mimics

›Surgical emergencies

›Perforated colon cancer

›ICD-10 C18.7 (sigmoid colon)

›CT may not distinguish from diverticular abscess

›Colonoscopy mandatory post-recovery

›Bowel obstruction

›ICD-10 K56.6

›Colonic narrowing from inflammation or stricture

›Air-fluid levels on CT

›Mesenteric ischemia

›ICD-10 K55.0

›Out of proportion pain

›Lactate elevation

›Intraabdominal inflammatory mimics

›Appendicitis

›ICD-10 K35.89

›Right-sided presentation overlap

›CT distinguishes in most cases

›Tubo-ovarian abscess

›ICD-10 N70.9

›Pelvic location overlap

›Gynecologic exam and history

›Crohn's disease

›ICD-10 K50.9

›Fistula and stricture overlap

›Younger age and skip lesions on CT

›Diverticulitis spectrum

05Laboratory Tests/lt54

Core infection labs

›Complete blood count

›Leukocytosis

›WBC > 15 x 10^9/L associated with higher complication risk

›Left shift supports bacterial infection

›Leukopenia as severe sepsis marker

›Especially in immunosuppressed patients

›Anemia

›Chronic disease or blood loss

›Relevant for surgical planning

›Inflammatory markers

›C-reactive protein

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

›Serial CRP useful for treatment response monitoring

›Rising CRP at 48 hours predicts treatment failure

›Procalcitonin

›Adjunctive for bacterial infection confirmation

›May guide antibiotic duration

›Not a standalone rule-out test

›Blood cultures

›Indicated when febrile or hemodynamically unstable

›Obtain before antibiotics when feasible

›Gram-negative bacteremia from enteric organisms

Metabolic and organ function labs

›Renal function

›Creatinine and eGFR

›Required before IV contrast administration

›Antibiotic dosing adjustment for impaired function

06Diagnostic Tests/dt90

Scoring Systems

›Modified Hinchey Classification

›Stage 0 - mild clinical diverticulitis

›Outpatient management appropriate

›No imaging findings of abscess or perforation

›Stage Ia - pericolic phlegmon

›IV antibiotics without drainage

›No discrete fluid collection

›Stage Ib - pericolic or mesocolic abscess

›IV antibiotics with or without percutaneous drainage

›Drainage if abscess >= 3 cm

›Stage II - pelvic or distant abscess

›IV antibiotics plus percutaneous drainage recommended

›Surgical consultation for all stage II

›Stage III - purulent peritonitis

›Emergent surgery required

›Hartmann procedure or primary anastomosis

›Stage IV - fecal peritonitis

›Emergent surgery required

›Highest mortality category

›Diplicab Nomogram predictors for emergency surgery

›Abscess size >= 5 cm

›Failure rate 25-34% with antibiotics alone

›Immunosuppression

›Independent predictor of surgical need

›Free pneumoperitoneum on CT

›Strongly predicts surgical requirement

›Morphine analgesic use

›OR 3.68 for emergency surgery

MRI

›MRI abdomen and pelvis role

›Primary indication

›Pregnancy when CT is contraindicated

›Contrast allergy with concern for abscess

›Imaging characteristics

›T2 hyperintensity of pericolonic fat stranding

›Fluid collection characterization as abscess

›Fistula tract visualization

›Limitations in acute setting

›Longer acquisition time

›Motion artifact from pain or bowel gas

›Limited availability after hours

›Protocol

›T1 and T2 sequences with fat suppression

›Gadolinium contrast for abscess wall enhancement when not contraindicated

CT

›CT abdomen and pelvis with IV contrast

›First-line imaging for suspected complicated diverticulitis

›Sensitivity 94-99%, specificity 99-100%

›Necessary for Hinchey classification and management planning

›Key CT findings

›Colonic wall thickening >= 4 mm

›Pericolic fat stranding

›Discrete fluid collection defining abscess

›Extraluminal gas suggesting perforation

›Free fluid in peritoneal cavity

›Abscess characterization on CT

›Size in maximum diameter

›Proximity to colon wall

›Accessibility for percutaneous drainage

›Loculation pattern

›Contrast protocol considerations

›IV contrast required for abscess wall enhancement

›Oral contrast optional in most centers

›Non-contrast CT if contrast contraindicated then correlate clinically

›CT colonography role

›Not indicated in acute phase

›Perforation risk in inflamed colon

›Reserve for follow-up after resolution

›Role post-recovery

›Alternative to colonoscopy in selected patients

›Cannot biopsy mucosal lesions

Ultrasound

›Abdominal ultrasound role

›Primary alternative when CT unavailable or contraindicated

›Pregnancy as primary indication

›Operator-dependent sensitivity limitation

›Ultrasound findings in diverticulitis

›Hypoechoic bowel wall thickening

›Hyperechoic pericolic fat

›Discrete hypoechoic abscess collection

›Sensitivity and specificity

›Sensitivity 84-98% in experienced hands

›Reduced in obese patients and those with bowel gas

›Guided procedures

›Ultrasound-guided percutaneous drainage when CT accessible

›Preferred over blind drainage for superficial collections

›Point-of-care ultrasound adjuncts

›FAST exam in unstable patients

›Free fluid in peritoneal cavity

›Not a substitute for CT

›Volume status assessment

›IVC collapsibility for fluid responsiveness

›Integrate with clinical exam findings

07Disposition/dispo51

Admission criteria

›All complicated diverticulitis requires hospitalization

›Abscess on CT regardless of size

›IV antibiotics required

›Drainage planning

›Failed outpatient treatment

›No improvement after 48 hours of oral antibiotics

›Worsening symptoms on treatment

›Systemic infection features

›Fever and leukocytosis

›Inability to tolerate oral intake

›ICU indications

›Septic shock

›Vasopressor requirement

›Lactate >= 4 mmol/l

›Hemodynamic instability despite initial resuscitation

›SBP < 90 mmHg unresponsive to 30 ml/kg IV fluid bolus

›Post-operative monitoring requirement

›After emergent or urgent surgery

Surgical consultation triggers

›Emergent surgical consultation

›Diffuse peritonitis or free perforation (Hinchey III or IV)

›Hemodynamic instability not responding to resuscitation

›Clinical deterioration despite antibiotics and drainage

›Urgent surgical consultation (within hours)

›Abscess >= 3 cm with drainage planning

›Interventional radiology coordination

›Failure to improve within 48 hours of IV antibiotics

08Treatment/t104

Initial stabilization

›Resuscitation priorities

›IV fluid resuscitation

›0.9% normal saline or lactated Ringer's 30 ml/kg for sepsis

›Reassess fluid responsiveness after initial bolus

›Avoid fluid overload in heart failure or renal disease

›NPO and bowel rest

›Acute phase management

›Advance diet as pain improves and bowel function returns

›Vasopressors if refractory hypotension

›Norepinephrine 0.01-0.5 mcg/kg/minute as first-line vasopressor

›Target MAP >= 65 mmHg

IV antibiotic regimens

›Clinically stable patient

›Ceftriaxone plus metronidazole

›Ceftriaxone 1-2 g IV every 24 hours

›Metronidazole 500 mg IV every 8 hours

›Non-inferior to piperacillin-tazobactam with lower C. difficile risk

›Ertapenem monotherapy alternative

›1 g IV every 24 hours

›Moderate-severe disease

›Clinically unstable or severe disease

›Piperacillin-tazobactam

›3.375-4.5 g IV every 6-8 hours

›Covers gram-negative enteric organisms and anaerobes

›Imipenem-cilastatin

›500 mg IV every 6 hours

›Reserved for severe sepsis or resistant organism risk

›Meropenem

›1 g IV every 8 hours

›Alternative carbapenem option

›Antibiotic duration and transition

›Total duration 7-14 days

›Transition to oral when afebrile, tolerating PO, WBC trending down

›Oral step-down options

›Amoxicillin-clavulanate 875/125 mg PO every 12 hours

›Ciprofloxacin 500 mg PO every 12 hours plus metronidazole 500 mg PO every 8 hours

›Fluoroquinolone cautions

›QT prolongation risk

›Tendinopathy risk

›C. difficile risk

Percutaneous abscess drainage

›Indications for drainage

›Abscess >= 3 cm (ASCRS strong recommendation, grade 1B)

›Some guidelines use 4-5 cm threshold

›Reduces recurrence compared to antibiotics alone

›Antibiotic success rates by abscess size

›<= 3 cm: approximately 100% success with antibiotics alone

›3-10 cm: 82% success with antibiotics alone

›> 10 cm: 66% success with antibiotics alone

›Pelvic abscess (Hinchey II)

›Drainage strongly recommended when technically feasible

›Drainage procedure details

›CT or ultrasound guided

›Drain placement in most accessible window

›Transabdominal, transgluteal, or transrectal approach depending on location

›Drain management

›Irrigate with normal saline daily

›Remove when output < 10 ml per day and imaging confirms resolution

›Complication rate approximately 2.5%

›Small bowel injury

›Fistula formation

›Bleeding

›Outcomes of drainage

›Recurrence after successful drainage 15-25%

›Lower than antibiotics alone recurrence of 25-60%

›Elective colectomy still recommended post-drainage in most cases

›Prevents complicated recurrence

Surgical management

›Emergent surgery (Hinchey III and IV)

›Operative options

›Hartmann procedure (end colostomy with rectal stump)

›Primary anastomosis with diverting ileostomy in selected stable patients

›Operative mortality

›Emergent surgery 10.6%

›Elective surgery 0.5%

›On-table lavage technique in selected Hinchey III cases

›Avoids stoma in purulent peritonitis subset

›Requires intraoperative assessment

›Elective colectomy planning

›Timing 4-6 weeks after successful nonoperative management

›After resolution of acute inflammation

›Pre-operative colonoscopy to exclude malignancy

›Sigmoid colectomy indication

›Abscess requiring drainage

›Recurrent complicated episodes

›Fistula formation

›Immunosuppression with first complicated episode

›Stoma requirement

›Approximately 4% after elective sigmoid colectomy

›Higher in emergent setting or complex fistula

Analgesic and supportive care

›Pain management

›Acetaminophen 1 g IV or PO every 6 hours

›First-line analgesic

›Avoid opioids when possible

›Opioid caution

›Morphine independently associated with emergency surgery need (OR 3.68)

›If opioid required, use lowest effective dose

›NSAID avoidance

›Associated with perforation risk

›Contraindicated in complicated diverticulitis

›Nutritional support

›NPO during acute phase

›Clear liquids when improving

›Advance to low-residue diet then high-fiber as tolerated

›Enteral nutrition if prolonged NPO required

›Post-pyloric feeding preferred if gastric dysmotility

›Parenteral nutrition for prolonged surgical recovery

09Special Populations/sp56

Pregnancy

›Pregnancy-specific considerations

›Anatomic displacement of sigmoid

›Pain location may be atypical in second and third trimester

›LLQ pain may be lateralized or superior

›Imaging approach

›Ultrasound first-line to minimize fetal radiation

›MRI without gadolinium as second-line

›CT with abdominal shielding if MRI unavailable and decision-critical

›Antibiotic safety in pregnancy

›Ceftriaxone is Category B and preferred

›Metronidazole generally avoided in first trimester

›Piperacillin-tazobactam Category B acceptable

›Avoid fluoroquinolones and tetracyclines

›Surgical risk in pregnancy

›Emergent surgery carries risk of preterm labor

›Obstetric team co-management mandatory

›Fetal monitoring when gestational age >= 24 weeks

›Percutaneous drainage preferred over surgery

›When abscess accessible and technically feasible

Geriatric

›Geriatric-specific presentations

›Atypical presentation common

›Afebrile infection in up to 30% of older adults

›Delirium as presenting symptom

›Blunted WBC response

›Comorbidity burden

›Anticoagulation complicates drainage planning

10Background/b88

Epidemiology

›Prevalence and incidence

›Diverticulosis prevalence increases with age

›Present in approximately 5-10% of those by age 50

›Present in approximately 65-70% of those by age 85

›Diverticulitis risk from diverticulosis

›Approximately 4-10% of patients with diverticulosis develop diverticulitis

›Risk factors modify individual patient risk significantly

›Complicated diverticulitis proportion

›Approximately 12-15% of acute diverticulitis presentations are complicated

›Abscess or phlegmon represents approximately 70% of all complications

›Mortality and outcomes

›Uncomplicated diverticulitis mortality very low

›< 1% in elective presentations

›Complicated diverticulitis mortality higher

›Emergent surgery mortality 10.6%

›Perforated with fecal peritonitis highest mortality

›Recurrence rates

›After first uncomplicated episode 20-30% recurrence rate

›After abscess with drainage 15-25% recurrence

›Risk of complicated recurrence justifies elective colectomy discussion

›Population distribution

›Higher incidence in Western populations

›Diet, inactivity, and obesity contributors

›Younger-onset diverticulitis increasing

›Rising BMI and dietary factors

›Right-sided predominance in Asian populations

›Malignancy risk after complicated diverticulitis

›CRC risk up to 11% when CT shows complicated disease

›Colonoscopy mandatory 6-8 weeks post-resolution

Pathophysiology

›Diverticulum formation

›Mucosal herniation through colonic wall at vasa recta penetration sites

›Areas of relative weakness

›Increased intraluminal pressure from low-fiber diet

›Sigmoid colon predominance

›Highest intraluminal pressure due to narrow caliber

›Right colon predominance in Asian populations may reflect genetic or dietary differences

›Diverticulitis mechanism

›Microperforation hypothesis

›Fecalith obstruction of diverticular neck

›Bacterial overgrowth and mucosal injury

›Perforation with pericolic contamination

›Inflammation-first hypothesis

›Chronic low-grade inflammation from microbiome dysbiosis

›Segmental colitis associated with diverticulosis

›Abscess and complication development

›Contained perforation forming abscess

›Pericolic fat and omentum wall off perforation

›Hinchey Ib or II depending on extent of spread

›Free perforation pathway

›Inadequate containment or delayed presentation

›Fecal or purulent contamination of peritoneal cavity

›Fistula formation

›Chronic inflammation and abscess tracking

›Colovesical fistula most common

›Colovaginal, coloenteric, and colocutaneous less common

Therapeutic Considerations

›Antibiotic strategy rationale

›Enteric gram-negative coverage essential

›Escherichia coli and Klebsiella pneumoniae predominant

›Bacteroides fragilis and other anaerobes in abscess

›Ceftriaxone plus metronidazole vs piperacillin-tazobactam

›Non-inferior efficacy in clinical studies

›Ceftriaxone combination associated with lower C. difficile rates

›Piperacillin-tazobactam preferred for higher severity or immunocompromised

›Duration de-escalation principle

›Shorter courses (7 days) may be as effective as longer courses in uncomplicated cases

›Procalcitonin-guided discontinuation reduces antibiotic exposure

›Source control principles

›Percutaneous drainage as bridge to surgery or definitive management

›Resolves sepsis source without operative risk

›Allows elective surgery in optimized patient

›Timing of elective surgery

›4-6 weeks post-resolution for tissue healing

›Pre-operative colonoscopy to exclude malignancy before resection

›Conservative vs operative management debate

›Routine elective colectomy after first abscess episode now questioned

›Decision should be individualized based on recurrence risk, comorbidities, patient preference

›Prevention of recurrence

›High-fiber diet

›Fruits, vegetables, whole grains, legumes

›Reduces recurrence in observational studies

›Weight management

›BMI target 18-25

›Obesity reduction reduces diverticular risk

›Tobacco cessation and physical activity

›Modifiable risk factor reduction

›Seeds, nuts, popcorn

›No longer restricted in evidence-based guidelines

›Historical restriction not supported by data

11Patient Discharge Instructions/pdi40

copy discharge instructions

›Home care instructions

›Complete entire antibiotic course as prescribed

›Do not stop early even if feeling better

›Diet progression

›Clear liquids for first 1-2 days at home

›Advance to soft low-residue diet over 1 week

›Transition to high-fiber diet after full recovery (4-6 weeks)

›Activity

›Rest with gradual return to normal activity over 1-2 weeks

›Avoid heavy lifting for 2 weeks

›Avoid NSAIDs and aspirin

›Use acetaminophen for pain relief instead

›If drain in place

›Keep drain site clean and dry

›Record daily output

›Follow drain care instructions from proceduralist

›Return to emergency department immediately for

›Worsening abdominal pain or pain becoming generalized

›Fever above 38.5 C (101.3 F) or chills

›Inability to tolerate oral fluids or medications

›Rectal bleeding

›Passing gas or stool through the urine (pneumaturia or fecaluria)

›Vaginal passage of stool or gas

›Drain falls out or drainage becomes foul-smelling

›Signs of infection at drain site (redness, swelling, pus)

›Dizziness, lightheadedness, or fainting

›Mandatory follow-up appointments

12References/r29

Guidelines and key sources

›Primary guidelines

›American Society of Colon and Rectal Surgeons (ASCRS) 2020 Clinical Practice Guidelines for Left-Sided Colonic Diverticulitis

›Hall J et al. Diseases of the Colon and Rectum 2020

›Percutaneous drainage recommendation grade 1B for abscess >= 3 cm

›American College of Physicians (ACP) 2022 Clinical Guideline

›Qaseem A et al. Annals of Internal Medicine 2022

›Diagnosis and management of acute left-sided colonic diverticulitis

›EAES and SAGES 2018 Consensus Conference

›Francis NK et al. Surgical Endoscopy 2019

›Evidence-based recommendations for clinical practice

›AGA Clinical Practice Update 2021

›Peery AF, Shaukat A, Strate LL. Gastroenterology 2021

›Medical management of colonic diverticulitis expert review

›Key clinical studies

›JAMA 2025 Diverticulitis review

›Brown RF, Lopez K, Smith CB, Charles A. JAMA 2025

›Comprehensive management overview

›JAMA Surgery 2024 Diverticulitis management review

›Sacks OA, Hall J. JAMA Surgery 2024

›Diplicab Study 2023

›Ocana J et al. Surgery 2023

›Outcomes of nonoperative management and nomogram for predicting emergency surgery

›Ceftriaxone vs piperacillin-tazobactam 2025

›Carns W et al. American Journal of Surgery 2025

›Non-inferiority of ceftriaxone plus metronidazole with lower C. difficile risk

›Coding reference

›ICD-10 K57.20 diverticulitis of large intestine with perforation and abscess without bleeding

Evidence & Review