A 50-year-old postmenopausal woman with a history of Gastroesophageal Reflux Disease (GERD), biliary dyskinesia, uterine fibroids, nephrolithiasis, and a previous episode of similar symptoms 5 years ago, presents with constant 6/10 abdominal pain, fever, bloating, and changes in bowel movements, what is the most likely diagnosis?

Acute Left Colonic Diverticulitis (ALCD)

This patient most likely has acute left colonic diverticulitis, and requires immediate CT abdomen/pelvis with IV contrast to confirm the diagnosis, assess for complications, and guide management. 1, 2

Clinical Reasoning

This 50-year-old woman presents with the classic triad for ALCD:

• Diffuse abdominal pain with left lower quadrant predominance (she states "it's all over" but has mid to LLQ tenderness) 1
• Fever and systemic symptoms (feverish, sweaty, T 37.7°C) 1
• Change in bowel habits (soft to loose thin ribbons to nothing, with tenesmus) 1

The positive guaiac test (rectal bleeding history 5 years ago, now guaiac positive) strongly supports diverticulitis over other diagnoses 1. Her hyperactive bowel sounds with distension and rebound tenderness indicate inflammatory process with possible early complication 1, 2.

Key diagnostic features present:

• Left lower quadrant tenderness with rebound 1
• Absence of vomiting (dry heaves only) 1
• Previous similar episode 5 years ago (recurrent diverticulitis pattern) 1
• Age 50 (prevalence increases significantly after age 50) 1

Differential Diagnosis (Rule In/Rule Out)

1. Acute Left Colonic Diverticulitis - MOST LIKELY

   • Supports: LLQ tenderness, fever, change in bowel habits, guaiac positive, previous episode, age 50, hyperactive bowel sounds 1

2. Infectious Colitis/Gastroenteritis

   • Against: No recent travel, no sick contacts, 24-hour duration too long for simple gastroenteritis, rebound tenderness unusual 1

3. Irritable Bowel Syndrome (IBS)

   • Against: Acute onset, fever, positive guaiac, rebound tenderness (IBS pain unrelated to defecation and lacks inflammatory signs) 1

4. Inflammatory Bowel Disease (IBD - Crohn's/UC)

   • Against: No prior diagnosis, colonoscopy 5 years ago unremarkable, acute presentation more consistent with diverticulitis 3

5. Bowel Obstruction

   • Against: Hyperactive (not absent) bowel sounds, passing some stool initially, no vomiting 2

6. Mesenteric Ischemia

   • Against: Pain not "out of proportion" to exam, gradual onset over 24 hours (not sudden), age 50 relatively young 2, 3

7. Colorectal Cancer

   • Consider: Age 50, change in bowel habits, but acute presentation and fever more consistent with diverticulitis; colonoscopy 5 years ago was normal 1

Pathophysiology of ALCD

Diverticulitis occurs when diverticula (outpouchings of colonic mucosa through the muscular layer) become inflamed due to microperforation or obstruction 1. The sigmoid colon is most commonly affected in Western populations (90% of cases) 1.

Inflammatory cascade:

• Fecal material or undigested food particles obstruct the diverticulum neck 1
• Increased intraluminal pressure causes mucosal ischemia and microperforation 1
• Bacterial translocation triggers local inflammation 1
• Pericolic fat stranding and bowel wall thickening develop 4
• Complications include abscess formation, free perforation, fistula, or obstruction 1, 4

Her clinical presentation suggests uncomplicated diverticulitis (no distant free air, though guaiac positive suggests mucosal inflammation) 1, 4.

Immediate Diagnostic Testing Required

Mandatory Imaging

CT abdomen and pelvis with IV contrast is the gold standard and must be performed immediately 1, 2:

• Sensitivity 79-99% for diverticulitis 4
• Distinguishes complicated from uncomplicated disease 1
• Rules out perforation, abscess, or alternative diagnoses 1, 2
• Identifies distant free air (stage 2B-4 disease requiring surgery) 1

Do NOT delay CT for concern about contrast-induced kidney injury - her eGFR is likely normal (no history of CKD), and prompt diagnosis in this potentially serious condition outweighs minimal CI-AKI risk 1.

Laboratory Studies

Obtain immediately: 1, 2

• Complete blood count - expect leukocytosis (90% of young patients with diverticulitis) 5
• C-reactive protein - CRP >50 mg/L supports diagnosis; CRP >170 mg/L predicts complicated disease requiring surgery/drainage 1
• Comprehensive metabolic panel - assess renal function, electrolytes 2
• Lactate - if elevated, raises concern for ischemia or sepsis 2, 3

Clinical decision rule validated: If she has (1) LLQ tenderness only, (2) CRP >50 mg/L, and (3) absence of vomiting, the diagnosis is 97% certain 1. However, CT is still mandatory to assess for complications 1.

Management Algorithm

Initial Management (Emergency Department)

Immediate steps: 1

1. NPO (nothing by mouth) - bowel rest 5
2. IV fluid resuscitation - she has dry mucosa and capillary refill >2 seconds indicating dehydration 5
3. IV broad-spectrum antibiotics covering gram-negative and anaerobic bacteria 1, 5
4. Pain control - avoid NSAIDs (she's already on ibuprofen 600mg BID, which may have contributed) 1

Disposition Based on CT Findings

Uncomplicated diverticulitis (bowel wall thickening, pericolic fat stranding only): 1

• Hospital admission for IV antibiotics, bowel rest, serial abdominal exams 1, 5
• Transition to oral antibiotics when tolerating diet 1
• Discharge when afebrile, tolerating diet, pain controlled 5

Complicated diverticulitis - Stage 1A (microperforation, no abscess): 1

• Hospital admission, IV antibiotics, close monitoring 1

Complicated diverticulitis - Stage 1B (abscess ≤4 cm): 1

• Hospital admission, IV antibiotics 1
• Consider percutaneous drainage if not improving in 48-72 hours 1

Complicated diverticulitis - Stage 2A (abscess >4 cm): 1

• Percutaneous drainage PLUS IV antibiotics 1

Complicated diverticulitis - Stage 2B-4 (distant free air, diffuse peritonitis): 1

• Immediate surgical consultation for emergency surgery 1, 2
• Hartmann procedure (sigmoid resection with colostomy) typically required 1

Diagnostic Criteria

Modified Hinchey Classification (CT-based): 1, 4

• Stage 0: Uncomplicated (bowel wall thickening, pericolic fat stranding)
• Stage 1A: Pericolic abscess or phlegmon
• Stage 1B: Pelvic/distant abscess ≤4 cm
• Stage 2A: Pelvic/distant abscess >4 cm
• Stage 2B: Distant free air >5 cm from inflamed segment
• Stage 3: Diffuse fluid without distant free air
• Stage 4: Diffuse fluid with distant free air (fecal peritonitis)

Treatment Options by Stage

Uncomplicated (Stage 0): 1

• IV antibiotics: Ceftriaxone 1-2g IV daily PLUS metronidazole 500mg IV q8h 1
• Alternative: Piperacillin-tazobactam 3.375g IV q6h 1
• Duration: 4-7 days IV, then transition to oral (total 10-14 days) 1

Complicated with abscess (Stage 1B-2A): 1

• Percutaneous drainage for abscesses >4 cm 1
• IV antibiotics as above 1

Perforated/peritonitis (Stage 2B-4): 1

• Emergency surgery: Hartmann procedure (sigmoid resection with end colostomy) 1
• Primary anastomosis with diverting ileostomy in selected cases 1

Long-Term Management

After resolution of acute episode: 1

• Colonoscopy in 6-8 weeks to rule out colorectal cancer (her last was 5 years ago, now due anyway) 1
• Elective sigmoid resection should be discussed if: 1
  • Recurrent episodes (she's had 2 now)
  • Complicated diverticulitis
  • Immunosuppressed patients
  • Unable to exclude cancer

Recurrence risk: Lower in patients >50 years (she's at the threshold) compared to younger patients 1. After first episode, 83% remain recurrence-free 1.

Risk Factors and Causes

Established risk factors: 1

• Age >50 years (prevalence 33% in 60-69 age group) 1
• Western diet (low fiber, high red meat) 1
• Obesity (her BMI 25.5 is borderline) 1
• NSAIDs (she takes ibuprofen 600mg BID - significant risk factor) 1
• Smoking 1

Her specific risk factors:

• Age 50 1
• Previous episode 5 years ago 1
• Chronic NSAID use (ibuprofen 600mg BID) - MUST BE DISCONTINUED 1

ICD-10 and ICD-11 Codes

ICD-10:

• K57.32 - Diverticulitis of large intestine without perforation or abscess without bleeding (if uncomplicated on CT)
• K57.20 - Diverticulitis of large intestine with perforation and abscess without bleeding (if complicated)
• K57.33 - Diverticulitis of large intestine without perforation or abscess with bleeding (if significant bleeding present)

ICD-11:

• DD71.0 - Diverticular disease of large intestine with diverticulitis

Rationale: The primary diagnosis is acute diverticulitis; the specific code depends on CT findings (complicated vs uncomplicated, bleeding vs non-bleeding) 1.

Critical Pitfalls to Avoid

1. Do NOT diagnose based on clinical exam alone - CT is mandatory to assess complications 1
2. Do NOT delay CT for kidney concerns - CI-AKI risk is minimal and diagnosis takes priority 1
3. Do NOT miss mesenteric ischemia - if pain seems out of proportion despite this presentation, consider CT angiography 2, 3
4. Do NOT continue NSAIDs - ibuprofen must be stopped immediately 1
5. Do NOT forget colonoscopy follow-up - mandatory in 6-8 weeks to exclude cancer 1
6. Elderly patients may have normal labs despite serious infection - she's 50, but this becomes critical in older patients 2

Patient Education Topics

Immediate education: 1

• Stop ibuprofen permanently - use acetaminophen for pain instead 1
• Expect hospital admission for IV antibiotics 1, 5
• NPO initially, gradual diet advancement 5
• Colonoscopy required in 6-8 weeks to rule out cancer 1

Long-term prevention: 1

• High-fiber diet (25-30g daily) to prevent recurrence 1
• Adequate hydration 1
• Avoid NSAIDs permanently 1
• Smoking cessation if applicable 1
• Weight management (BMI currently 25.5) 1
• Recognize warning signs of recurrence (LLQ pain, fever, bowel changes) 1

Discuss elective surgery: 1

• After second episode, elective sigmoid resection should be considered 1
• Prevents future episodes and complications 1
• Laparoscopic approach preferred 1

Medical-Legal Concerns if Unmanaged

Failure to diagnose: 1, 2

• Progression to perforation, abscess, sepsis, death 1
• Mortality 1.6% in patients <65 years, but increases dramatically with complications 1

Failure to obtain CT: 1

• Missed perforation or abscess requiring drainage/surgery 1
• Delayed treatment leading to worse outcomes 1

Failure to follow up with colonoscopy: 1

• Missed colorectal cancer (diverticulitis can mask cancer) 1

Continued NSAID use: 1

• Increased risk of recurrence and complications 1

Interprofessional Collaboration

Emergency Medicine: 2

• Initial stabilization, IV access, fluid resuscitation 2
• Order CT and labs 2
• Initiate antibiotics 1

Radiology: 1, 4

• Perform and interpret CT abdomen/pelvis with IV contrast 1, 4
• Stage disease using modified Hinchey classification 1, 4
• Perform percutaneous drainage if abscess >4 cm 1

General Surgery/Colorectal Surgery: 1

• Consultation for complicated diverticulitis (abscess, perforation) 1
• Emergency surgery for stages 2B-4 1
• Elective sigmoid resection discussion after resolution 1

Gastroenterology: 1

• Colonoscopy in 6-8 weeks post-resolution 1
• Long-term management of recurrent disease 1

Pharmacy: 1

• Antibiotic selection and dosing 1
• Medication reconciliation (discontinue ibuprofen) 1

Nursing: 5

• Serial abdominal exams 5
• Monitor vital signs for sepsis 2
• Pain management 5
• Diet advancement 5

Nutrition/Dietitian: 1

• High-fiber diet education for prevention 1
• Meal planning to achieve 25-30g fiber daily 1

Communication Approach

Initial conversation - be direct and reassuring: 1

• "Your symptoms and exam are very concerning for diverticulitis, which is inflammation of small pouches in your colon. We need to do a CT scan right away to see how serious this is and whether you need surgery."
• "You'll need to be admitted to the hospital for IV antibiotics and close monitoring."
• "The good news is that most cases respond well to antibiotics without surgery."

Address her fears: 1

• She's "afraid to eat" - explain NPO is medically necessary initially, not just to avoid pain 5
• She worries about bloody stools - explain this is common with diverticulitis and the guaiac test confirms inflammation 1

Discuss NSAID risk: 1

• "Your ibuprofen may have contributed to this episode. You need to stop it permanently and use Tylenol instead for your other pain."

Set expectations: 1, 5

• Hospital stay typically 3-5 days 5
• Gradual diet advancement 5
• Colonoscopy mandatory in 6-8 weeks 1
• Possible need for surgery if recurrent 1

Support if Distressed

Validate her concerns: 1

• "It's understandable you're worried, especially since this happened before."
• "The pain and fear of eating are very real and we're going to help you."

Provide concrete reassurance: 1, 5

• "With proper treatment, 85-90% of patients recover without surgery." 1
• "We have excellent antibiotics and imaging to guide your care." 1
• "You're in the right place and we're going to take good care of you." 5

Offer resources: 1

• Social work consultation if she has concerns about work (high-stress job) 1
• Pain management team if pain is severe 5
• Gastroenterology follow-up for long-term management 1

Wellness Plan

Domain	Patient	Family
Nutrition	High-fiber diet (25-30g daily); adequate hydration; avoid trigger foods [1]	Family meals emphasizing fiber-rich foods; support dietary changes [1]
Physical Activity	Regular exercise to maintain healthy weight (BMI 25.5); avoid straining [1]	Encourage family physical activities together [1]
Medications	STOP ibuprofen permanently; use acetaminophen for pain; complete antibiotic course [1]	Ensure medication compliance; remove NSAIDs from home [1]
Stress Management	Address high-stress job; consider counseling or stress reduction techniques [1]	Family support for work-life balance [1]
Preventive Care	Colonoscopy in 6-8 weeks; annual wellness visits; smoking cessation if applicable [1]	Encourage age-appropriate screening for family members [1]
Monitoring	Recognize warning signs of recurrence (LLQ pain, fever, bowel changes); seek care early [1]	Family awareness of symptoms requiring urgent evaluation [1]
Substance Use	Limit alcohol to 1-2 glasses wine 2-3x/week (current use acceptable) [1]	Family support for healthy alcohol limits [1]
Follow-up	GI follow-up post-colonoscopy; surgery consultation if recurrent [1]	Accompany to appointments; participate in decision-making [1]

PFC (Patient-Centered, Family-Focused, Community-Oriented) Matrix

Level	Assessment	Intervention	Outcome
Patient-Centered	50-year-old woman with acute LLQ pain, fever, bowel changes, previous episode 5 years ago; fears eating; high-stress job [1]	CT abdomen/pelvis with IV contrast; hospital admission; IV antibiotics; bowel rest; pain management; discontinue ibuprofen; colonoscopy in 6-8 weeks [1]	Resolution of acute diverticulitis; prevention of complications; long-term dietary modification; consideration of elective surgery if recurrent [1]
Family-Focused	Lives with family (implied by "family member" reference); family history non-contributory; family may be concerned about hospitalization and work absence [1]	Educate family about diverticulitis, treatment plan, expected hospital course; involve family in dietary planning; address work concerns with social work [1]	Family understanding of condition; support for dietary changes; assistance with stress management; family screening for diverticular disease if age-appropriate [1]
Community-Oriented	Access to emergency care, CT imaging, hospital admission, surgical services if needed; follow-up gastroenterology and primary care [1]	Ensure access to high-fiber foods; community resources for stress management; workplace accommodations if needed during recovery; public health education about diverticular disease prevention [1]	Reduced recurrence through community support; workplace understanding of medical needs; broader awareness of NSAID risks and fiber benefits [1]