What is the differential diagnosis and recommended work‑up for a patient with tenesmus and mid‑lower abdominal cramping/pain lasting several days?

Differential Diagnosis and Work-Up for Tenesmus with Mid-Lower Abdominal Cramping

For a patient presenting with tenesmus and mid-lower abdominal cramping over several days, you must first exclude inflammatory bowel disease (particularly ulcerative proctitis), infectious causes, and acute surgical conditions before considering functional disorders like IBS.

Priority Differential Diagnoses

Inflammatory/Infectious Causes (Rule Out First)

• Ulcerative proctitis – Tenesmus is a hallmark symptom 1
• Infectious proctocolitis: lymphogranuloma venereum, Neisseria gonorrhoeae, herpes simplex virus, syphilis, Giardia duodenalis, amoebiasis 1
• Acute appendicitis – Most common urgent surgical cause of lower abdominal pain 2, 3
• Acute diverticulitis – Can present with left or right lower quadrant pain 3, 4

Structural/Mechanical Causes

• Solitary rectal ulcer syndrome 1
• Rectal prolapse 1
• Crohn's colitis 1

Functional Disorders (Diagnosis of Exclusion)

• Irritable bowel syndrome – Consider only after 12 months of symptoms and exclusion of organic disease 5
• Concurrent IBS with proximal constipation – Can mimic or coexist with proctitis 1

Malignancy (If Risk Factors Present)

• Rectal/anal/perineal malignancy – Particularly if refractory pain 6

Recommended Work-Up Algorithm

Step 1: Clinical Assessment

Key history elements to elicit:

• Duration exactly (acute <5-7 days vs chronic) 2, 7
• Presence of red-flag symptoms:
  • Hematochezia or bloody diarrhea (suggests IBD/infection)
  • Fever (infection, diverticulitis, appendicitis)
  • Bilious vomiting (surgical emergency)
  • Severe localized pain that increases in intensity (surgical abdomen) 8

Physical examination priorities:

• Localize pain precisely (right vs left lower quadrant vs midline)
• Check for peritoneal signs: guarding, rigidity, rebound tenderness 2, 7
• Digital rectal examination to assess for masses, blood, prolapse 1

Step 2: Initial Laboratory Testing

Order the following based on clinical suspicion 2, 7:

• Complete blood count (leukocytosis suggests infection/inflammation)
• C-reactive protein (elevated in IBD, diverticulitis, appendicitis)
• Urinalysis (exclude urinary tract infection, urolithiasis)
• Pregnancy test (if applicable – mandatory before imaging)
• Consider: comprehensive metabolic panel, lipase if upper abdominal component

Important caveat: CRP and WBC alone cannot discriminate urgent from non-urgent causes but help guide imaging decisions 7.

Step 3: Imaging Strategy

First-line imaging: Transabdominal ultrasonography 3, 7

• European guidelines recommend ultrasound as first-line for suspected appendicitis and diverticulitis 3
• High positive predictive value comparable to CT 7
• No radiation exposure
• Can evaluate gynecologic/genitourinary causes simultaneously

If ultrasound is negative or inconclusive: Proceed to CT with IV contrast 2, 7

• CT has highest sensitivity and specificity for acute abdominal pain 7
• Preferred for generalized or lower abdominal pain when diagnosis unclear 2

Avoid conventional radiography – No added value beyond clinical assessment 7

Step 4: Endoscopic Evaluation

Flexible sigmoidoscopy or colonoscopy is indicated when: 1

• Tenesmus persists despite negative imaging
• Bloody diarrhea or rectal bleeding present
• To differentiate ulcerative proctitis from other causes
• To exclude proximal disease extension
• Obtain biopsies to rule out infection, IBD, malignancy

The differential diagnoses requiring endoscopic confirmation include: ulcerative proctitis, Crohn's colitis, psoriatic colitis, chemical colitis, infectious proctocolitis, and solitary rectal ulcer 1.

Critical Decision Points

When to Refer for Urgent Surgical Consultation

• Peritoneal signs on examination (guarding, rigidity) 8
• Imaging confirms appendicitis, diverticulitis with complications, or bowel obstruction
• Hemodynamic instability
• Severe pain preceding vomiting 8

When to Treat Empirically

If ulcerative proctitis is suspected clinically:

• Start 5-ASA suppositories 1g daily while awaiting endoscopy 1
• If intolerant or non-responsive, switch to corticosteroid suppositories/foam 1

If infectious cause suspected:

• Obtain stool cultures, ova and parasites, sexually transmitted infection testing before starting antibiotics
• Start empiric antibiotics within 1 hour if sepsis recognized 7

When to Consider Functional Diagnosis

IBS should only be considered after: 5

• Symptoms persist >12 months
• Organic causes excluded by appropriate testing
• Review diagnosis if symptoms become severe or refractory 5

Common Pitfalls to Avoid

1. Do not dismiss tenesmus as "just IBS" – This symptom strongly suggests rectal pathology requiring endoscopic evaluation 1

2. Do not delay imaging in acute presentations – Clinical assessment alone has insufficient diagnostic accuracy for urgent vs non-urgent causes 7

3. Do not withhold analgesia – Opioid administration decreases pain intensity without affecting physical examination accuracy 7

4. Do not forget sexual history – Multiple infectious causes of proctitis are sexually transmitted 1

5. In patients with known IBD, do not assume flare – Re-evaluate for infection, proximal constipation, or IBS overlap 1