What are the likely differential diagnoses for a 58‑year‑old man with worsening hypogastric pain over the past five hours, a firm lower abdomen, mild tenderness, and absence of stool and flatus since yesterday while remaining hemodynamically stable?

Differential Diagnosis: 58-Year-Old Male with Hypogastric Pain and Obstipation

In a 58-year-old man presenting with worsening hypogastric pain, firm abdomen, mild tenderness, and complete obstipation (no stool or flatus for 24 hours) while remaining hemodynamically stable, the primary differential diagnoses are large bowel obstruction (most commonly from colorectal malignancy or diverticular disease), early bowel ischemia, and less likely urinary retention or complicated diverticulitis.

Immediate Clinical Assessment

High-Priority Red Flags to Evaluate

• Assess for peritoneal signs beyond mild tenderness: Look specifically for involuntary guarding, rebound tenderness, and rigidity, which indicate perforation or advanced ischemia requiring emergency surgery 1
• Evaluate for systemic inflammatory response syndrome (SIRS): Check for fever, tachycardia (>90 bpm), tachypnea (>20/min), and leukocytosis, which strongly suggest bowel strangulation or ischemia 2
• Perform digital rectal examination: This is crucial to assess for rectal masses (60% of rectal cancers are palpable), impaction, or blood in the stool 1
• Check for abdominal distension and bowel sounds: Absence of bowel sounds with firm abdomen suggests advanced obstruction or ileus 1

Critical Laboratory Investigations

• Arterial lactate level: This is the single most reliable predictor of bowel ischemia; levels ≥2.0 mmol/L indicate non-viable bowel and mandate urgent surgical consultation 1, 2
• Complete blood count: Leukocytosis >14,000 suggests infection, ischemia, or inflammation; marked elevation indicates potential bowel strangulation 3, 2
• Metabolic panel: Look for elevated creatinine (urinary retention), hyperkalemia, and metabolic acidosis (bowel ischemia) 1
• D-dimer: Elevated levels strongly correlate with intestinal ischemia, though specificity is low 1, 2
• CPK (creatine phosphokinase): Relatively reliable indicator of early intestinal strangulation 2

Primary Differential Diagnoses

1. Large Bowel Obstruction (Most Likely)

• Colorectal malignancy causes 60% of large bowel obstructions in this age group 1, 3
• Clinical features: Gradual symptom development, absence of flatus/stool (90%), abdominal distension (65%), and hypogastric location suggests distal obstruction 1
• Diverticular disease is another common cause in this age group, potentially with associated inflammation 1

2. Acute Mesenteric Ischemia (Must Exclude Urgently)

• Risk factors to assess: Atrial fibrillation, recent MI, diffuse atherosclerotic disease, cardiac failure, or vasopressor use 1
• Clinical presentation: Continuous intense pain out of proportion to physical findings is classic, though this patient has only mild tenderness 1
• Time-critical: Every 6 hours of diagnostic delay doubles mortality 1

3. Bowel Strangulation (Closed-Loop Obstruction)

• Key differentiating features: Continuous pain unresponsive to analgesics, peritoneal signs, and SIRS 2
• This patient's mild tenderness and stable vitals make this less likely, but cannot be excluded without imaging 2

4. Urinary Retention with Secondary Ileus

• Consider in hypogastric pain: Bladder distension can cause lower abdominal firmness and referred pain 4
• Assess: Palpable suprapubic mass, inability to void, and percussion dullness 4

5. Complicated Diverticulitis

• Common in this age group: Can present with obstruction from inflammation or abscess 1, 5
• Typically left lower quadrant, but sigmoid involvement can cause hypogastric symptoms 1

Mandatory Imaging Strategy

CT abdomen and pelvis with IV contrast is the definitive diagnostic study and must be performed without delay 1, 3, 6

Why CT is Essential

• Changes diagnosis in 49% of cases and management in 42% of patients with nonspecific abdominal pain 3
• Identifies: Obstruction level and cause, bowel wall enhancement (ischemia), pneumatosis intestinalis, portal venous gas, perforation, and malignancy 1
• Perform despite renal concerns: The consequences of missed diagnosis far outweigh contrast risks 1

CT Findings to Assess

• Bowel obstruction: Transition point, bowel dilatation, and wall thickness 1
• Ischemia: Reduced wall enhancement, pneumatosis, portal venous gas, and mesenteric vessel occlusion 1
• Perforation: Free air, though absence doesn't exclude it 1
• Malignancy: Mass lesion, lymphadenopathy, and metastases 1

Alternative if CT Unavailable

• Plain abdominal X-rays (anteroposterior and lateral) can show bowel dilatation, air-fluid levels, and free air, but sensitivity is poor 1
• Do not delay surgical consultation if CT is unavailable and clinical suspicion is high 1

Critical Management Pitfalls

Do Not Dismiss Based on Stable Vitals

• Hemodynamic stability does not exclude serious pathology: Older patients may not mount typical responses to ischemia or perforation 5
• Physical examination can be misleadingly benign even with catastrophic conditions like mesenteric ischemia 5

Do Not Attribute to Functional Disorder

• Never diagnose functional dyspepsia or IBS without proper investigation in patients ≥60 years with new-onset symptoms 3, 7
• Age >55 years with treatment-resistant symptoms mandates exclusion of structural disease before considering functional diagnoses 3

Do Not Delay Imaging for Conservative Trial

• Complete obstipation (no stool or flatus for 24 hours) with firm abdomen requires urgent imaging, not empirical treatment 1, 3
• Early surgery (<24 hours) improves outcomes if obstruction or ischemia is confirmed 1

Immediate Management Pending Imaging

• IV crystalloid resuscitation: Begin immediately to enhance visceral perfusion and correct potential dehydration 1
• Nasogastric decompression: If significant distension or vomiting is present 1
• NPO status: Absolute bowel rest until diagnosis is established 1
• Broad-spectrum antibiotics: Consider if fever, leukocytosis, or peritoneal signs develop 1
• Foley catheter: To assess urinary retention and monitor output 4
• Avoid opioids: They mask symptoms, worsen ileus, and can cause narcotic bowel syndrome 1, 7

Surgical Consultation Timing

Obtain urgent surgical consultation if any of the following are present 1:

• Peritoneal signs (guarding, rebound, rigidity)
• Lactate ≥2.0 mmol/L
• SIRS criteria met
• CT shows perforation, ischemia, or high-grade obstruction
• Clinical deterioration despite conservative management