What are the possible causes and treatments for persistent abdominal pain and high fever?

Persistent Abdominal Pain and High Fever: Differential Diagnosis and Management

Persistent abdominal pain with high fever demands immediate assessment for life-threatening intra-abdominal infections, including anastomotic leaks, bowel perforation, intestinal ischemia, and complicated appendicitis or cholecystitis, with urgent imaging and surgical consultation if peritoneal signs or hemodynamic instability are present. 1

Immediate Clinical Assessment

The combination of fever, tachycardia, and tachypnea are significant predictors of serious intra-abdominal pathology requiring urgent intervention 1. Tachycardia ≥110 beats per minute, fever ≥38°C, hypotension, respiratory distress, and decreased urine output are alarming clinical signs that mandate immediate diagnostic workup 1.

Critical Initial Evaluation Steps:

• Check hemodynamic stability immediately - assess for tachycardia, hypotension, or signs of shock, which indicate potential bowel ischemia, perforation, or sepsis requiring emergency intervention 2

• Examine for peritoneal signs - guarding, rebound tenderness, and rigidity suggest perforation or ischemia and mandate urgent surgical consultation 2

• Assess for sepsis indicators - the triad of fever, tachycardia, and tachypnea strongly suggests anastomotic leak, bowel perforation, or complicated intra-abdominal infection 1

Essential Laboratory Investigations

A comprehensive laboratory panel is mandatory for risk stratification and cannot be omitted 1:

• Complete blood count - leukocytosis >14,000 suggests infection, ischemia, or inflammation; marked elevation indicates potential bowel ischemia 2

• C-reactive protein (CRP) - has remarkably higher sensitivity and specificity than white blood count for ruling out abdominal surgical disease, though normal CRP alone does not exclude complications 1

• Serum lactate levels - elevated lactate indicates intestinal ischemia, though it may occur late in the disease process 1

• Procalcitonin - helps differentiate bacterial infection from other inflammatory causes 1

• Metabolic panel - low bicarbonate, elevated lactate, and abnormal pH indicate intestinal ischemia 2

• Blood gas analysis - essential for assessing severity of sepsis and metabolic derangements 1

Important caveat: Normal laboratory values do not exclude serious pathology, especially in elderly patients who may present with normal white blood cell counts despite severe infection 2.

Imaging Strategy

CT abdomen and pelvis with IV contrast is the preferred initial imaging modality for persistent abdominal pain with fever 1, 2:

• CT changes diagnosis in 49% of cases and management in 42% of patients with nonlocalized abdominal pain 2

• CT has >95% sensitivity for appendicitis and high accuracy for diverticulitis, abscess formation, and bowel perforation 2

• CT is the most accurate method to diagnose ongoing or recurrent intra-abdominal infection 1

• Ultrasound is appropriate for right upper quadrant pain with suspected cholecystitis (81% sensitivity, 83% specificity) 2

Major Differential Diagnoses to Consider

Intra-Abdominal Infections:

• Complicated appendicitis - may present with abscess formation requiring percutaneous drainage plus IV antibiotics 1

• Acute cholecystitis - laparoscopic cholecystectomy remains treatment of choice 1

• Anastomotic or staple line leak - particularly in patients with prior bariatric surgery, presenting with fever, tachycardia, and abdominal pain 1

• Internal hernia - presents with acute onset, persistent crampy/colicky epigastric pain, especially after Roux-en-Y gastric bypass 1

• Intestinal ischemia - suggested by severe pain out of proportion to examination, elevated lactate, and metabolic acidosis 1, 2

• Bowel perforation - presents with peritoneal signs and requires emergency surgical intervention 1, 2

Extra-Abdominal Infections to Exclude:

• Pulmonary embolism - must be systematically excluded in presence of respiratory distress and hypoxia 1

• Nosocomial pneumonia - should be treated as healthcare-acquired infection with broad-spectrum coverage 1

• Urinary tract infection - particularly in patients with indwelling catheters 1

• Clostridioides difficile infection - should be considered even without diarrhea in hospitalized patients with persistent fever 1

Management Algorithm

For Hemodynamically Unstable Patients:

• Immediate IV crystalloid resuscitation 2

• Emergency surgical consultation for peritonitis, perforation, or septic shock 2

• Broad-spectrum IV antibiotics covering gram-negative, gram-positive, and anaerobic organisms 1

For Stable Patients with Persistent Symptoms:

• Continue appropriate antimicrobial therapy while investigation proceeds, particularly if patient manifests signs of sepsis such as organ dysfunction 1

• Perform thorough search for infection source if fever persists >3 days despite antibiotics, including new blood cultures and symptom-directed diagnostic tests 1

• Consider percutaneous drainage for well-defined abscesses when available, combined with IV antibiotics 1

• Supportive care including IV fluids, antiemetics, and bowel rest for stable patients 2

Surgical Intervention Criteria:

Do not delay prompt diagnostic workup and surgical exploration in patients presenting with persistent abdominal pain and gastrointestinal symptoms associated with fever, tachycardia, and tachypnea 1. Clinical presentation can be non-specific, and any new onset abdominal symptoms should raise suspicion for complications requiring intervention 1.

Antibiotic Selection

For confirmed intra-abdominal infection, empirical broad-spectrum coverage should include 1:

• Combination therapy with β-lactam or carbapenem plus aminoglycoside or antipseudomonal fluoroquinolone for healthcare-associated infections

• Add vancomycin or linezolid if MRSA is suspected or in severe cases

• Adjust regimen based on culture results and local antibiotic resistance patterns 1

• Continue antibiotics at least until neutrophil recovery or resolution of clinical signs, whichever is longer 1

Critical Pitfalls to Avoid

• Never rely on normal laboratory values alone - many serious infections present with normal white blood cell counts, especially in elderly patients 2

• Do not delay imaging based on clinical impression - CT changes diagnosis in approximately 50% of cases with nonspecific pain 2

• Avoid using elevated lactate as single marker to exclude internal herniation, as it can occur late with intestinal ischemia 1

• Do not terminate antimicrobial therapy prematurely - continue until clear evidence of infection resolution and clinical improvement 1

• Never delay surgical consultation when peritoneal signs are present, even if imaging is pending 1, 2