What is the differential diagnosis and management for a patient with peritoneal pain that worsens with erection and standing?

Differential Diagnosis for Peritoneal Pain Worsening with Erection and Standing

The most likely diagnosis is Fournier gangrene or another necrotizing soft-tissue infection of the genitoperineal region, which requires immediate surgical evaluation and intervention to prevent mortality. 1

Primary Differential Considerations

Fournier Gangrene (Most Critical)

• This necrotizing infection involves the scrotum, penis, and perineum with mean age of onset at 50 years, and can present with either insidious or explosive onset. 1
• Most patients have significant underlying disease, particularly diabetes (80% have comorbidities), though 20% have no discernible cause. 1
• The infection typically originates from perianal/retroperitoneal sources spreading along fascial planes to genitalia, urinary tract infections (commonly from urethral strictures), or previous genital trauma. 1
• Pain worsening with erection and standing suggests fascial plane involvement with increased tension on infected tissues during these activities. 1
• Physical examination reveals a discrete area of necrosis in the perineum progressing rapidly over 1-2 days with advancing skin necrosis, initially causing superficial gangrene limited to skin and subcutaneous tissue. 1
• The testes, glans penis, and spermatic cord are usually spared due to separate blood supply. 1
• Mixed aerobic and anaerobic flora are causative, with Staphylococci and Pseudomonas species frequently present. 1

Testicular Torsion

• Presents with acute testicular pain and swelling, often with red, swollen scrotum in the absence of trauma, and requires surgical intervention within 4-6 hours to salvage the testicle. 2
• More common during adolescence but can occur at any age. 2
• Pain may worsen with standing due to gravitational effects on the torsed spermatic cord. 2
• Nausea and vomiting are common associated symptoms. 2
• The testicle can torse and detorse, creating confounding intermittent symptoms. 3

Epididymo-orchitis

• Typically presents with testicular pain and swelling, with examination revealing swollen, tender testis and epididymal swelling starting at the lower pole moving toward the upper pole. 4
• In men under 35 years, sexually transmitted infections (N. gonorrhoeae and C. trachomatis) are most common; in men over 35 years, E. coli predominates. 4
• Pain may worsen with erection due to increased vascular congestion and inflammation. 4

Secondary Peritonitis from Gastrointestinal Perforation

• Develops from gastrointestinal tract perforation with multiple microorganisms typically isolated, and ascitic fluid showing high protein, elevated LDH, and low glucose (<50 mg/dL). 5
• Pain worsening with standing suggests free peritoneal fluid or air causing peritoneal irritation with positional changes. 5
• Abdominal rigidity strongly suggests peritonitis and requires immediate surgical source control. 5

Immediate Diagnostic Approach

Clinical Assessment

• Examine for abdominal rigidity, rebound tenderness, and guarding (present in 74-95% of peritonitis cases). 5
• Assess for signs of systemic toxicity: tachycardia (62.5% of cases), fever >38.5°C (38% of cases), hypotension, and altered mental status. 5
• Perform careful genital and perineal examination looking for discrete areas of necrosis, crepitus, skin color changes (pale to bronze to purplish-red), or bullae with reddish-blue fluid. 1
• Evaluate for testicular position, cremasteric reflex, and scrotal elevation test to differentiate torsion from epididymitis. 4, 2

Laboratory Studies

• Obtain complete blood count (leukocytosis in 40% of peritonitis), lactate, CRP (>75 suggests peritonitis), electrolytes, and BUN/creatinine. 5
• Leukocytosis with left shift (band neutrophils >20%) supports infectious peritonitis. 5

Imaging

• For suspected Fournier gangrene or peritonitis with hemodynamic stability: obtain contrast-enhanced CT scan of abdomen and pelvis immediately, as it has the highest sensitivity and specificity for detecting peritonitis and soft-tissue gas. 5
• For suspected testicular torsion: emergent Doppler ultrasound is most helpful in confirming diagnosis, showing decreased or absent testicular blood flow. 2
• Plain radiographs may show free air (perforation) or soft-tissue gas but have lower sensitivity. 5

Management Algorithm

If Hemodynamically Unstable or Signs of Necrotizing Infection

• Do NOT delay surgical intervention for imaging—proceed immediately to operating room for exploration and debridement. 1, 5
• Initiate broad-spectrum antibiotics covering mixed aerobic/anaerobic flora: penicillin plus clindamycin for clostridial coverage, with additional coverage for Staphylococci and Pseudomonas. 1
• Aggressive surgical debridement with meticulous intensive care support is required. 1

If Suspected Testicular Torsion

• Immediate urologic consultation for surgical exploration—do not wait for imaging if clinical suspicion is high, as delay beyond 4-6 hours significantly reduces testicular salvage rates. 2
• Manual detorsion may be attempted while awaiting surgery. 2

If Stable with Suspected Epididymo-orchitis

• Patients in severe pain or systemically unwell require hospital admission for IV antibiotics and analgesia. 4
• Empiric antibiotics based on age: cover STIs in men <35 years, urinary pathogens in men >35 years. 4

If Secondary Peritonitis Confirmed

• Source control procedure is required for nearly all patients with intra-abdominal infection—delay in treatment significantly increases mortality. 5
• Surgical intervention includes resection/repair of perforated viscus, drainage of fluid collections, and debridement of necrotic tissue. 5

Critical Pitfalls to Avoid

• Never dismiss genital/perineal pain as benign without thorough examination—Fournier gangrene can begin insidiously but progress to life-threatening infection within 24-48 hours. 1
• Do not delay surgical consultation for imaging in hemodynamically unstable patients—every 10-minute delay to laparotomy increases mortality by 1.5-fold. 1
• Remember that intermittent testicular torsion (torsion-detorsion) can present with recurrent pain that temporarily resolves, potentially delaying diagnosis. 3
• In diabetic or immunosuppressed patients, peritonitis may present with general decompensation without classic peritoneal signs. 6