Diagnosis: Pancreatic Fistula (Option D)
The diagnosis is pancreatic fistula presenting as pancreatic ascites. The combination of fluid thrill (indicating significant ascites), markedly elevated ascitic fluid amylase (>1000 IU/L), and high protein content (25 g/dL) occurring 4 months after a negative exploration is pathognomonic for internal pancreatic fistula with pancreatic ascites 1, 2.
Key Diagnostic Features
Ascitic fluid amylase >1000 IU/L is diagnostic of pancreatic ascites, which results from internal pancreatic fistula formation 3. The guideline specifically states that in pancreatic ascites, the amylase level is typically >1000 IU/L or greater than six times the serum amylase, with mean values exceeding 4000 IU/L 3.
The protein content of 25 g/dL (2.5 g/100 mL) is consistent with pancreatic ascites, as internal pancreatic fistulas produce fluid with protein levels ≥3 g/100 mL 1, 2. This high protein content distinguishes pancreatic ascites from cirrhotic ascites.
Why Other Options Are Incorrect
Chylous Ascites (Option A)
- Chylous ascites presents with milky appearance due to triglyceride content, not elevated amylase 3
- The markedly elevated amylase excludes this diagnosis 3
Chronic Pancreatitis (Option B)
- While chronic pancreatitis is the underlying cause of the fistula, it does not directly explain the ascites presentation 1, 2
- The question asks for the diagnosis of the current presentation (ascites with high amylase), not the underlying etiology 1
Tuberculosis (Option C)
- TB peritonitis would show adenosine deaminase >40 IU/L, not markedly elevated amylase 3
- The ascitic fluid amylase >1000 IU/L essentially excludes TB as the primary diagnosis 3
Clinical Context
The 4-month interval after negative exploration is highly characteristic of internal pancreatic fistula development 1, 2. Over half of patients with internal pancreatic fistulas have no history of inflammatory pancreatic disease at presentation, making the diagnosis challenging 2.
Serum amylase may be only mildly elevated or even normal, which is why ascitic fluid analysis is critical for diagnosis 1, 2. The dramatic elevation in ascitic fluid amylase (>800-1000 Somogyi units/100 mL) combined with high protein content establishes the diagnosis 1, 2.
Management Implications
Initial treatment should be conservative with nasogastric aspiration, nil per oral, antisecretory drugs, repeated paracentesis, and total parenteral nutrition 1, 2. This approach is successful in approximately 48% of cases 2.
ERCP should be performed to demonstrate pancreatic ductal disruption and potentially place a naso-pancreatic drain across the disrupted duct 1. If conservative management fails after 2-4 weeks, surgical intervention to drain or resect the internal fistula is indicated, with success rates of 82% 2.