Can amyloidosis cause ascites (abdominal fluid accumulation)?

Amyloidosis and Abdominal Fluid (Ascites)

Yes, amyloidosis can cause abdominal fluid accumulation (ascites), particularly in cases with peritoneal involvement, hepatic amyloid deposition, or cardiac amyloidosis leading to right heart failure. 1

Mechanisms of Ascites in Amyloidosis

Amyloidosis can lead to ascites through several mechanisms:

• Peritoneal amyloid deposition: Direct infiltration of amyloid proteins into the peritoneum, though relatively rare, can cause ascites in approximately 20% of patients with peritoneal involvement 1

• Hepatic involvement: Amyloid deposition in the liver can lead to portal hypertension and subsequent ascites, often presenting with elevated alkaline phosphatase levels and sometimes without the typical hepatomegaly 2

• Cardiac amyloidosis: Restrictive cardiomyopathy from cardiac amyloidosis can lead to right heart failure and subsequent ascites as part of anasarca 1

• Protein-losing enteropathy: GI tract amyloid infiltration can cause protein loss, contributing to hypoalbuminemia and ascites 3

Clinical Presentation

Patients with amyloidosis who develop ascites may present with:

• Abdominal distension with a positive fluid wave 2
• Anasarca (generalized edema) including extremity and scrotal edema 1
• Symptoms of heart failure if cardiac amyloidosis is present 1
• Gastrointestinal symptoms such as early satiety, weight loss, nausea, or altered bowel habits 4

Diagnosis

Diagnosis of amyloidosis-related ascites requires:

• Paracentesis: Analysis of peritoneal fluid may show characteristics consistent with portal hypertension in cases of hepatic involvement 2

• Tissue biopsy: The gold standard for diagnosis is tissue biopsy with Congo Red staining, which appears red in normal light and apple-green in polarized light 3

  • Peritoneal biopsy may be necessary to confirm peritoneal amyloidosis 1
  • Endoscopic biopsies throughout the GI tract can help diagnose GI amyloidosis, with duodenal biopsies having the highest yield 4

• Imaging:

  • Cross-sectional imaging may show hepatomegaly or other organ involvement 4
  • Advanced imaging such as 18F-FDG PET/CT and 99mTc-PYP SPECT/CT can reveal amyloid deposition in the peritoneum, omentum, and mesentery in rare cases 5

• Laboratory tests:

  • Liver function tests may show elevated alkaline phosphatase with mild elevations in other liver enzymes 2
  • Modified body mass index (mBMI) calculation (serum albumin multiplied by BMI) can help assess nutritional status, with mBMI <600 kg/m²·g/L indicating poor nutritional status 4

Management

Management of ascites in amyloidosis should focus on:

1. Treatment of underlying amyloidosis:

   • For AL amyloidosis: Chemotherapy and stem cell transplantation 3
   • For AA amyloidosis: Control of the underlying inflammatory disease 3

2. Symptomatic management of ascites:

   • Standard diuretic therapy, though ascites may be less responsive compared to other causes 1

3. Consultation with specialists:

   • Referral to a gastroenterologist is indicated for:
     • Symptoms not responding to dietary adjustments or over-the-counter medications 4
     • Significant malnutrition or unexplained weight loss 4
     • Need for endoscopy/colonoscopy for biopsies 4
     • Assessment of potential GI contraindications to heart transplantation 4

Prognosis

The presence of ascites in amyloidosis, particularly when due to peritoneal involvement, generally indicates advanced disease and may carry a poor prognosis 1. Pseudo-obstruction from GI amyloidosis carries a particularly grave prognosis and often does not respond to pro-motility agents 3.

Key Considerations

• Amyloidosis should be considered in the differential diagnosis when ascites is disproportional or not responsive to standard diuretic treatment, especially in patients with other features suggestive of amyloidosis (proteinuria, cardiomyopathy, peripheral neuropathy) 1

• To date, there is no specific treatment for peritoneal amyloidosis causing ascites 1

• The combination of various imaging techniques and characteristic CT features may help differentiate amyloidosis from other infiltrative diseases, but confirmative diagnosis requires tissue biopsy 6