What is the initial approach to a patient presenting with abdominal swelling?

Clinical Case Presentation and Approach to Abdominal Swelling

Case Presentation

A 62-year-old man presents with progressive abdominal swelling over 3 weeks, accompanied by early satiety and mild dyspnea when lying flat. He has a history of chronic hepatitis C and reports decreased alcohol intake over the past year. On examination, vital signs show blood pressure 118/72 mmHg, heart rate 88 bpm, temperature 37.2°C. Abdominal examination reveals marked distension with shifting dullness on percussion and a positive fluid wave test. No peritoneal signs are present. Spider angiomata are noted on the chest, and mild bilateral ankle edema is observed.

Initial Clinical Assessment

Begin with percussion of the flanks to detect shifting dullness—this is the most reliable physical examination maneuver for detecting ascites, requiring at least 1,500 mL of fluid to be present. 1 If shifting dullness is absent, the patient has less than a 10% chance of having ascites. 1 The fluid wave test is less reliable and more cumbersome than shifting dullness testing. 1

Key Physical Examination Findings to Identify:

• Flank dullness with shifting dullness: Indicates at least moderate ascites (Grade 2 or higher) 1
• Jugular venous distension: Suggests cardiac etiology rather than hepatic cause 1
• Stigmata of chronic liver disease: Spider angiomata, palmar erythema, gynecomastia point toward cirrhosis 1
• Peritoneal signs (guarding, rebound tenderness): Indicate possible infection, perforation, or ischemia requiring urgent intervention 1
• Hernia orifices and surgical scars: Essential to examine for incarcerated hernias or adhesive obstruction 1

Vital Sign Assessment:

• Tachycardia, tachypnea, hypotension: Suggest hypovolemic or septic shock requiring immediate resuscitation 1
• Fever with abdominal swelling: Mandates evaluation for spontaneous bacterial peritonitis 1

Diagnostic Imaging Strategy

For adults with abdominal swelling, abdominal ultrasound should be performed first to confirm the presence of ascites and can detect as little as 100 mL of fluid. 1, 2 Ultrasound is the initial imaging test of choice for right upper quadrant pathology and can identify liver cirrhosis, splenomegaly, and portal hypertension. 1, 2

Imaging Algorithm Based on Clinical Presentation:

For suspected ascites with hemodynamic stability:

• Abdominal ultrasound first: Confirms fluid, assesses liver morphology, detects masses 1, 2
• CT abdomen/pelvis with IV contrast: If ultrasound is inconclusive or malignancy is suspected 1, 2, 3

For hemodynamically unstable patients with abdominal swelling:

• Bedside ultrasound (FAST exam): Immediate assessment for free fluid/blood in trauma or suspected rupture 1, 2
• CT scan should NOT delay surgical consultation if peritoneal signs are present 1

Common pitfall: Plain radiographs have extremely limited diagnostic value for abdominal swelling and should not be routinely obtained except when bowel obstruction is suspected. 1, 2

Essential Laboratory Investigations

Obtain complete blood count, comprehensive metabolic panel, liver function tests, coagulation profile, and serum-ascites albumin gradient (SAAG) from paracentesis fluid. 1, 2

Specific Laboratory Tests:

• Complete blood count: Leukocytosis suggests infection or inflammation 1, 2, 3
• Metabolic panel: Assess renal function and electrolytes; hyponatremia is common in cirrhotic ascites 1
• Liver function tests: Elevated transaminases, bilirubin, and INR indicate hepatic dysfunction 1, 2
• BNP or pro-BNP: Helps differentiate cardiac from hepatic ascites when jugular venous distension is present 1
• Serum lactate: Elevated levels suggest bowel ischemia or severe sepsis 1, 3
• Serum amylase: Often elevated in perforation or pancreatic disease 1

Diagnostic Paracentesis

Abdominal paracentesis with ascitic fluid analysis is the most rapid and efficient test to diagnose the cause of ascites and must be performed in all patients with new-onset Grade 2 or 3 ascites. 1 The left lower quadrant is the preferred site due to greater fluid depth and thinner abdominal wall. 1

Indications for Diagnostic Paracentesis:

• All patients with new-onset clinically detectable ascites (Grade 2 or 3) 1
• All hospitalized patients with worsening ascites 1
• Any cirrhotic patient with fever, abdominal pain, gastrointestinal bleeding, hepatic encephalopathy, hypotension, or renal insufficiency 1

Ascitic Fluid Analysis:

• Cell count with differential: Absolute neutrophil count ≥250 cells/mm³ diagnoses spontaneous bacterial peritonitis 1
• SAAG calculation: SAAG ≥1.1 g/dL indicates portal hypertension (cirrhosis, heart failure); SAAG <1.1 g/dL suggests peritoneal disease (malignancy, tuberculosis, pancreatitis) 1
• Gram stain and culture: Mandatory when infection is suspected 1
• Cytology: If malignancy is a consideration 1

Critical safety note: Severe hemorrhage occurs in only 0.2-2.2% of paracenteses, with a mortality rate of 0.02%. 1 Coagulopathy and thrombocytopenia are NOT contraindications to diagnostic paracentesis. 1

Differential Diagnosis Framework

Approximately 75-85% of patients with ascites have liver cirrhosis as the underlying cause, but a systematic approach must exclude other etiologies. 1

Primary Causes by Mechanism:

Portal hypertension (SAAG ≥1.1 g/dL):

• Liver cirrhosis (most common: 60-85% of cases) 1
• Cardiac ascites (congestive heart failure, constrictive pericarditis) 1
• Budd-Chiari syndrome 1

Peritoneal disease (SAAG <1.1 g/dL):

• Peritoneal carcinomatosis 1
• Tuberculous peritonitis 1
• Pancreatic ascites 1

Other causes:

• Nephrotic syndrome 1
• Severe malnutrition 1

Approach to Bowel Obstruction as Cause of Abdominal Swelling

If abdominal distension is accompanied by colicky pain, vomiting, and absence of flatus/stool, bowel obstruction must be considered. 1

Clinical Features Distinguishing Obstruction:

• Colicky, intermittent pain rather than constant discomfort 1
• Nausea and vomiting: Earlier and more prominent in small bowel obstruction 1
• Absence of bowel movements and flatus: "Closed to gas" 1
• High-pitched bowel sounds or absent sounds: Suggests mechanical obstruction 1

Imaging for Suspected Obstruction:

• Abdominal plain X-ray: First-line study with 50-60% diagnostic accuracy for small bowel obstruction and 84% sensitivity for large bowel obstruction 1
• Water-soluble contrast study: 96% sensitivity and 98% specificity for large bowel obstruction; predicts need for surgery in adhesive small bowel obstruction 1
• CT abdomen/pelvis with IV contrast: Definitive study to identify obstruction level, cause, and complications (ischemia, perforation) 1, 2

Management Priorities

Hemodynamically unstable patients with abdominal swelling require immediate resuscitation with isotonic crystalloids, nasogastric decompression if obstruction is suspected, and urgent surgical consultation. 1, 3

Immediate Interventions:

• IV crystalloid resuscitation: Isotonic dextrose-saline or balanced crystalloids with potassium supplementation 1
• Nasogastric tube placement: Prevents aspiration and decompresses proximal bowel in obstruction 1
• Foley catheter: Monitor urine output as marker of perfusion 1
• Broad-spectrum antibiotics: If infection or perforation is suspected 1, 3

Disposition Decisions:

Patients requiring hospital admission:

• Hemodynamic instability (hypotension, tachycardia) 3
• Peritoneal signs (guarding, rebound tenderness) 3
• New-onset Grade 2 or 3 ascites requiring diagnostic workup 1
• Suspected bowel obstruction, perforation, or ischemia 1

Patients suitable for outpatient management:

• Mild, chronic ascites with known cirrhosis already on diuretic therapy 1
• No fever, normal vital signs, no peritoneal signs 3
• Reliable follow-up within 24-48 hours 3

Critical Pitfalls to Avoid

Never delay paracentesis in patients with new-onset ascites or suspected infection—this is the single most important diagnostic test and cannot be replaced by imaging. 1 Coagulopathy is not a contraindication. 1

Do not rely on physical examination alone in obese patients—ultrasound is essential to confirm or exclude ascites when body habitus limits examination. 1

Avoid assuming all abdominal swelling is ascites—bowel obstruction, massive organomegaly, abdominal masses, and pregnancy can mimic ascites and require different management. 1

Never administer diuretics before diagnostic paracentesis in new-onset ascites—this delays diagnosis and can mask spontaneous bacterial peritonitis. 1

Do not obtain CT scan in hemodynamically unstable patients with peritoneal signs—proceed directly to surgical exploration after bedside ultrasound. 1