A 29-year-old woman presents to the emergency department with a 1-week history of progress… — USMLE Step 2 CK

A 29-year-old woman presents to the emergency department with a 1-week history of progressively worsening right upper quadrant abdominal pain and significant abdominal swelling. She has no chronic medical conditions. Two years ago, she developed a deep vein thrombosis in her left leg following a long-haul flight, for which she completed a 3-month course of anticoagulation. Her only current medication is an oral contraceptive pill.

Her temperature is $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure is $122/78\,\text{mmHg}$ , and heart rate is $98/\text{min}$ . Physical examination reveals mild scleral icterus. Jugular venous pressure is estimated at $6\,\text{cm H}_2\text{O}$ (normal). The abdomen is distended with shifting dullness and a positive fluid wave. The liver edge is tender and palpable $4\,\text{cm}$ below the right costal margin.

Laboratory results are as follows:

Test	Result
Hemoglobin	$14.2\,\text{g/dL}$
Platelets	$410,000/\text{mm}^3$
Total bilirubin	$3.2\,\text{mg/dL}$
Aspartate aminotransferase (AST)	$450\,\text{U/L}$
Alanine aminotransferase (ALT)	$410\,\text{U/L}$
Alkaline phosphatase	$160\,\text{U/L}$
Total protein	$6.8\,\text{g/dL}$
Albumin	$3.5\,\text{g/dL}$

A diagnostic paracentesis is performed, yielding clear, yellow fluid. Ascitic fluid analysis reveals:

Test	Result
White blood cell count	$120/\text{mm}^3$ ( $15\%$ neutrophils, $85\%$ mononuclear cells)
Total protein	$3.2\,\text{g/dL}$
Albumin	$2.0\,\text{g/dL}$

Which of the following is the most appropriate next step in establishing the diagnosis?

A
Echocardiography
Doppler ultrasonography of the abdomenAnswer
C
Intravenous ceftriaxone therapy
D
Non-contrast computed tomography of the abdomen
E
Percutaneous liver biopsy

Answer

Doppler ultrasonography of the abdomen

The correct answer accurately reflects the next diagnostic step for Budd-Chiari syndrome. This patient presents with acute right upper quadrant pain, hepatomegaly, and ascites in the setting of hypercoagulability (oral contraceptive use and prior DVT). The ascitic fluid analysis shows a Serum Ascites Albumin Gradient (SAAG) of

1.5\,\text{g/dL}

(

3.5 - 2.0

), indicating portal hypertension. Furthermore, the ascitic fluid total protein is elevated at

3.2\,\text{g/dL}

, which rules out cirrhosis (where protein is typically

< 2.5\,\text{g/dL}

) and points toward post-sinusoidal causes like right heart failure or Budd-Chiari syndrome. Because the jugular venous pressure is normal, cardiac causes are excluded, making hepatic vein thrombosis the most likely diagnosis. The diagnostic test of choice is Doppler ultrasonography of the abdomen to evaluate hepatic blood flow.

Step-by-Step Solution

Calculate the Serum Ascites Albumin Gradient (SAAG) to determine the hemodynamic mechanism of the ascites.

SAAG = Serum albumin (

3.5\,\text{g/dL}

) - Ascites albumin (

2.0\,\text{g/dL}

) =

1.5\,\text{g/dL}

A SAAG

\geq 1.1\,\text{g/dL}

accurately identifies the presence of portal hypertension with

97\%

accuracy.

Evaluate the ascitic fluid total protein to narrow the differential diagnosis of portal hypertension.

Ascitic total protein is high at

3.2\,\text{g/dL}

An ascitic protein

\geq 2.5\,\text{g/dL}

indicates intact hepatic sinusoids, pointing toward post-sinusoidal etiologies such as cardiac ascites or Budd-Chiari syndrome, distinguishing it from cirrhosis (typically

< 2.5\,\text{g/dL}

Integrate laboratory analysis with physical examination findings to identify the most likely etiology.

The jugular venous pressure is normal (

6\,\text{cm H}_2\text{O}

Normal JVP makes cardiac etiologies (e.g., right heart failure, constrictive pericarditis) highly unlikely. This leaves Budd-Chiari syndrome (hepatic vein thrombosis) as the primary diagnosis, supported by her hypercoagulable risk factors (oral contraceptive use, history of DVT).

Select the most appropriate initial diagnostic study based on the suspected etiology.

Doppler ultrasonography of the abdomen is chosen.

This non-invasive imaging modality assesses hepatic vein patency and blood flow direction, serving as the highly sensitive and specific first-line test for diagnosing Budd-Chiari syndrome.

Key Concept

The diagnostic approach to new-onset ascites requires calculating the SAAG and ascitic total protein; a high SAAG (> 1.1 g/dL) with high total protein (> 2.5 g/dL) and normal jugular venous pressure strongly suggests Budd-Chiari syndrome, which is initially evaluated with Doppler ultrasonography.

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