A 55-year-old man comes to the clinic due to a 4-week history of progressive abdominal swe… — USMLE Step 2 CK

A 55-year-old man comes to the clinic due to a 4-week history of progressive abdominal swelling, early satiety, and lower extremity edema. He has a 15-year history of heavy alcohol consumption but stopped drinking one month ago. His temperature is 37.0°C (98.6°F), blood pressure is 112/68 mm Hg, and pulse is 88/min. Physical examination reveals scleral icterus, multiple spider angiomas on the upper chest, and shifting dullness on abdominal percussion. Trace pitting edema is present bilaterally in the lower extremities. A diagnostic paracentesis is performed.

Test	Result
Serum albumin	3.4 g/dL
Ascitic fluid albumin	0.8 g/dL
Ascitic fluid total protein	1.5 g/dL
Ascitic fluid leukocyte count	200/mm³ (10% neutrophils)

What is the primary pathophysiologic mechanism responsible for this patient's abdominal fluid accumulation?

A
Elevated right atrial and post-hepatic venous pressure
Increased intrahepatic vascular resistanceCevap
C
Heavy proteinuria leading to decreased plasma oncotic pressure
D
Direct peritoneal inflammation due to an infectious pathogen
E
Transmural bowel ischemia secondary to mechanical obstruction

Cevap

Increased intrahepatic vascular resistance is the correct mechanism, as evidenced by a SAAG >= 1.1 g/dL and ascitic total protein < 2.5 g/dL, which strongly points to cirrhosis.

The correct mechanism is increased intrahepatic vascular resistance, which is the hallmark of cirrhosis. This patient's clinical signs (spider angiomas, icterus, alcohol history) strongly suggest cirrhosis. Diagnostically, the Serum-Ascites Albumin Gradient (SAAG) is calculated by subtracting ascitic albumin from serum albumin (

3.4 - 0.8 = 2.6

g/dL). A SAAG

\geq 1.1

g/dL indicates portal hypertension. To differentiate the cause of portal hypertension, ascitic total protein is evaluated: levels

< 2.5

g/dL point to intrahepatic (cirrhotic) causes, while levels

\geq 2.5

g/dL point to post-hepatic causes like right heart failure. This patient's low protein confirms cirrhosis.

Adım Adım Çözüm

Calculate the Serum-Ascites Albumin Gradient (SAAG).

SAAG = 3.4 \text{ g/dL} - 0.8 \text{ g/dL} = 2.6 \text{ g/dL}

SAAG is the most accurate initial test to differentiate ascites caused by portal hypertension from other causes.

Interpret the SAAG value.

A SAAG of

2.6

g/dL is

\geq 1.1

g/dL, confirming the presence of portal hypertension.

Portal hypertension drives fluid into the peritoneal cavity via increased hydrostatic pressure, leaving larger albumin molecules in the serum.

Evaluate the ascitic fluid total protein.

The total protein is

1.5

g/dL, which is

< 2.5

g/dL.

In the setting of portal hypertension, a low ascitic protein (< 2.5 g/dL) indicates an intrahepatic source (cirrhosis), whereas a high protein (>= 2.5 g/dL) indicates a post-hepatic source (right heart failure).

Anahtar Kavram

Cirrhotic ascites is characterized by a Serum-Ascites Albumin Gradient (SAAG) >= 1.1 g/dL and an ascitic fluid total protein < 2.5 g/dL, resulting from increased intrahepatic vascular resistance.

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Cevap

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