Learn the cause of ascites in a 58-year-old man with shortness of breath and abdominal distention. Explore his medical history, vital signs, and physical examination findings. Learn about the diagnostic clues and the significance of a serum-ascites albumin gradient (SAAG) of 1.5. Enhance your medical knowledge with this USMLE® Step 2-style practice question.
A 58-year-old man presents to the emergency department to be evaluated for 1 month of shortness of breath and abdominal distention. Past medical history is significant for hypertension, morbid obesity, and obstructive sleep apnea. The patient takes losartan for his hypertension but does not always take it consistently, and he does not use his continuous positive airway pressure (CPAP) device. Temperature is 36.7°C (98.1°F), pulse is 90/min, blood pressure is 144/95 mmHg, respiratory rate is 18/min, and SpO2 is 97% on room air. On physical examination, the lungs are clear upon auscultation. The abdomen is nontender to palpation. There is a fluid wave and dullness to percussion. There is bilateral lower extremity edema. Serum white blood cell count and creatinine are normal. Paracentesis is performed, which shows a serum-ascites albumin gradient (SAAG) of 1.5. Which of the following findings would likely confirm the cause of this patient’s ascites?A. Right atrial pressure measurement on echocardiogram
B. Urine protein/creatinine ratio
C. Amylase level in ascites fluid
D. Cytology from ascites fluid
E. Alpha-1-antitrypsin level in stool
The correct answer to today’s USMLE® Step 2 CK Question is…
A. Right atrial pressure measurement on echocardiogram
Before we get to the Main Explanation, let’s see why the answer wasn’t B, C, D, or E. Skip to the bottom if you want to see the correct answer right away!
Incorrect answer explanations
B. Urine protein/creatinine ratio
Incorrect: Urine protein/creatinine ratio can be used to diagnose nephrotic syndrome if it is >3 (or >3.5 per some definitions). However, nephrotic syndrome is not the likely cause of this patient’s ascites given the SAAG of 1.5 and normal serum creatinine.
C. Amylase level in ascites fluid
Incorrect: An elevated amylase level in ascites fluid would be seen in ascites due to pancreatitis. This patient’s history is largely inconsistent with pancreatitis, and the condition is usually associated with an SAAG <1.1 which is not seen in this patient.
D. Cytology from ascites fluid
Incorrect: Malignant cells found on cytology from ascites fluid would indicate peritoneal carcinomatosis. Patients often have weight changes (weight gain from significant ascites or weight loss from cancer-related cachexia) and may have leukocytosis. More importantly, ascites associated with peritoneal carcinomatosis would be associated with an SAAG <1.1 which is not present in this patient.
E. Alpha-1-antitrypsin level in stool
Incorrect: An elevated alpha-1-antitrypsin level in the stool would be seen with protein-losing enteropathy. This patient has no diarrhea or steatorrhea. Moreover, protein-losing enteropathy is associated with an SAAG <1.1
Main Explanation
Ascites (excessive or abnormal free fluid in the peritoneal cavity) usually occurs due to intra-abdominal pathologies, but it is also associated with many different systemic disease processes. Clinical history, physical examination, and serum-ascites albumin gradient (SAAG) can help determine the underlying etiology of the ascites. This patient with dyspnea, abdominal distension, and a SAAG ≥1.1 g/dL likely has ascites secondary to right-sided heart failure. Hypertension, morbid obesity, and untreated sleep apnea can lead to pulmonary hypertension, which eventually causes right ventricular failure. Elevated right atrial pressures on echocardiogram indicates pulmonary hypertension.
Careful history and physical examination can give clues to the cause of ascites. History should focus on chronicity and progression of the ascites. Slowly progressive ascites usually suggests more chronic etiologies, such as cirrhosis, peritoneal malignancy, nephrotic syndrome, or right-sided heart failure. Acute onset ascites usually suggest more acute etiologies, such as portal vein thrombosis, acute pancreatitis, or acute liver failure. Assessing for symptoms of volume overload (e.g. dyspnea, lower extremity swelling) and abdominal pain is important. It is also important to inquire about coexisting diseases, such as malignancy as well as kidney, liver, or heart disease.On physical examination, patients should be assessed for signs of volume overload. Patients with cirrhosis or nephrotic syndrome will generally have systemic volume overload, whereas patients with ascites from acute pancreatitis or portal vein thrombosis generally do not. Patients with cirrhosis may have stigmata of cirrhosis. Significant abdominal tenderness to palpation may be seen in acute pancreatitis, acute liver failure, and spontaneous bacterial peritonitis.
Major Takeaway
Clinical history, physical examination, and the serum-ascites albumin gradient can be used to identify the underlying cause of ascites. Right-sided heart failure can cause ascites with SAAG ≥1.1.
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