Case 1: A 18-year-old male patient with severe mitral stenosis, severe pulmonary hypertension, tricuspid regurgitation and right heart failure was scheduled for mitral valve replacement surgery. Intraoperative transesophageal echocardiographic (TEE) transgastric view revealed large collection of fluid around the posterior aspect of heart giving picture of tamponade compressing heart [Figure 1] and [Video Clip 1].
Figure 1: Transesophageal echocardiographic transgastric view showing collection around heart (marked by red arrow) yellow arrow showing falciform ligament of liver margin. RV: Right ventricle, LV: Left ventricle
Case 2: A 48-year-old male patient operated case of mitral valve replacement 1 month back presented with severe breathlessness. Patient was intubated in view of respiratory distress and TEE was done. TEE revealed normal prosthetic valve function, but a large pericardial collection on the anterolateral aspect of heart giving tamponade effect [Figure 2].
Figure 2: Transesophageal echocardiographic transgastric view showing collection around heart (marked by red arrow)
In images of above presented two cases, collection compressing heart is evident in the same transgastric short axis view. However, other TEE views in case 1 did not show pericardial effusion [Figure 3]. In transgastric view, falciform ligament is seen which indicates that the collection is of ascitic fluid [Figure 1]. Hence, this case depicts false appearance of pericardial effusion in presence of ascites. In case 2, other views also demonstrated pericardial effusion giving compression effect [Figure 4]. This was a case of true pericardial effusion with tamponade. Effusion was drained by creating pleuropericardial window.
Figure 3: Transesophageal echocardiographic midesophageal view showing no collection around heart. Colour Doppler suggesting severe mitral regurgitation. LA: Left atrium, RA: Right atrium
Figure 4: Transesophageal echocardiographic midesophageal four chamber view showing pericardial collection around left side of heart. LA is huge with spontaneous echo contrast. Pr MV: Prosthetic mitral valve
The echo-free spaces near the heart which can be confused with pericardial effusion are-mediastinal cysts, lymphomas, thymomas, diaphragmatic hernia, left the atrial aneurysm, left ventricular pseudoaneurysm and coronary artery aneurysm. 
Echocardiographically, such ascitic echo-free spaces can be mistaken for pericardial effusions and pericardial cysts, which can also present as echolucent spaces anterior to the right ventricle.  Understanding the anatomical relationship of the space to the diaphragm, the liver, and the midline linear echo of the falciform ligament can help to distinguish ascites from pericardial fluid accumulation as in this case. The pericardium, diaphragm and parietal peritoneum separates the heart from ascitic fluid. 
On transthoracic echocardiography, falsiform ligament can be seen in the subdiaphragmatic view. Identification of falsiform ligament helps in the differential diagnosis of echofree space around the right heart border and the liver. Ascites is always recognized by visualizing falsiform ligament in this echolucent space. 
Transesophageal echocardiographic is definitely diagnostic in pericardial effusion, but comprehensive TEE examination will give proper diagnosis after ruling out other things.