Easily confused with duodenum (hint - look for peristalsis)
Only measure the anterior wall as the posterior can be enlarged secondary to artifact
Gallbladder wall thickening can be caused by:
Acute cholecystitis
Ascites
CHF
Nephrotic syndrome
HIV / AIDS
Renal failure
Multiple myeloma
Contracted GB:  Three distinct wall layers is not pathological
GB Polyp: Soft tissue masses attached to the wall of the gallbladder and differentiated from gallstones by their lack of mobility and shadowing
Renal Cyst: Cysts in the superior pole of the kidney (hint - get two views)
Ascitic fluid: Located throughout peritoneum, including Morison’s pouch though pericholecystic fluid is localized to the anterior side of the gallbladder
Acute cholecystitis
Ascites
CHF
Nephrotic syndrome
HIV / AIDS
Renal failure
Multiple myeloma
Biliary ultrasound
Ultrasound: Abdomen
Liver function tests
GI antibiotics
Gastric lavage
Acute abdominal series
Paracentesis
Diagnostic peritoneal lavage