Grey Turner's sign

Gray-Turner's sign is a sign that indicates hemorrhage in the peritoneum. It is a bruise seen in the side of the abdomen (flank).  When pancreas enzymes got released into the retroperitoneal cavity, it  causes bleeding from the retroperitoneum to the subcutaneous tissues of the area between the the end of the rib cage and the ilium (hip bone), aka the flank area (1). Even tho it's commonly thought to be attributed to acute pancreatitis, it can also occurs in AAA (abdominal aortic aneurysm).

Why it works?:
In normal physiology: pancreas releases enzymes that dissolve fat and nutrients in the small intestines. Remember that the pancreas lies behind the stomach and in front of the spine, it is, therefore, a retroperitoneal organ. Also, remember that the pancreas releases enzymes to the duodenum which is the first part of the small intestine that connects directly to the stomach. Therefore, you can image how the pancreas releases enzymes directly into the intestines.

In pancreatitis pathophysiology: pancreatic enzymes destroy the pancreas parenchyma and blood vessels. The damage of the blood vessels causes retroperitoneal hemorrhage.

In pancreatitis, the anatomic pathways of the pancreatic hemorrhage: "hemorrhage originates from the anterior pararenal space => spreading to posterior renal fascia => then to the lateral edge of the quadratus lumborum muscle (flank wall structures).: "The lumbar triangle is a site of anatomic weakness"=> "structural predisposition" to hemorrhaging spreading (according to (2)).

Mnemonics: Grey TURNer’s sign is located when you TURN towards your flank 

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Sources:
1 - Clinical images of Gray Turner's & Cullen's signs: http://www.nejm.org/doi/full/10.1056/NEJMicm1504339

2- Anatomic pathways: http://www.ncbi.nlm.nih.gov/pubmed/2910743

Peritoneal anatomic pathways: http://pubs.rsna.org/doi/full/10.1148/rg.322115032

Pancreatitis basic info. for patients from Nytimes: http://www.nytimes.com/health/guides/disease/acute-pancreatitis/overview.html

Pancreas basic info. for patients from Hopkins pathology: http://pathology.jhu.edu/pc/BasicOverview1.php?area=ba

Acute pancreatitis basic info.: http://drkupe.blogspot.com/2011/02/acute-pancreatitis.html

Mnemonics: http://www.internalizemedicine.com/2012/01/grey-turners-sign-and-cullens-sign-mnemonic.html

Retroperitoneal organs embryology development: https://academic.amc.edu/martino/grossanatomy/site/Medical/Lab%20Manual/Gastrointestinal/answers/mediastinum11.htm

Retroperitoneal organs anatomy & pathophysiology lecture: http://www.slideshare.net/dhruvtaneja1/reproteritoneum-anatomy-and-pathology

Chronic pancreatitis: http://www.ddc.musc.edu/public/diseases/pancreas-biliary-system/chronic-pancreatitis.html