From the description, I would imagine this is referring to the pain elicited on abdominal examination when peritoneal inflammation is present. One of the terms normally used in Spain is "dolor de rebote" because the pain occurs on the sudden release of the pressure of the hands during palpation of the abdomen. The idea of "despegue" sounds very similar.
This idea is supported by the presence of "defensa" ("guarding") which is another sign of intra-abdominal pain/inflammation and which is always present when there is peritoneal inflammation.

The general method for an acute abdomen - [ Traduzca esta página ]Rebound tenderness is tested for by pressing firmly and steadily on a ... and (4) prevent him immediately guarding his abdomen whenever you touch it, ...
www.meb.uni-bonn.de/dtc/ primsurg/docbook/html/x2980.html - 32k -

Chapter 13 - Section 2: First Principles of Gastroenterology - [ Traduzca esta página ]Severe cases exhibit peritoneal signs: guarding and local rebound tenderness. ... The abdominal findings of acute cholecystitis are accompanied by systemic ...
gastroresource.com/GITextbook/en/Chapter13/13-2.htm - 34k - En caché - Páginas similares

Gall stones in a child (a case report). Ahmed MN, Ram TT, Ali MM ... - [ Traduzca esta página ]There was also a history of a swelling in the right hypochondrium, ... becoming diffuse and there was rebound tenderness and guarding after eight hours of ...
www.jpgmonline.com/article.asp?issn=0022-3859; year=1987;volume=33;issue=2;spage=84;epage=6;aulast=Ahmed - 38k -

Best Practice Medicine- Professional Reference - Abdominal Pain - [ Traduzca esta página ]Gastroenterology, Abdominal Pain. ... the location and degree of tenderness, and any signs of peritoneal involvement (guarding, rebound tenderness). more ...
merck.micromedex.com/index.asp?page=bpm_ report&article_id=BPM01GA12 - 101k -

I have done a search for "despegue" in the context of abdominal pain but come up with nothing sensible. Could you give us the diagnosis? That might help make sense of the term.