Decubitus

Question 1

Indications for decub projection

Answer 1

• distension
• free gas in peritoneal cavity
• fluid levels in the intestine
• evidence of aortic aneurysm
• imperforate anus

Question 2

describe lateral decub positioning

Answer 2

• pt lies on the left side for about 10 mins to allow free air to rise towards the right flank
• ensure the MSP is perpendicular to IR
• central ray at level of LCM

Question 3

alternative to lateral decub

Answer 3

dorsal decub

• CR directed to the centre of IR along the MCP at level of LCM

Question 4

prone lateral projection

Answer 4

for imperforate anus in infant

• allow about 10 mins for any free air to rise towards the topmost part of the rectum
• prone position is preferred as it provides extra info on the gas content of sigmoid and rectum
• if anal opening is absent, pediatrician/surgeon may indicate desired position of the anus and ask radiographer to mark region with radio-opaque marker