Best way to diagnose lower small intestine obstruction?

Ans. (b) Multiple air fluid levelsRef: Bailey 26th edition, Page 1189* Two views are allowed to diagnose Small intestinal obstruction:# Supine abdominal film# Erect abdominal film* Bailey and Love says:"Erect films are no more advised, only supine films are enough to diagnose obstruction. In cases of doubt -- erect films are taken"Author's note: But we practically depend more on erect film -- if more than 5 air fluid levels are seen we confirm obstruction.* Findings:# Supine film: Gas filled bowel loops# Erect film: Stepladder pattern of air fluid levels# Air fluid levels appear late.# Number of air fluid levels is directly proportional to the degree of obstruction and distance of obstruction, more distal obstruction has more fluid levels.