Table 3.

Definitions of postoperative ileus used in studies.

Study	Definition of postoperative ileus
Akiyoshi et al (2011)33	‘Persistent ileus’ – not otherwise defined.
Artinyan et al (2008)4	Patient’s ability to tolerate a solid diet in the absence of nausea, vomiting or abdominal distention.
Bakker et al (2015)45	Prolonged inability to pass flatus and stool resulting in nausea and vomiting and requiring the use of a nasogastric tube and/or total parenteral nutrition.
Barletta et al (2011)15	Three episodes of vomiting over 24 hours, cessation of oral diet or the need for a nasogastric tube within 5 days after surgery.
Bickenbach et al (2013)35	Not defined.
Bisanz et al (2008)16	Lack of return of bowel function; no passage of flatus; unable to tolerate oral intake; abdominal distention, nausea and vomiting, and absence of bowel movement by postoperative day 3.
Chapuis et al (2013)5	Presence of abdominal distension with lack of bowel sounds in a patient who has experienced nausea or vomiting and has failed to pass flatus or stool for more than 3 days postoperatively, in the absence of mechanical bowel obstruction.
Englesbe et al (2010)46	An ileus lasting more than 7 days from the index operation.
Franko et al (2006)31	Ileus defined as the inability to tolerate any diet combined with abdominal distension beyond the third postoperative day.
Grosso et al (2012)26	Not defined.
Hamel et al (2000)30	Any placement of a nasogastric tube during the initial hospitalisation; the criterion was vomiting 200ml or more, two or more times.
Huang et al (2015)27	Two or more of the following five criteria met on or after postoperative day 4 without prior resolution of ‘postoperative ileus’: nausea or vomiting, inability to tolerate oral diet over 24 hours, absence of flatus over 24 hours, abdominal distension and radiological confirmation of ileus.
Ichikawa et al (2016)47	Not defined.
Juarez-Parra et al (2015)17	The absence of passage of flatus/stool or inability to tolerate oral diet on or after four postoperative days.
Kim et al (2013)28	Absence of adequate bowel function on postoperative day 5 or the need for insertion of a nasogastric tube in the absence of a mechanical obstruction.
Kronberg et al (2011)25	Not defined.
Le et al (2011)21	Any transient cessation of coordinated bowel motility following surgery that prevented the effective transit of intestinal contents or tolerance of oral intake within 7 days of surgery.
Millan et al (2012)29	No bowel recovery at postoperative day 6.
Moghadamyeghaneh et al (2016)22	No return of bowel function within 7 days.
Murphy et al (2016)23	Nasogastric tube or nil by mouth on postoperative day 4 or later.
Petros et al (1995)18	Passage of flatus or stool, or the ability to tolerate a clear liquid diet, were regarded as evidence of the resolution of postoperative ileus. Postoperative ileus ≥ 7 days.
Pikarsky et al (2002)34	Ileus defined as a condition requiring reinsertion of a nasogastric tube due to two or more episodes of emesis of more than 200ml.
Tian et al (2017)19	ICD-10 diagnostic code K56. Abdominal plain x-ray and computed tomography, and the presence of clinical manifestations including nausea, vomiting, abdominal pain, abdominal distension, and/or delay in the passage of flatus and stool for more than 7 days postoperatively, in the absence of mechanical bowel obstruction.
Valenti et al (2007)48	Continued nasogastric tube on the fifth postoperative day or reintroduction of the tube
Vather et al (2013)20	Prolonged postoperative ileus was recorded as occurring if this was clinically diagnosed and documented by the overseeing surgical team.
Vather et al (2015)24	Prolonged postoperative ileus was defined as occurring if patients met two of the following five criteria on or after postoperative day 4: nausea or vomiting over the preceding 12 hours, inability to tolerate a solid or semisolid oral diet over the preceding two meal times, abdominal distension, absence of flatus and stool over the preceding 24 hours.
Yamamoto et al (2013)32	Not defined.

ICD-10, International Classification of Diseases and Related Health Problems, 10th revision.