Table 1.

Characteristics and methodological summary of studies

Reference	Study characteristics								Outcomes measured
	Year	Country	Period	Data type	No of patients	No of hospitals	Low*	High*	Mortality	Complications (breakdowns)	Transfusion	LOS	Conversions	Others	Case mix	Quality score (18)
Radical nephrectomy
Hjelle29	2016	Norway	2008–2013	Admin	3273	40	20	40	30 day	−	−	−	+	−	Demographics, tumour stage, nephrectomy type	8
Becker30/Sun31 †	2014/ 2012	USA	1998–2007	Admin	48 172	N/S	5	16	In-hospital	+ (17 events including haemorrhage, cardiac arrest, infection, wound disruption, seroma, pneumothorax, VTE, etc)	+	+	−	−	Demographics, comorbidity, nephrectomy type, laparoscopy, payer/hospital type	9
Hanchanale32	2010	England	1998–2005	Admin	20 672	1181	14	35	In-hospital	−	−	+	−	−	Demographics	9
Yasunaga33	2010	Japan	2006–2007	Admin	7988	646	26	65	In-hospital	+ (11 events including surgical site infection, UTI, VTE, sepsis, ileus, stroke, cardiac events, renal, failure, peritonitis, etc)	−	−	−	−	Demographics, comorbidity, laparoscopy, hospital type, tumour location	9
Mitchell34	2009	USA	2003–2007	Clinical	42 988	134	99/4.5 year	500/4.5 year	In-hospital	+ (not specified)	−	+	−	ICU admission	None	9
Yasunaga18	2008	Japan	2006–2007	Clinical	1704	461	9	40	In-hospital	+ (wound infection, pneumonia, ileus, renal dysfunction, others)	−	−	−	OT, EBL	Demographics, comorbidity, laparoscopy, tumour stage and location	11
Davenport35	2005	England	2004	Clinical	598	48	<1/month	>1/month	N/S	+ (12 events including bleeding, bowel injury, GI bleed, renal failure, pneumothorax, VTE, MI, splenic injury, etc)	+	−	+	OT	None	4
Keoghane41	2004	England	2001–2002	Clinical	263	25	5	6	-	+ (16 events including renal failure, sepsis, wound infection, bowel injury, incisional hernia, peri hepatic collection, etc)	−	−	+	−	None	3
Taub36	2004	USA	1993–1997	Admin	16 858	962	14	34	In-hospital	−	−	+	−	−	Demographics, comorbidity, admission acuity	9
Birkmeyer37	2002	USA	1994–1999	Admin	58 990	3292	6	33	30 day or in-hospital	−	−	−	−	−	Demographics, comorbidity, admission acuity	7
Partial nephrectomy
Couapel38	2014	France	2010	Clinical	570	53	4/7 month	19/7 month	N/S	+ (medical and surgical events, not further specified)	−	+	+	OT, EBL, totalisation, +ve margin	N/S	8
Monn42	2014	USA	2009–2011	Admin	17 583	322	13	35	−	+ (organ-based complications not further specified, pain, seroma, shock, haematoma, hypotension, VTE, pneumothorax)	+	+	−	Hospital cost	Demographics, comorbidity, payer, region, hospital type	9
Abouassaly39	2012	Canada	1998–2008	Admin	4292	181	146/10 year	797/10 year	In-hospital	+ (not specified)	−	−	−	−	Demographics, comorbidity, region	12
Taub36	2004	USA	1993–1997	Admin	1172	962	14	34	In-hospital	−	−	+	−	−	Demographics, comorbidity, admission acuity	9
Nephrectomy with venous thrombectomy
Toren40	2013	Canada	1998–2008	Admin	816	120	N/S	N/S	In-hospital	+ (40 medical and surgical events including MI, CHF, PE, infection, organ injury, pneumothorax etc)	+	−	−	−	Demographics, comorbidity, region	11
Yap19	2012	Canada	1995–2004	Admin	433	N/S	2/10 year	8/10 year	30 day	−	−	−	−	−	Demographics	11

*Low, cut-off value for lowest volume group; high, cut-off value for highest-volume group. Volume units are cases per year unless specified.

 †Becker and Sun were equal in the data source used, outcomes evaluated, periods covered and quality scores, but employed different analyses to evaluate the benefit of regionalisation and volume–outcome relationship in nephrectomy.^{30 31} We therefore treated them as one single cohort, with no duplicates in our analysis.

Admin, administrative; CHF, congestive heart failure; EBL, estimated blood loss; GI, gastrointestinal; ICU, intensive care unit; LOS, length of stay; MI, myocardial infarction; N/S, not specified; OT, operating time; PE, pulmonary embolism; UTI, urinary tract infection; VTE, venous thromboembolism.