Morbid obesity is a global chronic disease, and bariatric procedures have been approved as the best method to control obesity. Roux-en-Y gastric bypass is one of the most common bariatric surgeries in the world and has become the gold standard procedure for many years. However, some patients experience weight regain or weight loss failure after the initial bypass surgery and require revisional or conversional interventions. International databases including PubMed, International Scientific Indexing (ISI), and Scopus were considered for a systematic search of articles that were published by 5th of May 2020. Forty-one published studies, which reported revision procedure on 1403 patients, were selected and analyzed for this review. The selected studies were categorized into six groups of revision procedures, including laparoscopic pouch resizing and/or revision of gastro-jejunal anastomosis (GJA), adjustable or non-adjustable gastric band over pouch ± pouch/GJA resizing, endoscopic revision of gastric GJA ± pouch, distal Roux-en-Y gastric bypass (DRGB), biliopancreatic diversion with duodenal switch (BPD-DS) or single anastomosis duodeno-ileal bypass with gastric sleeve (SADI-S), DRGB + Band or pouch/GJA resizing. Revision procedures result in more weight loss after the initial weight loss procedures. In the one-year follow-up, DRGB by itself with standardized mean difference (SMD) of - 1.24 presented a greater decrease in body mass index (BMI). DRGB plus band or pouch/GJA resizing, BPD-DS or SADI, adjustable or non-adjustable gastric banding over pouch ± pouch/GJA resizing, endoscopic pouch and/or GJA revision and laparoscopic pouch or/and GJA resizing revealed a lower decrease in BMI in order, respectively. In the three-year follow-up, BPD-DS or SADI-S method with SMD of - 1.40 presented the highest decrease in BMI. In follow, DRGB alone, adjustable or non-adjustable gastric banding over gastric pouch ± pouch / GJA resizing, DRGB + Band or gastric pouch/GJA resizing, laparoscopic pouch and/or GJA resizing and endoscopic revision of pouch and/or GJA revealed less reduction in BMI, respectively. In the five-year follow-up, DRGB alone procedures with SMD of - 2.17 presented the greatest reduction in BMI. Subsequently, BPD-DS or SADI-S, laparoscopic pouch and/or GJA size revision, and endoscopic revision of GJA/pouch revealed less overall decrease in BMI in order. All methods of revision procedures after the initial RYGB have been effective in the resolution of weight regain. However, based on the findings in this systematic review, it seems DRGB or BPD-DS/SADI-S is the most effective procedure in the long-term follow-up outcome. More studies with a higher number of patients and even longer follow-ups will be required to obtain more accurate data and outcome.
