Table 1. Urinary profiles following Roux-en-Y gastric bypass surgery, grouped by stone history and study design.
| Article | Procedures [n] | F/U (mo.) | Urinary oxalate (CaOx SS) | Other urinary changes and study comments |
|---|---|---|---|---|
| Primarily non-stone formers, prospectively collected | ||||
| Park 2009 (10) | RYGB [45] | 9.6 | Pre-op: 32 (1.27) | De novo hyperoxaluria occurred in 90%. No symptomatic stone events during study |
| Post-op: 40 (2.23) | ||||
| Duffey 2010 (11) | RYGB [21] | 24 | Pre-op: 33 (1.73) | De novo hyperoxaluria occurred in 52%. Hypocitraturia increased from 10% at baseline to 48% but relative CaOx SS was unchanged |
| Post-op: 63 (2.2) | ||||
| Kumar 2011 (12) | RYGB [9] | 6, 12 | Pre-op: 26 (1.0) | Decreased total urine volume and higher fecal fat excretion at 6 and 12 months. Oral oxalate loading test at 6 and 12 months resulted in higher urine oxalate excretion |
| BPD [2] | Post-op: 32 (1.8) | |||
| Wu 2013 (13) | RYGB [38] | 6 | Pre-op: 38 (4.9) | Urine calcium increased by 43 mg/day (perhaps due to higher supplementation) while urine volume decreased by ½ liter/day. Stone formation or passage events were not recorded |
| Post-op: 48 (10.5) | ||||
| Agrawal 2013 (14) | RYGB [13] | 6 | Pre-op: 12.6 (1.4) | Prospective 24-hr urine study that included one stone former. Urinary oxalate was elevated 2, 4, and 6 months after RYGB. Both citrate and urine volume decreased by 30% |
| Post-op: 28.4 (5.7) | ||||
| Valezi 2013 (15) | RYGB [151] | 12 | Pre-op: 24 (NR) | Prospective 24-hr urine study that included 16 stone formers. Mean urinary uric acid levels increased 30% while volume decreased 40%. A total of 100% of patients were hypocitrituric at year 1 |
| Post-op: 41 (NR) | ||||
| Non-stone formers, retrospectively collected | ||||
| Nelson 2005 (7) | RYGB [13] | NR | RYGB =88 (2.38) | CaOx SS was reported in µmL/L (normal range <1.77). Long limb RYGB results in a shorter common channel resulting in more malabsorption |
| LL-RYGB [9] | LL-RYGB =95 (2.69) | |||
| Patel 2009 (16) | RYGB [52] | 14.2 | RYGB =62 (NR) | Comparisons made to healthy and stone forming adults from a commercial database |
| BPD [6] | BPD =90 (NR) | |||
| Penniston 2009 (17) | RYGB [27] | 32 | RYGB =48 (1.89) | Urine calcium decreased ~50% in RYGB versus GB, and 52% RYGB had urinary citrate <370 mg/day vs. 9% in GB. Urine volume decreased in both groups |
| GB [12] | GB =41 (2.78) | |||
| Maalouf 2010 (18) | RYGB [19] | 42 | RYGB =45 (7.0) | ~50% reduction in urinary citrate level compared to controls (mean 358 vs. 767 mg/day) |
| Con [19] | Con =30 (5.0) | |||
| Froeder 2012 (19) | RYGB [58] | 48 | RYGB/BPD =26 (NR) | Oxalate loading (RYGB =22, Con =21) showed higher urine oxalate in RYGB. No difference in O. formigenes colonization between subgroups (RYGB =10, Con =13). 6 patients had stones pre-op. No difference in CaOx SS, reported as Tiselius index |
| BPD [3] | Con =29 (NR) | |||
| Con [30] | ||||
| Primarily stone formers, retrospectively or prospectively collected | ||||
| Sinha 2007 (20) | RYGB [31] | N/A | Post-op: 60 (2.23) | Post-RYGB data compared to normal population references for urinary oxalate excretion |
| Asplin 2007 (21) | JIB [27] | N/A | JIB =102 (NR) | GB and RYGB surgeries were not separated for analysis. Mean time from procedure to stone event of 3.6 years. Stone formers identified in a corporate stone database |
| GB/RYGB [132] | GB/RYGB =83 (NR) | |||
| Con [2,210] | Con =34 (NR) | |||
| Pang 2012 (22) | JIB [1] | N/A | Entire cohort | Recurrent stone forming bariatric patients mean 11 years after surgery had increased pH, urine volume, and citrate on Met (controlled metabolic) diet. No significant changes in urine oxalate excretion was noted, even on low oxalate diet |
| RYGB [6] | Free Diet =65 (1.97) | |||
| BPD [2] | Met Diet =62 (1.13) | |||
F/U, follow-up in months, some means are number of months post-procedure; CaOx SS, calcium oxalate supersaturation; RYGB, Roux-en-Y gastric bypass; NR, not recorded; LL-RYGB, Long-limb Roux-en-Y gastric bypass; BPD, biliopancreatic diversion with duodenal switch; JIB, jejunoileal bypass; GB, gastric band; Con, control.