In Reply to "Abdominal Pressure and Fluid Status After Kidney Transplantation".

The Authors Reply:

We thank Yehuda and Nicolau-Raducu for their commentary on our recent publication. They first question the use of intra-abdominal pressure (IAP) as a surrogate of hydration status. We previously established a positive correlation between IAP and both central venous pressure and weight gain in our cohort. We also reported that severe intra-abdominal hypertension was associated with higher fluid balance. Others have previously revealed a correlation between IAP and other fluid status indicators, such as extravascular lung water index., These data suggest IAP as a fluid status indicator of interest, notably when it comes to optimizing kidney perfusion.

We agree with the authors that common risk factor of intra-abdominal hypertension include obesity (as we reported elsewhere), postoperative ileus, and bed position. We would like to clarify that none of the patients included in our study developed postoperative ileus (median time to resumption of transit: 2 days) and that all IAP measurements were performed in supine position according to our local protocol.

Second, CVP, Δweight, and IAP decreased between 36 hours and 72 hours from 9 ± 5 to 6 ± 4 cm H2O, +8 ± 4 to +6 ± 4%, and 15 ± 6 to 11 ± 5 mm Hg, respectively. These findings are consistent with the positive correlation found between these 3 variables in a linear mixed effect model.

Third, as pointed out by the authors, the pathophysiology of intra-abdominal hypertension-related acute kidney injury is multifactorial.S1 Although renal venous congestion represents the main driver of kidney failure in this setting,S2 Yehuda and Nicolau-Raducu also suggest increased ureteral pressure as a trigger. However, anticipated ureteral stenting failed to prevent oliguria when IAP was mechanically raised in an animal model.S3

Finally, we thank Yehuda and Nicolau-Raducu for pointing out the risk of fluid restriction-induced hypovolemia. Moderate hyperhydration has been widely used after kidney transplantation, consistently with the idea that large fluid administration would improve graft function recovery.S4 However, we and others have now reported that these patients could develop fluid overload complications.S4–S6 Our findings suggest that IAP could be useful to help decision once the patient is out of operatory room to optimize graft perfusion while avoiding fluid overload.