Spontaneous volume changes in gastric banding devices: complications of a semipermeable membrane

The goal of this study was to prove that adjustable laparoscopic gastric ba nding (LAP-BAND) is semipermeable and that luminal adjustment with saline l eads to spontaneous fluid loss, luminal widening, and effect loss which mak es repeated readjustments necessary. In 64 patients stoma adjustment was pe rformed with saline according to the guidelines of the manufacturer (group 1). In 32 patients hyperosmolar contrast material was used for stoma readju stments with the intention to detect a system leakage after spontaneous flu id loss and spontaneous luminal widening was observed (group 2). After spon taneous luminal narrowing had occurred in group 2, all patients from group 2 and all additional patients (n = 148) underwent stoma (re-) adjustment wi th iso-osmolar contrast material (group 3). Spontaneous fluid changes which led to spontaneous changes of the luminal width were then analyzed for the different filling substances in each group. Fifty-two patients from group 1 presented with effect loss because a spontaneous luminal widening had occ urred secondary to a fluid loss of 0.1-0.2 ml/month. All 32 patients from g roup 2 presented with increasing obstruction and food intolerance because a spontaneous luminal narrowing had occurred secondary to a spontaneous flui d gain of 0.1-0.3 ml/month. In our patients from group 3, where stoma adjus tment was performed with iso-osmolar contrast material, no spontaneous flui d changes were observed and luminal width/degree of obstruction did not cha nge. The LAP BAND is semipermeable. Stoma adjustment should not be performe d with saline in order to avoid spontaneous luminal widening and the need f or repeated readjustments. Stoma adjustments with hyperosmolar contrast mat erial are clearly contraindicated since osmotic fluid gain leads to increas ing obstruction. Stoma adjustments should be performed using iso-osmolar fi lling media which provide a stable luminal obstruction.