<< Back to abstract listing

Na⁺/Ca²⁺ exchange by the gallbladder: a potential cause of gallstones.
AJ Moser, ZR Abedin, P Weber, MZ Abedin, JJ Roslyn.
Department of Surgery, Allegheny University of the Health Sciences, and Research Service, Philadelphia VA Medical Center, Philadelphia, PA.

Gallbladder (GB) bile Ca²⁺ concentrations are increased prior to gallstone formation and may serve as a nidus for cholesterol crystallization. This phenomenon may be due to passive concentration of lumenal Ca²⁺ by H₂O absorption or active Ca²⁺ secretion by the GB wall. We have shown that stimulation of epithelial Na⁺ transport in vitro leads to increased Ca²⁺ secretion. The mechanisms responsible for increased GB bile Ca²⁺ concentrations are unknown. Recent studies have identified the Na⁺/Ca²⁺ exchanger (NCX) as a rapid Ca²⁺ transport mechanism in cardiac myocytes. We hypothesize that the Na⁺/Ca²⁺ exchanger is also expressed by the GB and may play an important role in Ca²⁺ secretion. Total RNA was isolated from prairie dog and rabbit GB tissues and reverse transcribed into cDNA using the Perkin Elmer protocol. Template cDNA was then amplified by PCR using primers constructed from the conserved transmembrane domains of human cardiac NCX-1. The amplified PCR product was electrophoresed on 2% agarose gel and stained with ethidium bromide. {figure not available}

Both prairie dog (lane A) and rabbit (lane B) gallbladders demonstrated expression of a single band at approximately 684bp as predicted from the known sequence of NCX. This is the first reported isolation of NCX in the GI tract and specifically in the gallbladder. Its presence across species suggests a conserved role for Na⁺/Ca²⁺ exchange in Ca²⁺ homeostasis by the gallbladder. Future studies are directed to the contribution of NCX to Ca²⁺ secretion during gallstone formation.

Methods: Patients scheduled for an elective antireflux surgery at one institution were randomly assigned to one of two groups. Group I had a standard laparoscopic Nissen with a large esophageal bougie (56 Fr). Group II had exactally the same repair with no bougie. Patients with giant paraesophogeal hernias, Collis lengthening procedures or partial fundoplications (done for motility disorders) were excluded from this analysis. Complications related to bougie use were recorded. Dysphagia was assessed according to a frequency and severety score preop, immediately postop (< 4 weeks) and for long term (>4 weeks). Results were tabulated and subjected to a student - T test for statistical validity.

Results: Between 3/96 and 12/96 88 laparoscopic antireflux surgeries were randomized to the study. 38 met the criteria of simple, uncomplicated Nissen fundoplications and were analyzed for this study. Data was collected in a blinded fasion. There were 20 patiens in the no stent group and 18 in the stented group. The incidence of bougie injuries in group I was 5%(I pharyngeal laceration). Preoperative dysphagia was present in 40% of group I and 67% of group II. Early postop dysphagia was noted in 84% of group I and 62% of group II. Late dysphagia was described in 47% and 36% respectedly for group I and II. No patients in either group have recieved intervention for their dysphagia. The mean dysphagia score for group I for the three time frames was 3.4, 10.5, 1.9 respectively. For group II the scores were 7.1, 4.2, 1.9. These differences were significant for the early postop group (p=.03) but not for the preop score (p=.13) or for the late post op period (p=.93).

Conclusion: We present the first randomized prospective study that attempts to validate the use of esophageal stenting in Nissen fundoplication and show that there is, infact, a higher incidence of transient dysphagia in patients when a bougie is not used. On the other hand, long term dysphagia rates were not different. The avoidence of early dysphagia must be balanced against an incidence of bougie related injuries (5%) during the laparoscopic procedure. Based on these results we feel that the routine use of an esophageal stent during a laparoscopic fundoplication is not indicated.