Feline model of chronic obstructive pancreatitis: effects of acute pancreatic duct decompression on blood flow and interstitial pH.

Background: The mechanism by which duct decompression (DD) relieves pain in patients with chronic pancreatitis (CP) is unknown. CP is associated with increased tissue pressure (IP), low pancreatic microvascular blood flow (PMBF), and interstitial pH (pH(I)). The aims of this study were to examine the effects of acute DD on PMBF, increased IP, and pH(I) in cats with CP.
Methods: The main pancreatic duct was partially obstructed. At 6 weeks PMBF (ml/min/100g H2 gas clearance), IP (mmHg needle electrode), and pH(I) (microelectrode) were measured before and after secretin stimulation. The duct was then opened, and the studies were repeated.
Results: PMBF normally increased with secretin stimulation (118 +/- 20 versus 271 +/- 52, P < 0.05). IP was unaltered, and pH(I) decreased as hydrogen ions produced during bicarbonate secretion were dissipated (7.41 +/- 0.01 versus 7.38 +/- 0.01, P < 0.05). In CP, basal PMBF was lower than normal (51 +/- 6 versus 118 +/- 20, P < 0.05) and decreased with stimulation (51 +/- 3.5 versus 31 +/- 3.5, P < 0.05). Basal pancreatic IP was increased (3.47 +/- 0.7 versus 0.05 +/- 0.3, P < 0.05) and increased further with secretory stimulation (3.47 +/- 0.7 versus 4.41 +/- 0.7, P < 0.05) (a compartment syndrome). The low basal pancreatic pH(I) (7.23 +/- 0.02) did not change with secretin stimulation, since bicarbonate secretion was minimal. DD decreased IP (3.66 +/- 0.5 versus 2.81 +/- 0.5, P < 0.05) and increased PMBF (50 +/- 6 versus 79 +/- 6, P < 0.05) and pH(I) (7.24 +/- 0.02 versus 7.34 +/- 0.02, P < 0.05). The normal increase in PMBF after stimulation was restored (79 +/- 6 versus 218 +/- 54, P < 0.05). pH(I) now increased with stimulation (7.34 +/- 0.002 versus 7.37 +/- 0.002, P < 0.05), perhaps due to the marked hyperaemic response.
Conclusions: DD acutely restored basal and stimulated PMBF and IP towards normal. Basal pancreatic pH(I) also improved and reflects the underlying ischaemia.