Technical limitations of lymph node mapping in pancreatic cancer.

AIM: The high incidence of lymphatic and peri-neural invasion in pancreatic cancer results in poor loco-regional control. Radical pancreatico-duodenectomy may achieve better loco-regional control, but is accompanied by increasing morbidity. Our hypothesis was that if intra-operative mapping of pathological lymph nodes (LN) is technically feasible in pancreatic cancer, it would allow for selective radical resection. METHODS: In an ethically approved and statistically powered feasibility study of 72 (stopped after 20% enrollment) patients with suspected pancreatic cancer undergoing resection, we injected methylene blue dye peri- and intra-tumorally and studied its progress to identify putative 'sentinel lymph node(s)'. The Kausch-Whipple procedure (or total pancreatectomy, if required) was carried out in addition to radical LN dissection, which was evaluated histopathologically according to the Japanese criteria. RESULTS: Over 18 months, 14/16 patients prospectively recruited underwent lymph node mapping and a mean of 20 (range 11-37) LNs per patient were harvested. Methylene blue dye injection identified blue LN(s) in 4/14 patients, none of which were positive for malignant deposits, whilst 10/14 patients had LN metastases. The commonest stations for LN metastasis were 17A or B (9/10), 8A (2/10) and 6 (3/10). The median survival for the 13 patients with cancer was 22.3 months (IQR: 10.4-30 months). CONCLUSION: Sentinel lymph node mapping is not technically feasible in pancreatic cancer.

The teaching of surgery in the undergraduate curriculum--reforms and results.

In the past decade, the teaching of surgery in the undergraduate curriculum has undergone considerable changes in quantity, mode and method of delivery. This is a result of the radical reforms of higher education, the health service and the undergraduate medical curriculum. These reforms are often interrelated and are occurring in conjunction with major changes in healthcare delivery. In this article we discuss this reorganisation, the rationale behind it and the impact on surgical teaching.

The teaching of surgery in the undergraduate curriculum. Part II--Importance and recommendations for change.

In the past decade, the teaching of surgery in the undergraduate curriculum has undergone considerable changes in quantity, mode and method of delivery. This is a result of the radical reforms of higher education, the health service and the undergraduate medical curriculum. The changes are complex and require us to ask the questions: how important is the teaching of surgery in the modern medical undergraduate curriculum and is there a need for change? We aim to tackle these questions and propose practical action which medical schools can take to ensure that they deliver effective surgical teaching within the modern medical curriculum and health service.

The teaching of surgery in the undergraduate curriculum--reforms and results.

In the past decade, the teaching of surgery in the undergraduate curriculum has undergone considerable changes in quantity, mode and method of delivery. This is a result of the radical reforms of higher education, the health service and the undergraduate medical curriculum. These reforms are often interrelated and are occurring in conjunction with major changes in healthcare delivery. In this article we discuss this reorganisation, the rationale behind it and the impact on surgical teaching.

Location and function of intrahepatic shunts in anaesthetised rats.

BACKGROUND: In the present study we determined the proportion of shunt flow due to patent intrahepatic portal systemic shunts in the normal rat liver and its relationship with microsphere induced portal hypertension. METHODS: Systemic and hepatic haemodynamics were measured continuously before, during, and after intraportal injection of 15 micro m diameter microspheres in anaesthetised male Wistar rats. Functional hepatic blood flow and intrahepatic shunt flow were determined by the use of constant intraportal infusion of sorbitol and simultaneous measurements in the portal vein, hepatic vein, and carotid artery. The percentage of large shunts of diameter >15 micro m were estimated by intraportal injection of (51)Cr labelled 15 micro m diameter microspheres. RESULTS: Hepatic sorbitol uptake was 97.9 (0.5)% in normal control rats, with functional hepatic blood flow equalling total hepatic blood flow (2.52 (0.23) ml/min/100 g body weight). Microsphere injection decreased sorbitol uptake to 12.8 (4.3)% and further to 4.1 (0.7)% when followed by hepatic arterial ligation. In the latter two groups, intrahepatic shunt flow (1.46 (0.15) and 1.16 (0.19) ml/min/100 g body weight, respectively) was not significantly different from portal venous flow (1.36 (0.20) and 1.20 (0.20) ml/min/100 g body weight, respectively). Portal venous flow remained at 70% of basal values and portal venous pressure only increased by 50% from baseline. (51)Cr labelled microsphere shunt fraction through large shunts (>15 micro m) was less than 1.0%. CONCLUSION: The site of confluence between the hepatic artery and portal vein is in zone II. Intrahepatic shunts originate in presinusoidal regions in zone I in the normal liver and, when activated by intraportal injection of microspheres, divert 70% of the total portal blood flow away from zone III and thereby reduce acute increases in portal venous pressure.

Pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) as a tool for differentiation of P2Y2-receptor-mediated vasorelaxation in guinea pig aorta.

The action of the putative P2Y1-receptor antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) was studied in guinea pig aorta for potential use in the differentiation between P2Y1 and P2Y2 purine receptors. Concentration-effect curves to 2-methylthioadenosine triphosphate (2MeSATP) and uridine triphosphate (UTP), agonists at P2Y1- and P2Y2-receptor sites, respectively, and the common agonist adenosine triphosphate (ATP) were constructed in guinea pig aortic ring preparations with the tone raised by 5 microM of noradrenaline. A ranked order of agonist potency of 2MeSATP > ATP > UTP resulted from the construction of concentration response curves to vasorelaxation of the agonists. Deendothelialization virtually abolished vasorelaxation to UTP but made no significant difference to 2MeSATP-induced responses. PPADS exhibited noncompetitive inhibition at P2Y1-receptor sites by reducing the maximal response to 2MeSATP, although a trend towards a right shift of the concentration-effect curves was observed. In total contrast, PPADS enhanced P2Y2-mediated vasorelaxation to UTP by shifting the concentration-effect curves to the left and increasing maximal responses. Thus, PPADS is a noncompetitive antagonist at P2Y1 receptors but enhances responses, at least to UTP, at P2Y2 receptors in guinea pig aorta via a hitherto unknown mechanism. Thus, PPADS is a potentially useful substance that may be used for differentiation between P2Y1 and P2Y2 receptors in the guinea pig aorta.

Long-term outcome of hepaticojejunostomy with routine access loop formation following iatrogenic bile duct injury.

BACKGROUND: Hepaticojejunostomy is the 'gold standard' procedure for repairing iatrogenic bile duct injuries. The aim of this study was to examine the long-term outcome following hepaticojejunostomy for iatrogenic bile duct injury and the utility of routine construction of an access loop. METHODS: Patients with iatrogenic biliary injuries were treated with hepaticojejunostomy and access loop by a single surgeon. Injuries were classified according to the Bismuth level. An 'excellent' outcome was achieved if the patient never experienced jaundice or cholangitis in the follow-up period, and the outcome was 'good' if the patient developed symptoms but was asymptomatic for more than 12 months. RESULTS: Forty-eight patients underwent such operation. There was one operative death. Thirty-three patients were followed for 3 years or more (mean follow-up 80.4 (range 46-118) months). Thirteen of the 33 injuries were Bismuth level II, 13 were Bismuth level III and seven were Bismuth level IV. Outcome was dependent on the Bismuth level (P < 0.001). It was excellent in all 13 patients with Bismuth level II injuries, excellent in seven and good in six of the 13 patients with Bismuth level III injuries, and excellent in one and good in six of the seven patients with Bismuth level IV injuries. Moreover, the need for access loop intervention was dependent on the Bismuth level (P < 0.001). No patient with Bismuth level II injury required intervention, compared with five of 13 with Bismuth level III and six of seven with Bismuth level IV injuries. CONCLUSION: Biliary reconstruction affords satisfactory long-term outcome. The likelihood of needing the access loop for radiological intervention is dependent on the Bismuth level. The authors recommend that an access loop be constructed in all patients with Bismuth level III and IV injuries.

Functional and compositional studies of arteries stored in University of Wisconsin solution compared with Krebs-Bülbring buffer.

Endothelium-dependent and -independent vasorelaxation in ring segments of rabbit thoracic aorta is reduced and noradrenaline-induced vasoconstriction unaltered after prolonged storage in University of Wisconsin solution (UW) compared to arteries stored in extracellular-type solutions such as Krebs-Bülbring buffer (KBB). The aims of the present study were to determine whether angiotensin-II-induced vasoconstriction, alterations in myosin light chains, protein synthetic capacity, and subcellular structures are altered after 8 days of UW storage at 4 degrees C. The present study showed reduced contractility to angiotensin II, following 8 days of cold storage in UW, that was not reversed in the presence of a nitric oxide synthase inhibitor, N(G)-nitro-l-arginine methyl ester (100 microM). Measurements of contractile protein ratios in the same tissues after cold storage in UW or KBB did not show any significant alterations in smooth muscle myosin light chains or protein synthetic capacity (reflected by total RNA). It is concluded that reductions in vasoconstriction in UW-stored tissue are unlikely to be due to increased release of nitric oxide nor reduced availability of myosin light chains for phosphorylation and vasoconstriction.

Nitric oxide modulates acetylcholine-induced vasodilatation in the hepatic arterial vasculature of the dual-perfused rat liver.

The role of nitric oxide in the modulation of hepatic arterial vascular reactivity was investigated in an isolated dual-perfused rat liver preparation. Twelve male Wistar rats (200-250 g) were anaesthetized with sodium pentobarbitone (60 mg kg-1 i.p.). The livers were then excised and perfused in vitro through hepatic arterial and portal venous cannulae at constant flow rates. Concentration-dependent dose-response curves to acetylcholine (10(-8)-10(-5) M), sodium nitroprusside (10-6(-5) x 10(-4) M), and adenosine triphosphate (ATP) (10(-8)-10(-5) M) in the hepatic artery were constructed after the tone was raised by addition of methoxamine (3 micorM L(-1)). Acetylcholine-induced vasodilatation in the hepatic artery was significantly attenuated with inhibition of nitric oxide synthase by using NG-nitro-L-arginine methyl ester (30 microM), Emax = 51.7 +/- 2.8 vs. 32.5 +/- 3.1 mmHg, before vs. after NG-nitro-L-arginine methyl ester, respectively. ATP-induced hepatic arterial vasoconstriction which was significantly enhanced with L-NAME, Emax = 94.0 +/- 9.3 vs. 127.0 +/- 8.0 mmHg, before vs. after NG-nitro-L-arginine methyl ester, respectively. Sodium nitroprusside-induced hepatic arterial vasodilatation remained unchanged with NG-nitro-L-arginine methyl ester, Emax = 57.0 +/- 3.4 vs. 57.0 +/- 4.1, before vs. after NG-nitro-L-arginine methyl ester, respectively. The data from the present study suggest that acetylcholine-induced vasodilatation in the intrahepatic arterial vasculature of the rat liver is at least, in part, mediated by the release of nitric oxide. In addition, ATP-induced hepatic arterial vasoconstriction is also modulated by the release of nitric oxide (*P < 0.05, Student's paired t-test).

A quantitative evaluation of the permeability of the blood brain barrier of portacaval shunted rats.

The integrity of the blood-brain barrier (BBB) was measured in male Sprague Dawley rats subjected to 16 weeks of portacaval shunting (PCS), the optimal time required for the cerebral changes to develop, by using an in situ brain perfusion technique. The penetration of a vascular space marker 14C mannitol, and labelled amino acids 3H-phenylalanine or 3H-glutamate were measured in brain and cerebrospinal fluid (CSF) using an in situ brain perfusion technique, over 2 or 20 minutes. The patency of the surgical shunt was confirmed by measurement of significantly increased plasma ammonia (131.5 +/- 14.8 micromol x l(-1)) and AST (159.5 +/- 19.9 IU x l(-1)) concentrations compared to controls 39.9 +/- 3.7*, and 82.5 +/- 6.6* respectively. Brain and CSF 14C-mannitol space (ml x 100g(-1)), was not increased by PCS where brain space was 1.31 +/- 0.27 mL x 100g(-1) compared to control 1.19 +/- 0.49 mL x 100g(-1), and CSF was 0.14 +/- 0.06 mL x 100g(-1) compared to control 0.15 +/- 0.05 (PCS n=10, control n=8). The uptake for 3H-glutamate, which is required for cerebral ammonia detoxification, was also unchanged in both brain and CSF. However, brain uptake of 3H-phenylalanine was significantly reduced from 871 +/- 80 microL x min(-1) x g(-1) to 356 +/- 154* microl x min(-1) x g(-1) (n=4), although there was no change in CSF uptake. These data suggest that there is no generalized breakdown of the blood-brain or blood-CSF barriers during PCS as assessed by mannitol penetration. The reduction in phenylalanine uptake into the brain may help stabilize high cerebral aromatic amino acid levels. *P<0.05, Two-tailed, Student's unpaired t-test.

Effect of perfusate albumin on organ viability and vascular responses in the in vitro dual-perfused rat liver.

Inclusion of albumin in the perfusate has been previously shown to be detrimental to liver function, but its effect on hepatic vascular reactivity remains unknown. The aim of this study was to determine the effects of albumin on hepatic arterial vascular reactivity and liver viability in the isolated dual-perfused rat liver. A total of 12 rat livers were perfused with Krebs-Bülbring buffer without (Group 1) and with (Group 2) addition of 1% bovine serum albumin (BSA) through the hepatic artery and portal vein for up to 5 h. Hepatic arterial responses to acetylcholine and sodium nitroprusside were studied at 30-min intervals. Liver viability was assessed by bile volume production, release of aspartate serine aminotransferase (AST) and lactic acid dehydrogenase (LDH), and histological examination. Hepatic arterial responses to acetylcholine were significantly attenuated in Group 2. No significant differences in sodium nitroprusside responses were noted. However, bile volume production in Group 2 was significantly decreased compared to Group 1. Effluent AST and LDH release increased significantly in Group 1 but not in Group 2. Histological results showed that sinusoidal endothelial cells and hepatocytes were well preserved without significant deterioration in either group, although there was a marked decrease in vasodilatation to acetylcholine in Group 2. This data suggested that the presence of albumin in the perfusate did not improve retention of smooth muscle reactivity and reduced endothelium-dependent vasodilatation and bile volume production during perfusion. However, improved liver parenchymal cell function was observed.

A simple and accurate mathematical method for calculation of the EC50.

A simple, accurate, and speedy noncomputational technique for the calculation of the EC50 or any other concentration-related parameter of concentration-effect curves is presented. It avoids the necessity for graph construction or computational curve-fitting programs and allows accurate calculation of the EC50, where the value falls between two known concentrations The technique has been applied to a concentration-response curve constructed to hepatic arterial (HA) vasoconstrictor responses to HA injections of noradrenaline in an isolated dual-perfused rat liver preparation. EC50 values calculated by the new technique were compared to those calculated by conventional, established, noncomputational techniques. The new technique is faster, more accurate, and simpler to perform than other established noncomputational techniques used for the calculation of the EC50 and can be widely applied to many other pharmacological investigations.

Hypoxia attenuates hepatic arterial vasodilatation and enhances portal venous vasoconstriction to ATP in the perfused rabbit liver.

Dose-related responses to acetylcholine, adenosine 5'-triphosphate (ATP), adenosine and sodium nitroprusside were studied in an in vitro perfused rabbit liver gassed with (95% N(2)/5% CO(2), Group 1) and without carbon dioxide (100% N(2), Group 2). At raised tone, achieved by addition of methoxamine to the perfusate, significantly attenuated hepatic arterial vasodilatation to sodium nitroprusside, acetylcholine, ATP and adenosine was measured in Group 1 and responses to all but sodium nitroprusside were abolished in Group 2. Portal venous responses to acetylcholine, adenosine and sodium nitroprusside were not significantly altered in either Group 1 or Group 2. However, portal venous vasoconstriction to ATP was significantly enhanced in Group 1 and less so in Group 2. It is concluded that carbon dioxide-free hypoxia attenuated hepatic arterial vasodilatation to acetylcholine and ATP and enhanced vasoconstriction to ATP. Both these effects may be characteristic of damage to the microvascular endothelium and may be the result of decreased synthesis of nitric oxide.

Surgical possibilities for bile duct cancer: standard surgical treatment.

There is no consensus on the surgical treatment of bile duct cancer, which varies from total nihilism to an extremely aggressive resectional policy. This paper describes the adoption of a 'middle road' approach to these difficult cancers, and suggests that selective use of stenting, bypass and resection with judicious application of adjunctive chemotherapy is an appropriate attitude until controlled studies of the alternatives are available. The main aims of treatment are (a) relief of obstructive jaundice, (b) prevention and treatment of future recurrent obstruction and cholangitis, and (c) eradication of tumour when possible. Local resection carries a low morbidity and mortality and is always a reasonable option in patients fit for surgery, but the relative value of non-radical resection and stenting with chemotherapy remains to be determined. Extended resections, including major hepatectomy and radical lymph node dissection, are only justified when the intent is curative, and some patients may not be suitable for such extensive surgery. In patients who are explored and determined to be unsuitable for major resection, surgical bypass is an option, but there is little evidence that this produces better palliation or quality of survival than optimal percutaneous or endoscopic stenting. Of 76 patients referred to the author over 7 years, 27 (35%) underwent surgical resection, and 23 (30%) had no operation. In patients followed up for more than 1 year, median survival following curative resection (9 patients) was 26 months, and after palliative resection (15 patients) it was 11 months. Median survivals after palliative biliary-enteric bypass (11), exploration alone (9), or no operation (20) were 2, 4, and 5 months respectively. A cautious and selective approach to surgery for these tumours is advocated.

Paradoxical cholinergic and purinergic vascular reactivity of rabbit thoracic aorta cold-stored in University of Wisconsin solution.

Endothelial dysfunction has been reported in donor blood vessels destined for organ transplantation following cold-storage preservation with University of Wisconsin solution (UW). This was investigated in the present work. Segments of rabbit thoracic aorta were mounted on isometric fine-wire myographs at 37 degrees C and gassed with 95% O2/5% CO2. Concentration-dependent vasodilatations to acetylcholine and adenosine-5'-triphosphate (ATP) were obtained in freshly-harvested rabbit aortic rings, with and without the endothelium, and after 8 days of cold-storage, at 4 degrees C, in either UW, Krebs-Bülbring buffer (KBB) or saline. The action of the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) (100 microM) was evaluated upon the concentration-response curves to determine whether nitric oxide (NO) exerted any modulatory actions. Endothelium-dependent, NO-mediated responses to acetylcholine were unaltered after eight days of storage in UW, reduced after storage in KBB and absent after removal of the vascular endothelium, saline storage or after testing in the presence of L-NAME, suggesting improved NO-mediated endothelial function with the use of UW. Structural preservation was also confirmed using scanning electron microscopy. In contrast, endothelium-dependent responses to ATP were unchanged after eight days of storage in KBB but were reduced after storage in UW and saline, suggesting purinergic (ATP) endothelial dysfunction after storage in UW. L-NAME markedly reduced vasodilatation to ATP in freshly harvested rings and after eight days of storage in KBB. This reduction was statistically significant (P < 0.05, Student's two tailed, unpaired t-test) at -log (M) ATP concentrations of 5.5, 5.0, 4.5, 4.0 and 3.5. NO-dependent vasodilatation to ATP was not attenuated by L-NAME in UW-stored rings. Eight days' UW-storage of rabbit thoracic aortic rings appeared to have differential and paradoxical effects upon NO-dependent vasodilatation to acetylcholine and ATP. Morphological observations using electron microscopy suggested that UW preserved the vascular endothelium and this was verified by retained vascular reactivity of endothelium-dependent vasodilatations to acetylcholine. UW-storage however, significantly reduced endothelium-dependent relaxation to ATP thereby suggesting that P2Y-purinoceptors, which are located on the vascular endothelium, may be more susceptible to biodegradation than cholinergic receptors and may be responsible for endothelial dysfunction following transplantation.

Intimal hyperplasia within biliary Wallstents: failure of recanalisation by insertion of a second endoprosthesis.

We report two patients with benign biliary strictures in whom we attempted recanalisation of metallic biliary endoprostheses, occluded by intimal hyperplasia, by the insertion of further endoprostheses within the occluded stents. Initial technical success was achieved in deploying the stents and restoring patency with elimination of mural filling defects. However, we found the intimal hyperplasia to be restrained for less than 48 h. From our initial results it appears that biliary metallic stent occlusion by intimal hyperplasia is not effectively treated by insertion of a second endoprosthesis.

Localisation of hepatic vascular resistance sites in the isolated dual-perfused rat liver.

The locations of the vascular resistance sites which regulate vascular tone in the hepatic arterial and portal venous vasculatures of the rat liver were identified using a new, in vitro, dual-perfused liver preparation. Twelve livers of male Wistar rats were perfused via the hepatic artery and portal vein at fixed flow and at physiological pressure. Dose-related vasoconstriction to injections or infusions of noradrenaline was measured as transient or sustained increases in perfusion pressure, respectively, in the hepatic arterial and portal venous vasculatures. Direct injections/infusions of noradrenaline refer to those administered into the vasculature from which pressure was recorded, e.g., the effects of hepatic arterial (direct) injections/infusions of noradrenaline upon hepatic arterial perfusion pressure. Indirect injections/infusions of noradrenaline were those administered to the adjacent afferent vasculature, e.g., the effects of portal venous (indirect) injections of noradrenaline upon hepatic arterial perfusion pressure. The converse applies for recordings of portal venous perfusion pressure. The -log(M) ED50 values to direct (hepatic arterial) and indirect (portal venous) injections in the hepatic artery were 4.25+/-0.20 and 3.40+/-0.10, respectively, and were significantly different (P < 0.01, Student's unpaired t-test); the -log(M) ED50 values to direct (portal venous) and indirect (hepatic arterial) injections in the portal vein were 3.91+/-0.08 and 3.85+/-0.11, respectively, and were not significantly different (P > 0.05, Student's unpaired t-test). Similarly, the -log(M) ED50 values to direct (hepatic arterial) and indirect (portal venous) infusions in the hepatic artery were 5.28+/-0.11 and 3.75+/-0.12, respectively, and were significantly different (P < 0.01, Student's unpaired t-test); the -log(M) ED50 values to direct (portal venous) and indirect (hepatic arterial) infusions in the portal vein were 5.31+/-0.19 and 5.70+/-0.16, respectively, and were not significantly different (P > 0.05, Student's unpaired t-test). These results demonstrated that there is little transfer of noradrenaline from the portal venous to the hepatic arterial resistance sites, but significant transfer from the hepatic artery to the portal venous suggesting that; (a) the portal venous resistance sites are located at the sinusoidal or post-sinusoidal level; and (b) the hepatic arterial resistance sites are located at the pre-sinusoidal level.

An investigation of the relationship between the liver and brain using an isolated perfused rat brain preparation.

The pathogenesis of portal-systemic encephalopathy (PSE) and hepatic encephalopathy (HE), disorders of the brain attributed to abnormal liver function, are poorly understood. This study was conducted to examine if a fundamental, and possibly exclusive, homeostatic interrelationship exists between the liver and brain that might deteriorate during liver failure to result in the syndrome of PSE and HE. An isolated organ perfusion circuit was devised to accommodate an isolated rat brain and an isolated rat liver preparation perfused concomitantly. The survival time of the brain preparation was measured by the maintenance of the spontaneous electroencephalocorticogram and was extended from a median survival time of 35 min (range 22 to 53 min), when perfused alone, to 210 min (range 172 to 480 min), when perfused simultaneously with a liver. Also, concomitant perfusion with an isolated rat liver reduced perfusate glucose concentrations from 200 mg% to a range between 45 to 60 mg%. These data support our hypothesis that a homeostatic interrelationship exists between the liver and brain that is independent of other metabolic influences; disturbance of this relationship may contribute towards the syndrome of PSE and HE.