Portocaval shunt

Elevated in deficiencies of galactokinase, galactose-1-phosphate uridyltransferase (classical galactosemia), UDP galactose-4-epimerase, and Fanconi-Bickel-syn drome, portocaval shunt, and cirrhosis, depending on time after lactose consumption. 

When portosystemic shunting is present total hepatic blood flow (Q) equals the sum of perfusion flow (Q ) and shunt flow (Qs). Portocaval shunting will impair the efficiency of hepatic extraction and reduce the extraction ratio as indicated by the following modification of Equation 7.5 (23). 

Because Q and Qp are both reduced in patients with severe cirrhosis in whom portocaval shunting is most pronounced/ hepatic clearance will be reduced more for nonrestrictivefy than for restrictively metabolized drugs. 

Similarly/ restrictively metabolized drugs exhibit little first-pass metabolism even in patients with normal liver function/ so portocaval shunting will have little impact on drug bioavailability. On the other hand/ portocaval shunting will decrease the extraction ratio and increase the bioavailability of nonrestric-tively metabolized drugs as follows ... 

Equation 7.13 emphasizes the central point that changes in perfusion and protein binding, as well as intrinsic clearance, will affect the hepatic clearance of a number of drugs. The intact hepatocyte theory has been proposed as a means of simplifying this complexity (33). This theory is analogous to the intact nephron theory (see Chapter 5) in that it assumes that the increase in portocaval shunting parallels the loss of functional cell mass, and that the reduced mass... 

Jessy, J., Mans, A.M., DeJoseph, M.R., Hawkins, R.A. Hyperammonaemia causes many of the changes found after portocaval shunting. 

Ldscher, W., Kretz, F.-J., Karavlas, T., DilUnger, U. Marked increases of plasma gamma-aminobutyric acid concentrations in cirrhotic patients with portocaval shunts are not associated with alterations of cerebral functions. Digestion 1991 49 212—220... 

Schroeder, E.T., Numann, P.X, Chamberlain, B.E. Functional renal failure in cirrhosis. Recovery after portocaval shunt. Ann. Intern. Med. 

Planas, R., Boix, X, Broggi, M., Cabre, E., Gomes-Vieira, M.C., Mor-illas, R., Armengol, M., de Leon, R., Humbert, R, Salva, J.A., Gassull, M.A. Portocaval shunt versus endoscopic sclerotherapy in the elective treatment of variceal hemorrhage. Gastroenterology 1991 100 1078-1086... 

Roberts, J.R, Ring, E., Lake, J.R., Sterneck, M., Ascher, N.L. Intrahepatic portocaval shunt for variceal hemorrhage prior to liver transplantation. Transplantation 1991 52 160-162... 

No significant differences were demonstrated between the mean serum alkaline phosphatase activities of patients who had portocaval shunts for the prevention of variceal bleeding and control patients who did not undergo such surgery (C26). 

It is clear from the transplant literature that graft survival requires portal blood flow and the hepatotrophic effect of hepatectomy is well established(33). To take full advantage of circulating hepatotropic factors, we created portocaval shunts (PCS) in the recipient rats to eliminate first pass clearance of these factors by the native liver. We therefore repeated the studies with prevascularized polymeric foams, but additionally created a PCS in one group of animals, a 70% hepatectomy in another group of animals, and both a PCS and hepatectomy in yet another group studied. 

Although insulin probably affects glucose transport in muscle (see below), in liver a primary effect of insulin on hexokinase could not be excluded. Studies performed on dogs with complete end-to-side portocaval shunt, on dog liver perfused in situ, and on liver slices suggested that insulin had no effect on glucose uptake in liver. 

Bilodeau, M., Rioux, L., Willems, B., Pomier-Layrargues, G. Transjugular intrahepatic portocaval stent shunt as a rescue treatment for life-threatening variceal bleeding in a cirrhotic patient with severe liver failure. Amer. J. Gastroenterol. 1992 87 369-371... 

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