Functional relations of the proximal components of the portal system

W.

G.

WADDELL,

hl.D.,

F.IW.S.(C’),

A.G.

F.IW.S.(,(“),

1\-;-\RREK

IXTRODUCED

.4ND

THE

BOrCHAIED, J.

I3.

M.D., EWISG,

[31’ In rwicwing the shunt procedures advocatcd in tlw trcatmcnt of portal hypertension, four types of operation emerge as distinct enprocedures and two tities. Two are port’acaval arc selective techniques. The classical end-toside portacaval shunt [l] differs aif;nificantly from the double end-to-side or side-to-side anastomoses [lo]. However, most, of the other praccdures described [4, 5, 8, 9, 111 are functionally equivalent to the side-to-side shunt. The only exceptions are t’he different selective of Surgery, Faculty of Medicine, UniOttawa and Department of Surgery, Ottwa General Hospital. Department

of

Supported the Medical Submitted

by the Ontario Heart Research Council. for publication November

Foundation

* c.f. Proximal

and

blood flow: downstream.

24, 1971. 281

Copyright

0 1072 by Acndemic

Press, Inc.

J. I,.

WELLISGTOS,

M.D.,

F.lW.S.((‘)

olwxtious atlrocaled by Warreii [I 5] and Inokuchi [6]. The c*oncept’ of selcctirc decomprwsion rains an iutcresting question. The distal slAworc~~nl shunt, implies some degree of func~ol):tration l)etwecn t,he lcescr aud tional greater splanchnic systems.* IXrect left gastric \-ein diversion must he haset upon the uust,atcd lwcmise that the left gastric aystcm is at least pnrt8inlly discrete from the other coml~oiiciit,s of the lesser splanchnio spstcm. If the portal components arc functionally continuous, tlicn selective decompression i.5 riot possible since diversion from ally rite would effectivcly tll&ii t’lw entire portal 1~1. Is the ~~rosimal portal system functionally continuous or functioiially discrete? hlternatiwly, what arc the functional relations of the anatomic components of the portal system? Thc~ question is illustrated in Fig. 1, with functional discretion represented in the upper diagram and functional continuity hetn-een compoiicnts represcnt~cd below. Study of functional relations of the portal components may 1~ undertaken only by selcctivc manipulation of one component in comparison with tlic gcncral portal system. One method of study is to produce venous hypertension in one component and to compare measurahlc parameters in altIered and unaltered components. This approach was utilized since it is direct and technically simple al-

COKCI~:PT

of wlcctive decom1~ression of csopliagog:tetric varicch in 1967 [15, 161. The operation hc pro1)oml iuvolwd distal rather thaIi 11rosiinnl end-tu+itle q~lcnorcnnl anastomosis aiid distal ligature of thr l(lft, F;:istric win. Concurwnt,ly, T&cira pul)liahcd cxperimcntal ;4tudiw of a tlist:il rplcrioca\-al aiias1wiwis with distal liaaturc of both gastric and the right. gwstrocpiploic I-Gus in 1967 and 1968 [13, 141. Inokuclii suggcstctl direct left gastric vein di\-crsion iu 1968 [6] awl pul~lished his iuitial in 1970 [7]. Rrit’ton ant1 Voorhws qwricwcc ath-ocntt~d :I central sitlc-to-side rplciiorennl an:wtomosis as I selective sliiuit ill 1970 [2] but subwqucntly conwrtccl to an end-to-side procctlurc by distal ligsturc of t’hc splenic win

\-crsit,y

F.R.C.S.(C’), M.D.,

Proximal

and dist,al refers

are used to upst,ream

in

relation and distal

to to

282

JOURNAL

LEFT GASTRIC

LEFT GASTRIC

GASTRO DUODENAL

SPLENIC

GASTRO DUODENAL

SPLENIC

IS THE PORTAL FUNCTIONALLY FUNCTIONALLY

OF

SURGICAL

RESEARCH,

SUPERIOR INFERIOR MESENTERIC

SUPERIOR INFERIOR MESENTERIC

VENOUS SYSTEM DISCRETE OR CONTINUOUS ?

Fig. I. The question raised by the concept of selective decompression of esophagogastric varices is illustrated diagrammatically. Functional barriers between discrete components is represented above and functional continuity between anatomic components is represented below.

VOL.

12,

Operative ments

4,

NO.

APRIL

1972

Procedures-Long-term

Experi-

Operations were carried out under general anesthesia with standard aseptic precautions. The abdomen was opened by a midline supraumbilical incision and the wound was closed in three layers after creation of the arteriovenous fistula. 1. Reversed splenic distal left gastric arteriovenous fistulae. In ten animals, the splenic artery was ligated proximally close to the celiac axis and the distal or reversed end of the artery was stapled to the transected distal left gastric vein close to the gastrosplenic junction. In later experiments, a short length of autogenous vein was used to create fistulae with less tension on the vessels involved. The procedure is illustrated in Fig. 2. Z?.Reversed left gastric distal splenic arteriovenous fistulae. In 20 dogs, t,he left gastric artery was ligated proximally close to the celiac axis and the reversed or distal end was

though the alternative method has definite appeal in its relation to the clinical problem. Pressure was the only parameter determined primarily because of simplicity. METHODS Two different experiments, each involving the four canine portal components, were undertaken. In the first series of long-term survival experiments, reversed or distal arterial distal venous fistulae were created surgically. These operations produced total venous outflow obstruction with component overload at collateral arterial pressure. In the second series of acute, nonsurvival experiments, direct or proximal arterial distal venous fistulae were created by very similar operations. Pilot experiments demonstrated that animals did not survive the procedure. The direct arteriovenous fistulae also achieved total venous out’flow obstruction but produced component overload at systemic arterial blood and pulse pressures.

MESENTERIC

VEIN

Fig. 2. The reversed splenic distal left gastric arteriovenous fist.ula is represented diagrammatically. The proximal end of the splenic artery is ligated close to the celiac axis and the distal end is stapled to the transected distal left gastric vein.

WADDELL

ET

AL:

PI~OXlJlAL

COMI’OSESTS

MESENTERIC

Fig. 3. The reversed pancreatico-duodellal mesenteric.

splenic distal gastroduodenal and paraduodenal t,ributaries

OF

PORTAL

283

SYSTEM

VEIN

fist& is represented diagrammatically to illustrate the large available for anastomosis with the tributaries of the cephalsd

turned through the epiploic foramen into the lesser sac and stapled to the transected distal splenic vein close to the gastrosplenic junction with or without an intcrposcd autogenous vein graft. S. Reversed splenic distal gastroduodenal crrferiovenous fktulae. In 10 animals, the splcnic artery was ligated proximally close to the celiac axis and the reversed or distal end of the vessel was anastomosed to the transected dist’al gastroduodenal vein close to the portal vein with an interposed short autogenous vein graft. The procedure is illustrated in Fig. 3 to demonstrate the large pancreaticoduodenal and paraduodenal tributaries capable of anastomosis with branches of the cephalad mesenteric vein. 4. Reversed left gastric mesenteric arteriovenous fistulae. In the final group of four animals, arteriovenous fistulae were achieved by anastomosing the reversed left gastric artery to the mesent,eric vein close to the mesentero-

splenic junction rein graft. Operative

with

an interposed

Procedures-Acute

autogenous

Experiments

Similar operations were performed in four pairs of animals except that in each instance, the appropriate artery was ligated distally and the proximal end of the artery was anastomosed to the distal transected vein with or without an interposed autogenous vein graft. 1. Direct splenic distal left gastric arteriovenous fistulae. 2. Direct left gastric dist’al splenic arteriovenous fistulae. 3. Direct splenic distal gastroduodenal arteriorenous fistulae. 4. Direct left gastric distal mesenteric arteriovenous fistulae. Pressure

Studies

Pressure studies were performed by simple water manometry immediately after establish-

284

JOURNAL

OF

SURGICAL

RESEARCH,

VOL.

ing the arteriovenous fistula and four weeks to 6 months later, when the long term experiments were terminated, with the animal under general anesthesia. Pressure sampling was undertaken at multiple sites in the proximal portal system, including the component under study and two of the other portal components. Three readings were taken at each site and the three readings from t’he component under study were averaged for the component pressure. The general portal pressure was derived from the average of six readings from at least two sites in t’he intact portal system. Arterial pressure was measured in cm. of water in a closed system by cannulat,ing the artery prior to anastomosis. In order to simplify a rather complex operative procedure, all readings were recorded in cm. of water above tabletop to avoid establishing baselines for pressures in the caval and portal veins at multiple sites at somewhat different levels. Statistical

Pressure

Reversed splenic distal left gastric A.V. fistulae Reversed left gastric distal splenic A.V. fistulae Reversed splenic distal gastroduodenal A.V. fistulae Reversed left gastric mesenteric A.V. fistulae

Number

1972

Studies-Long-term

Experiments

The pressure data obtained in the four groups of survival experiments are given in Tables 2-5. Differences in pressure are expressed in cm. of wat’er giving the arithmetic mean (Mean) and standard error (SE) of the mean. The p values reflect the statistical significance of the differences between the mean portal and mean component pressures and between mean component and mean arterial input pressures. 1. Reversed splenic distal left gastric arteri-

An attempt was made to cannulate the artery proximal to the arteriovenous fistula after the pressure recordings had been completed in

Procedure

APRIL

The overall results in the first series of survival experiments are given in Table 1. Arteriovenous manipulations within the lesser splanchnic system were well tolerated with three apparently unrelated deaths in 40 animals. However, similar manipulations within the greater splanchnic system were poorly tolerat’ed and 3 of 4 animals died within 24 hours of operation with obvious enterocolonic venous congestion and int’estinal hcmorrhagc at autopsy. The one survivor ultimately demonstrated an occluded fistula.

Studies

1. Overall

4,

RESULTS

The individual readings and the average pressures were recorded. The differences in pressure were determined by subtracting caval pressure from the portal pressure, the component pressure and the arterial pressure. The figures were analysed by a suit,ably programmed computer giving the arithmet’ic mean, the standard error of the mean and the value. Probability was derived from student t tables.

Table

NO.

the long-term experiments and in the acute experiments. Films were made after the injection of 5-15 cc. of contrast material to demonstrate the channels of venous diversion from the component under study. When the anastomosis was blocked in the late survival experiments, venograms were obtained by cannulating the vein as close t’o the occluded fistula as possible, and injecting dye in a retrograde fashion to demonstrate the venous collaterals.

Analyses

Angiographic

12,

Results-Long-term Interval

Experiments Follow-up

Patent Fistulae

Occluded Fistulae

Deaths

10

4-26 weeks

4

3

I

20

4-22 weeks

4

14

2

10

6-10 weeks

2

8

4

1 day 12 weeks

3

1

3

WSDDELL

ET

Table Pressure

Early results Significance Late patent Significance I,ate results Significance

d. Reve,sed

Splenic

fistulae

occluded

Distal

shunts

Gastric

PORTAL

A.V. Left

SYSTEM

(SE)

11.96

4

9.83

4

10.68

3. Reversed

Left

Gastric

Fistulac Gastric-Caval (SE)

(0.89) 36.32 p <.O.OOl (1.72) 42.65 p < 0.001 (0.90) 17.79 p <.O.l

(1.78)

Distal

Splenic

*Mean

(SE)

103.48 0.001 (3 .;iS) 89.76 p < 0.001 (3.-t;,)

(6.25)

p<

A.V.

fistulae

3

shunts

Splenic-Caval

Mean

(SE)

9.81

(0.64)

ArterialNaval

Mean

(SE)

38.42

(1.67)

Splenic

Distal

GastToduodenal

shunts

10

9.58

2

10.00

6

8.43

(SE)

Table

5. Reversed

Left

Gastric

Distal

Mesenteric

Portal-Caval measurements

(13.19)

A.V.

7.83

(0.77)

87.77

(!I .08)

Mean

(SE)

(1.16) 96.63 p < 0.001 (0.80) 74.70 p < 0.0.5 (2.4.5)

(.5.30)

Mean

A.V.

Arterial-Caval (SE)

Mean

(SE)

43.50

(1.53)

(9.00)

~ Fistulae

Mesenteric-Caval (SE)

(10.92)

Fistdue

ArterialkCaval --~~______~_ Mean (SE)

Sumher Mean

87.94

p < 0.01 (2.73)

(1.09) 31.99 p < 0.001 (0.20) 22.10 p < 0.2 (1.36) 9.07 p < 0.9 .. ___

___..~~_____

(SE)

GastroduodenalCaval

Portal-Caval Number Mean

Mean

p <.O.OOl

(3.68) 41.40 p < 0.0023 (1.32) 17.19 p < 0.2

13.09

4. Reversed

fistjulae

occluded

13.30

12

Pressure measurements (cm. water)

A.V.

(3 .79)

Fistulae

p
occluded

AArterial-Caval

Mean

Portal-Caval

20 A.V.

28.5

Sumlw

l’able

Pressure

OF

Lejt

Mean 10

A.V.

C!O.\lPONESTS

Sumlxr

Pressure measurements (cm. water)

Early results Significance Late patent Significance Late results Significance _~.-___

PIZOXIMAL

Portal-Caval

Measurements (cm. water)

Table

Early results Significance Late patent Siguificance Late results Significance

AL:

~__. Early results Significance

4

p < 0.001

fistulae. Significant localized venous hypertension relative to the general portal pressure was achieved by arteriovenous manipulation in the left gastric system and persisted in animals with patent fistulae in the late studies. In addition, t’he level of pressure in the left gastric component was significantly below t#he arterial input pressure in both instances. The alteration in left gastric pressure relative

wenow

76.53

(1.62)

p < 0.001

to the other portal components is represented in Fig. 4. 2. Reversed left gastric distal splenic arteriovenous fktulae. Reversed arteriovenous fistulate in the splenic system produced significant elevation of splenic venous pressure relative to the general portal pressure but at levels significantly below the arterial input pressure. Loralized venous hypertension persisted in ani-

286

JOURNAL

REVERSED SPLENIC ARTERY

LEFT GASTRIC

PORTAL

OF

GASTRO DUODENAL

SURGICAL

SPLENIC

RESEARCH,

MESENTERIC

VElN

Fig. 4. The alteration in pressures induced by arteriovenous manipulation of the left gastric venous system is represented schematically with localized venous hypertension relative to the general portal system.

LEFT GASTRIC

PORTAL

REVERSED LEFT GASTRIC ARTERY

SPLENIC

12,

NO.

4,

APRIL

1972

4. Reversed left gastric distal mesenteric arteriovenous fitulae. Mesenteric pressureswere significantly above general portal pressures and significantly below arterial input pressures after surgical arteriovenous manipulation. A slightly greater degree of localized hypertension was observed in the mesenteric component than in any of the individual components of the lessersplanchnic system. No late pressure records are available since animals with patent fistulae did not survive the operative procedure. The pressure data are given for the late esperiments demonstrating fistula occlusion. In the left gastric and splenic components, the pressures were slightly but not significantly higher than the portal pressure while hhere was little elevation in the gastroduodenal component.

MESENTERIC

Pressure Studies-Acute

VEIN

Fig. 6. The alteration in pressures venous manipulation within the tem is represented schematically nous hypertension relative to the sure.

VOL.

induced by arteriosplenic venous syswith localized vegeneral portal pres-

mals with patent fistulae at sacrifice. The alteration in pressures induced surgically is represented in Fig. 5. 3. Reversed splenic distal gastroduodenal arteriovenous jktulae. Significant elevation of pressure was obtained in the gastroduodenal system after establishing indirect arteriovenous fistulae and the level of pressure was significantly below the arterial input pressure. The degree of venous hypertension was somewhat lower than that observed in either the left gast,ric or splenic components. Modest elevation was noted in the two animals with patent fistulae after 6 to 8 weeks.

Experiments

The pressure data from the acute series of direct arteriovenous fistulae are given in Table 6. The direct arteriovenous fistulae produced higher pressures in each of the four canine portal components with levels significantly below arterial input pressures. The highest levels were observed in the mesenteric system and the lowest were obtained in the gastroduodenal. Pressures in the left gastric and splenic systems were comparable and intermediate as in the reversed arteriovenous fistulae. Angiographic Studies In the long-term experiments adequate channels of venous collateral diversion from each of the components in the lesser splanchnit system were demonstrated by either the arteriovenograms or retrograde venograme. For example, diversion from t’he left gastric system to t’he right gastric and gastroduodenal and to the splenic via the short gastric system was apparent by both methods of study. Similarly, diversion from the splenic component was observed by the short, gastric veins to the left gastric system, by the gastroepiploic to the gastroduodcnal vein and by tributaries of the caudal mesenteric vein. With few exceptions, there was no significant diversion to the

WADDELL

ET

Table

AL:

PIZOXIMAL

6. Pressure

COJIPOSEI\;TS

Studies-Acute

Portal-Caval Procedure _____-__ lkcct spleuic left. gastric i4.V. fistulae I)irect, left gastric splenic A.V. fistulae Significance Direct splenic gastroduodcual A.V. fistulae Sigulficance Direct left gastric meseuteric -4.V. fistulae Significance

Number

PORTAL

Experiments Arterial-Caval ~ _.. ~~~~~Mean (A SE) -. ___

Component-Caval

Mean

(k

9.9

(fO.l)

SE)

Mean

(AZ SE)

57.9

(*3.4j

p <.0.02 2

9.05

(fl.6)

2

6.2

(zt0.01)

2

I) .3

p < 64.0

(+1.9)

47.0

(ztz3.8)

i7.3

&1.-l)

p < 0.00.5

venous system. Two angiographic studies demonstrated a small tributary from the left gastric to the phrenicoabdominal when the left gastric venous system was subjected to component overload. In summary, the late angiographic studies demonstrated diversion to anat’omically related components in the lesser splanchnic system. In contrast to the long-term experiments, the acute studies frequently demon&rated diversion to the systemic venous system in anatomical relation to the component subjected to direct arterial pressure in addition to variable diversion t’o anatomically related portal components. systemic

Pomc explanation of the experiment,al design is warrant’ed. In a static situation, the simplest method of testing the integrity of a chamber or a vascular compartment is to attempt to fill it. Volume measurements will define the capacity of the chamber or compartment and pressure measurements will indicate the level of integrity of the walls of the chamber or boundaries of the vascular compartment if the capacity of the space is fully utilized. In a dynamic situation where the vascular compartment to be studied has a variable capacity, pressure measurements will, nonet,he1~s:: define the levels of integrity or levels of functional discretion of the component being studied provided the capacity of the component is challenged. Moreover, the difference between input pressure measured in a closed

p < 0.001

139.8

(+ll.l)

128.1

(+6

131.7

(zk5.1)

136.2

(h2.9,

0.025 .O)

p < 0.01

p < 0.01 (dzO.9)

287

SYSTEM

-

___~-~. 2

OF

p <

0.05

p < 0.005

system and final component pressure reflects indirectly the potential for collateral diversion. The alternate method of inducing component hypotension in a situation where general portal hypertension exists or can be induced will accurately reflect the dimensions of barriers between components only if the capacit,y of the portal bed is fully utilized and if selective drainage is accomplished at minimal resistance values. A variety of experiments have been undertaken employing Thal and Tamiya’s technique of portal arterialization and partial subhepatic portal occlusion [12], but none have given sustained portal hypertension of significant degree. Pressure was the only parameter studied and the simplest technique available was used. Volume studies would be of interest in attempting to achieve a conceptual model of the proximal portal system but are not easily measured on a repetitive basis and are of significance only when determined at various pressure levels in a system of variable capacity. Venous flow studies would not he particularly useful except in attempting to quantitate the role of various routes of collateral diversion from the component under study. Water manometry is considered an entirely adequate technique for stat’ic measurements of ln+eseure levels of considerable difference attained surgically. As mentioned, pressure differentials were derived from tabletop measuremcnts to obviate the difficult’y of leveling in various posit,ions for absolute pressure measurements.

288

JOURNAL

OF

SURGICAL

RESEARCH,

Early localized venous hypertension was achieved by arteriovenous manipulation selectively in each of the components of the lesser splanchnic system with a slightly greater degree of hypertension in the mesenteric system. The localized hypertension persisted when the fistulae remained patent 1 to 4 months postoperatively. The pressure studies and the animals’ reaction to arteriovenous manipulations suggest significant separation or functional discretion between the lesser and greater splanchnic venous system and, in addition, significant, functional barriers between components in the lesser splanchnic system. The higher pressures attained in the acute experiments indicate that functional barriers between components are present above the pressure levels at which collateral diversion to related components occurs, and that the potential for collateral diversion is limited. It must be emphasized that the operations producing both the direct and indirect arteriovenous fist’ulae at’ the distal end of the venous component under study do not interfere with proximal component relations, and that great care was exercised in pressure sampling in order not to create artificial barriers between components. The normal or slightly elevated pressures in the animals with occluded fistulae are not considered evidence of functional continuity since the component capacities are not known and were not, challenged by additional arterial

VOL.

12,

NO.

4,

APRIL

197%

input. However, the complex interrelationships between component capacity, pressure and collateral diversion cannot be fully explained and the angiographic patterns of diversion were very similar in animals with patent and occluded fistulae. CONCLUSIONS The pressure data indicate that the proximal components of the port’al system are functionally discrete to pressure levels well above the general portal pressure (40-70 cm. of water). There is a definite but limited potential for collateral diversion between the greater and lesser splanchnic systems and a slightly greater potential for diversion between components of the lesser splanchnic system. Diversion to the systemic system was demonstrable at high pressures in the dog but was insufficient to prevent venous disruption. Schematic representation of the proximal port’al relations is offered in Fig. 6 wit’h the functional relations represented in the diagram on the left and the anatomic relations represented on the right. The pressure level initiating collateral diversion has not been identified. There is greater anatomic potential for diversion from the splenic and gastroduodenal systems in the dog than either the left gastric or mesenteric system.

CASTRO DUODENAL LEFT GASTRIC

SPLENIC

MESENTERIC SPLENIC

GASTRODUODENAI

PORTAL

Fig. 6’. The proximal matically on the left

VEIN

relations of the portal and the anatomic relations

venous components; functional are represented diagrammatically

relations are represented on the right.

sche-

\vADl)ELL

ET

AL:

PIZOXI\1.41,

olwrvations on the proximal portal system in dogs arc relevant if canine and human portal physiology are comparable. Comparison of the trio qwcies reveals considerable similarit,y in the lnvximal anatomical relations of the left gastric and splcnic systems with slight differeiicc’s in the proximal anatomical relations in tht gaatrotluodcnal and mcscntcric components. The distal anatomical relations are not dissimilar with respect to left gastric and splenic wins, Ijut, gastroduodcnal and mcsentcric veins arc entirely different. If human and canine portal physiology are comparable and if the method of study is accel)tablc, t,hen selcctiw decompression of esophagogastric variccs is a valid therapeutic concept. The functional barriers bet’ween coml)oncnts in the lesser splanchnic system suggest that direct diversion of the left gastric vein is the iiiok+t rational surgical objective in any attempt, to control bleeding from esophageal varices. The procedure is attractive theoretically and adequate reduction of left gastric pressure might be anticipated with a short’, rclativrly direct route of diversion. In addition, the major portal flow to the liver would bc maintained and, conceirahly, the incidence of postoperative encephalopathy might be reduced to that, observed in patients who are not subjected to a major portal systemic shunt’. The late results with small caliber, low flow shunts remain a matter of concern but can only Iw determined by expcricnce. REFERENCES 1. Blakemore. A. H. Portacaval port of fourteen wscs. &t/l. 22:254,1946.

anastomoeis: S. Y. Acad.

A reNed

COJ1PONENTS

OF

PORTAL

SI-STEJI

“8!)

2. Britton. R. C.. Voorhees, A. B., and Priw. J. B. Splcctive portal tlecomprtwion. SrcrrJery 67 :104113. 1970. 3. Brit ton. Ii. C. Surgical treatment of complication* of portal hypertension. Axn. X.1-. Acad. SC~. 170:358-366. 1970. H. W., Jr.. n-all. T.. ancl m-atman. I!. 4. Clatnorthy, S. .-\ nfw type of portal to-systemic wnous shunt for portal hypertension. Arch. SwB. 71:588, 1955. 5. Erlich. D.. and Bnrzilai, rl. Porto-renal shunt. A/it!. S/ug. 159:72. 1964. K. .I wlfvati\-e port:tca\-111 51~~~~~1. LuIccct 6. Inokuc~hi. So. 7558. ])p. 51-52. 1968. 7. Inolrwhi. K.. Kobayashi. M.. Kusaba. A., Oga~a. y.. Sd~u. M.. and Shiizaki. T. Sew selective clcc~ompres,sion of c~sol~lragral varicw. Arch. Sfcvq. 100 : 157-162. 1970. S. Linton. R. R.. Jones. C. M. and Volwilcr, W. Portal Hypertension-The treatment by splenectomy and splenorenal annstomosis with prcservation of the kidney. Surg. C/in. N. Amer. 23:1162, 1947. 9. hlarion, P. Lee obstructions portales. Sem. Hop. his 29:2781, 1953. 10. McDermott. W’. V.. Jr. The Do~~ble Portacawl Shunt in the Treatmrnt of Cirrhotic Ascites. S~crq. Gyttec. Obstet., pp. 457-469, 1960. 11. Simeonc, F. A. and Hopkins, R. W.: Porto-renal shunt for hepatic cirrhosis and portal hqpertenrion. Surgery 61 :153, 1967. 12. Tamiya. T.. and Thai. &I. P. Esophageal variers produwd experimentally in the dog. Szcrg. Gy,lec. obstet. pp. 147-154. 1960. 13. Trkeira E. D., YLI, H.. and Bergan J. J. Kol-za Technica nn Circurgia da Hipertensao Porta Eslutl. Ekpcrimcntnl. Ret:. Rrd. C~IX. 53 :443. 1967. 14. Teixrira E. D., Tu. H.. Conn. J. Jr., and Bergan, J. J. Selective decompression of esophagogastric varices. Arch. Stug. 96:4 1968. 15. Warren, W. D., Zeppa, K., and Fomon, J. J. SelecI i1.c tran+splenir decompression of gastroesophaawl varices by distal sl~lenormnl shunt. An/,. swq. 166:437-455, 1967. 16. Warren. W. D.. Fomon. J. J.. and Zeppa, R. Further elaluation of selective decompression of varices by distal splenorrnal shunt. Ann. Suq. 169:652-660, 1969.