Congenital Absence of the Portal Vein

HISAO NAKASAKI, M.D., YUTAKA TANAKA, M.D., MASATOSHI OHTA, M.D., TOKITAKA KANEMOTO, M.D.,TOSHIO MITOMI, M.D., YOSHIROH IWATA, M.D., and ATSUSHI OZAWA, M.D.

A 14-year-old girl presented at the hospital after discovering anabdominal tumor. CT scan and ultrasonography indicated a he-patic tumor and also revealed the absence of the portal vein. Thepatient was admitted to excise the hepatic tumor. It was foundthat the venous blood from the small intestines flowed into theleft renal vein and then emptied directly into the inferior venacava. A tumor extending from the right lobe through the middleportion of the liver was excised. The postoperative course wassatisfactory and marked regeneration of the residual hepatic tis-sue was observed. Also the blood level of ammonia in the superiormesenteric vein was low, approximately 120gg/dl, compared tothe normal value of 350 ,ug/dl in the portal vein. This low bloodlevel may indicate the presence of some homeostatic controlmechanism.

ONGENITAL ABSENCE OFTHE PORTAL VEIN is anextremely rare abnormality that has only beenreported two or three times in the literature. 2

The cases mentioned in these reports were discovered ac-cidentally in the course of examinations for metabolicdisturbances or tumors of the pancreaticocholecystohe-patic system. The present case report concerns a patientwho presented at the hospital with a massive hepatic tu-mor. Preoperative examination revealed the absence ofthe portal vein. In view of this preoperative finding, theblood levels ofammonia at all the sites where blood sam-ples were obtained during angiographic examinations wereentirely within normal limits, and no abnormalities weredetected in this respect. In particular, even the blood levelof ammonia in the superior mesenteric vein was about120 ,ug/dl, which is within the normal range. In general,reports of portal vein absence are rare, and there appearto be no previous reports concerning measurement of ve-nous ammonia levels in such cases. The fact that the blood

From the Department of Surgery, Radiology andMicrobiology, Tokai University School of Medicine,

Bohseidai, Isehara, Kanagawa, Japan

level of ammonia in the superior mesenteric vein wasclose to the upper limit ofthe normal range indicates thatsome homeostatic mechanism controls the intestinal bac-terial flora.

Case Report

The patient was a 14-year-old girl who had undergone herniorrhaphyas radical surgery for an inguinal hernia at the age of 3 years. At age 6years she underwent surgical closure of an atrial septal defect.The patient's postoperative course was satisfactory until the age of 14

years when she began to experience a persistent dull pain in the righthypochondrium. The patient palpated a tumor in the epigastric region,and subsequently developed subjective symptoms of fatiguability.The patient was then examined by a general practitioner who noted

the presence of an abdominal mass as well as mildly abnormal liverchemistry. The serum levels of SGOT and SGPT were each 112 U/Land 142 U/L. Other liver chemistries were in the normal range (normalrange, 30 to 45 U/L).

In May 1987 the patient was admitted to this hospital to investigatethe abdominal tumor. Physical examination disclosed a large induratedtumor in the right hypochondriac region. A CT scan performed afteradmission indicated a large mixed attenuated mass extending from theright lobe to the middle region of the liver (Fig. 1). Ultrasonographicexamination performed at about the same time revealed the absence ofthe portal vein (Fig. 2). Selective arteriovenography also showed a largetumor in the right lobe and middle lobe of the liver (Fig. 3). Superiormesenteric portography revealed that the superior mesenteric vein emp-tied into the left renal vein. Similarly, the splenic vein also flowed intothe left renal vein, and the left renal vein joined with the inferior venacava (Figs. 4 to 6), and thus no flow from the intestinal circulation intothe liver was observed. The hepatic emptying veins were present in normalpositions, emptying into the inferior vena cava. Hepatochemical findingsincluded GOT 280 U/L, GPT 132 U/L (normal range, 30 to 45 U/L),and total bilirubin 1.4 mg/dl, indicating mildly abnormal liver chemistry.When selective venography was performed, blood samples were taken

from the superior mesenteric vein, inferior vena cava, hepatic vein, andsuperior vena cava, and the ammonia contents of these samples were

190

Correspondence and reprint requests to: Hisao Nakasaki, M.D., De-partment of Surgery, Tokai University, School of Medicine, Bohseidai,Isehara, Kanagawa, 259-11, Japan.

Accepted for publication: January 5, 1989.

CONGENITAL ABSENCE OF THE PORTAL VEIN

FIG. 1. Findings ofCT scanning. The right hepatic lobe as a whole dis-played a heterogeneous pattern. A tumor was discovered. Enlargementof lymph nodes and ascites, and so on were not observed.

measured (Fig. 8, Table 1). The serum level ofammonia in the superiormesenteric vein was 129 ug/dl, which is slightly high, but the ammonialevels of samples from other sites were within the normal range.

Blood glucagon, insulin, and Blood Urea Nitrogen (BUN) were alsowithin normal limits.The blood level of total bile acids was 30 ttM, which is evidently high

as compared to the normal range of I to 1.5 utM.Bacteriological examinations were performed with respect to fecal

specimens obtained before, during, and after surgery. The fecal specimenobtained during surgery was taken from the distal end of the jejunum.The tumor was resected surgically and found to be a massive neoplasmextending from the right lobe to the middle portion of the liver. Only alateral segment ofthe liver remained after the resection. During operation,the portal vein was not found in the hepatoduodenal ligament; moreover,a vestige of the portal vein was detected. The only blood supply to theliver was provided by the hepatic artery. The superior mesenteric andsplenic veins flowed into the left renal vein, which in turn emptied nor-

FIG. 2. Findings of ultrasonographic examination. A massive tumor wasobserved on the epigastrium. Also, no portal vein was seen in the echo-gram.

FIG. 3. Preoperative angiographical findings. A massive tumor occupiesalmost the entire right lobe of the liver.

mally into the inferior vena cava. On the first postoperative day, he-matochemical examinations revealed no abnormality.The postoperative course was satisfactory and the patient was dis-

charged from hospital 24 days after operation. During the fourth monthafter surgery, angiography revealed pronounced hypertrophic regenerationin the left lobe of the liver (Fig. 7).

Discussion

The development of the portal vein normally startsfrom the venous plexus of the vitelline sac and is com-

FIG. 4. Venography of the superior mesenteric vein. The superior mes-enteric portography revealed that the superior mesenteric vein emptiedinto the left renal vein.

VOl. 210.- NO. 2

NAKASAKI AND OTHERS

FIG. 5. Venography ofthe splenic vein. The splenic vein also flowed intothe left renal vein.

pleted between the fourth and tenth week ofthe embryonicperiod.3 4 Known abnormalities of the portal venous sys-

tem include duplication and in some case, defects in theportal vein. Defects of the portal vein system include a

condition in which the portal vein is completely absentbut intrahepatic portal venules are still present, as well as

a state of complete absence of portal vasculature even

within the liver.4 In the present case, no trace ofthe portalsystem could be found. The histopathologic categorizationof the excised tumor was hepatocellular adenoma. Theadenomatous portion presented the form of a group of

FIG. 6. Venography of the inferior vena cava. The left renal vein joinedthe inferior vena cava.

FIG. 7. Postoperative angiography ofthe left hepatic artery; angiographicfindings 4 months after resection of right hepatic lobe displays markedproliferation.

fibrous tissue. These lesions were composed almost en-

tirely of hepatocytes without portal tracts.The hepatic tissue other than the tumor was composed

of hepatic arteries and bile ducts, and no portal veinbranches whatsoever were detected. Thus, the present case

appeared to be one of complete portal vein agenesis.Congenital defects of the portal vein can result in

congestive heart failure due to shunting ofblood flow fromthe superior mesenteric vein to the inferior vena cava. Inreviews ofthe literature concerning congenital absence ofthe portal vein, concomitant atrial and ventricular septaldefects have also been reported.5 This may be attributedto a congenital adaptive change, occurring during theprocess ofdevelopment from the embryonic stage, whichtends to compensate for the congestive effects of portalvenous aplasia.

Normally the enterohepatic circulation affects, via theportal vein, the return to the liver ofconjugated bile acidsthat have been reabsorbed in the distal ileum. In the pa-tient in our case study, the concentration of bile acids inthe peripheral blood was 30 ,M, which is far above nor-

mal. This was, presumably, due to the absence ofthe portalvein, resulting in the influx into the inferior vena cava ofconjugated bile acids that normally would be returned tothe liver via the porta hepatis, so bile acid levels measuredin peripheral blood would include these conjugated bileacids as well as the free bile acids of the systemic circu-

TABLE 1. Ammonia Levels in Venous Bloodfrom Various Locations

Location of the vein 1 2 3 4 5

Ammonia (jsg/dl) 43 129 82 77 55

192 Ann. Surg. * August 1989

Vol. 210 - No.2 CONGENITAL ABSENCE OF THE PORTAL VEIN 193

vcI

-Jv ~~Aorta

l!~~~c

FIG. 8. Venous blood samples were taken at all the sites shown in Figures4, 5, and 6 when venography was performed. The respective serum levelsof ammonia at these sites are shown in Table 1. In particular, the am-monia concentration in the superior mesenteric vein (2) was 129 Ag/dl,which is just slightly higher than normal.

lation.6 This patient also displayed pronounced obesity,with a body weight of 78 kg and a height of 147 cm.Normally medium-chain fatty acids originating in nu-trients are conveyed to the liver by the portal vein andmetabolized, but when the portal vein is absent, thesefatty acids, after absorption by the intestinal tract, assumethe form of chylomicrons that are transported into thevena cava. Before arriving at the liver, the blood from thevena cava reaches the capillaries of the peripheral tissues,including adipose and muscular tissue, where fat is ac-cumulated, and this presumably constitutes the cause ofobesity in such cases.The next problem to be considered is that of the en-

terohepatic circulation. In the patient in our case study,the superior mesenteric vein bypasses the liver, emptiesdirectly into the inferior vena cava, and thereby conveysblood to the systemic circulation. This may give rise tohepatic encephalopathy. In fact, hepatic encephalopathy

has occasionally been reported as a sequea ofanastomosisbetween the portal and the inferior vena cava performedfor the treatment of portal hypertension.The blood levels ofammonia in the superior mesenteric

vein of normal individuals range from 350 to 400 ,ug/dl,and the influx of such high concentrations of ammoniainto the systemic circulation would be expected to inducedisturbances of consciousness. However, the ammoniaconcentration in the superior mesenteric venous blood ofthe ammonia levels in blood sampled at other sites wereentirely within the normal range. Since the patient hadwhat might be called a congenital Eck fistula,5 these nor-mal ammonia levels indicate that some sort of homeo-static control was operating.

Accordingly, the patient's intestinal bacterial flora,which are ordinarily considered to be the source of theammonia in the superior mesenteric venous blood, weresubjected to laboratory investigation, and distinct differ-ences from the intestinal flora of normal individuals withrespect to both varieties and numbers were discovered.Among the varieties ofbacteria displaying urease activity,9only three species were detected: Klebsiella pneumonia,Enterococcus avium, and Peptostreptococcus productus.Moreover, the numbers of these bacteria were extremelysmall. No significant differences were observed among theflora in fecal specimens obtained before, during, and aftersurgery. The results were interpreted as indicating the op-eration ofsome mechanism for ecological homeostasis ofthe intestinal flora.Phenomena relating to the urease activity and bile acid

metabolism ofthe intestinal bacterial flora in this patientare currently under further investigation.

Acknowledgment

The authors wish to thank Nadia E. L. Borai, M.Sc., for correctingthe English text.

References

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3. Brandy M. Patten Human Embryology, 3rd edition. New York:McGraw-Hill, 1986;529-530.

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