Yan-ying Gao, Qing Tang, Yan-cun Liu, Xiao-he Liu, Bao-xin Qian, Yan-fen Chai, Li-jun Wang

1 Department of Hepatology, the Third Central Hospital of Tianjin; Tianjin Institute of Hepatobiliary Disease, Tianjin 300170, China 2 Department of Emergency Medicine, Tianjin Medical University General Hospital, Tianjin 300052, China

Congenital extrahepatic portosystemic shunt (CEPS), also known as Abernethy malformation, is a rare disorder characterized by the partial or complete diversion of portal blood into systemic veins. CEPS is classified into two types: type I is an end-to-side portocaval shunt, whereas type Ⅱ is a side-to-side shunt, diverting blood from the portal vein to the inferior vena cava (IVC) (Figure 1).[1]

Since the first description of CEPS in 1793 by Abernethy,[2]the number of cases has increased progressively. There were only 185 CEPS patients reported until 2013, and this number dramatically increased to 300 in 2019.[3,4]In addition, most patients were children or adolescents.[5,6]Currently, only 13 elderly patients with CEPS (aged ＞65 years) have been reported in the literature (s upplementary Table 1). In addition, clinical presentation and treatment vary according to age. Hence, we report a case of an elderly patient with recurrent encephalopathy caused by Abernethy malformation and review the literature to increase the recognition of this disease.

A 75-year-old woman was referred to our emergency department complaining of intermittent sleep, arm tremor, and speech confusion in the past three years. She had a history of gastric ulcers, hypertension, diabetes, and constipation but no history of liver disease. The interictal serum ammonia level was 61-92 μmol/L but rose to 112-155 μmol/L in an episode of encephalopathy ( Figure 2).

Physical examination revealed a blood pressure of 140/65 mmHg (1 mmHg=0.133 kPa) and pulse rate of 69 beats/min. No liver palms, spider nevus, or jaundice were observed. Laboratory examination showed a serum ammonia level of 123 μmol/L, but liver and renal functions were normal. Autoimmune hepatitis and hepatitis B/C tests were negative. Ultrasound and computed tomography (CT) scans were normal, except for a thinner portal vein with a diameter of 5 mm. Hepatic encephalopathy was suspected because of recurrent hyperammonemia. However, liver function, ultrasound, and CT scans excluded liver cirrhosis. Contrast-enhanced CT revealed a tortuous and dilated shunt communicating with the superior mesenteric vein and IVC via the left renal vein (Figures 3 AC). Conservative treatment was adopted because of the patient’s elderly age. She did not develop encephalopathy, and serum ammonia remained at 69-134 μmol/L during the 6-month follow-up.

Figure 1. CEPS classification. CEPS: congenital extrahepatic portosystemic shunts; IVC: inferior vena cava; PV: portal vein; SV: splenic vein; SMV: superior mesenteric vein.

Figure 2. Changes in serum ammonia levels over time. Black arrows indicate an episode of encephalopathy.

Figure 3. Contrast-enhanced computed tomography (CT) showing a tortuous and dilated shunt. Green arrow (B and C) communicating with the superior mesenteric vein (purple arrow, C) and inferior vena cava (white arrow, C) via the left renal vein (red dot, A); the yellow arrow indicating the thinner portal vein in B; the red arrow indicating a spleen vein in C; narrow portal vein (D), abnormal blood signal (E), and dilated left renal vein (F).

Adult patients with CEPS develop encephalopathy after 50 years of age, but the reason for this remains uncertain.[1]One may speculate that the aging brain is less capable of tolerating the presence of ammonia and other metabolic products.[7]In elderly patients, even a slight increase in serum ammonia can induce severe encephalopathy.[8]Alterations in shunt flow also appear to be a major consideration.[9]However, another case reported that encephalopathy occurred even in the absence of increasing shunt flow.[10]Constipation could also induce hyperammonemia and encephalopathy. The incidence of constipation is higher in elderly people, with elderly females suffering more often from severe constipation.[11]

Although these patients presented with hyperammonemia and encephalopathy, most had no history of hepatic disease. Unlike in children or young adults, encephalopathy is a cardinal clinical presentation in elderly people. Patients in previous studies presented with encephalopathy and had intermittent ataxia,[7,8,12]asterixis,[8,13]altered mental status,[13,14]discrepant conversation,[10]dysarthria,[12]or stupor.[7,8,12,15]Other cases are usually discovered incidentally or during work-up for liver nodules or dysfunction.[9,16]

Venous stasis induced by shunts plays a major role in the development of thrombosis formation. Two patients presented with unexplained deep venous thrombosis (DVT), indicating a relationship between DVT and Abernethy malformation.[11]In addition, narrowing of the portal vein may be a potential indication of CEPS. The portal vein in one patient was diminutive with a transverse diameter of 9 mm but was normal 10 years ago with a transverse diameter of 15 mm.[9]In another case, the diameter of the portal vein was only 4 mm.[7]In our case, both CT and ultrasound demonstrated a thinner portal vein with a diameter of approximately 5 mm (Figures 3 B and D).

Contrast-enhanced CT and magnetic resonance imaging are the gold standards in diagnosis. However, ultrasound is also important due to its non-invasiveness and convenience. Aside from the narrow portal vein, abnormal blood signals and a dilated left renal vein (12.7 mm, reference value 4-6 mm) were also observed in our case (Figures 3 E and F).

Currently, no standard therapeutic approach is available for elderly patients with CEPS. The treatment strategy is usually decided based on the shunt type and location, symptom severity, and related complications (supplementary Figure 1).

Overall, CEPS should be suspected in elderly patients with unexplainable hyperammonemia and encephalopathy. A history of DVT and narrowing of the portal vein may be potential indications of CEPS, and ultrasound may reveal relevant findings. Conservative therapy should be the primary treatment of choice for patients with encephalopathy.

Funding:This study was funded by the Tianjin Health Technology Project (20188) and Peking Union Medical Foundation-Ruiyi Emergency Medical Research Fund (R2020010).

Ethical approval:The patient provided written permission for the publication of this case report. The study was approved by the ethics committee of Tianjin Medical University General Hospital, Tianjin, China.

Confl icts of interest:The authors declare that they have no confl icts of interest or financial ties to disclose.

Contributors:YYG and LJW drafted the manuscript and analyzed and interpreted the data. LJW and YFC conceived and designed the study. QT, YCL, XHL, and BXQ collected the data. All authors have read and approved the final manuscript.

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