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ORIGINAL ARTICLE
Year : 2015  |  Volume : 5  |  Issue : 3  |  Page : 143-148

Determination of normal portal vein diameter on ultrasound scan among adults in northeastern Nigeria


1 Department of Radiology, Federal Teaching Hospital, Gombe, Nigeria
2 Department of Radiology, Ahmadu Bello University Teaching Hospital, Zaria, Nigeria
3 Department of Radiology, University of Maiduguri Teaching Hospital, Maiduguri, Nigeria

Date of Web Publication19-Oct-2015

Correspondence Address:
Dr. Aminu Umar Usman
Department of Radiology, Federal Teaching Hospital, Gombe
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2278-9596.167507

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  Abstract 

Background: Despite the safety, affordability, and widespread use of ultrasound (US); there is paucity of literature on ultrasonographic assessment of portal vein (PV) diameter in adult patients in our environment. This study was aimed at determining the mean and range of PV diameter in normal adults in northeastern Nigeria.
Patients and Methods: This cross-sectional prospective study was carried out at the University of Maiduguri Teaching Hospital between January and June, 2013. Two hundred and fifty normal adult male and female patients aged 18 years and above underwent abdominal ultrasonography for measurement of their main, right, and left PV diameter in both inspiration and expiration. The relationship between the PV diameter and age was correlated using Pearson's correlation test. While the difference between the two sexes and phases of respiration were compared using Student's t-test.
Results: There were 187 (74.8%) males and 63 (25.2%) females aged between 19 and 77 years, mean 43.78 ± 12.97 years. The mean diameter of the main PV was 10.87 mm ± 0.81. The mean diameter of the right and left PVs were 4.35 mm ± 0.52 and 4.12 mm ± 0.52, respectively. The PV diameter correlated with age and respiratory phases (P < 0.05). There was statistically significant difference in PV diameter between males and females (P < 0.05) with values higher in females.
Conclusion: The mean PV diameter in normal adults has been established in northeastern Nigeria. The diameter correlated with age and showed significant difference between the two sexes and respiratory phases.

Keywords: Normal portal vein, portal vein diameter, portal vein disease, portal hypertension


How to cite this article:
Usman AU, Ibinaiye P, Ahidjo A, Tahir A, Sa'ad ST, Mustapha Z, Tahir N, Garko S. Determination of normal portal vein diameter on ultrasound scan among adults in northeastern Nigeria. Arch Int Surg 2015;5:143-8

How to cite this URL:
Usman AU, Ibinaiye P, Ahidjo A, Tahir A, Sa'ad ST, Mustapha Z, Tahir N, Garko S. Determination of normal portal vein diameter on ultrasound scan among adults in northeastern Nigeria. Arch Int Surg [serial online] 2015 [cited 2023 Feb 1];5:143-8. Available from: https://www.archintsurg.org/text.asp?2015/5/3/143/167507


  Introduction Top


The portal vein (PV) is a unique vein that drains blood from the capillaries of the intestinal walls and spleen to the capillaries of the hepatic sinusoids. It is less prone to anatomical variation than the hepatic artery and is normally formed posterior to the neck of the pancreas, by the union of the superior mesenteric vein (SMV) and the splenic vein (SV) at the level of the L1/L2 disc space. [1],[2] It runs posterior to the bile duct and the hepatic artery at the porta hepatis, where it divides into right and left branches to supply the right and left lobes of the liver. [1] The PV supplies 75-80% of blood flow to the liver, while hepatic artery supplies 20-25%.

PV disease is a common clinical presentation of portal venous disease with multiple causes and several sequelae. It is responsible for substantial economic, social, psychologic, and mental burdens; and its causes could either be pre-hepatic, hepatic, or post-hepatic. [3],[4],[5] The most common cause of portal hypertension is cirrhosis of the liver. Cirrhosis results from scarring of the liver, an injury caused by hepatitis, alcohol abuse, schistosomiasis, or other causes of liver damage. Low flow velocity, reversal of flow, high diameter, and area are seen in portal hypertension. High flow velocity, reduced diameter, and area are seen in PV stenosis; while absence flow, high diameter, and area are seen in PV thrombosis.

Conventional angiography, computed tomographic angiography (CTA), and magnetic resonance angiography (MRA) can be used to evaluate PV diameter. However, ultrasound (US) is preferred because it is a safe, noninvasive, cheap, and readily available diagnostic tool for evaluating PV diameter. [6] US is a valuable tool for diagnosing abnormalities of the portal venous system, and with real-time grey-scale and Doppler US, evaluation of the PV has become relatively simple and reliable. [7] This takes into account PV dilatation, decreased flow velocity, and flow reversal which are the physiological changes associated with portal hypertension; however, the sensitivity of PV dilatation in the diagnosis of portal hypertension is relatively high. [8],[9],[10],[11] There is a need for a local ultrasonographic reference value of normal PV diameter in our environment as most values in the literature are from the Caucasian population.

This study aimed at determining the mean and range of PV diameter in normal adults in northeastern Nigeria.


  Patients and Methods Top


Study design

This cross-sectional prospective study was carried out from January to June 2013. The case group consists of apparently normal individuals who met the inclusion criteria. Subjects were recruited using simple random sampling technique.

Study area

The study was carried out at the University of Maiduguri Teaching Hospital (UMTH), Maiduguri, Nigeria. Maiduguri is the capital of Borno State in northeastern Nigeria lying between latitude 11.5°N and longitude 13.5°E. The estimated population based on 2007 census is about of 4,150,893, which are made up of almost equal number of males and females. [12] The inhabitants are mostly Kanuri, Shuwa, Babur-Bura, Margi, Mandara, Hausa, Fulani, and people from the other Nigerian states and the neighboring countries of Cameroun, Niger, and Chad. UMTH is the largest tertiary referral health care center in the region.

A total of 250 subjects out of the 300 recruited subjects were eligible for the study. Informed written consent was obtained from the patients, while approval to carry out the study was obtained from the Ethical Committee of the UMTH. Subjects were recruited from volunteer hospital staff and medical students, patients on routine medical check-up from the General Out-Patient or Family Medicine Department of the institution. Excluded from the study were those with known hepatobiliary diseases, cardiac diseases, portal hypertension and splenomegaly, history of cholecystectomy or cardiac operation, abnormal liver function test (LFT), pregnancy, and any hepatobiliary abnormality on abdominal US. The presence of gas in the upper abdomen of some subjects resulted in obscuration of the PV, making it particularly difficult or impossible to measure the PV parameters. Such participants were excluded from the study. There was difficulty in assessing PV in some obese patients and such patients were also excluded from the study. The age, sex, height, weight, and BMI [13] of each participant were measured. The last menstrual period of female participants was documented and this, in conjunction with pelvic US was used to exclude pregnancy. Blood samples of the subjects were taken for LFT assessment. Data collected was recorded in the data collection form.

US technique

Prior to the examination, patients were asked to fast for 6-8 h. This reduces excess bowel gas that may obscure the main PV and distends the biliary ducts. The examination was performed using a high-resolution real-time Doppler US scanner (Aloka, SSD-3500) equipped with 3.5 MHz curvilinear transducer. This transducer provides excellent resolution for deep abdominal visceral organs such as the liver. The US examination was conducted in supine position. US gel was applied and transducer placed in the epigastrium in both transverse and longitudinal planes to evaluate the main PV, and right hypochondria region to evaluate the right and left PVs. The intrahepatic PVs in some patients were also examined in subcoastal or intercoastal approach with the patient either in supine, right anterior oblique, or left posterior oblique as needed. In patients with excess gas in the duodenum and antrum that obscured the distal extrahepatic PV, they were placed in an erect right anterior oblique position to displace the air.

The PV is visible on US as it passes towards the liver posterior to the common bile duct and hepatic artery. Its wall appears hyperechoic on US and color flow Doppler helps in identification of the vessel as direction of flow in normal PV is continuous antegrade flow toward the liver during quiet respiration. The main PV diameter was measured at a point which was midway between the confluence of the splenic and superior mesenteric veins and bifurcation of the PV during quiet inspiration by the same sonologist as described by Anakwue et al. [14] Anteroposterior (AP) and transverse diameter of the main PV were measured at its midpoint mentioned above (A to B), while the values for right PV (C to D) and left PV (E to F) were measured at the level of their bifurcation [Figure 1] and [Figure 2]. The AP diameter from proximal to distal wall was obtained using the longitudinal view, while the transverse diameter from the medial to lateral wall was obtained from the transverse view.
Figure 1: Longitudinal view of the abdomen showing the levels of measurement of the portal vein (white arrows), right portal vein (black star), and left portal vein (white star). IVC = Inferior vena cava

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Figure 2: Transverse view of the portal vein (PV) showing the levels of measurement (white arrows)

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All measurements were taken twice by the same observer, and the average calculated to enhance accuracy of the results and reduce intraobserver variability. [14]


  Data analysis Top


Data management and statistical analysis was done using Statistical Package for Social Sciences (SPSS) for Windows version 16.0 (SPSS Inc, IL, USA). Descriptive statistics which include mean, mode, median, and standard deviation were used to describe the diameter of the PVs. The correlation between the diameters with age was evaluated using Pearson's correlation test. Statistical significance was assessed using Student's t-test to compare the mean PV diameter between the two sexes, compare the difference between the mean right and left PV diameters and respiratory phases with a P-value set at 0.05.


  Results Top


The study was performed on 250 consenting normal adults, 187 (74.8%) were males while 63 (25.2%) were females. The age range was 19-77 years, mean of 43.78 ± 12.97 years. Seventy-eight were in the age group of 41-50 years (31.2%), while the least number of patients (2.8%) were in the younger age group of <20 years [Table 1]. [Table 2]a shows the difference in mean PV diameter in the various age groups in males which was statistically significant (P = 0.000). The main PV diameter in males was highest in 71-80 year age group with a value of 12.51 mm ± 0.47. The values tend to increase with age confirming to a positive correlation (r = 0.756). The overall main PV diameter was 10.94 mm ± 0.84.
Table 1: Sex distribution pattern based on age group


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Table 2


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The value of the right PV in males was 4.38 mm ± 0.54, which was higher than the left (4.15 mm ± 0.56); and their difference was statistically significant (P = 0.000).

[Table 2]b also shows difference in the mean PV diameter in the various age groups in females which was statistically significant (P = 0.000). The main PV diameter in females was highest in 71-80 year age group with a value of 12.41 mm ± 0.02. The values tend to increase with age confirming to a positive correlation (r = 0.606). The overall main PV diameter was 10.65 mm ± 0.66. The value of the right PV in the females was 4.24 mm ± 0.41, which was higher than that of the left (4.02 mm ± 0.39); and their difference was statistically significant (P = 0.000). The mean diameter of the main PV in males was 10.94 mm ± 0.84, which was higher than that of females (10.65 mm ± 0.66); and the difference was statistically significant (P = 0.000).

[Table 3] shows summary of the range and mean diameter of the main, right, and left PVs of the subjects. [Table 4] shows that the mean diameter of the main, right, and left PV diameter of males on inspiration were 10.95 ± 0.84, 4.15 ± 0.56, and 4.38 mm ± 0.54, respectively, which were higher than the corresponding values on expiration (10.23 ± 0.79, 4.02 ± 0.47, and 4.15 mm ± 0.56, respectively). The difference was statistically significant (P = 0.000).
Table 3: Descriptive statistic of the total diameter of the main, right and left portal veins


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Table 4: Total mean PVD and respiratory phase in the male and female subjects


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The values in females on inspiration were 10.64 ± 0.65, 4.01 ± 0.39, and 4.25 mm ± 0.42, respectively, which were also higher than the corresponding values on expiration (10.23 ± 0.52, 3.89 ± 0.23, and 4.02 mm ± 0.40, respectively). The difference was also statistically significant (P = 0.000). The PV diameter did not show any correlation with the height, weight, and body mass index with P - values of 0.71, 0.62, and 0.53, respectively.


  Discussion Top


In the present study, the mean main PV diameter in Nigerian adults in Maiduguri was 10.9 mm ± 0.81, while the right and left PVs diameters were 4.35 ± 0.52 and 4.12 mm ± 0.52, respectively. These findings are similar to that of Anakwue et al., [14] in southeast Nigeria. They studied 200 apparently healthy adult Nigerians aged 20-79 years and found the mean main PV diameter to be 11.5 mm ± 0.15, while the right and left PVs diameters were found to be 4.25 ± 0.42 and 4.22 mm ± 0.32, respectively. The similarity between their results and the present study may be due to the fact that both studies were carried out among Nigerians, but of different ethnicity. Thus, ethnic variations seem not to have significant influence on PV dimensions. [15] The findings of Tasu et al., [16] in France on PV diameter are also similar to the findings of this study. They studied 30 healthy adults and documented a mean PV diameter of 11.0 mm ± 2.6. Cosar et al., [17] also found a mean PV diameter of 11.7 mm ± 0.3 among 30 healthy adults in Turkey, which is similar to the findings of this study. These findings further support the fact that race and ethnicity have no influence on PV parameters. [15]

On the other hand, Rokni-Yazdi and Sotouden [18] reported that the mean PV diameter was 9.6 mm ± 1.9 among 37 healthy Iranian volunteers, which is lower than the mean diameter (10.9 mm ± 0.81) obtained in the current study. Difference in sample size and technique of measurement may have accounted for this. [19]

In our study the values of PV diameter increase with age, confirming a positive correlation (r = 0.756). This finding is in agreement with Hawaz et al., [20] who reported an increase in diameter of PV with increase in age in normal individuals which is also consistent with the finding of Anakwue et al. [14] Similar findings were also found by other researchers. [21],[22],[23] However, Jeffry et al., [7] and other researchers [14] found no significant correlation between PV diameter and age. Difference in sample size and technique of measurement may also have accounted for this. [19]

The PV dimensions obtained in this study were higher in males than females. The sex differences were statistically significant (P = 0.000). Similarly, Moriyasu et al., [8] studied 88 normal subjects and noted significant differences in diameter of the PV between males and females (P < 0.001). Also in the study carried out in Iran by Rokni-Yazdi and Sotouden, [18] significantly higher PV dimensions were observed among male subjects (P = 0.0001) [8] On the contrary, Chuo et al., [15] did not find any significant difference in the PV dimensions by sex. This may be due to differences in techniques and equipments used for the study. They used two different US machines for their study and Jee et al., [19] had observed that US indices of the portal and splenic veins showed significant inter-equipment variability even when the same technique of measurement is used.

A study by Trigaux et al., [22] on 50 normal adults found the right PV diameter to be higher than the left. This study found a significant difference between right and left PVs diameter (P = 0.0005). The current study is in agreement with this finding as we found the right PV diameter to be significantly higher than the left. In this study, there was a statistically significant difference between the values of PV diameter with phases of respiration (P < 0.000) in the subjects with values higher in inspiration. This finding is similar to that of Rokni and Khalilian [24] who studied 36 normal subjects and found an increase in the diameter of the PV on inspiration, which also agrees with another study by Bolondi et al. [25] The PV diameter did not show any correlation with the height, weight, and body mass index. This is similar to the findings among Caucasians. [8]

As a limitation of our study, difficulties in Doppler examination could occur due to involuntary breathing movement. This was overcomed by perfoming the scan in arrested respiration until a better view is achieved.


  Conclusion Top


The mean PV diameter in normal adults has been established in northeastern Nigeria. The diameter correlated with age and show significant difference between the two sexes and respiratory phases. A similar study in other parts of the country is recommended. This will help in establishing a normative data for Nigerians.

 
  References Top

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    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]


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