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Table of Contents
ORIGINAL ARTICLE
Year : 2022  |  Volume : 71  |  Issue : 2  |  Page : 123-127

Demonstration of the Epigastric Vessels Surface Anatomy with Equation Model: An Anatomical Feasibility Study


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Date of Submission20-Dec-2021
Date of Acceptance25-Mar-2022
Date of Web Publication30-Jun-2022

Correspondence Address:
Alper Ileri
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jasi.jasi_207_21

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  Abstract 


Introduction: The objective of this study is to design a patient-specific model to predict the location of epigastric vessels on the abdominal surface and to show clinicians safe areas before surgical intervention. Material and Methods: A total of 200 patients who underwent color Doppler ultrasound evaluation of the deep epigastric vessel before gynecological laparoscopic surgery were recruited in the study. The deep epigastric vessels were identified at three equal levels between the xiphoid and umbilicus, and five equal levels between the umbilicus and the symphysis pubis. The distance between the epigastric vessels and the midline was measured bilaterally at each level. Linear mixed effect modeling was used to assess the anatomical location of the epigastric vessels. Results: The model with waist circumference term was found to be the model with best performance metric. This model included waist circumferences as a covariate, the region of the epigastric vessel as a categorical variable, and random effects for patients. The model that calculates the expected distance from the midline of the epigastric vessels for different regions and waist circumferences are presented as “Distance to midline (cm) = 2.57 + Region A + Region B × Waist Circumference.” Discussion and Conclusion: With the equation model, we proposed, the location of the epigastric vessels can be determined specifically for the patient and the abdominopelvic regions. This model can be a guide to prevent vascular injury.

Keywords: Epigastric vessels, laparoscopy, obesity, ultrasound


How to cite this article:
Karaca SY, Ince O, Adiyeke M, Ileri A, Vural T, Töz E, Demir A, Karaca I, Pulur A, Ertas IE. Demonstration of the Epigastric Vessels Surface Anatomy with Equation Model: An Anatomical Feasibility Study. J Anat Soc India 2022;71:123-7

How to cite this URL:
Karaca SY, Ince O, Adiyeke M, Ileri A, Vural T, Töz E, Demir A, Karaca I, Pulur A, Ertas IE. Demonstration of the Epigastric Vessels Surface Anatomy with Equation Model: An Anatomical Feasibility Study. J Anat Soc India [serial online] 2022 [cited 2022 Aug 17];71:123-7. Available from: https://www.jasi.org.in/text.asp?2022/71/2/123/349527




  Introduction Top


Epigastric arteries are at risk of injury during abdominal procedures close to the artery, such as laparoscopic trocar placement, intra-abdominal drain placement, and paracentesis due to their anatomical position.[1] Abdominal wall vascular injuries during surgical procedures have been reported in 0.2%–2% of cases.[2] These vessels include the superficial epigastric vessels, the superficial circumflex iliac vessels, the superior epigastric vessels, and the inferior epigastric vessels.

Unlike the superficial vessels, the superior and inferior epigastric vessels are larger and their injury can cause significant morbidity and mortality.[3] The inferior epigastric artery (IEA) arises from the external iliac artery just above the inguinal ligament.[4] It rises along the medial edge of the inguinal ring, pierces the transversalis fascia, and lies anterior to the arcuate line between the rectus abdominis and the posterior rectus sheath.[4] Above the umbilicus, it anastomoses with the superior epigastric artery. The superior epigastric artery is the terminal continuation of the internal thoracic artery. It begins at the level of the sixth rib and runs down between the costal and xiphoid muscle slips of the diaphragm. The artery then reaches the anterior surface of the abdomen and runs over the transversus thoracis and transversus abdominis muscles.[4] It enters the rectus sheath and descends toward the umbilicus.[4]

Although the transillumination method in laparoscopic surgery largely defines the superficial vessels, transperitoneal imaging of the deep epigastric vessels is difficult, especially in obese patients.[5] Various studies have been conducted in the literature to map the location of the deep epigastric vessel.[5],[6],[7],[8] These studies evaluated the distance from the midline of the epigastric arteries in different several abdominal segments and suggested a more lateral location of the deep epigastric vessels in obese patients. Although the previous studies show lateralization of epigastric vessels in obese patients, patient-specific localization is far from estimating. The most important reason for this situation was the anatomical variations and the inability to show the body mass index (BMI) and waist circumference changes between patients.

The aim of this study is to create a patient-specific model to predict the location of epigastric vessels on the abdominal surface and to show clinicians safe areas before surgical intervention.


  Material and Methods Top


This study was conducted with patients scheduled for laparoscopic surgery for benign gynecological indications at Health Sciences University Tepecik Education and Research Hospital between July 2021 and October 2021. Following the approval of the study protocol by the local ethics committee of Health Sciences University Tepecik Education and Research Hospital, the patients were included in the study.

Since the superficial epigastric vessels were interrupted during the pfannenstiel incision and both the superficial and lower epigastric vessels were interrupted during the Maylard incision, patients who had undergone previous transverse lower abdominal incisions, including cesarean section, were excluded from the study. In addition, patients with large skeletal deformities that may displace the epigastric vessels, large abdominal tumors, tense ascites, incisional hernia, or any condition such as diastasis recti were not included in the study.

The location of the deep epigastric vessels was mapped across the abdomen at three equal levels between the xiphoid and umbilicus, and five equal levels between the umbilicus and the symphysis pubis, for a total of eight levels with Doppler ultrasound. The reliability of Doppler ultrasonography to measure the distance of epigastric vessels has been demonstrated in previous studies.[9] The distance between the epigastric vessels and the midline was measured bilaterally at each level. A total of 16 measurements were made from the right and left abdominal region from the xiphoid line to the symphysis line for each patient. L1-R1; xiphoid line measuring point, L4-R4; the umbilical line represents the measurement point, and the L8-R8 the symphysis pubis line measurement points. To control for interoperator variability, localization of the vessels was performed by a single-experienced ultrasonographer (M. A) using the Voluson 750 Pro ultrasound machine [Figure 1]. After determining the short and long axes of the vessels with Doppler, their projections to the abdominal skin were marked. At each level, the most lateral branch of the IEA and vein or superior epigastric artery and vein was marked. The data set consisted of the epigastric vessel (200 × 16 = 3200) localization obtained by Doppler ultrasound of a total of 200 patients.
Figure 1: Demonstration of epigastric vessels by Doppler ultrasound in different abdominal planes

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Afterward, patients' waist circumference, weight, and height were measured. Waist circumference was measured at the horizontal plane between the inferior costal margin and the iliac crest on the midaxillary line. Height and weight were measured in the standing position while the participants were barefoot and in light clothing. Demographic data, including age, gravidity, and parity, were collected from the patients and their electronic medical records.

Statistics

The primary outcome of the study is the distance of the epigastric vessels to the midline of the abdomen which passes through the umbilicus. For predicting the distance, linear mixed model analysis and maximum likelihood estimation were used. The independent variables were gravida, parity, age, weight, height, BMI, and waist circumference. In the model, random effect for patients was included, based on their identification. Linearity, normality of the residuals, homogeneity of residual variance (homoscedasticity), and no autocorrelation assumptions were verified. The intercepts for different patients were assumed to be normally distributed. A concern for the statistical analysis is potential multicollinearity between the predictor variables. In this respect, gravida, parity, age, weight, height, BMI, and waist circumference were found to be highly correlated, with most pairwise Pearson correlation coefficients > 0.75. Therefore, these predictors are not included in the multivariate model together. The literature does not indicate direct effects of gravida parity and age on the anatomical location of the epigastric vessels. Hence, only the effects of weight, height, BMI, and waist circumference were analyzed. Since weight, BMI, and waist circumference have Pearson correlation coefficients of around 0.90 with each other, we estimate three separate candidate models each including only one of the three as fixed effects. For each of these three models, we estimate hierarchical and nonhierarchical versions, resulting in a total of six models. The six candidate models and their performance metric are presented in [Table 1]. For all three models, hierarchical and nonhierarchical versions had same log-likelihood and same number of parameters, therefore, the same Bayesian information criterion (BIC) value. The two models with waist circumference as the fixed effect have the lowest BIC value. The Wald test of waist circumference as the main effect is not statistically significant. The model that includes only waist circumference as the interaction term has the same likelihood and BIC as the model that includes waist circumference both as the main effect and in the interaction term. Therefore, the former nonhierarchical model was chosen as the best predictor model. To present the results of the linear mixed model, the marginal and conditional R2 values are used.[10] Ninety-five percent confidence intervals for the distance of epigastric vessels in different regions were calculated by taking the uncertainty due to random effect variance in addition to uncertainty of variance due to fixed effects into account [Figure 1]. A two-tailed P < 0.05 was considered statistically significant. Statistical analyses were performed using R is available as Free Software under the terms of the Free Software Foundation's GNU General Public License.
Table 1: Comparison of the models including waist circumference, body mass index, and weight plus height

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Table 2: The formula for calculating the distance of the epigastric artery from the midline in different regions (height level: 1-8, sides: L for left and R for right)

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  Results Top


Linear mixed effect modeling was used to assess the anatomical location of the epigastric vessels. The distance of the artery to the midline is defined as the response variable. Compared to models including weight and height or BMI, the model with waist circumference term was found to be the model with best performance metric [Table 1]. This model included waist circumferences as a covariate, the region of the epigastric vessel as a categorical variable, and random effects for patients. The model used was nonhierarchical and did not include waist circumference as main effect but only in the interaction term. The marginal R2 value of the linear mixed model was 69.3% and the conditional R2 value was 87.6%. Therefore, 69.3% of the variability in the distance to the midline (dependent variable) is explained by the region of the vessel and waist circumference, and the 18.3% variability (87.6% - 69.3%) is explained by the random effects of the patients. The standard deviation of the random effects due to the patients was 0.6532. The remaining 12.4% variability is due to model error. The model to calculate the expected distance of epigastric vessels to the midline for different regions and waist circumferences is presented in [Table 1]. The 95% confidence interval for the location of IEA of a woman with a waist circumference of 85.3 is presented in [Figure 2].
Figure 2: The estimated anatomical trace of the inferior epigastric artery in a woman with waist circumference of 85.3 with 95% confidence interval for different height levels (1–8) and sides (the left or right) using the formula in [Table 2]

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  Discussion Top


To the best of our knowledge, this study is the first equation model to make a patient-specific topographic marking of deep epigastric vessels. Our findings showed that lateralization of vessels from the midline increased in correlation with the increase in the values of weight, BMI, and waist circumference variables. A patient-specific equation was created to predict the localization of epigastric vessels by analyzing the inter-patient variations. In this equation, the best metric performance was achieved with waist circumference. A safe entry point could be determined to prevent epigastric vessel damage by placing the patient's waist circumference measurement and the Region A and Region B values of the abdominal region where the surgical intervention will be performed into this equation.

The topographic definitions of deep epigastric vessels have been studied in many previous studies. However, the results of these studies could not provide a consensus to explain how far the vessels are from the midline. For example, Saber et al. found that the mean distance of the epigastric vessels from the midline at the level of the symphysis pubis was 7.5 cm.[11] Rao et al. reported that the farthest distance from the midline of the epigastric vessels at this level was 6.9 cm.[12] Rao et al. reported that the average distance from the midline of the epigastric vessels at the umbilicus was 3.5 cm,[12] whereas Epstein et al. reported an average of 4.8 cm.[13] Some authors, who suggested that the reason for this anatomical inconsistency in the studies was the disregard of obesity, reported that the vessels were located more laterally in obese patients.[6],[11] The most important deficiency in these studies with a limited number of patients was the categorical classification of patients as obese or nonobese. However, BMI is a continuous variable. As expected, the studies in the literature were insufficient to evaluate the effect of the degree of obesity on the lateralization of the epigastric artery. For example, if a patient with a BMI of 40 40 kg/m2 and a patient of 30 kg/m2 are in the same group, it may lead to the misconception that the epigastric vessel trace is more medial than it should be in patients with high BMI.

The main purpose of clinical studies in the literature is to define a safe zone to prevent possible epigastric vessel injuries. Pun et al. successfully detected epigastric vessels using color Doppler ultrasound and recommended sonographic localization of vessels before laparoscopic procedures, especially in obese patients, to avoid injury to these vessels.[14] Tinelli et al. showed that the adipose subperitoneal tissue located in the lateral third of the line between the anterior superior iliac spine and the umbilicus is the site for a safe auxiliary trocar port.[5] We created a patient-based equation for a similar purpose, and we found that the model with the term waist circumference had a better performance metric than BMI. With the help of this equation, it was possible to determine the distance of the epigastric artery from the midline at different levels of the abdominal surface of a patient whose waist circumference was known. For example, in a patient with a waist circumference of 100 cm (BMI = 31 kg/m2), we found the distance of epigastric vessels from the midline (2.56 + [−0.4] + [0.049 × 100]) 7.06 cm at the level of the right symphysis pubis (R8). In another obese patient, whose abdominal circumference was 130 cm (BMI = 40.5 kg/m2) in our model, the distance of the epigastric vessels was 8.53 cm from the midline. This equation model can be of great value as a real-time guide for many interventions, such as port site placement for abdominopelvic surgeons, epigastric perforator flap breast reconstruction for plastic surgeons, and perforation of the anterior abdominal wall for anesthesiologists.

With this study, we performed an equation model showing epigastric vessel location, but we are aware of some limitations of our study. First, our study population consisted of women. Although some studies reported that epigastric vessel location did not differ according to gender, we think that our results should not be generalized to the entire population. Second, since ultrasonography is subjective and dynamic imaging, all measurements were performed by a single ultrasonographer to limit interobserver variability. In addition, we could not show the perforator branches of the epigastric vessels in the model.


  Conclusion Top


We believe that this study is a model of equations that show the localization of epigastric vessels based on anthropometric and ultrasound imaging and is useful to prevent vessel damage in surgical procedures. Therefore, clinicians who follow the recommendations of this study should first measure their patients' abdominal circumference. They can determine the appropriate entry localization for each patient by inserting the constant values of the localization to be operated into the equation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Wong C, Merkur H. Inferior epigastric artery: Surface anatomy, prevention and management of injury. Aust N Z J Obstet Gynaecol 2016;56:137-41.  Back to cited text no. 1
    
2.
Vasquez JM, Demarque AM, Diamond MP. Vascular complications of laparoscopic surgery. J Am Assoc Gynecol Laparosc 1994;1:163-7.  Back to cited text no. 2
    
3.
Fuller J, Ashar BS, Carey-Corrado J. Trocar-associated injuries and fatalities: An analysis of 1399 reports to the FDA. J Minim Invasive Gynecol 2005;12:302-7.  Back to cited text no. 3
    
4.
Ireton JE, Lakhiani C, Saint-Cyr M. Vascular anatomy of the deep inferior epigastric artery perforator flap: A systematic review. Plast Reconstr Surg 2014;134:810e-21e.  Back to cited text no. 4
    
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Tinelli A, Gasbarro N, Lupo P, Malvasi A, Tsin DA, Davila F, et al. Safe introduction of ancillary trocars. JSLS 2012;16:276-9.  Back to cited text no. 5
    
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Burnett TL, Garza-Cavazos A, Groesch K, Robbs R, Diaz-Sylvester P, Siddique SA. Location of the deep epigastric vessels in the resting and ınsufflated abdomen. J Minim Invasive Gynecol 2016;23:798-803.  Back to cited text no. 6
    
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Bowness J, Seeley J, Varsou O, McKinnie A, Zealley I, McLeod G, et al. Arterial anatomy of the anterior abdominal wall: Evidence-based safe sites for ınstrumentation based on radiological analysis of 100 patients. Clin Anat 2020;33:350-4.  Back to cited text no. 7
    
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Joy P, Simon B, Prithishkumar IJ, Isaac B. Topography of inferior epigastric artery relevant to laparoscopy: A CT angiographic study. Surg Radiol Anat 2016;38:279-83.  Back to cited text no. 8
    
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Sriprasad S, Yu DF, Muir GH, Poulsen J, Sidhu PS. Positional anatomy of vessels that may be damaged at laparoscopy: New access criteria based on CT and ultrasonography to avoid vascular injury. J Endourol 2006;20:498-503.  Back to cited text no. 9
    
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Nakagawa S, Schielzeth H. A general and simple method for obtaining R2 from generalized linear mixed-effects models. Methods Ecol Evol 2013;4:133-42.  Back to cited text no. 10
    
11.
Saber AA, Meslemani AM, Davis R, Pimentel R. Safety zones for anterior abdominal wall entry during laparoscopy: A CT scan mapping of epigastric vessels. Ann Surg 2004;239:182-5.  Back to cited text no. 11
    
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Rao MP, Swamy V, Arole V, Mishra P. Study of the course of inferior epigastric artery with reference to laparoscopic portal. J Minim Access Surg 2013;9:154-8.  Back to cited text no. 12
    
13.
Epstein J, Arora A, Ellis H. Surface anatomy of the inferior epigastric artery in relation to laparoscopic injury. Clin Anat 2004;17:400-8.  Back to cited text no. 13
    
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Pun TC, Chau MT, Lam C, Tang G, Leong L. Sonographic localization of abdominal vessels in Chinese women: İts role in laparoscopic surgery. Ultrasound Obstet Gynecol 1998;11:59-61.  Back to cited text no. 14
    


    Figures

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    Tables

  [Table 1], [Table 2]



 

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