Surgical Anatomy of Transversus Abdominis Muscle for Transversus Abdominis Release: A CT-Based Study in Three Patient Groups.

BACKGROUND: The anatomy of the transversus abdominis muscle and its aponeurosis is important in transversus abdominis release surgery. We studied the CT anatomy of the transversus abdominis muscle medial to the linea semilunaris at different levels in the abdomen and measured the thickness of this muscle. METHODS: In this retrospective study, we analysed 150 abdominal computed tomography at L1, L3, and L5 vertebral levels corresponding to subxiphoid, umbilical, and suprapubic regions, respectively. The patients were divided into three groups based on age and sex: women aged 15-20 years (nulliparous), women aged 30-60 years (multiparous), and men aged 15-60 years, with each group having 50 patients. We compared the thickness of the TA muscle at the L1 level between men and women and between nulliparous and multiparous women. RESULTS: Transversus abdominis muscle was consistently present medial to the linea semilunaris at L1 vertebral level in the subxiphoid region (150/150). At the L3 vertebral level in the mid-abdomen, only eight patients had the transversus abdominis muscle there (8/150, 5%). At the L5 vertebral level in the suprapubic region, no patient had the transversus abdominis muscle medial to the linea semilunaris. The mean thickness of the transversus abdominis muscle at the L1 level was 3.4 mm, and at the L3 level, it was 1.6 mm. There was no statistically significant difference in the transversus abdominis muscle thickness between the men and women; however, a significant difference was found between the nulliparous and multiparous women, with thinner TA muscle in later. CONCLUSION: There is good transversus abdominis muscle bulk medial to the linea semilunaris for doing transversus abdominis muscle division in the upper abdomen. However, as we move towards the mid-abdomen, we have TA aponeurosis or rarely TA muscle of little bulk.

Multivariate Analysis of Effective Dose and Size-Specific Dose Estimates for Thorax and Abdominal Computed Tomography.

The study aimed to compute the effective dose (E) and size-specific dose estimate (SSDE) of routine adult patients undergoing thorax and abdominal computed tomography (CT) imaging and to present their multivariate analysis. All adult thorax and abdominal CT examinations conducted from March 2022 to June 2022 were prospectively included in this study. The Water Equivalent Diameter (Dw) and SSDE of all the examinations were computed from CT dose index volume (CTDIvol) and Dose length product (DLP) displayed on the dose report in the CT console. The multivariate statistical analysis was performed to investigate the correlation of SSDE and E on CTDIvol, Dw area of the region of interest (ROI) (AreaROI), body mass index (BMI), conversion factor (fsize) and hounsfield (HUmean) number in the ROI at 95% level of significance (P < 0.05). The linear regression analysis was performed to investigate the dependence of SSDE and E on other parameters for both abdominal and thorax patients. A total number of 135 (Abdomen = 61 and Thorax = 74) measurements were performed. The mean value of effective dose for abdomen and thorax patients was found to be 7.17 ± 3.94 and 4.89 ± 2.16 mSv, respectively. The SSDE was observed to be 13.24 ± 3.61 and 13.04 ± 3.61 mGy for thorax and abdomen respectively. The multivariate analysis suggests that SSDE for abdominal CT is found significantly dependent on CTDIvol, Dw and fsize with P < 0.05 and E is found to be significantly dependent on DLP, AreaROI, Dw and fsize at 95% level of confidence for abdominal CT imaging. SSDE for thorax CT was found significantly dependent on BMI, CTDIvol, HUmean, Dw and fsize at 95% level of confidence. Furthermore, E was observed dependent on DLP at P < 0.05. The linear regression analysis also shows that E is strongly correlated with DLP (r = 1.0) for both thorax and abdominal CT, further the SSDE was observed strongly correlated with CTDIvol with r = 0.79 and r = 0.86 for abdomen and thorax CT respectively. A strong correlation was observed between BMI and for Dw abdominal CT imaging (r = 0.68). The mean value of SSDE for thorax is slightly greater than abdomen. The average value of effective dose for abdomen and thorax measurements was found to be 7.17 ± 3.94 and 4.89 ± 2.16 mSv and , correspondingly. SSDE for both abdomen and thorax CT is significantly dependent on CTDIvol, Dw and fsize at 95% level of confidence. The strong correlation was also observed E on DLP and SSDE on CTDIvol for both Abdomen and Thorax CT. The strong dependence of Dw on BMI (r = 0.68) is due to the excessive fat concentration around the stomach and abdomen.