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Question 3
Anatomy → Region
Classification
Question
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During a Pfannenstiel incision, the surgeon finds that the rectus sheath is unusually difficult to separate from the rectus abdominis below the umbilicus. Which anatomical feature most directly explains this finding?
Question Stem
A) Fusion of the external and internal oblique aponeuroses
B) Presence of a tendinous intersection below the umbilicus
C) Absence of fascia transversalis below the arcuate line
D) Fusion of pyramidalis with rectus abdominis
E) Continuation of Scarpa’s fascia into the rectus sheath
B) Presence of a tendinous intersection below the umbilicus
C) Absence of fascia transversalis below the arcuate line
D) Fusion of pyramidalis with rectus abdominis
E) Continuation of Scarpa’s fascia into the rectus sheath
Options
A
Fusion of the external and internal oblique aponeuroses
B
Presence of a tendinous intersection below the umbilicus
C
Absence of fascia transversalis below the arcuate line
D
Fusion of pyramidalis with rectus abdominis
E
Continuation of Scarpa’s fascia into the rectus sheath
Explanation
Each rectus abdominis has three or more tendinous intersections. These are usually situated above the umbilicus. When a tendinous intersection is present below the umbilicus, however, the rectus sheath is attached to the rectus muscle at that point. Consequently, the sheath and muscle may be difficult to separate during a Pfannenstiel incision. This operative difficulty therefore reflects the anatomical attachment produced by a low tendinous intersection rather than fusion of the oblique muscles, loss of fascia transversalis, involvement of pyramidalis, or continuity of Scarpa’s fascia with the rectus sheath.
Option Validity
A) Fusion of the external and internal oblique aponeuroses does not explain focal adherence of the rectus sheath to rectus muscle.
C) Fascia transversalis is a separate deeper layer and does not account for this attachment.
D) Pyramidalis does not produce the described rectus sheath adherence.
E) Scarpa’s fascia is a subcutaneous membranous layer and does not continue into the rectus sheath.
Further Reading
Part 1 MRCOG Revision Notes and Sample SBAs. Cambridge University Press, 2020. Section 1: Anatomy, Chapter 1. https://doi.org/10.1017/9781108644396