J. Anat. (1984), 138, 4, pp. 603-616 603 With 14 figures Printed in Great Britain

The formation of abdomino-perineal sacs by the fasciae of Scarpa and Colles, and their clinical significance*

B. F. MARTIN Department of Pathology, University of Birmingham, Birmingham B15 2TJ (Accepted 23 September 1983)

INTRODUCTION By the middle of the nineteenth century the existence of a membranous layer on the deep aspect of the superficial of the lower was well known. This layer was first mentioned by Scarpa (1809) in a report on hernia, but his descrip- tion was far from clear (Tobin & Benjamin, 1944). In addition, Colles (1811) had demonstrated in the a membranous layer attached to the conjoined rami of the ischium and pubis, so determining the forward passage of urine from the perineum following urethral rupture. In 1854, Struthers made a detailed study of the membranous fascia, showing that the abdominal and perineal components are in direct continuity. He suggested that the use of a short, specific name for each component would be advantageous and, although the original descriptions were incomplete, proposed that they be referred to as the fascia of Scarpa and the fascia of Colles. His account of the fascia may be summarised as follows. The fascia of Colles (membranous layer of superficial perineal fascia) is attached to the base of the triangular ligament, or true deep fascia of the perineum (perineal membrane), and both are continuous with the fascia over the muscle. Laterally, the fascia is attached to the rami of the ischium and pubis; from there it crosses the origins of the gracilis and adductor longus muscles and becomes con- tinuous with Scarpa's fascia, which is attached to the fascia lata just below the . Traced forwards from the triangular ligament it enters the , where it blends with the common superficial fascia and continues around the sperm- atic cord into Scarpa's fascia. Colles' fascia thus forms a closed pouch in the peri- neum (the superficial perineal pouch or space in current terminology), which opens forwards into the scrotum, and thence into a wide space between Scarpa's fascia and the aponeurosis of the external oblique muscle, which contains lax cellular tissue. He noted that the fascia is more distinctly membranous at its attach- ment sites, where it separates from the overlying layer. Although he described a dissection procedure for demonstrating the attachment of Scarpa's fascia in the groin, and showed that the superficial vessels and transverse group of inguinal lymph nodes lie in the space between it and the fatty layer, he did not trace it far above the groin but assumed its upward continuation. His observations on the relationships of the fascia to hernia and urinary extravasation will be presented later.

* This investigation was undertaken whilst the author was in post in the Department of , University of Birmingham. 20 ANA 138 604 B. F. MARTIN Accounts of the fascia by more recent investigators (Wesson, 1953) have not differed significantly from that of Struthers, and current textbooks of anatomy (Williams & Warwick, 1980) and surgical anatomy (DuPlessis, 1975) provide a similar description, although it is now recognised that on entering the scrotum the superficial layer loses its fat, acquires smooth muscle, and is known as the scrotal dartos muscle. A similar layer, known as the penile dartos, ensheathes the penile shaft as far as the coronary sulcus. Deep to the dartos, a dense membranous layer also ensheathes the shaft and is closely adherent to the . Originally described by Buck (1848), it was reinvestigated by Wesson (1923, 1953), who stated that it arises from the deep fibres of the suspensory ligament of the , reinforced by an aponeurosis from the ischiocavernous muscles, and extends from the tri- angular ligament (the perineal membrane) to the coronary sulcus. He confirmed Buck's description of its arrangement in a figure ofeight, one compartment enclosing the corpora cavernosa and the other the corpus spongiosum. He also noted that the fasciae of Scarpa and Colles, together with the penile dartos, which he regarded as a continuation of Colles' fascia, are adherent to the superficial fibres of the sus- pensory ligament (the fundiform ligament). Not all investigators, however, have been convinced that the of the lower abdominal wall is composed of two distinct layers, or that deep attach- ments exist. In their study of normal cadavers and those in which extravasation of urine had either occurred clinically or been simulated, Tobin & Benjamin (1944, 1949) concluded that the deep membranous layer of the superficial fascia is created by dexterous dissection of a cleavage plane and, furthermore, their histological studies of the lower abdominal wall revealed only interlacing collagen bundles within a single fascial layer. Although the superficial fatty layer is sometimes re- ferred to as the fascia of Camper, these authors found no reference to this layer in any of Camper's publications. In the present investigation, dissection of the fascia of the lower abdominal wall and its continuation into the perineum has been undertaken on embalmed cadavers and, in the light of the observations made, radiological studies on fresh cadavers performed. These studies confirm the arrangement and attachments of the mem- branous layer revealed by dissection.

METHODS AND OBSERVATIONS Studies by dissection This part of the investigation was carried out on nineteen cadavers (nine males and ten females). The initial observations on the fascia of the abdominal wall were made on three male and three female specimens. More detailed studies of its overall distribution, including its perineal extension, were then undertaken on six males and seven females. In one male cadaver, the sac of a left indirect inguinal hernia was present and this specimen was considered separately. Following close dissection of the skin from the subcutaneous fascia, it was noted that the latter was very loosely attached to deeper structures just above the pubic tubercle. When the fascia was pinched up and incised, a subcutaneous sac with clearly defined margins was exposed. The sac was oval in form and oblique in direction. The long axis extended from the pubic tubercle to the mid-point of a vertical line between the anterior superior iliac spine and the costal margin. This point lay approximately at the level of the umbilicus or a little below it. In most cases the Superficialfascia ofabdomen andperineum 605 .i"...Y. ..

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Fig. 1. Male cadaver. The subcutaneous abdominal sacs have been opened along their main axes. The right sac is shorter than average. Fig. 2. Female cadaver. The right sac is shorter than average. The outer margin of the sac crosses the inguinal ligament medial to the anterior superior iliac spine (arrow) and becomes attached to the crease-line of the groin (CR). See Figure 5. Fig. 3. Female cadaver. The entrances to the perineal pockets of the sac are separated by fascial bands. The medial pocket (L) is a little anterior to the others and is associated with the labium majus. The intermediate (R) is associated with the round ligament of the uterus and the lateral (P) with the superficial perineal pouch. Compare Figure 6. Fig. 4. Female cadaver. The whole of the fatty subcutaneous layer (held in outer forceps) has been reflected from the incisions into the sacs. The sacs are formed by Scarpa's membranous fascia (held in inner forceps), which does not extend beyond their attached margins.

20-2 606 B. F. MARTIN length of the axis was 18-20 cm but in four specimens the sac of one side was shorter than the other and measured 12-5 cm; examples are shown in Figure 1 (male) and Figure 2 (female). In one male specimen both sacs were only 12-5 cm in length. The deep surface of the subcutaneous fascia which enclosed the sac was formed by a thin membranous layer which was intimately adherent to the overlying fatty layer, whilst its free surface was smooth and glistening. This layer, which will be referred to as Scarpa's fascia, formed the margins of the sac by its adhesion to the thin layer of deep fascia covering the aponeurosis of the external oblique muscle, described by Gallaudet (1931). Inferiorly, the abdominal sac extended into the perineum by means of three pocket-like diverticulae, each of which admitted a finger. In the female, they were narrower and commonly occupied by adhesions, which needed to be broken down by finger pressure before they were clearly defined. It was found that they extended to the level of the clitoris. The diverticulae, referred to for convenience as pockets, originated just below the superior margin of the pubis, which was therefore taken to be the level at which Scarpa's fascia continued into the fascia of Colles. The entrances to the pockets, shown in Figure 3 (female) and Figure 6 (male), were formed by the subdivision of the perineal extension of the abdominal sac by two dense fascial bands. From each band a thin septum continued inferiorly and thereby subdivided the extension into three pockets. In both sexes the medial pocket lay a little anteriorly to the other two. Investigations to determine the overall distribution of Scarpa's fascia and the relationships of the pockets in the perineum were also commenced by removing the abdominal skin from the subcutaneous fascia and incising the abdominal sac along its axis. It was possible to separate Scarpa's fascia from the overlying fatty layer by commencing the dissection at the margins of the incision. The fatty layer was continuous with the general fatty layer of the abdominal wall, and this layer continued without interruption into the thigh. By contrast, Scarpa's fascia did not extend beyond the attached margins of the sac, and it was noted that its attachment to the deep fascia of Gallaudet was a little weaker at the upper extremity of the sac. In a female cadaver (Fig. 4) the whole fatty layer of the ventral abdominal wall was reflected away from both sacs. From the upper margins of the incisions it was reflected as a single sheet towards the thorax and from their lower margins it was reflected to the groins. The sacs, formed by Scarpa's fascia, were left in situ. Inferiorly, the medial wall of the sac was attached to the fundiform ligament in the male and to the suspensory ligament of the clitoris in the female. The lateral wall crossed the outer part of the inguinal ligament, approximately 2-5 cm medial to the anterior superior iliac spine, and finally became attached to the fascia lata at the crease-line of the groin (Figs. 2, 5). This line was described by Holden (1877) as the furrow at the bend of the thigh, and he pointed out that it overlies the hip joint. Just beyond the crease-line, the transverse group ofinguinal lymph nodes was located within the deeper part of the fatty layer. Beyond and below the pubis the fatty layer became more membranous and blended with Colles' fascia, so that they were not readily separable. However, the relationships of the pockets could be determined following incision through the ventral wall of the scrotum or labium majus. Superficialfascia ofabdomen andperineum 607 In the male, the entrance to the lateral pocket (P in Fig. 6) lay adjacent to the crease-line of the groin, and the fascia of the pocket was formed ventrally by the fascial continuation from the abdominal wall, laterally by the fascial continuation from the crease-line and medially from the septal band separating the lateral and intermediate pockets. The pocket continued into the superficial perineal pouch (into which the lateral rod (P) is inserted in Figure 7) and it will be referred to as the pouch pocket. The entrance to the intermediate pocket (C in Figure 6) lay immediately below the superficial inguinal ring and was crossed by the ilio-inguinal (removed in the specimen shown in Figure 6). This pocket was closely associated with the sperm- atic cord and will be referred to as the cord pocket. Its fascia was derived from a continuation from the abdominal wall and from the septal bands separating its orifice from those of the adjacent pockets. The pocket occupied the posterolateral region of the scrotum and terminated 1-2 cm proximal to the superior pole of the testis. It did not surround the cord but was situated anterolateral to it, except in one case where it was anteromedial, and its fascia blended posteriorly with the coverings of the cord. Thus, the pocket appeared to be invaginated by the cord and its cover- ings. Its extent, and its position within the scrotum is illustrated in Figure 7, where a finger has been introduced into its entrance. The medial pocket occupied the scrotum and will be referred to as the scrotal pocket. It was situated a little anterior to the other pockets (as shown by the medial rod (S) in Figure 7). Its entrance was bounded laterally by the septal band separating it from the cord pocket and medially by the fundiform ligament (Fig. 6). Its fascia, derived from these structures and from the abdominal wall, lined the scrotal cavity where it blended with the fascia of the cord pocket. Below the latter it was reflected over the testis and formed its outermost fascial covering. In the female, the lateral pocket also continued into the superficial perineal pouch. The medial pocket, which corresponded with the scrotal pocket, was situated within the labium majus. The intermediate pocket, which corresponded with the cord pocket, was also situated within the labium majus and its entrance was crossed by the ilio-inguinal nerve. The round ligament of the uterus was adherent to its fascia posteriorly. Relationships of a hernial sac The scrotal pocket of the specimen with an inguinal hernia was opened through a ventral incision. Beyond the superficial inguinal ring the hemial sac, which was free of contents, was contained within the cord pocket. The fascia of the pocket was not adherent to the sac and was readily dissected from it, except posteriorly where both sac and pocket blended with the fascial coverings of the . It was then apparent that the fundus of the sac had reached the fundus of the pocket which, as in normal cadavers, was situated approximately 2 cm above the testis (Fig. 8). The proximal part of the sac was about 1 cm in diameter but its distal part was expanded and it had enlarged the cord pocket to a diameter of approximately 3 cm. Radiological investigations These investigations were undertaken on four female and six male cadavers. Apart from one male 14 years old they were elderly subjects with an age range from 69 to 94 years. Two had been recently embalmed but the remainder were investigated prior to embalming. One male cadaver showed a scar from an appendicectomy and 608 B. F. MARTIN another showed a scar following repair of a left inguinal hernia. These specimens will be considered separately. Normal subjects The contrast medium Micropaque was injected directly into the abdominal sac through a wide-bore needle attached by rubber tubing to a metal aural syringe. A concentration of 75 % (3:1 medium: water) provided a fluid of suitable viscosity for injection and good radiographs were obtained. The skin and subcutaneous tissue pinched up readily over the sac region and the injection was made 3 cm above and lateral to the pubic tubercle. As injection proceeded in male subjects, a well-defined ovoid swelling appeared on the lower abdominal wall and presented the same contour as the sac when demonstrated by dissection. The lateral margin descended medial to the anterior superior iliac spine to gain the crease-line of the groin, which then appeared as a deep furrow, and the medial margin reached the mid-line in the pubic region (Fig. 9). Although the sac was well distended following injection of 200 ml of fluid there was no apparent distension of the scrotum. Radiographs showed that the medium was confined to the region of the sac, including the pockets of its perineal extension (Fig. 10; same specimen as Fig. 9). When the pockets were well filled, two fundi were apparent (Figs. 10, 12), and it is probable that the lateral was the fundus of the perineal pocket and the medial that of the scrotal pocket, which had masked the cord pocket over which it lay within the scrotum. The medium neither entered the contralateral sac nor did it pass between the fascial layers of the penile shaft. The latter finding was well illustrated following injection of both sacs in succession, when the medium skirted around the base of the shaft, delineating it clearly (Figs. 12, 13). In female subjects the sacs were less completely filled. Although in two subjects nearly 200 ml of fluid was injected, in the other two subjects the sacs were well distended with 70 ml only. In each case only the lower part of the sac distended and formed a rounded swelling. The radiograph in Figure 11, taken after injection of both sacs in succession, shows that the medium did not enter the upper part of the sac and, furthermore, did not enter the pockets of the perineal extension. The failure of the medium to enter these regions of the sac in the specimens examined was probably due to the presence of adhesions which, as noted during dissection, were common in female subjects.

Fig. 5. Male cadaver. A hand within the opened left sac shows that its outer margin crosses the inguinal ligament medial to the anterior superior iliac spine (indicated by finger-tip) and becomes attached to the fascia lata at the crease-line of the groin. Inguinal lymph nodes (L) lie in the fatty layer (held in forceps) below this line. Fig. 6. Male cadaver. The entrances to the perineal pockets are medial to the crease-line of the groin (CR). The medial pocket (S) is associated with the scrotum, the intermediate (C) with the spermatic cord (held by hook) and the lateral (P) with the superficial perineal pouch. The fundiform ligament is held in forceps. Fig. 7. Male cadaver. The medial rod (S) lies within the scrotal pocket and the lateral rod (P) within the superficial perineal pouch. A finger within the intermediate (cord) pocket shows that it lies within the scrotum and terminates above the testis. Fig. 8. Male cadaver: left indirect inguinal hernia. The margins of the incised scrotal skin are held in the lower forceps and the margins of the incised cord pocket in the upper forceps. The hernial sac (H), from which the rod protrudes, is contained within the cord pocket and its fundus reaches the fundus of the cord pocket, indicated by the finger. The testis lies just below it. Superficialfascia of abdomen and perineum 609

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Subjects with post-operative scars In the male cadaver with the appendicectomy scar, the left sac was injected first and marked distension was obtained with 130 ml of medium. Radiography showed that the sac was well filled, although the perineal pockets were not completely out- lined (Fig. 12). The right sac was then injected and marked distension was produced with 180 ml, although the swelling did not extend above the level of the scar. After 610 B. F. MARTIN

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/p Superficialfascia of abdomen andperineum 611 placing a long metal pin along the scar a second radiograph was taken, which revealed that the medium had not risen above the level of the pin, and also that the radio- opacity fell considerably short of the mid-line at the pubis. The perineal extension was well filled, however, and the fundi of two pockets were outlined (Fig. 12). The cadaver with the left inguinal scar following hernial repair was that of a 69 years old male. The right sac was injected first and 200 ml was required to produce marked distension. Radiography showed that, in addition to the sac, the whole of the homolateral half of the scrotum was outlined. The left sac was then injected below the scar and it became markedly distended following the introduction of 150 ml, but the swelling did not extend above the level of the scar. After placing a long metal pin along the scar a second radiograph was taken. This confirmed that the medium had been arrested at the level of the scar and, furthermore, the left half ofthe scrotum was also outlined so that a complete scrotal shadow resulted (Fig. 13). Since dissection had shown that the sacs were sometimes unequal in size in normal individuals, there remained the possibility that in this cadaver the left sac was naturally smaller than the right. Dissection of the sacs was therefore undertaken following embalming for five weeks. The injected Micropaque, which was white in colour, had become somewhat gelatinous following embalming and it had not diffused away from the sacs. The right sac was filled with the medium almost -to its upper extremity. The left sac was similar in size but it was subdivided into two compartments by a broad band of adhesion underlying the cutaneous scar. The lower compartment was filled with the medium but none had entered the smaller, upper compartment (Fig. 14; compare with Fig. 13). Some displacement of fascia had also resulted from the adhesion, so that the two compartments were not quite in alignment (Fig. 14). The radiographs of both this specimen and the specimen with the appendicectomy scar confirmed the displace- ment. Reference to Figures 10,12 and 13 shows that as the outer margin of a normal sac gained the crease-line of the groin it crossed the line of the hip joint, which con- firmed Holden's (1877) observation, cited earlier. However, the outer margin of a

Fig. 9. Male cadaver. Injection of Micropaque (prior to embalming) into the right abdominal sac has produced a well-defined ovoid swelling and its lateral margin lies precisely at the crease- line of the groin. Fig. 10. Radiograph of cadaver shown in Figure 9. The contrast medium has outlined the abdominal sac and its perineal extension, where the fundi of two pockets (F) are seen. The outer margin of the sac crosses the hip joint. Fig. 11. Female cadaver: radiograph following injection of both sacs. Only the lower parts of the sacs are filled and the medium has not entered the perineal extension, probably due to adhesions. Fig. 12. Male cadaver: appendicectomy scar. Radiograph of both sacs with a metal pin (P) placed over the scar. The right sac, which is somewhat displaced, has not filled above the scar. The medium has entered the perineal extensions around the base of the penis and outlined the fundi (F) of two pockets on the right. Fig. 13. Male cadaver: left herniotomy scar. Radiograph of both sacs with a metal pin (P) placed over the scar. The left sac, which is somewhat displaced, has not filled above the scar. The medium has entered the perineal extensions around the base of the penis and produced a complete scrotal shadow (see text). Fig. 14. Same specimen as Figure 13: dissection of sacs five weeks after embalming. The white contrast medium has filled the right sac. At the scar site the left sac is subdivided by a broad band of adhesion (A) and only the segment below it has filled. The two segments are not quite in alignment. 612 B. F. MARTIN divided sac lay below the level of the joint line (Figs. 12, 13), which suggested that the partly displaced lower segment had bulged over the crease-line during distension. Further study of the cadaver with the inguinal scar involved examination of the perineal pockets following dissection of the scrotal skin from the underlying mem- branous fascia. The right sac exhibited the usual three perineal pockets. The pouch pocket was narrow and admitted only a finger-tip. The cord pocket, as in other specimens, lay anterolateral to the spermatic cord and terminated just above the testis, but it was very thin-walled. The scrotal pocket was particularly large and ex- tended well below the testis. In addition, the fascia was thin and the contrast medium had penetrated between it and the skin. On first inspection it appeared that only a large scrotal pocket with a wide entrance was associated with the left sac. However, a pouch pocket was also present but its entrance was obscured by adhesions although these yielded to finger pressure. Theie was no independent pocket associated with the spermatic cord, which was attached to the posterior wall of the scrotum by a fascial sling. Since it was shown by dis- section that a hernial sac occupied the cord pocket, it is probable that during operative removal of the sac the fascia of the pocket, together with the fascial band separating its entrance from that of the scrotal pocket, had been broken down and in consequence the entrance to the scrotal pocket had been enlarged. The large, complete scrotal shadow seen in the radiograph of this specimen (Fig. 13) probably resulted from seepage of the medium through the thin fascia of the scrotal pockets.

DISCUSSION Although it is confirmed that a thin membranous layer, commonly known as Scarpa's fascia, is present on the deep surface of the subcutaneous tissue of the lower abdominal wall, it is limited to an obliquely directed oval area, with no evidence of a further fatty layer deep to it, which some investigators have reported (Forster, 1937; Congdon, Edson & Yanitelli, 1946; Tobin & Benjamin, 1949). Since its margins are attached to the underlying deep fascia, except inferiorly, it encloses a subcutaneous abdominal sac, open to the perineum. Its limited distribution prob- ably explains the failure of some investigators (Tobin & Benjamin, 1949) to confirm its existence, especially when examination has been particularly directed to the central area below the umbilicus, where it is absent. Since the medial margins of the sacs blend inferiorly with the fundiform ligament and its continuation around the base of the penile shaft, they do not communicate with each other or with the potential space between the penile dartos and Buck's fascia. The lateral margin, by its attachment inferiorly to the fascia lata just below the inguinal ligament, firmly anchors the superficial to the deep fascia and thereby creates the crease-line of the groin. From these inferior attachments the fascia con- tinues, as the fascia of Colles, into the perineum. The perineal extension is in the form of three pockets. The medial is associated with the scrotum or labium majus, the intermediate with the spermatic cord or round ligament of the uterus and the lateral with the superficial perineal pouch. In the female, the pockets are commonly occupied by adhesions. Some previous investigations have indicated that the perineal extension is sub- divided. In male cadavers, Uhlenhuth, Smith, Day & Middleton (1949) observed that the scrotal cavity is separated from the superficial perineal pouch by the 'major leaf' of Colles' fascia, and communicates with the abdominal subcutaneous space Superficialfascia of abdomen andperineum 613 independently ofit by means of a fascial canal which opens at the superficial inguinal ring. In female cadavers, McVay & Anson (1938) observed a diverticular process of the fascia, lateral to the bulb of the vestibule, which extends from the superficial inguinal ring to the level of the urethral orifice, and contains the round ligament of the uterus. This diverticulum corresponds with the intermediate pocket, described above. It is likely that the localised development of a membranous layer on the lower abdominal wall is determined by the necessity to form a crease (flexure) line at the groin and to provide important fascial layers associated with the external genitalia. Clinical interest in the fascia has been chiefly directed to the significance of its attachments in directing the pathway of extravasated urine following rupture of the male distal to the . The results of the present study, however, have demonstrated a further significant feature, namely, the provision by the fascia of the intermediate pocket of an outer covering for the sac of an indirect inguinal hernia. Extensive clinical studies (Hertzler, 1913; Watson, 1938; Ogilvie, 1959) have shown that in nearly all cases the occurrence of an indirect inguinal hernia is de- pendent upon the persistence, in whole or part, of the processus vaginalis which, together with its coverings derived from the abdominal wall, forms the hernial sac. Although the hernia is less common in females, it also enters a persistent processus vaginalis (the canal of Nuck). Posteriorly the sac is attached to the spermatic cord or the round ligament of the uterus (Ogilvie, 1959). The level to which the hernia descends depends upon the extent to which the processus is obliterated. If it enters the scrotum it is commonly arrested just above the testis but occasionally, and usually in young children, the processus is completely patent and the hernia enters the . The hernial sac examined occupied the cord pocket as far as its fundus, just above the testis. The pocket, which was expanded distally, was not adherent to the hernial sac except posteromedially, where both were attached to the cord coverings. In view of the observations on normal cadavers this finding is not unexpected and shows that beyond the superficial inguinal ring the hernial sac, which bulges forwards from the ductus deferens, is invaginated into the cord pocket which contains and supports it. The clinical observation that the ductus deferens is always adherent to the medial side of the sac (Watson, 1938) is in accord with the position of the pocket which normally lies anterolateral to the spermatic cord. Since the hernia is normally arrested at the fundus of the pocket, it must be inferred that in those occasional cases where the hernia enters the tunica vaginalis, the cord pocket, which is probably developed in relationship to the processus vaginalis, does not terminate above the testis but continues distally to surround the testis and its coverings, with which it would presumably blend posteriorly. Examination of a subject in which hernial repair had been effected showed that the pocket was absent. It is probable that damage to the pocket fascia is inevitable during removal of the hernial sac. The existence of this outer fascial layer enclosing the distal part of a hernia does not appear to have been recognised. Although Struthers (1854) pointed out that Colles' fascia forms a tube around the spermatic cord and forms one of the coverings of a hernia, he apparently referred to the fascial lining of the scrotal cavity. An indirect inguinal hernia in the female seldom enters the labium majus, and usually forms a bubonocele in the pubic region (Watson, 1938). The reason may well be that the perineal pockets in the female are commonly occupied by adhesions. 614 B. F. MARTIN Rupture of the male urethra distal to the urogenital diaphragm, which results in urinary extravasation, may follow trauma or spontaneous perforation of an in- flammatory lesion, and commonly occurs just behind the penoscrotal junction (Culp, 1942). If the layer of Buck's fascia which closely invests the corpus spongi- osum is not perforated, it confines the extravasate to the region of the penile urethra (Buck, 1848; Wesson, 1923, 1953; Culp, 1942). In most cases this layer is perforated and the extravasate enters the superficial perineal pouch. The early claims (Colles, 1811; Struthers, 1854) that the attachments of the membranous fascia prevent the extravasate from entering the ischiorectal fossa or the thigh, but allow its forward passage to the scrotum and lower abdominal wall, have been repeatedly substantiated. The penis is not infrequently involved, however, and the extravasate may also enter the opposite half of the scrotum, usually after some delay (Culp, 1942; Smith, 1949; Wesson, 1953). Experimental studies have been undertaken on fresh cadavers to investigate the pathway taken by various media, introduced under pressure deep to the mem- branous layer of the superficial fascia of the perineum. In some experiments the medium has been introduced directly into the superficial perineal pouch, whilst in others it has been injected into the penile urethra following ventral puncture of its bulbar segment, to simulate the clinical condition. When air is injected directly into the perineum, Struthers (1854) and later Tobin & Benjamin (1944) found that it travels forwards and inflates the scrotum. Finestone (1941) introduced both coloured fluids and contrast medium into the superficial perineal pouch. He traced the course of the former by dissection and the latter by radiography. The fluids spread to the scrotum and the inguinal region but not to the penile shaft. These results provide further evidence that the abdominoperineal sac does not communicate with the interfascial space on the penile shaft. Injections into the artificially ruptured urethra have been made with coloured fluid (Wesson, 1923) and with coloured latex (Tobin & Benjamin, 1944, 1949). If Buck's fascia is not ruptured, the latex is confined to the region of the penile urethra, as in the comparable clinical conditon. When the fascia is perforated, fluids enter the superficial perineal pouch and pass to the scrotum and lower abdominal wall. How- ever, as in clinical cases, spread to the penile shaft is frequent, although this only occurred in the experiments with coloured fluid when pressure was exerted on the pubic part of the tumescence. It is probable that the frequent involvement of the penis following urethral rupture is a consequence of the breach in the penile fascia, which must occur before the perineal pouch can be entered. With increasing hydrostatic pressure, it is to be ex- pected that in some cases the extravasate would penetrate between Buck's fascia and the penile dartos. In cases where the extravasation becomes bilateral it is likely that the rupture is sufficiently extensive to breach both pouches, although a delayed contralateral spread in clinical cases may be the result of fascial damage from infection. In clinical studies (Culp, 1942; Smith, 1949; Wesson, 1953) it has been observed that there is a delay, which Smith (1949) states may be as long as six to eight hours, before the extravasate reaches the scrotum from the pouch. Smith demonstrated experimentally the relative impermeability of the 'major leaf' of Colles' fascia which separates the pouch from the scrotum (Uhlenhuth et al. 1949), and concluded that this accounts for the delay. The results of the present investigation, however, suggest a different explanation. An initial delay would occur while the pouch fills and over- Superficialfascia of abdomen andperineum 615 flows in the pubic region, from whence the extravasate is free to enter the scrotum via the entrances to the scrotal and cord pockets. A further delay would occur before the pockets are sufficiently filled to produce obvious scrotal tumescence. Further- more, the ready distensibility ofthe scrotum undoubtedly delays further spread to the abdominal wall. In this context it is noteworthy that when the abdominal sac was distended with contrast medium in the present study there was no obvious scrotal tumescence, although the medium had entered and clearly outlined the perineal pockets. Finally, it is confirmed that Scarpa's fascia plays a role in the repair of abdominal incisions. It has been pointed out (Forster, 1937) that its incised edges should be sutured to prevent the scar becoming too wide. In two cases examined, an incision had completely traversed the fascia, which had become adherent to the deep fascia along the length of the scar. As a result the abdominal sac was completely sub- divided. This deep adhesion of the scar undoubtedly contributes to its soundness.

SUMMARY It has been shown that the membranous layer ofthe subcutaneous tissue, known as Scarpa's fascia, is confined to an oval area on each side of the abdominal wall. By its attachment to the deep fascia it encloses an obliquely directed oval sac which extends into the perineum by three pocket-like diverticulae. The fascial extension which forms the pockets is known as the fascia of Colles. Medially, the sac blends with the fundiform ligament, so that the sacs do not communicate with each other or with the interfascial space deep to the penile dartos. Laterally, the inferior margin creates the crease-line of the groin by its attachment to the fascia lata. Between these attachments the pockets arise from the sac. The lateral pocket continues into the superficial perineal pouch. The medial pocket, together with the intermediate, occupies the scrotum or labium majus. The intermediate pocket is associated with the spermatic cord or the round ligament of the uterus and blends with their coverings posteriorly. In the male it terminates just above the testis. The significance of the fascial arrangements in relation to urinary extravasation is discussed, and also the relationship of the intermediate pocket to an indirect inguinal hernia. I should like to express my gratitude to the Anatomy Department for providing facilities to undertake this investigation, and also to Mrs Joan Farr, Mr G. Lee and Mr A. Greenhalgh for their technical assistance.

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