Improving laparoscopy in embalmed cadavers: a new method with a lateral abdominal wall muscle section.

BACKGROUND: Rigor mortis can be a problem when laparoscopy is performed in embalmed cadavers for surgical training. METHODS: To improve the laparoscopic view, a new technique for managing the abdominal wall with a cutaneous-subcutaneous flap, pneumoperitoneum (14-15 mmHg), and a progressive (step-by-step) bilateral section of the lateral muscles of the abdomen was attempted in 10 embalmed cadavers. The degree of abdominal wall increase was calculated by measuring changes in the size of the abdominal wall after each step. Improvement in the peritoneal laparoscopic view was also assessed. RESULTS: For abdominal wall size, no constant relationship was observed between initial (after creation of the pneumoperitoneum) and final increment (after each muscular layer section). Cumulative degrees of increase in the dimensions of the abdominal wall were the only parameters that showed a significant difference among the four groups of cadavers. Bilateral sectioning of both oblique muscles was sufficient to obtain an adequate view of the abdominopelvic cavity; thus, the risk of an unexpected peritoneal opening during sectioning of the transversum abdominis muscle was obviated. CONCLUSIONS: In embalmed cadavers, the laparoscopic view in the presence of a pneumoperitoneum can be facilitated by a section of the lateral muscles of the abdomen, with a previous cutaneous-subcutaneous flap. To obviate an incidental opening of the peritoneum, resulting in air leakage, preservation of the deep muscular layer is advisable.

Separation between the digestive and the respiratory lumina during the human embryonic period: morphometric study along the tracheo-oesophageal septum.

An isolated tracheo-oesophageal fistula could be caused by close proximity of the epithelia of both organs (O'Rahilly & Müller, 1984; Kluth et al. 1987) at certain embryonic stages, the most frequent location being the tracheal bifurcation. Thus the relative position and degree of separation between the digestive and the respiratory tubes throughout their development may be relevant to the origin of this anomaly. The aim of this study was to analyse along the different segments of the tracheo-oesophageal septum (TES) where the closest relationship between both lumina occurred and what degree of separation was present at each segment. Computer imaging techniques were applied on cross sections of a graded series of normal human embryos (Carnegie stages (CS) 13-23). In addition, the differentiation of the primitive TES was also studied (from CS 12) by light microscopy. Between CS 13 and 16 both tubes tended to separate (phase of separation), principally at the proximal segments of the laryngopharyngeal and the tracheo-oesophageal portions of the TES. During this phase the separation between the trachea and oesophagus was wider than between the larynx and pharynx. From CS 17 to CS 23 the digestive and respiratory lumina reached their widest separation at different levels of the laryngopharyngeal portion. Below these levels they tended to come closer together, principally at the proximal segment of the tracheo-oesophageal portion, but also at the distal part of the laryngopharyngeal portion. During this phase of approximation they reached their closest relationship at the proximal (CS 17) and the distal (from CS 18) segments of the tracheo-oesophageal portion. When finally the distal segment of the trachea (which includes the bifurcation) comes closest to the oesophagus, the coats of both organs have already undergone an appreciable differentiation. According to these observations, the origin of the most frequent isolated tracheo-oesophageal fistula at the bifurcation region could not be explained from the normal development of the TES.

Factors involved in the 'rotation' of the human embryonic stomach around its longitudinal axis: computer-assisted morphometric analysis.

The majority of studies as to whether gastric and nongastric factors are involved in the 'rotation' of the human embryonic stomach around its longitudinal axis have been morphological. The aim of this study was to analyse, with morphometric support, the influence on the angular modifications during gastric rotation of the simultaneous changes of the gastric walls and mesenteric growth, and the volumes of organs adjacent to the stomach (right, left and posterior groups). Computer imaging techniques were applied on cross sections of a graded series of 10 human embryos (from Carnegie stage (CS) 11) and 2 fetuses. A clockwise gastric rotation occurred during the embryonic period. The most rapid angular modifications took place from CS 11 to 16, after the rotation became oscillatory with angular changes in clockwise and anticlockwise directions, reaching the highest value at CS 18 (at the supraomental part of the stomach: 54.37 degrees; at the omental part: 68.03 degrees); after this period the angular values tended to stabilise. The predominant growth of the left gastric wall over the right and the changes in the width of the gastric mesentery were the most persistent factors involved in the modifications of the transverse gastric angle during the embryonic period although without relationship to their direction. During the increasing angular phases, clockwise rotation was promoted by the decrease of the volume of any group of organs adjacent to the stomach. When the volume of the left and posterior groups increased simultaneously, clockwise or anticlockwise angular directional change was related to the respective decrease or increase adjacent organ volume to the right. We conclude that the stomach of the human embryo undergoes heterogeneous and multifactorial rotation as a consequence of the overall increase in gastric wall growth to the left and the increase of gastric mobility produced by the previous mesenteric enlargement, and that the rotational direction results from the forces exerted on the stomach and the gastric mesenteries by the adjacent organs.

Computer-assisted stereological analysis of gastric volume during the human embryonic period.

Morphometric data concerning human embryos and fetuses have become more clinically informative since ultrasound was employed to make prenatal measurements and software preprocessing techniques improved the previous fuzzy ultrasound signals (Mahoney, 1992). The aim of this study was to determine the volume of the human stomach during the embryonic period and to compare its rate of growth with that during the early fetal period. To calculate gastric volume, computer imaging techniques were applied on cross sections of a graded series of human embryos (from Carnegie stage 11) and fetuses. Gastric volume increased progressively, except for a decrease between stages 12 and 13 due principally to the reduction of the right gastric wall. The growth of the left wall of the stomach was predominant over that of the right. Until stage 20 the stomach volume increased due to the predominant growth of the walls, after this stage the gastric cavity volume increased rapidly, and the rate of growth of the gastric volume reached similar values to that of the early fetal period. We concluded that in the beginning the human stomach grows due to the predominant growth of its walls, chiefly of the left, and from stage 20 because of the predominant expansion of its cavity, which may be related to the capacity to swallow amniotic fluid at the end of the embryonic period. The diminution of the right gastric wall volume (stages 12-13) is consistent with an extension of the omental bursa into the mesodermal anlage of the stomach.

Biceps brachii muscle attached to the extensor carpi radialis brevis muscle: an unreported anatomical variation in humans.

We report a new muscular variation in humans. It consisted of a biceps brachii muscle attached to the extensor carpi radialis brevis muscle by means of an accessory fasciculus. It was a trapezoid tendinous connection band that arose from the terminal tendon of the biceps brachii muscle and ended in the internal margin of the extensor carpi radialis brevis muscle. This intermuscular connection band was the external slip of the insertion tendon of the biceps brachii muscle, which was also attached by means of two other fascicles to the radial tuberosity (intermediate slip) and the flexor digitorum superficialis muscle (internal slip). This variation was observed in only one of the sixty upper limbs examined.

Accessory fasciculi of the human pronator teres muscle: incidence, morphological characteristics and relation to the median nerve.

The purpose of this study is to determine the incidence of the accessory fasciculi of the pronator teres muscle and to evaluate the predispositional role of its morphological characteristics to median nerve entrapment. The accessory fasciculi of the pronator teres muscle have been found in 8.3% of 60 upper extremities which were studied. These fasciculi arose from the tendon of the brachialis muscle (5.0%), from the radial tendon of the biceps brachii muscle (3.3%), from the Gantzer's muscle (1.6%) or from the flexor digitorum superficialis muscle (1.6%). They were slips of origin of the deep head of the pronator teres muscle. They represented the deep head, when there was no other origin slip, or they were additional origin slips when the deep head also had a coronoid origin. Only the accessory fasciculi that represented the deep head and the accessory fasciculi located inside to the coronoid fasciculus were related directly to the median nerve. Three characteristics of these accessory fasciculi adjacent to the median nerve could be considered to be factors that predispose to the nerve entrapment: 1) the location dorsal to the superficial head of the pronator teres muscle, because it increases the area of contact with the median nerve; 2) the location between the superficial head and the coronoid fasciculus, because it reduces the space occupied by the median nerve; and 3) the tendinous nature of considerable segments of short accessory fasciculi because they are less extensible.

Variations of the pronator teres muscle: predispositional role to median nerve entrapment.

The variability of the human pronator teres muscle is studied in 60 upper limbs. The humeral head was present in all cases and was double in 3 cases (5.0%). The ulnar head was present in 47 cases (78.3%). The ulnar head was muscular in 11 cases, tendinous in 6 cases, and mixed in 30 cases. The collateral branches of the median nerve destined to the pronator teres muscle were found to be arranged in three main patterns: arising directly from the median nerve, arising from the superficial flexor antebrachial muscles nerve, and mixed type. Special reference is made to the influence of variations in the pronator teres muscle on the compression or the entrapment of the median nerve (pronator syndrome). The proposed determinant variations are: short and tendinous ulnar head, ulnar head joined to the arch of the flexor digitorum superficialis muscle, ulnar head with triple origin slips, and humeral head perforated by the median nerve.

Effects of L-asparaginase on rat embryonic development and yolk sac membrane in vitro.

A comparative analysis of the teratogenic effects of L-asparaginase on 10.5- and 11.5-day rat embryos after 24 and 48 hours of exposure in vitro, respectively, were performed. Several medium concentrations of L-asparaginase (0.05, 0.25, and 1.5 IU/ml) were tested in both embryo series. Resulting embryos were submitted to morphological studies in a search for a specific route of pathogenesis. Morphological alterations of the visceral yolk sac were also studied to investigate its contribution to L-asparaginase teratogenicity in rats. Main embryonic malformations (open truncal neural tube, open encephalic vesicles, anophthalmia, lack of inversion, abnormal frontolateral protrusions, great vascular dilations at the cephalic level) and developmental retardation were already generated after the first 24 hours of culture (embryos of 10.5 days) and presented a dose-response relationship. Vascular dilations and neurulation disturbances seemed to be related to an early mesenchyme deficiency. Reduced number of mesenchymal cells was more evident in embryos of 10.5 days than those of 11.5 days, suggesting the existence of a later compensatory mechanism of cellular proliferation in the older embryo. Visceral yolk-sac endodermal cells at both embryonic stages were greatly deformed and enlarged by an increase of the high electron-dense vacuolar system. Therefore, both a blockage of the processes of lysosomal digestion and derived trophic deficiencies probably existed. A double teratogenic mechanism for L-asparaginase is postulated: a direct action mainly in younger embryos (before invagination of the embryo into the yolk sac) and a yolk sac-mediated one.

Association of tracheoesophageal anomalies with visceral and parietal malformations in a human embryo (Carnegie stage 21).

A human embryo (Carnegie stage 21) with tracheoesophageal malformations (esophageal atresia and tracheoesophageal fistula) and anomalies at the caudal end of the embryo (anorectal atresia, rectovesical fistula, vertebral and notochordal defects, and agenesis of the metanephros) was studied. Other anomalies observed were: absence of right umbilical artery, fusion of spinal ganglia, and absence of cloacal outlet of mesonephric ducts. The possible pathogenesis of these associated malformations is discussed.

Intrahepatic termination of the left gastric vein (vena gastrica sinistra): a new case of this unusual anatomic variation.

The intrahepatic termination of the left gastric vein is an unusual anatomic variation. A new case studied after dissection is described. The left gastric vein is divided in 2 terminal branches which enter the left liver lobe after flowing through the pars condensa of the lesser omentum. One is a terminal branch which contributes to the portal irrigation of the superior lateral subsegment. The other anastomoses to the ramus cranialis of the left branch of the portal vein. The diameter of the left gastric vein, portal vein and splenic vein obtained after morphometric study can be considered normal. The existence of portal hypertension prior to death is discarded.

Teratogenic effects of L-asparaginase in rat embryos in vitro.

The teratogenic potential of L-asparaginase has been assayed in New cultures of explanted rat embryos. Embryos treated on day 9.5 with 1.5 IU L-asparaginase/ml of culture medium exhibited growth and development retardation together with malformations of the brain (exencephalia), eyes (anophthalmia or rudimentary sulcus opticus), face (characteristic appearance with anomalous frontolateral protrusions) and trunk (myeloschisis and turning absence). Neural ectoderm alterations were observed upon histological examination (anomalous fusions between the confronted neural folds as a consequence of the lack of turning and thickening) together with strong vascular dilatations at the cephalic level. Treatment on day 10.5 only caused minor differences in growth and protein content with respect to the control embryos. The possible teratogenic mechanism of this enzyme is discussed.

Ontogenetic study of the hepatogastroesophageal anastomotic omental veins.

The ontogenetic study of connections between the foregut venous plexus and the intrahepatic venous system through the omentum minus was studied. This study was performed in 20 embryos (6-30 mm crown-rump (CR) length) and 10 human fetuses (31-71 mm CR length). One or two anastomotic veins were observed in each of the 6-19 mm CR length embryos. These veins run through the cranial area of the omentum minus. Their enteric extremity is located at the level of the gastroesophageal junction while the hepatic extremity runs into the ductus venosus (9 cases), sinusoids of the left liver lobe (1 case), left branch of the portal vein (1 case) or into the subdiaphragmatic intervitelline anastomosis (1 case). The transient feature of anastomotic omental veins was enhanced, and its chronological relationship with the vena gastrica sinistra was analyzed in order to obtain an ontogenetic explanation to the uncommon adult cases which have been published.