SMALL BOWEL MANIFESTATIONS OF
SYSTEMIC DISEASES
CONNECTIVE TISSUE DISORDER AND DERMATOLOGIC DISEASES
Scleroderma frequently involves the small bowel, primarily causing dysmotility. It is characterized by a dilated bowel, associated with scattered wide-mouthed diverticula and even intestinal pseudoobstruction, and small intestinal bacterial overgrowth.
INTESTINAL OBSTRUCTION
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| OBSTRUCTION AND ADYNAMIC ILEUS OF SMALL INTESTINE |
Small intestinal obstruction occurs when the normal propulsion of luminal contents is hindered by either mechanical obstruction or abnormal intestinal motility. The obstruction may be partial or complete and can occur at any level of the small bowel.
ANOMALIES OF THE ATRIA
Juxtaposition Of The Atrial Appendages
In juxtaposition of the atrial appendages (auricles), the main bodies of the atria are normally located, but there is levoposition of the right atrial appendage. Instead of being to the right of the arterial trunks, the right atrial appendage crosses behind them to appear on their left, interposing itself between the great arteries and the left atrial appendage. Juxtaposition of the atrial appendages has no functional significance because it causes no hemodynamic disturbance itself. Its presence, however, always indicates the coexistence of other major cardiac anomalies. Transposition of the great vessels and a ventricular septal defect are invariably present, and atresia of the tricuspid valve is common. Plate 5-5 also depicts a double aortic arch.
ANOMALOUS PULMONARY VENOUS CONNECTION
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| TOTAL ANOMALOUS PULMONARY VENOUS CONNECTION |
In patients with anomalous pulmonary venous connection (APVC), all or some of the pulmonary veins fail to communicate with the left atrium, instead discharging blood into major systemic veins or directly into the right atrium. This discussion only considers the isolated forms of APVC. When these occur with other cardiac malformations, the clinical and hemodynamic features are usually modified or are chiefly determined by the complicating defect.
ANOMALIES OF THE GREAT SYSTEMIC VEINS
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| CARDIAC VEIN ANOMALIES |
Anomalies can involve the large systemic venous trunks because of the complex embryogenesis and tremendous variability of the venous system in general. Abnormal channels almost always empty into other systemic veins and rarely cause functional changes disturbing to the patient, usually discovered incidentally at postmortem examination or during cardiovascular diagnostic or surgical procedures. Venous trunk anomalies may occur as isolated malformations but more often are associated with other cardiovascular anomalies. The presence of an anomaly, if unsuspected, may lead to troublesome or even dangerous situations when total cardiopulmonary bypass techniques are employed.
PHYSICAL EXAMINATION
Although many forms are not seen in adult patients, cardiologists often do see simple clues to the diagnosis of certain forms of congenital heart disease (CHD), usually acyanotic or cyanotic and postoperative. Any child with or suspected with CHD should be seen by a pediatric cardiologist at an institution with interventional pediatric cardiologists and cardiac surgeons. Adult patients with CHD should be seen and advised by a pediatric cardiologist or adult cardiologist (prefer ably both) at a surgical center with experts in congenital heart surgery and percutaneous procedures. Many adult patients present with arrhythmias, heart failure, or failure of the original childhood surgery. Occasionally, older patients or patients with anomalous coronary artery disease present with ischemic heart disease symptoms.
Fetal Circulation and Changes
at Birth
The primary vascular concept of prenatal circulation is the requirement that the intraembryonic circulation of blood bypass the nonfunctioning lungs and liver (see Plate 4-18). The placenta (villous chorion) serves the role of these organs with gas and metabolic exchange between maternal and fetal blood. The airway in the lungs is filled with amniotic fluid, and pulmonary vascular resistance is high. The lungs only receive enough blood to nourish the tissues, and pulmonary venous blood flow into the left atrium is minimal. The plan for the prenatal circulation also requires that it convert the postnatal pattern soon after the first breath of the newborn. Two lung shunts (and a liver shunt) and the design of the interatrial septum serve these needs.
Development of Major Blood Vessels
The early embryonic vascular system is plexiform (intercalating).
Preferential flow related to the development of organ systems, however, leads
to enlargement of certain channels in the plexus. This expansion is brought
about in part by the fusion and confluence of adjacent smaller vessels and by
the enlargement of individual capillaries. Thus a number of vascular systems develop.
As the embryo grows, new organs appear; others are transient and disappear. The
various vascular systems are also continuously modified to satisfy changing
needs.
Initially, the arteries and veins consist simply of endothelial tubes and cannot be distinguished from each other histologically. In later development, typical vessel walls are differentiated from the surrounding mesenchyme. The final pattern of the vascular system is genetically determined and varies with the animal species. Variations are, however, extremely common in both arterial and venous patterns, and local modifications occur in cases of abnormal development of organs.
Formation of Cardiac Septa
At the close of the preceding phase of development, the heart completely occupies the pericardial cavity. Blood flows in a single path through the sinus venosus and atrium, through an atrioventricular canal into the left ventricle, though an interventricular canal above the free edge of the primordial interventricular septum into the right ventricle, then out the bulbus cordis and truncus arteriosus. The stage is now set for the septation of the heart, which lasts about 10 days. No major changes occur in the external appearance of the heart. The formation of the various cardiac septa occurs more or less simultaneously; for descriptive purposes, however, it is necessary to consider their development separately.
Formation of the Heart Loop
At the beginning of the next phase of development, the heart, as described earlier, is essentially a straight tube with a caudal venosus end and cranial arterial end. It lies within the pericardial cavity and is attached posteriorly only by the dorsal mesocardium.
