A system of practical medicine. By American authors. Vol. 2

by Unknown

Until the middle of the seventeenth century the prevalent views upon the functions and diseases of the pancreas were vague in the extreme. By some the organ was regarded simply as a cushion provided for the protection of the neighboring blood-vessels and nerves; by others it was looked upon as the seat of lesion in many very diverse diseases, as ague, hypochondriasis, melancholia, and so on.

In 1642, Wirsung's discovery of an excretory duct demonstrated the fact that the pancreas was a special organ, and initiated the successful investigation of the physiology and pathology of the gland. For many years after this, however, little progress was made, and it is only comparatively recent investigations that have furnished definite and reliable information upon the subject. Even now our knowledge of the clinical and pathological features of diseases of the pancreas is far behind that of many of the other viscera of the body, the chief reasons for this being the uncertainty in regard to the physiology of the gland and the rarity with which its lesions are primary and uncomplicated.

ANATOMY AND PHYSIOLOGY.—The pancreas is a long, somewhat flattened, narrow, acinous gland, pinkish-white in color, and of looser texture than the salivary glands, which it otherwise closely resembles in structure. It is hammer-shaped, measures from six to eight inches in length, one and a half inches in breadth, and about three-fourths of an inch in thickness, and varies in weight from three to five ounces. The gland is situated in the upper part of the abdominal cavity; the expanded portion, or head, lies in the concavity of the duodenum; thence it extends transversely across the epigastric and both hypochondriac regions on a level with the first lumbar vertebra and in contact with the posterior abdominal wall. As it passes toward the left it gradually decreases in size, and the narrowest part, or tail, rests against the spleen. Behind the organ are the crura of the diaphragm, the aorta, the inferior cava, the superior mesenteric vessels, and the solar plexus; in front of it, the stomach and the left lobe of the liver. Its anterior surface alone is invested with peritoneum, being covered by the posterior layer of the lesser omentum. The ascending portion of the head is intimately connected with the duodenum by dense connective tissue, and at times the descending portion, by extending backward and outward, forms an almost complete ring around the gut; the body is loosely attached by connective tissue to the posterior abdominal wall, and the left extremity and tail are joined to the left kidney and suprarenal capsule and to the spleen by loose areolar tissue. The gland is supplied with arterial blood by branches springing from the pancreatico-duodenal and splenic vessels; its veins join the splenic and superior mesenteric veins; its lymphatics communicate with the lumbar glands; and its nerves are branches from the solar plexus. The principal excretory duct, the canal of Wirsung, has at its widest part the calibre of a goose-quill. It begins by the union of five small branches at the tail, and extends transversely through the substance of the gland from left to right, nearer the lower than the upper border, and the anterior than the posterior surface; it is joined throughout its course by numerous small branches from the acini, which enter it at acute angles. In the head the duct curves slightly downward, and as a rule opens with the ductus choledochus into the ampulla of Vater in the second portion of the duodenum; sometimes, however, it has a separate opening into the intestine. A second, smaller, duct runs from the ascending portion of the head, and usually joins the main duct, but may also open independently.

The acini of the gland are from .045 mm. to .090 mm. in diameter, and are composed of a very thin membrane lined with pavement cells. The thin walls of the excretory ducts are formed of connective tissue and elastic fibres, and are lined by a single layer of small cylindrical epithelial cells. The terminal extremities of the ducts form a complete network around the glandular cells, resembling the intralobular biliary canaliculi. The acini are imbedded in a mass of adipose tissue which contains the vessels and nerves.

The topographical relation of the head of the pancreas to the ductus choledochus is of clinical importance. As a rule (fifteen times in twenty-two, Wyss), the bile-duct descends near the head, toward the duodenum; frequently it runs through this part of the organ, being either partially or entirely surrounded by the gland substance. Now, when the bile-duct merely passes over the pancreas, any enlargement, unless excessive, would simply push it aside, but when it passes through the head, a comparatively slight amount of disease is sufficient to close it entirely and cause jaundice.

It is only since the observations of Bernard in 1848 that the prominence of the pancreatic juice as a digestive fluid has been recognized. It fulfils several important purposes: in the first place, it emulsifies the fatty articles of food; secondly, it converts starch and cane-sugar into glucose; and, finally, it supplements the action of the gastric juice upon nitrogenous materials and completes their digestion. Each of these changes is probably brought about through the agency of a special ferment (Danilewsky). The pancreatic juice is not secreted continuously. According to the observations of Bernstein, there are two separate secretory flows following each ingestion of food—one occurring shortly after the food enters the stomach; the other a few hours later, corresponding in time to the passage of the food from the stomach into the intestine, the latter being followed by a period of rest until the next meal. Both the condition of nausea and the act of vomiting arrest the secretion. When the vagus is divided and the central extremity of the cut nerve is irritated, the secretion is also arrested, and remains checked for a long time. The arrest in each instance is attributed to reflex action of the spinal cord and sympathetic nerve. At the same time, irritation of the mucous membrane of the stomach caused by the presence of food increases the flow of pancreatic juice, and so too does simple section of the nerves which accompany the arteries. It would seem, therefore, that the gland is under the influence of two sets of nerves from the vagus—one inhibiting, the other exciting, its secretion.

GENERAL ETIOLOGY.—Pancreatic disease occurs more frequently in men than in women. No period of life is exempt from it, but it is most commonly met with in the aged. The predisposing causes are constitutional syphilis, pregnancy, and hereditary tendency. Among the apparent exciting causes may be mentioned the habitual over-use of alcoholic drinks, gluttony, the excessive use of tobacco, suppression of the menstrual flux, the abuse of purgatives, excessive and prolonged mercurial medication, and mechanical injuries, either prolonged pressure or blows upon the epigastrium. As a secondary affection, disease of the pancreas is associated with chronic diseases of the heart, lungs, liver, alimentary canal, and abdominal glands, and the organ may be the seat of metastatic abscesses and tumors.

GENERAL SYMPTOMATOLOGY.—The objective symptoms are—rapid and extreme emaciation of the entire body; sialorrhoea; obstinate diarrhoea with viscid stools; fatty stools; lipuria; and the presence of masses of undigested striped muscular fibres in the stools.

The well-established fat-absorbing and peptonizing properties of the pancreatic juice furnish a ready explanation of the wasting of the body which occurs when this secretion is arrested, diminished in quantity, or altered in quality by disease. Emaciation is not a constant symptom of pancreatic disease. A number of cases are mentioned by Abercrombie, Claessen, and Schiff in which, notwithstanding disease of the gland and complete closure of the duct, revealed by post-mortem examination, the patients during life were not only well nourished, but even moderately corpulent. In such instances it is probable that the digestive functions of the absent pancreatic juice are more or less adequately performed by the bile and succus entericus. When present, emaciation is an early symptom; it is at the same time progressive, and is usually very intense in degree, being most marked in those cases where there is associated hepatic disease or obstruction to the passage of bile into the intestine, where the disease of the pancreas interferes mechanically with the processes of nutrition by pressing upon the pyloric extremity of the stomach or upon the duodenum, and when the organ is the seat of carcinomatous growths. In the last-named condition, in addition to the perversion or arrest of the secretion, the loss of flesh is attributable to the general causes of malnutrition attendant upon carcinoma wherever situated.

Sialorrhoea, or an excessive secretion from the salivary glands, is noticeable as a symptom of disease of the pancreas only when there is an associated lesion of the stomach, either of a catarrhal or cancerous nature. Under these circumstances a quantity—six or eight fluidounces—of a colorless, slightly opalescent, and adhesive and alkaline fluid may be expelled from the mouth at once as an early morning pyrosis; or by frequent and repeated acts of expectoration, following a sudden filling of the mouth with fluid, a large bulk of thin saliva may be expelled during the day. This hypersecretion must not be looked upon as any indication of an especial sympathy existing between the salivary glands and the pancreas, neither can it be regarded as a pancreatic flux with a regurgitation of the fluid from the duodenum into the stomach and thence through the oesophagus into the mouth, since during the nausea that must always attend the passage of the intestinal contents into the stomach the pancreatic secretion is arrested, and since the liquid contains salivary, and not pancreatic, elements.