Intestinal Tract

In the presence of tumors or other pathologic lesions involving the duodenum, papilla of Vater, head of pancreas, or hepatoduodenal ligament, the duodenum should be opened in situ. Precise orientation may become impossible after removal of these organs. This is particularly important in postoperative autopsies.

Routinely, the intestinal tract is opened with an enterotome, that is, large scissors with one blunted branch that lies in the lumen of the intestine. The procedure is greatly facilitated when the mesentery has been cut close to the wall of the small intestine. The specimen usually is opened in a sink under running water. If possible, specimens for histologic study should be obtained before they are exposed to tap water. We no longer use or recommend the use of the stationary enterotome, illustrated in the last edition, mainly because of the risk of injury during cleaning of this instrument.

Fig. 5-1. Esophageal varices, injected with barium sulfategelatine mixture. Varices stand out and are white; the features are enhanced in a roentgenogram.

A tumor with predominantly intraluminal growth and its associated obstruction can be displayed after formalin fixation of the unopened specimen and subsequent dissection. A glass tube at the hose from an elevated formalin container is simply tied into the hollow viscus; the other end is clamped or tied off. The whole preparation is suspended in a formalin bath.

For proper histologic orientation, long strips of gastric or intestinal mucosa can be cut parallel with the long axis of the organ, fixed, and embedded in a spiral fashion, for example, with the proximal end at the center. Isolated histologic specimens of gastrointestinal tract should always be fixed on cork-board or cardboard to keep the samples flat. This will allow embedding and cutting the specimens properly on edge.

PRESERVATION OF SMALL INTESTINAL MUCOSA The small bowel is tied at the duodenojejunal junction and at the terminal ileum close to the cecum. A cannula is inserted into the most superficial presenting loop of the small intestine. Con-

Fig. 5-2. Esophageal varices in cleared specimen. The mucosal layer has been stripped from the muscularis and cleared in benzene, as described in ref. (2).

centrated formalin (40% formaldehyde) solution is instilled through the cannula until the small bowel is distended. During this procedure, the small intestine should be handled as little as possible. The formalin-filled bowel should be left untouched as long as possible. The bowel is then removed and soaked for another 24 h in 10% formalin solution. Satisfactory results can be expected if the fixation is begun within 6 h after death (6).

PREPARATION OF SPECIMENS FOR STUDY UNDER DISSECTING MICROSCOPE Postmortem autolysis causes the loss of intestinal epithelium. Thus, the dissecting microscope often shows villi that appear thinner than the ones seen on biopsy specimens. The openings of the crypts become more prominent. In spite of these differences, the extent and character of abnormal mucosal patterns can easily be evaluated with a dissecting microscope.

Specimens can be viewed after they have been rinsed in saline or they can be processed further (7) by pinning square pieces of corkboard, and fixing them in buffered 10% formalin solution. After at least 24 h of fixation, the specimens are put into one change of 70% alcohol and two changes of 95% alcohol for 2 h each. The specimens are stained with 5% alcoholic eosin for 4 min and subsequently treated with two changes of absolute alcohol for 2 h each. The fixed stained and dehydrated intestinal wall is placed in xylol. The preparation is now ready

Celiac Trunk Superior Mesenteric Artery

Fig. 5-3. Partitioned abdominal viscera for celiac and mesenteric arteriography. Celiac trunk specimen: Note rotation and upward sweep of duodenum. Root of superior mesenteric artery remains with celiac artery but is hidden behind pancreas. Superior mesenteric artery specimen: This includes intestine from middle of first jejunal loop to middle of transverse colon. Inferior mesenteric artery specimen: This extends from middle transverse colon to anus; pelvic viscera (uterus and bladder) are attached. Adapted from ref. (9).

Fig. 5-3. Partitioned abdominal viscera for celiac and mesenteric arteriography. Celiac trunk specimen: Note rotation and upward sweep of duodenum. Root of superior mesenteric artery remains with celiac artery but is hidden behind pancreas. Superior mesenteric artery specimen: This includes intestine from middle of first jejunal loop to middle of transverse colon. Inferior mesenteric artery specimen: This extends from middle transverse colon to anus; pelvic viscera (uterus and bladder) are attached. Adapted from ref. (9).

for examination. Unstained specimens or specimens stained with a hematoxylin-alum solution (8) also can be studied.

DRY PRESERVATION Air-drying or paraffin infiltration yields interesting permanent museum specimens. After rinsing the unopened bowel with saline, glass tubes are tied into both ends. One tube is connected to a tank with compressed air, the other tube is connected to a rubber hose that can be slowly clamped while the air inflated the organ. After 1-3 d, air-drying is completed. No fixation is necessary. Lesions such as diver-ticula are well-displayed by this method but again, histologic specimens become unsatisfactory and interest in this technique has waned.

MESENTERIC ANGIOGRAPHY The celiac, superior mes-enteric, or inferior mesenteric artery can be injected with a barium sulfate-gelatin mixture, either in situ or after en block removal of the abdominal viscera. If all three vessels are injected (Fig. 5-3), the abdominal organ block must be partitioned so that the three vascular compartments can be displayed properly (9).

Clearing methods and India ink or latex injection techniques are largely obsolete.

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